Rozprawy doktorskie na temat „Food packaging film”

L'attuale tendenza nel confezionamento degli alimenti è orientata alla sostituzione di polimeri non biodegradabili a base di petrolio con materiali di imballaggio ecologici e che possano prolungare anche la shelf-life degli alimenti. In questo contesto, il progetto Ph.D. ha preso in considerazione lo sviluppo di film misti a base di chitosano arricchiti con composti antimicrobici naturali (oli essenziali) e di sintesi (etil lauroil arginato) per applicazioni di confezionamento alimentare sostenibile. L'intero progetto è stato diviso in cinque parti principali. Il capitolo I presenta una breve introduzione sui recenti progressi dei film costituiti da miscele a base di chitosano. Il motivo per cui è stato scelto il chitosano come biopolimero principale in questo studio e nella revisione della letteratura riguardante la miscelazione del chitosano con altri biopolimeri è stata descritta. Nel capitolo II, i film attivi a base biologica e doppio strato sono sviluppati mediante tecnica solvent casting, usando chitosano e gelatina come biopolimeri, glicerolo come plastificante e etil lauroil arginato (LAE) come composto antimicrobico. I risultati hanno mostrato che i film di miscelazione presentavano una resistenza alla trazione e un modulo elastici più elevati e una permeabilità al vapore acqueo inferiore rispetto ai film a doppio strato (p <0,05). I film bilayer hanno dimostrato un’efficace barriera contro la luce UV e valori di trasparenza inferiori (p <0,05). Gli spettri FT-IR hanno indicato la presenza di interazioni tra chitosano e gelatina, in particolare interazioni elettrostatiche e formazione di legami idrogeno. Tuttavia, l'aggiunta di LAE non ha interferito nella struttura della rete. I film attivi contenenti LAE (0,1%, v / v) hanno inibito la crescita di quattro patogeni alimentari tra cui Listeria monocytogenes, Escherichia coli, Salmonella typhimurium e Campylobacter jejuni. Nel capitolo III, sono sviluppati film a base di miscela chitosano-gelatina arricchita con cannella, citronella, chiodi di garofano rosa, noce moscata e oli essenziali di timo (1%, v / v) e le loro proprietà fisiche, ottiche, meccaniche, di barriera all'acqua e microstrutturali sono state valutate per applicazioni di confezionamento alimentare attivo. I risultati hanno confermato le interazioni intermolecolari tra i gruppi funzionali degli oli essenziali con i gruppi idrossile e amminico della rete di film di chitosano-gelatina. L'incorporazione di diversi oli essenziali ha migliorato notevolmente le proprietà di barriera UV. I film sviluppati, con particolare riguardo a quelli integrati con l'olio essenziale di timo, erano efficaci contro i quattro comuni patogeni alimentari testati. Il capitolo IV si concentra sullo sviluppo di film attivi basati sulla miscelazione di biopolimeri naturali (chitosano) e sintetici (polivinilico alcool). Sono stati sviluppati film in miscela di chitosano, polivinil alcool e LAE, incorporato in questi film a diverse concentrazioni (1-10%, p / p). I risultati hanno mostrato che alti livelli di LAE hanno influenzato negativamente sulle proprietà di barriera meccanica e permeabilità all'acqua. Anche in questo caso film attivi sviluppati erano efficaci contro quattro agenti patogeni alimentari testati. Il capitolo V rappresenta la conclusione di questa tesi, e presenta una sintesi dei punti salienti dei risultati importanti, ottenuti in questo studio.
The current trend in food packaging is oriented towards the substitution of non-biodegradable petroleum-based polymers by packaging materials that are eco-friendly and can prolong the food shelf life as well. In this context, this Ph.D. project aims to the development of chitosan-based blend films enriched with natural (essential oils) and synthetic (ethyl lauroyl arginate) antimicrobial compounds for sustainable food packaging applications. The overall project has been divided into five main parts. The brief description of each chapter is presented here: Chapter I presents a brief introduction to the recent advances of chitosan-based blend films for food packaging applications. The reason for selecting chitosan as the main biopolymer in this study and literature review concerning blending chitosan with other biopolymers has been described. Chapter II aims to develop blend and bilayer bio-based active films by solvent casting technique, using chitosan and gelatin as biopolymers, glycerol as a plasticizer and ethyl lauroyl arginate (LAE) as an antimicrobial compound. The results showed that blend films had higher tensile strength and elastic modulus and lower water vapor permeability than bilayer films (p<0.05). Bilayer films demonstrated as effective barriers against UV light and showed lower transparency values (p<0.05). FT-IR spectra indicated that interactions existed between chitosan and gelatin due to electrostatic interactions and hydrogen bond formation. However, the addition of LAE did not interfere in the network structure. Active films containing LAE (0.1%, v/v) inhibited the growth of four food bacterial pathogens including Listeria monocytogenes, Escherichia coli, Salmonella typhimurium, and Campylobacter jejuni. Chapter III focuses to develop films based on chitosan-gelatin blend enriched with cinnamon, citronella, pink clove, nutmeg, and thyme essential oils (1%, v/v) and evaluating their physical, optical, mechanical, water barrier and microstructural properties for active food packaging applications. The results confirmed intermolecular interactions between functional groups of the essential oils with the hydroxyl and amino groups of the chitosan-gelatin film network. The incorporation of different essential oils notably improved the UV barrier properties. The developed films, with special regards for those including thyme essential oil, were effective against four common food bacterial pathogens. Chapter IV aims to develop active films based on blending chitosan and polyvinyl alcohol enriched with LAE at different concentrations (1-10%, w/w). The results showed that high LAE levels negatively affected mechanical and water barrier properties. Addition of LAE improved UV barrier properties. The developed active films were effective against four common food bacterial pathogens.

Les plastiques sont aujourd'hui des matériaux ubiquitaires utilisés dans tous les aspects de notre vie quotidienne, en particulier pour l'emballage alimentaire. Cependant, après usage, les plastiques sont une source de pollution de notre environnement naturel. Certains plastiques biodégradables et biosourcés sont déjà disponibles sur le marché, comme l’acide polylactique (PLA), mais ils présentent des performances inférieures. Ce travail de thèse vise à: 1) étudier la stabilité des films de PLA dans diverses conditions de température, d'humidité relative, de pH, d'exposition à des liquides ou à des vapeurs... 2) mieux comprendre l'impact de certains procédés industriels tels que les traitements corona ou pressage à chaud sur le PLA 3) combiner le PLA à des couches de gluten de blé afin de produire des complexes ayant des propriétés barrière plus élevées.Les films de PLA ont été produits par la société Taghleef Industries sur demande et avec des traitements de surface spécifiques, comme le traitement Corona. Des films et des enductions à basede gluten de blé ont été développés à l’échelle laboratoire ainsi que des complexes tricouches PLA- gluten-PLA. Les propriétés physiques et chimiques des films ont été étudiées par différentes techniques issues des sciences des matériaux et des aliments ont été utilisées, telles que l’analyse enthalpique différentielle (DSC), l'analyse thermogravimétrique (TGA), la chromatographie d'exclusion de taille (SEC), la microscopie de force atomique (AFM), la microscopie électronique (SEM), la spectroscopie infrarouge à transformée de Fourier (ATR-FTIR) et la spectroscopie de rayons X (XPS). Les propriétés fonctionnelles telles que la perméabilité à la vapeur d'eau, à l'oxygène (O2), au dioxyde de carbone (CO2) ou à l'hélium (He), la sorption de gaz et de vapeurs, les propriétés mécaniques et de surface ont également été étudiées.Exposés au CO2, les films de PLA présentent une isotherme de sorption linéaire avec l’augmentation de pression. Cependant les modifications physiques et chimiques induites à des pressions élevées n'affectent pas son utilisation dans le domaine d’application alimentaire. Au contraire, lorsque les films de PLA sont exposés à l'humidité à l'état liquide ou vapeur, leur dégradation survient après deux mois à 50 ° C (essai accéléré) suite à son hydrolyse. Cette détérioration chimique, mise en évidence par une diminution significative de la masse molaire, entraine une perte de transparence, mais également par une augmentation de la cristallinité. Par ailleurs, le pH n'affecte pas le taux d'hydrolyse, ce qui est d'un intérêt essentiel pour conditionner des aliments humides.Les films à base gluten de blé ont été choisis pour leurs propriétés de barrière élevées lorsque l’humidité relative reste faible. L'incorporation de lipides n'a pas apporté d'amélioration de leurs performances barrières. Cependant, l'utilisation d’un procédé d’homogénéisation à haute pression a permis une meilleure dispersion du gluten, ce qui a conduit à des films plus homogènes ayant ainsi de meilleures propriétés fonctionnelles. Ces conditions ont donc été retenues pour réaliser des complexes à 3 couches par assemblage d'une couche de gluten de blé entre deux couches de PLA en utilisant un pressage à chaud (10 MPa, 130 ° C, 10 min).La technologie de pressage à chaud montre une forte influence sur les films de PLA, de gluten et sur les tricouches. Elle induit une cristallisation accrue du PLA, ce qui augmente ses propriétés de barrière d'environ 40% et 60%, respectivement pour l'eau et l'oxygène. Cela masque par contre l’effet du traitement corona. D’autre part, le pressage à chaud induit une restructuration du réseau de gluten qui améliore les propriétés de barrière aux gaz des complexes, mais provoque aussi une évaporation de l'eau à l'interface gluten / PLA défavorable à l’adhésion des couches (...)
Poly(lactic acid) (PLA) is a biodegradable and renewable polyester, which is considered as the most promising eco-friendly substitute of conventional plastics. It is mainly used for food packaging applications, but some drawbacks still reduce its applications. On the one hand, its low barrier performance to gases (e.g. O2 and CO2) limits its use for applications requiring low gas transfer, such as modified atmosphere packaging (MAP) or for carbonate beverage packaging. On the other hand, its natural water sensitivity, which contributes to its biodegradation, limits its use for high moisture foods with long shelf life.Other biopolymers such as wheat gluten (WG) can be considered as interesting materials able to increase the PLA performances. WG is much more water sensitive, but it displays better gas barrier properties in dry surroundings. This complementarity in barrier performances drove us to study the development of multilayer complexes PLA-WG-PLA and to open unexplored application scenarios for these biopolymers.This project was thus intended to better understand how food components and use conditions could affect the performances of PLA films, and how these performances could be optimized by additional processing such as surface modifications (e.g. corona treatment and coatings).To that aim, three objectives were targeted:- To study the stability of industrially scale produced PLA films in contact with different molecules (CO2 and water) and in contact with vapour or liquid phases, with different pH, in order to mimic a wide range of food packaging applications.- To better understand the impact of some industrial processes such as corona or hot press treatments on PLA.- To combine PLA with WG layer to produce high barrier and biodegradable complexes.Different approaches coming from food engineering and material engineering were adopted. PLA films were produced at industrial scale by Taghleef Industries with specific surface treatments like corona. Wheat gluten films, coatings and layers were developed and optimized at lab scale as well as the 3-layers PLA-WG-PLA complexes. Different technologies able to mimic industrial processes were considered such as hot press, high pressure homogenization, ultrasounds, wet casting and spin coating. The physical and chemical properties of PLA films were then studied at the bulk and surface levels, from macroscopic to nanometer scale. The functional properties like permeability to gases (e.g. O2 and CO2) and water, gas and vapour sorption, mechanical and surface properties were also investigated.Exposed to CO2, PLA films exhibited a linear sorption behaviour with pressure, but the physical modifications induced by high pressure did not affect its use for food packaging. However, when exposed to moisture in both liquid and vapour state (i.e. environments from 50 to 100 % relative humidity (RH)), PLA was significantly degraded after two months at 50 °C (accelerated test) due to hydrolysis. This chemical deterioration was evidenced by a significant decrease of the molecular weight, which consequently induced a loss of transparency and an increase of the crystallinity. The hydrolysis was accelerated when the chemical potential of water was increased, and it was surprisingly higher for vapour compared to liquid state. In addition, pH did not affect the rate of hydrolysis.Knowing much better the limitation of PLA films, the challenge was to improve its functional properties by combining them with WG, as a high gas barrier bio-sourced and biodegradable polymer. The use of high pressure homogenization produced homogeneous WG coatings, with improved performances. This process was thus selected for making 3 layer complexes by assembly of a wheat gluten layer between two layers of PLA, together with corona treatment and hot press technologies.Corona treatment applied to PLA physically and chemically modified its surface at the nanometer scale (...)
I materiali plastici convenzionali trovano impiego in tutti campi della nostra vita, specialmente nel settore del packaging alimentare, ed in seguito all’utilizzo contaminano e danneggiano il nostro ecosistema. Materiali plastici derivanti da risorse naturali e biodegradabili, come acido polilattico (PLA), sono attualmente disponibili sul mercato anche se caratterizzati da performances inferiori.Questo progetto di dottorato è mirato 1) allo studio della stabilità di film di PLA a varie condizioni di stoccaggio come temperatura, umidità relativa, pH, o esposizione a vapori o gas; 2) a comprendere meglio le influenze di alcuni processi industriali come trattamento corona e hot press nelle proprietà dei film di PLA; 3) a sviluppare complessi multistrato tra film di PLA e di glutine che abbiano proprietà barriera più elevate rispetto ai singoli film.Gli imballaggi a base di PLA sono stati prodotti da Taghleef Industries, produttore leader nel settore e dotato di infrastrutture atte ai trattamenti di modificazione di superfice come il trattamento corona. I film a base di glutine e i coatings sono stati sviluppati e ottimizzati su scala di laboratorio, così come i complessi trilaminari PLA-glutine-PLA.Le proprietà fisiche e chimiche dei film di PLA sono state investigate a livello di superficie, così come a livello di bulk. Diverse tecniche analitiche, provenienti dal campo delle scienze dei materiali e delle scienze degli alimenti, sono state adottate in questo progetto di dottorato come calorimetria differenziale a scansione (DSC), termogravimetria (TGA), cromatografia di esclusione molecolare (SEC), microscopia a forza atomica (AFM), microscopia elettronica a scansione (SEM), spettrofotometria infrarossa a trasformata di Fourier in riflettanza totale attenuata (ATR-FTIR) e spettroscopia fotoelettronica a raggi X (XPS).Le proprietà funzionali come le permeabilità al vapore acqueo (H2O), all’ossigeno (O2), al diossido di carbonio (CO2) o all’elio (He) sono state investigate, cosi come l’assorbimento di gas e/o vapori, le proprietà meccaniche e le proprietà di superfice.Nonostante i film di PLA assorbano linearmente CO2 a pressioni crescenti, l’assorbimento di tale gas è ridotto a basse pressioni in modo da non modificare le sue proprietà fisiche – come contrariamente osservato quando il PLA è esposto a CO2 ad alte pressioni – e da non influenzare negativamente il suo utilizzo come imballaggio alimentare. Ad ogni modo, quando i film di PLA sono esposti ad ambienti umidi, o quando sono immersi in acqua liquida, sono significativamente degradati per idrolisi dopo due mesi di stoccaggio a 50 °C (test accelerato). Questo deterioramento chimico è stato evidenziato da una significativa riduzione del peso molecolare del PLA che, conseguentemente, induce una sua perdita di trasparenza e ne incrementa la sua cristallinità. Inoltre, è stato evidenziato che il pH non influenza la velocità di idrolisi. Quest’informazione ha importanza pratica per possibili utilizzi di PLA come imballaggio di alimenti ad alta umidità.Il glutine è stato scelto per le sue alte proprietà barriera, quando è protetto da ambienti ad alta umidità. Si è visto che l’incorporazione di lipidi non porta con sé grandi miglioramenti nelle performances dei film a base di glutine. Invece, l’utilizzo della tecnologia di omogeneizzazione ad alte pressioni permette una migliore dispersione del glutine, ottenendo film più omogenei e con migliori proprietà funzionali. Questa tecnologia è stata quindi scelta per produrre i complessi multistrato, intercalando i film di glutine tra due film di PLA, usando il trattamento hot press (10 MPa, 130 °C, 10 min). Si è osservato che il trattamento hot press modifica le proprietà dei film di PLA, di glutine e dei film multistrato Hot press induce cristallizzazione in PLA, e conseguentemente aumenta le sue proprietà barriera complessive, approssimativamente al 40 % all’acqua e al 60 % all’ossigeno (...)
Los materiales plásticos tradicionales son utilizados en todos los campos de nuestra vida y en particular modo como embajales de productos alimenticios; los cuales después de ser utilizados contaminan y dañan nuesto medio ambiente. Materiales plásticos derivados de recursos naturales y biodegradables, como el ácido poliláctico (PLA) se encuentran actualmente disponibles en el mercado a pesar de sus menores performances. Este proyecto de doctorado está orientado 1) al estudio de la estabilidad de películas de PLA bajo diferentes condiciones como temperatura, humedad relativa, pH o exposición a vapores o gases, 2) comprender los efectos en las propiedades de las películas de PLA de algunos procesos industriales como el tratamiento corona y hot press, 3) desarrollar complejos multicapas de PLA y gluten que tengan propiedades barrera mejores que las de las películas individuales.Los embalajes a base de PLA han sido producidos por Taghleef Industries, productor líder en el sector y dotado de las infraestructuras industriales adaptadas a los tratamientos superficiales como el tratamiento corona. Las películas de gluten y los coatings han sido desarrollados a escala de laboratorio, así como los complejos tricapa PLA-gluten-PLA.Las propiedades físicas y químicas de las películas de PLA han sido investigadas a nivel de superficie así como a nivel de bulk. Diferentes técnicas de análisis, frecuentemente utilizadas en los campos de las ciencias de los materiales y de las ciencias de los alimentos, han sido empleadas en este proyecto como calorimetría diferencial de barrido (DSC), análisis termogravimétrico (TGA), cromotagrafía de exclusión por tamaño (SEC), microscopía de fuerza atómica (AFM), microscopía electrónica de barrido (SEM), espectroscopía de infrarrojos por transformada de Fourier con reflectancia total atenuada (ATR-FTIR) y espectroscopía fotoelectrónica de rayos X (XPS).Las propiedades funcionales de los embalajes como las permeabilidades al vapor de agua, al oxígeno (O2), al dióxido de carbono (CO2) o al helio (He) han sido investigadas, asi como la absorción de gases/vapores, las propiedades mecánicas y las propiedades superficiales. A pesar de que las películas de PLA absorven linealmente CO2 a presiones mayores, la absorción del gas es reducida a bajas presiones y no modifica las propiedades físicas del PLA, como contrariamente sucede cuando el PLA es expuesto a altas presiones de CO2. Por lo tanto, su influencia en las propiedades funcionales del PLA es mínima en las normales aplicaciones alimentarias. De todos modos cuando los embalajes de PLA son expuestos a ambientes húmedos o cuando son sumergidos en agua, procesos de hidrólisis los degradan significativamente después de dos meses de conservación a 50 °C (test acelerado). Este deterioramiento químico ha sido evidenciado por una significativa reducción del peso molecular del PLA, que en consecuencia induce una pérdida de transparencia y un aumento de su cristalinidad. Además, se ha observado que el pH no influye en la velocidad de hidrólisis. Esta información tiene una importancia práctica para posibles usos del PLA como embalajes de alimentos a alta humedad. El gluten ha sido elegido por sus altas propiedades barrera cuando es protegido de ambientes a alta humedad. La incorporación de lípidos en las películas de gluten no han mejorado sus performances. Pero la tecnología de la homogenización a altas presiones ha permitido mejorar la dispersión del gluten, obteniendo películas más homogéneas y con mejores propiedades funcionales. Esta tecnología ha sido, por lo tanto, elegida para producir los complejos multicapa, intercalando las películas de gluten entre dos de PLA, utilizando el tratamiendo hot press (10 MPa, 130 °C, 10 min) (...)

[EN] In the present Doctoral Thesis, antimicrobial active packaging materials, at lab and at semi-industrial scale, have been developed with the aim to reduce the natural flora of peeled and cut fruit and extend its shelf life. Packaging prototypes have been developed for their further application. Prior to developing the active materials, the most suitable active agents were selected. To that end, the antimicrobial properties of the volatile active agents citral, hexanal and linalool and mixtures thereof were evaluated against typical microorganisms related to fruit spoilage, molds and yeast, concluding that the effectiveness of the mixture is higher than the sum of the effectiveness of the individual agents. Likewise, non-volatile antimicrobial agents such as potassium sorbate and sodium benzoate were selected, which are widely used in the food industry due to their antifungal properties. With the selected active agents, monolayer polypropylene (PP) films with different concentration of the active mixture citral, hexanal and linalool, at lab scale by means of extrusion, and bilayer films at semi-industrial scale with different active layer thickness by means of coextrusion were prepared. Besides, active packaging trays were developed at semi-industrial scale by thermoforming active sheets obtained by coextrusion of PP and ethyl vinyl acetate (EVA) compounds containing potassium sorbate and sodium benzoate as active agents. Mechanical, barrier and thermal properties of the developed active packaging materials, as well as their sealability and transparency were evaluated. In general, the materials' properties were not affected in a significant manner. However, active trays decreased in transparency due to the incorporation of non-volatile active agents. The release kinetics of the volatile and non-volatile active agents were studied at different temperatures, defining their diffusion coefficients by the adjustment to mathematic models based on Second's Law Fick. Among the volatile active agents, hexanal showed a higher diffusion coefficient, followed by citral and linalool. On the other hand, very small differences were observed between potassium sorbate and sodium benzoate diffusion coefficients, being of the same order of magnitude. In vitro tests were also performed at different temperatures to evaluate the antimicrobial properties of the developed materials. In general, the active packaging materials showed high antimicrobial properties which were enhanced with the increment of temperature. Once the properties of the developed materials were evaluated, in vivo tests with peeled and cut orange and pineapple were performed by packing these fruits with the active film, active tray and their combination (active packaging system). In general, the active packaging system improved the microbiological preservation of the fruit for longer times, between 2 and 7 days for orange and pineapple, respectively, and maintained quality parameters of the fruit at stable levels for longer times. Lastly, the safety of the active packaging materials was evaluated according to the European food contact materials and food legislation, and it was concluded that these materials were not of any safety concern for the consumers.
[ES] En la presente Tesis Doctoral se han desarrollado materiales de envase activo antimicrobiano, a escala laboratorio y a escala semi-industrial, con el objetivo de reducir la proliferación de la flora natural de la fruta pelada y cortada y extender su vida útil. Se han desarrollo distintos prototipos para su posterior aplicación industrial Previo al desarrollo de los materiales de envase, se ha realizado una selección de agentes activos más idóneos. Para ello se han estudiado mediante ensayos in vitro las propiedades antimicrobianas de agentes activos volátiles, citral, hexanal y linalool y diferentes mezclas de los mismos, frente a distintos microorganismos típicos del deterioro de las frutas, mohos y levaduras, concluyendo que la efectividad de la mezcla de los tres es superior a la suma de la efectividad de los activos de forma individual. Así mismo, también se han seleccionado antimicrobianos no volátiles como el sorbato potásico y benzoato sódico, los cuáles son ampliamente empleados en la industria alimentaria debido principalmente a sus propiedades antifúngicas. Con los agentes activos seleccionados, se han desarrollado películas monocapa de polipropileno (PP) con distintas concentraciones de la mezcla activa, citral, hexanal y linalool, a escala laboratorio, mediante técnicas de extrusión, y películas bicapa a escala semi-industrial con distintos espesores de capa activa mediante coextrusión. Por otra parte, se desarrollaron bandejas activas a escala semi-industrial mediante termoconformado de láminas obtenidas por coextrusión de compuestos de PP y etilvinilaceteto (EVA) con sorbato potásico o benzoato sódico como agentes antimicrobianos. Se han evaluado las propiedades mecánicas, barrera y térmicas de los materiales activos desarrollados, así como su sellabilidad y transparencia. En general, las propiedades de los polímeros no se vieron afectadas de manera relevante. Sin embargo, las bandejas activas perdieron su carácter transparente debido a la incorporación de los agentes activos no volátiles. Se ha estudiado la cinética de liberación de los compuestos activos volátiles y no volátiles a distintas temperaturas, determinando los coeficientes de difusión de los agentes activos mediante el ajuste a modelos matemáticos de difusión basados en la Segunda Ley de Fick. Entre los agentes volátiles, el hexanal mostró un mayor coeficiente de difusión seguido de citral y linalool. Por otra parte, no hubo apenas diferencia en los coeficientes de difusión del sorbato potásico y benzoato sódico, siendo éstos del mismo orden de magnitud. Igualmente, se han realizado diferentes experimentos in vitro a distintas temperaturas para determinar las propiedades antimicrobianas de los materiales desarrollados. En general, los materiales activos presentan una elevada capacidad antimicrobiana que se ve potenciada al aumentar la temperatura de exposición. Una vez evaluadas las características de los materiales desarrollados, se han efectuado ensayos de envasado de naranja y piña pelada y cortada con las películas y las bandejas activas y con la combinación del sistema de envase bandeja activa termosellada con la película activa. En general, el sistema de envase activo mejoró la conservación de la fruta por un mayor tiempo, entre 2 y 7 días para la naranja y piña, respectivamente, presentando una gran capacidad antimicrobiana y manteniendo los parámetros de calidad de la fruta en niveles estables por un mayor tiempo. Por último, se ha estudiado la seguridad de estos materiales de acuerdo a la legislación de materiales en contacto con alimentos y la legislación alimentaria europea, concluyendo que los materiales activos desarrollados no presentan preocupación para la seguridad de los consumidores.
[CAT] En la present Tesi Doctoral s'han desenvolupat materials d'envasament actiu antimicrobià, a escala de laboratori i a escala semi-industrial amb l'objectiu de reduir la proliferació de la flora natural de la fruita pelada i tallada i estendre la seua vida útil. S'han desenvolupament diferents prototips per a la seua posterior aplicació industrial. Previ al desenvolupament dels materials actius, s'han seleccionat els agents actius mes idonis estudiant mitjançant assajos in vitro les propietats antimicrobianes d'agents actius volàtils, citral, hexanal i linalool i diferents mescles dels mateixos, enfront de diferents microorganismes típics de la deterioració de les fruites -floridures i llevats- concloent que l'efectivitat de la mescla dels tres és superior a la suma de l'efectivitat dels actius de forma individual. Així mateix, s'han seleccionat antimicrobians no volàtils, sorbat potàssic i benzoat sòdic, els quals son àmpliament empleats a l'industria alimentaria per les seues propietats antifúngiques. Amb els agents actius seleccionats, s'han desenvolupat pel·lícules monocapa de polipropilè (PP) amb diferents concentracions de la mescla activa, citral, hexanal i linalool, a escala laboratori, mitjançant tècniques d'extrusió, i pel·lícules bicapa a escala semi-industrial amb diferents espessors de capa activa mitjançant coextrusió. D'altra banda, s'han desenvolupat safates actives a escala semi-industrial mitjançant termoconformació de làmines obtingudes per coextrusió de compostos de PP i etil vinil acetat (EVA) amb sorbat potàssic o benzoat sòdic com a agents antimicrobians. S'han avaluat les propietats mecàniques, barrera i tèrmiques dels materials actius desenvolupats, així com la seua sellabilidad i transparència. En general, les propietats dels polímers no es van veure afectades de manera rellevant. No obstant això, les safates actives van perdre el seu caràcter transparent a causa de la incorporació dels agents actius no volàtils. S'ha estudiat la cinètica d'alliberament dels compostos actius volàtils i no volàtils a diferents temperatures, determinant els coeficients de difusió dels agents actius mitjançant l'ajust a models matemàtics de difusió basats en la Segona Llei de Fick. Entre els agents volàtils, l' hexanal va mostrar un major coeficient de difusió seguit de citral i linalool. D'altra banda, no va haver-hi a penes diferències en els coeficients de difusió del sorbat potàssic i benzoat sòdic, sent aquests del mateix ordre de magnitud. Igualment, s'han realitzat diferents experiments in vitro a diferents temperatures per determinar les propietats antimicrobianes dels materials desenvolupats. En general, els materials actius presenten una elevada capacitat antimicrobiana que es veu potenciada en augmentar la temperatura d'exposició. Una vegada avaluades les característiques dels materials desenvolupats s'han efectuat assajos d'envasament de taronja i pinya pelada i tallada amb la safata, la pel·lícula activa i la seva combinació (sistema d'envàs actiu). En general, el sistema d'envàs actiu va millorar la conservació de la fruita per un major temps, entre 2 i 7 dies per a la taronja i pinya respectivament, presentant una gran capacitat antimicrobiana i mantenint els paràmetres de qualitat de la fruita en nivells estables per un major temps. Finalment, s'ha estudiat la seguretat d'aquests materials d'acord a la legislació de materials en contacte amb aliments i la legislació alimentària europea, concloent que els materials actius desenvolupats no presenten preocupació per a la seguretat dels consumidors.
Lara Lledó, MI. (2016). Antimicrobial packaging system for minimally processed fruit [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61388
TESIS
Premiado

Oggi frutta e verdura sono trasportate e distribuite sul mercato in imballaggi chiusi con film plastici o bio. La confezione assicura una migliore protezione del prodotto contro gli impatti meccanici e climatici, permettendo di prolungare la loro shelf-life. A questo fine e' fondamentale conoscere le proprieta' di barriera presentate dai film nei confronti di ossigeno, anidride carbonica e vapore acqueo. Scopo del mio lavoro di tesi e' stato quello di ricercare un nuovo e diverso metodo, alternativo ai tradizionali citati in letteratura e basati per lo piu' sull'impiego di costose attrezzature tipo gas cromatografi, per la determinazione e il calcolo del coefficiente di permeabilita' ai gas e al vapore acqueo di film plastici e biodegradabili usati per il confezionamento di frutta e vegetali freschi/freschissimi senza l'impiego della MAP (atmosfera modificata). Le prove sono state condotte mediante l'utilizzo di una strumentazione a basso costo appositamente realizzata in laboratorio e consistente in due cilindri di plexiglas recanti all'interno due box di plastica contenenti frutti climaterici e coperti con i film oggetto di studio (2 plastici e due biodegradabili). Sia i cilindri sia i box erano equipaggiati con un kit di sensori collegati a data logger per misurare i valori di concentrazione dell'ossigeno e dell'anidride carbonica, l'umidita' relativa e la temperatura con tempo di campionamento di 2 minuti. Questa struttura cosi' organizzata era inserita all'interno di una camera termica in maniera tale da poter controllare e regolare opportunamente i valori di temperatura. Si sono simulate due condizioni di temperatura, corrispondenti a due differenti condizioni di stoccaggio: temperatura progressivamente crescente da circa 0 a circa 25à à °C e temperatura fluttuante da circa 0 a circa 10à à °C. Il principio di misura applicato sfrutta la variazione naturale della composizione dell'atmosfera all'interno delle confezioni conseguente alla normale attivita' respiratoria della frutta. Misurando la variazione nel tempo della concentrazione dei gas chiave (anidride carbonica, ossigeno, vapor d'acqua) nei due ambienti (cilindro e box) separati dal film oggetto di studio, si e' messa a punto una procedura che consente di pervenire alla determinazione della permeabilita' del film ai gas considerati. Tutta la procedura di calcolo e' stata basata sull'equazione di stato dei gas perfetti e sulle leggi della psicrometria dell'aria umida. Tutte le fasi preliminari di trattamento dei segnali e tutte le equazioni per il calcolo delle quantita' di interesse sono state implementate utilizzando il linguaggio di programmazione del software open source R. I risultati hanno permesso di testare la validita' del metodo proposto, nel senso che hanno condotto alla determinazione di coefficienti di permeabilita' all'anidride carbonica, all'ossigeno e al vapore acqueo comparabili con quelli riscontrati in letteratura per film simili a quelli utilizzati (film per la conservazione di frutta fresca). Inoltre, i risultati hanno confermato pure gli aspetti teorici del modello diffusionale circa la tendenza crescente della permeabilita' al crescere della temperatura. Infine, sulla base delle leggi della psicrometria, le prove hanno permesso di evidenziare che le fluttuazioni di temperatura possono portare alla formazione di condensa sulla superficie dei film, con possibile deterioramento dell'alimento e quindi riduzione della sua shelf-life. Il lavoro svolto e' da considerarsi solamente un primo approccio, certamente suscettibile di ulteriori sviluppi futuri. Esso ha sostanzialmente dimostrato la validita' della metodologia proposta, che puo' essere perfezionata in modo da pervenire a determinazioni piu' precise ed accurate. A tal fine: Si potrebbero utilizzare sensori di ossigeno e anidride carbonica caratterizzati da un range di misura piu' ampio, cosi' da permettere l'esecuzione di prove di durata maggiore. Si potrebbero utilizzare data logger con una risoluzione piu' elevata, cosi' da agevolare o addirittura da rendere superflue le operazioni di pre-trattamento dei segnali. Si potrebbero aggiungere sensori di pressione, per tenere conto delle effettive variazioni di tale grandezza sia per cambiamenti nelle condizioni barometriche ambientali sia perche' indotte dalle variazioni di temperatura. Ancora, si potrebbe approfondire l'analisi dei dati, provando a modellizzare anche le fasi di assorbimento e desorbimento del gas o vapore, cosi' da valutare le caratteristiche dei film anche durante i transitori. Infine, per approfondire le problematiche legate alla formazione di condensa, si potrebbe studiare l'influenza esercitata sul coefficiente di permeabilita' da diversi tipi assorbitori di umidita' da includere all'interno delle confezioni.

Bakgrund: Trots plastfilmen negativa miljöpåverkan används den idag i hög utsträckning som förpackningsmaterial vid lastsäkring, detta då plastens materialegenskaper överträffar andra konkurrerade material. Plastfilm är ett förbrukningsmaterial, vilket gör att det inte kan återanvändas och stora mängder avfall skapas. Trots vetskapen om plastavfallets negativa påverkan på miljön läggs tonvikten på den ekonomiska aspekten när förpackningsmaterial diskuteras, medans miljön utlämnas eller har mindre fokus. Syfte: Studiens syfte är att utifrån identifierade faktorer utvärdera alternativa lastsäkringsmetoder som leder till en minskad användning av plastfilm utan att äventyra kvalitén på livsmedelsvaror under transport. Frågeställningar: (1) Vilka faktorer påverkar val av lastsäkringsmetod vid samlastade livsmedel? (2) Vilka alternativa lastsäkringsmetoder kan vidtas för att minska användningen av plastfilm i lastsäkringsprocessen? Genomförande: Denna studie motsvarar en enfallsstudie som är utförd hos Martin & Servera. Empiri insamling har främst skett via semi-strukturerade intervjuer och direkta observationer. I och med Covid-19 har även strukturerade intervjuer behövs genomföras. Utifrån observationer och intervjuer har en kartläggning av Martin & Serveras utgående logistik samt lastsäkringsprocess skett för att finna faktorer som påverkar valet av lastsäkringsmetod. Faktorerna har stått till grund vid framtagning av utvärderingskriterier, som har använts för att utvärdera alternativa lastsäkringsmetoder. De alternativa metoderna är funna genom intervjuer. Resultat: Totalt identifierades sju faktorer som påverkar val av lastsäkring metod: förpackningsformer, typ av lagersystem, lagerarbetare, krav/lagar/regleringar, typ av lastbärare, omslagsmaterialets egenskaper samt vilket typ av produkt som hanteras. Utifrån faktorerna framställdes utvärderingskriterier som sedan applicerades på fyra alternativa lastsäkringsmetoder (Plastskiva, Add-On Door Flex, 2 Kompletterande Dörrar samt Bioplastfilm). Samtliga metoder bidrog till minskad användning av plastfilm. Utifrån utvärderingskriterierna; Skydd & Stabilitet, Krav/Lagar/Reglering, Kostnad, Tidsåtgång, Miljö rekommenderas plastskivan som första alternativa lastsäkringsmetoden till plastfilm.

Mestrado em Biotecnologia
A produção de plásticos, baseados no uso de combustíveis fósseis, está a aumentar e estima-se que esta tendência continuará no futuro com impactos ambientais consideráveis. Os bioplásticos são uma alternativa amiga do ambiente. Biopolímeros como quitosana já foram adotados com sucesso para produzir bioplásticos que agem como substitutos do plástico em embalagem. A quitosana foi selecionada devido às suas numerosas vantagens para embalagem alimentar, principalmente devido às suas atividades antioxidantes e antimicrobiana. Por outro lado, o dióxido de titânio foi selecionado como aditivo devido à sua capacidade de retirar oxigénio do ambiente e devido à possibilidade de poder ser facilmente funcionalizado para a formação de um sensor. Isto permitiria a formação de uma embalagem ativa e inteligente na proteção do alimento. Assim, nanopartículas homogéneas arredondadas e monofásicas de anatase de dióxido de titânio (TiO2) foram usadas para melhorar os filmes de quitosana, criando um bionanocompósito. Estas nanopartículas de TiO2 foram produzidas por síntese hidrotermal, tendo sido otimizadas as condições de síntese, como a temperatura e tempo, para selecionar as condições que originam as nanopartículas com as caraterísticas desejadas. As condições escolhidas para a produção do TiO2 foram 200 ºC e 2,5 h devido ao tamanho, dispersão e tipo de nanoparticulas de TiO2 produzidas. Os filmes de quitosana foram preparados com cerca de 9 mg de nanopartículas de TiO2. Para criar uma embalagem ativa e inteligente compostos fenólicos (principalmente antocianinas) de arroz preto (Oryza sativa L. Indica) foram adicionados para funcionalizar o TiO2 (4,1 mg de extrato por filme). Os filmes foram caracterizados em relação à sua atividade antioxidante, humidade, solubilidade, hidrofobicidade da superfície e propriedades mecânicas. Os melhores resultados foram obtidos nos filmes com nanopartículas e compostos fenólicos e foi demonstrado que a forma como cada componente é adicionado altera as suas propriedades. Os melhores resultados foram o aumento da atividade antioxidante, diminuição da solubilidade e da elasticidade, elongação e resistência à tração no filme composto por pigmento e TiO2,. No entanto nestes últimos três parâmetros, a sua diminuição pode ser um aspeto positivo ou negativo dependendo das propriedades desejadas para o filme e o produto alimentar a embalar
Plastic production based in fossil fuels is rising, and predictions supports it continuous and enhanced use, with consequent environmental damage. Bioplastics are an environmentally friendly alternative. Biopolymers as chitosan have already been successfully used to produce bioplastics that act as plastic substitutes in packaging. Chitosan was chosen for its numerous advantages for food packaging namely due to its antioxidant and antimicrobial activities. On the other hand, TiO2 was selected due to its oxygen scavenging ability and due to its possibility to be easily functionalised to create a sensor. This would allow the construction of an active and intelligent packaging for food protection. Thus, monophasic anatase homogeneous round-shaped nanoparticles of titanium dioxide (TiO2) were used as filler to improve the chitosan films, creating a bionanocomposite. These TiO2 nanoparticles were produced via a hydrothermal method and its synthesis was optimized testing various reaction times and temperatures to find the conditions that create TiO2 nanoparticles with the desired features. The conditions used for the chosen TiO2 were 200 ºC and 2.5 h due to the size, dispersion and TiO2 of the nanoparticles produced. The chitosan films were prepared with about 9 mg of TiO2 nanoparticles. To develop an active and intelligent food packaging, phenolic compounds (mainly anthocyanins) from black rice (Oryza sativa L. Indica) were used to functionalise the TiO2 (4.1 mg of extract in each film). The films were characterised regarding its antioxidant activity, humidity, solubility, surface hydrophilicity and mechanical properties. The best results were from films with both nanoparticles and phenolic compounds, and it was established that the order in which they are added alters its properties. The more notable improvements are an increase in antioxidant activity and a decrease in solubility, elasticity, elongation and tensile strength in the film containing pigment and TiO2. However, the reduction of the later three properties can either be positive or negative, it depends on desired properties for the film for a chosen food product

Inspiré par la technique couche par couche traditionnelle (LBL), Ce travail de thèse démontre le premier effort pour développer une nouvelle méthodologie pour l’auto-assemblage des multicouches sur la base des interactions hydrophobes et d'adsorption physique pour fabriquer des films composites stratifié en Polyéthylène (LLDPE) - organoargile (OMMT). Contrairement à la technique LbL électrostatique, ici, les films multicouches ont été synthétisés en partant d'un substrat de polymère non polaire/non chargé et successivement le dépôt de couches d’organo-argile apolaire et de couches de PE non polaires/non chargés avec des dépôts répétitifs qui se suivent. La variation alternative de l'angle de contact (85° en moyenne pour l’organo-argile et 107° pour les couches de PE) a confirmé la profilométrie et les résultats de la microscopie électronique à balayage, ainsi que le modèle de croissance linéaire, la formation très stratifiée réussie de bicouches répétitives composées de 450 nm couches d’organo-argiles et 2,25 µm couches de PE. Ultérieurs essais de caractérisation ont été effectués pour évaluer l'effet de la variation des principaux paramètres de processus identifiés (concentration, température, les étapes de rinçage et de séchage, et le type de solvant), sur la formation et la croissance d'épaisseur des films. En conséquence, la forte dépendance de l'auto-assemblage aux paramètres du procédé testés a été montrée par les résultats expérimentaux obtenus. Les propriétés de barrière des films multicouches ont également été évaluées par la caractérisation de la perméabilité à la vapeur d'eau, à l'oxygène (O2) et au dioxyde de carbone (CO2), ainsi que la sorption de la vapeur d'eau. Un revêtement de 5 bicouches (OMMT/PE) (~ 14 µm d'épaisseur) a réduit la perméabilité à l'O2 d'un film de PE de 160 µm d'épaisseur de 84,4% et la perméabilité au CO2 de 70%, tandis que la perméabilité a la vapeur d’eau a été réduite de 45%. Ces réductions de perméabilité obtenues par seulement l’ajout de 2,4% (v/v) de nano-argile se sont révélés être significativement plus élevée par rapport aux valeurs de réduction rapportées dans la littérature pour les nanocomposites dispersés préparés à base de PE/organo-argile. Cette connaissance peut être utilisée dans la mise en place d'une approche pour produire des micro/nanostructures stratifiés ayant des propriétés de barrière sur mesure pour l'application dans l'emballage alimentaire
Inspired by the traditional Layer-by-Layer (LbL) assembly technique, this PhD study demonstrates the first effort to develop a novel methodology for multilayer self-assembly on the basis of hydrophobic interactions and further physical adsorption to fabricate stratified Polyethylene(LLDPE)-organoclay(OMMT) nano-enabled composite film. In contrary to the electrostatic LbL technique, here, the multilayer films were synthesized by starting from an uncharged apolar polymer substrate and successively depositing apolar organoclay and uncharged apolar PE layers with subsequent repeating depositions. The alternate variation of contact angle (85° average for organoclay and 107° for PE layers) confirmed the profilometry and the scanning electron microscopy results as well as the linear growth pattern, i.e. the successful highly stratified assembly of repetitive bilayers comprised of 450 nm organoclays and 2.25 µm PE layers. Further characterization tests were performed to evaluate the effect of the main identified process parameters (concentration, temperature, rinsing and drying steps, and solvent type) variation on the formation and thickness growth of the films. As a consequence, the high dependence of the self-assembly’s growth to the tested process parameters was showed by the obtained experimental results. The barrier properties of the multilayer films were also evaluated by characterizing the Water vapour, Oxygen (O2), and Carbon dioxide (CO2) permeability as well as the water vapour sorption. A 5-bilayer (OMMT/PE) coating (∼14 µm thick) reduced the O2 permeability of a 160 µm-thick PE film by 84.4% and the CO2 permeability by 70%, while the WVP was reduced by 45%. These permeability reductions obtained by only 2.4 v/v % of nanoclay addition level were found to be significantly greater compared to the reduction values reported in the literature for prepared blend PE/organoclay nanocomposites. This knowledge can be used in the establishment of an approach to produce stratified micro/nanostructures with tailored barrier properties for food packaging application

Se desarrollaron películas biodegradables activas a base de PHBV, combinadas con otros biopolímeros (PLA y almidón) y diferentes compuestos antimicrobianos (aceites esenciales (AE)), las cuales se caracterizaron en cuanto a sus propiedades funcionales y estructurales a fin de obtener materiales que satisfagan mejor los requisitos de envasado de alimentos. La plastificación del PHBV se llevó a cabo mediante el uso de diferentes compuestos con el objetivo de mejorar el rendimiento mecánico de los films. Asimismo, se incorporaron diferentes activos (AE de orégano y clavo, así como sus respectivos compuestos mayoritarios, carvacrol (CA) y eugenol (EU)) en películas bicapa de PHBV pulverizando los activos entre dos monocapas obtenidas por termocompresión. También se analizó la potencial sinergia entre diferentes compuestos de AE, así como sus aplicaciones a diferentes alimentos cuando se incorporan en películas bicapa de PHBV. Se desarrollaron películas antimicrobianas multicapa donde se combinaron láminas polares (almidón), apolares (poliéster) y CA, ya sea pulverizado entre ambas capas o incorporado en la solución filmogénica de poliésteres, a fin de optimizar la funcionalidad del material. El proceso de valorización de la cascarilla de arroz, basado en extracción con agua subcrítica, permitió obtener xilanos bioactivos y fracciones celulósicas con potenciales aplicaciones en el envasado de alimentos. Pese a que la adición de polietilenglicol (PEG) de diferente peso molecular o ácido láurico disminuyó significativamente la rigidez y la resistencia de las películas de PHBV, solo el PEG1000 dio lugar a películas más extensibles. No obstante, estrategias adicionales fueron necesarias a fin de adaptar las propiedades mecánicas de los films de PHBV a ciertos requisitos de envasado. La pulverización de activos en la interfaz de ambas monocapas de PHBV generó películas antimicrobianas con propiedades físicas adecuadas. Además, la liberación de los activos desde las películas permitió controlar el crecimiento de Escherichia coli y Listeria innocua en condiciones in vitro. Ambos activos, CA y EU, se liberaron de manera efectiva en diferentes simulantes alimentarios. En este sentido, la tasa de liberación mejoró cuando disminuyó la polaridad de los simulantes. El efecto sinérgico más notable para los compuestos de AE se observó para las mezclas CA/cinnamaldehído para ambas bacterias, pero usando diferentes proporciones de compuestos. De esta forma, los resultados obtenidos permitieron la optimización de la dosis de activos utilizados para la aplicación de alimentos, minimizando así su impacto sensorial. Las películas de PHBV con compuestos activos de AE fueron altamente efectivas contra L. innocua y E. coli in vitro, pero mucho menos activas en alimentos. Asimismo, no se observó ninguna correlación entre la cantidad de activo migrada al alimento y el efecto antibacteriano en las diferentes matrices, lo que refleja que existen numerosos factores composicionales que afectan a la disponibilidad de los activos a la hora de ejercer su acción antibacteriana sobre un alimento determinado. La formulación 75:25 PLA-PHBV con PEG1000 exhibió las mejores propiedades físicas y, por lo tanto, se utilizó como soporte del CA mediante casting, así como para desarrollar bicapas con almidón. La incorporación de CA pulverizarlo entre las láminas de poliéster y almidón no fue eficaz a la hora de retener el compuesto activo en las bicapas. Sin embargo, la incorporación de CA en películas de poliésteres mediante casting dio lugar a una retención de CA prácticamente total, lo que condujo a una notable actividad antimicrobiana. Además, estas bicapas exhibieron propiedades físicas altamente mejoradas con respecto a la monocapa de almidón. La valorización de la cáscara de arroz mediante extracción con agua subcrítica, permitió obtener hemicelulosas mejor conservadas, con actividad antioxi
Biodegradable active films based on PHBV, combined with other biopolymers (PLA and starch) and different antimicrobial compounds (essential oils (EO)), were developed and characterized as to their functional and structural properties to obtain materials that better meet food packaging requirements. Plasticization of PHBV was analysed by using different compounds to enhance the PHBV mechanical performance. Likewise, different active compounds (oregano and clove EO, as well as their respective main compounds, carvacrol (CA) and eugenol (EU)) were incorporated into PHBV bilayer films by spraying the actives between two thermo-compressed monolayers. The potential synergy between different EO compounds and their applications to different food when incorporated into PHBV films was also analysed. Multilayer antimicrobial films combining polar (starch) and non-polar (polyester) sheets, incorporating CA, either by spraying it between both layers or incorporating it in the polyester casting solution, were developed to optimise the material functionality. Bioactive xylans and cellulosic fractions from rice husk, which are useful for food packaging applications, were obtained by using an eco-friendlier valorization process based on subcritical water extraction. Although the addition of polyethylene glycol (PEG) of different molecular weight and lauric acid significantly decreased the stiffness and the resistance to break of PHBV films, only PEG1000 yielded more extensible films. Nonetheless, additional strategies would be required to adapt PHBV mechanical properties to certain packaging requirements. Spraying actives at the interface of both PHBV monolayers produced antimicrobial films with appropriate physical properties. The release of the actives from the films was adequate to control the growth of E. coli and L. innocua in vitro. Both actives, CA and EU were effectively released into different food simulants. The release rate was enhanced when the polarity of the simulants decreased, but it fell markedly in fatty systems. The most remarkable synergistic effect for the EO compounds was observed for CA/cinnamaldehyde blends for both bacteria but using different compound ratios. Thus, the results allowed for the optimization of the dose of actives used for food application, thus minimizing their sensory impact. PHBV films with active EO compounds were highly effective against L. innocua and E. coli in the in vitro tests, but they were much less effective in foods. Likewise, no correlation between the amount of active that migrated to the food and the antibacterial effect was observed, which reflected that many compositional factors affect the availability of the antimicrobials to exert their action on a specific food. The 75:25 PLA-PHBV formulation with PEG1000 exhibited the best properties in terms of physical properties and, thus it was used to be the carrier of CA by casting and to develop bilayers with starch. Incorporating CA by spraying it between the polyester and starch sheets was not effective at retaining this active in the bilayers. However, the incorporation of CA into casted polyester films was highly effective at providing practically total CA retention, which led to a notable antimicrobial activity. Moreover, these bilayers exhibited highly improved tensile and water vapour barrier capacity with respect to the starch monolayer. The rice husk valorization, based on subcritical water extraction, allowed for obtaining better preserved hemicelluloses, with antioxidant and antibacterial activity, useful as additives for food or food packaging applications, and cellulosic reinforcing agents to develop biocomposites with enhanced mechanical performance.
Es van desenvolupar pel·lícules biodegradables actives a base de PHBV, combinades amb altres biopolímers (PLA i midó) i diferents compostos antimicrobians (olis essencials (OE)), les quals es van caracteritzar quant a les seues propietats funcionals i estructurals a fi d'obtindre materials que complisquen millor els requisits d'envasament d'aliments. La plastificació del PHBV es va dur a terme per mitjà de diferents compostos amb l'objectiu de millorar el rendiment mecànic dels films. Així mateix, es van incorporar diferents actius (OE d'orenga i clau, així com els seus respectius compostos majoritaris, carvacrol (CA) i eugenol (EU)) en pel·lícules bicapa de PHBV polvoritzant els actius entre dos monocapas, obtingudes per termocompressió. També es va analitzar la potencial sinergia entre diferents compostos d'OE, així com les seues aplicacions a diferents aliments quan s'incorporen en pel·lícules bicapa de PHBV. Es van desenvolupar pel·lícules antimicrobianes multicapa on es combinaren làmines polars (midó) i apolars (polièsters) i carvacrol, ja siga polvoritzat entre ambdós capes o incorporat en la solució filmogénica de polièsters, a fi d'optimitzar la funcionalitat del material. El procés de valoració de la corfeta d'arròs, basat en extracció amb aigua subcrítica, va permetre obtindre xilans bioactius i fraccions cel·lulòsiques amb potencials aplicacions en l'envasament d'aliments. A pesar que l'addició de polietilenglicol (PEG) de diferent pes molecular o àcid làuric va disminuir significativament la rigidesa i la resistència de les pel·lícules de PHBV, només PEG1000 va donar lloc a pel·lícules més extensibles. No obstant això, estratègies addicionals varen ser necessàries a fi d'adaptar les propietats mecàniques dels films de PHBV a certs requisits d'envasament. La polvorització d'actius a la interfase d'ambdós monocapes de PHBV va generar pel·lícules antimicrobianes amb propietats físiques adequades. L'alliberament dels actius des de les pel·lícules va permetre controlar el creixement d'Escherichia coli i Listeria innocua en assajos in vitro. Ambdós actius, CA i EU, es van alliberar de manera efectiva en els diferents simulantes alimentaris. La taxa d'alliberament va millorar quan va disminuir la polaritat dels sistemes aquosos. L'efecte sinèrgic més notable per als compostos d'OE es va observar per a les mescles de CA/cinnamaldehído per a ambdós bacteris, però utilitzant diferents proporcions. D'esta manera, els resultats van permetre l'optimització de la dosi d'actius utilitzats per a l'aplicació en aliments, minimitzant així el seu impacte sensorial. Les pel·lícules de PHBV amb actius d'OE van ser altament efectives front L. innocua i E. coli en les proves in vitro, però van ser molt menys efectives en aliments. Així mateix, no es va observar cap correlació entre la quantitat d'actiu migrada a l'aliment i l'efecte antibacterià en les diferents matrius, la qual cosa reflectix que hi ha molts factors composicionals que afecten la efectivitat del dels compostos actius per a exercir la seua acció sobre un aliment en concret. La formulació 75:25 PLA-PHBV amb PEG1000 va exhibir les millors propietats físiques i, per tant, es va utilitzar com a suport del CA per mitjà de càsting, així com per a desenvolupar bicapes amb midó. La incorporació de CA polvoritzat entre les làmines de polièsters i midó no va ser eficaç per a retindre el compost actiu en la bicapa. No obstan, la incorporació de CA en pel·lícules de polièster per càsting va permetre una retenció de CA pràcticament total, la que va conduir a una notable activitat antimicrobiana. A més, estes bicapas van exhibir una capacitat de barrera al vapor d'aigua i a la tracció altament millorades respecte a la monocapa de midó. La valoració de la corfa d'arròs, basada en l'extracció amb aigua subcrítica, va permetre obtindre fraccions hemicelulósiques millor conservades, amb activ
Requena Peris, R. (2018). Multilayer biodegradable active films based on PHBV for food packaging [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/110079
TESIS

L'utilisation de ressources renouvelables et la production de matériaux biodégradables sont des solutions adaptées afin de diminuer l'impact environnemental du secteur des plastiques. Il existe donc une demande du marché pour des produits écoresponsables, à condition que ces derniers soient techniquement et économiquement compétitifs par rapport aux matériaux classiquement utilisés. Dans le domaine de l'emballage alimentaire, une technique très employée permettant la réalisation de matériaux performants est la création de structures multicouches combinant avantageusement les propriétés de différents thermoplastiques. Néanmoins, de tels matériaux multi-matières sont difficilement recyclables, leur biodégradabilité devient alors une propriété pertinente. Cette étude propose la réalisation de films souples biosourcés et biodégradables pour l'emballage alimentaire, à partir du polylactide et de coproduits de l'huilerie en tant qu'additifs, notamment les condensats de désodorisation. Parmi ces derniers, la solubilité partielle de leurs molécules ainsi que l'effet synergique des constituants liquides et solides à température ambiante, en fonction de la longueur et du degré d'insaturation de leurs chaînes alkyles, ont été montrés comme responsables de l'augmentation de la ductilité du PLA, permettant néanmoins de conserver sa vitrosité à température ambiante et son intéressante rigidité. L'ajout de PHBV au PLA formulé avec les coproduits de l'huilerie a également été étudié, engendrant principalement une amélioration significative de la tenue thermomécanique du matériau. Des essais d'accroissement d'échelle comprenant la production de granulés, l'extrusion à plat de films ainsi que leur impression sur des machines industrielles ont été réalisés. Enfin, avec l'aide du Laboratoire National de Métrologie et d'Essais (LNE), la conformité du film développé avec les exigences légales concernant les matières thermoplastiques destinées au contact des aliments, mais également son aptitude à la biodégradation selon la norme EN 13432, ont été vérifiées
The use of renewable resources and the production of biodegradable materials are appropriate solutions to reduce the environmental impact of the sector of plastics. There is thus a demand for eco-friendly products on the market provided they obtain performance equal or superior to synthetic materials currently used. One possibility, widely used in the food sector, to achieve efficient packaging film is the creation of multilayer structures by combining advantageous properties of different plastics. In this case, recycling of materials is difficult and the biodegradability of the packaging becomes relevant. This study proposes designing biobased and biodegradable films for food packaging from polylactide and co- products of the oil mill industry as additives, in particular the deodorization condensates. Among these lasts, the partial solubility of their molecules and the synergetic effect of the liquid and solid fat components at room temperature, depending on their alkyl chain length and unsaturation ratio, have both been observed to be responsible for the ductility increase, while the higher than room temperature glass transition of PLA and its interesting rigidity were retained. Addition of PHBV to the formulated PLA with oil by-products has also been studied, mainly leading to a significant improvement in the thermomechanical resistance of the material. Scaled-up trials comprising the production of formulated pellets, cast extruded films and their printing using industrial devices were performed. Finally, with the help of the “Laboratoire National de Métrologie et d’Essais” (LNE), the compliance with requirements of Food Contact Material regulation of a formulated film of PLA, as well as its biodegradability according to the EN 13432 standard, have both been proved

Aunque la plata se usa como componente clave en el control microbiano en incontables aplicaciones, las tecnologías basadas en plata disponibles son escasas. Esto radica en la dificultad para evaluar su eficacia debido a problemas de estabilidad y de especiación. En la presente tesis, iones de plata fueron incorporados en matrices biopoliméricas para obtener materiales de prolongada capacidad antimicrobiana basados en su liberación sostenida. Se realizó un estudio profundo de las interacciones químicas entre las especies activas de plata, las bacterias, y posibles ligandos presentes en el medio de acción. En condiciones óptimas, la plata demostró ser eficaz en el rango de los nanomoles. Sin embargo, interacciones químicas con varios ligandos afectaron drásticamente tanto su eficacia como la evaluación de la viabilidad bacteriana. La incorporación de iones de plata en películas de EVOH no alteró las propiedades físico-químicas de los materiales que mostraron una rápida liberación del contenido de plata al entrar en contacto con la humedad. Esto se reflejó en la inactivación de las bacterias a concentraciones muy bajas (0.0001wt.%) en condiciones óptimas. Cuando se incorporaron iones de plata en PLA por casting o mezclado-fundido, la liberación y el rendimiento antimicrobiano se prolongaron de días a meses, dependiendo del contenido, el método de incorporación, la humedad o el pH del medio de liberación. Una etapa inicial de liberación mayor pudo ser atenuada gracias a la aplicación de una capa de cera de abejas, lo que permitió adaptar los perfiles de liberación a demanda y cumplir con la legislación vigente en diversas condiciones de liberación. Las películas demostraron un alto efecto antibacteriano y antiviral contra los patógenos transmitidos por los alimentos más comunes en medios sintéticos, en superficie y en alimentos líquidos y sólidos. Este estudio representa un avance en la comprensión de la eficacia antimicrobiana de la plata y destaca su posible idoneidad para la fabricación de materiales de envasado de alimentos, de contacto con alimentos u otras aplicaciones.
Martínez Abad, A. (2014). Development of silver based antimicrobial films for coating and food packaging applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36738
TESIS
Premiado

This PhD dissertation thesis has been focus on the development and characterization of antimicrobial packaging films based on the incorporation in the polymer matrix or on the attachment to the film surface of naturally occurring antimicrobial compounds with the purpose of inhibiting the proliferation of microorganisms and extend the microbiological shelf life of packaged food products. The studied active films are based on the use of ethylene vinyl copolymers (EVOH) containing 29% (EVOH29) or 44% (EVOH44) molar percentage of ethylene as polymeric vehicle for the incorporation of several antimicrobial compounds -oregano essential oil (OEO), citral, ethyl lauroyl arginate (LAE), epsilon-polylysine (EPL), green tea extract (GTE) and lysozyme. These antimicrobial agents have been incorporated in the film-forming solution or immobilized to the film surface by covalent bonding. Prior to the preparation of the active films, the antimicrobial activity of the selected compounds against selected microorganism was demonstrated, confirming that they could be good candidates to be used as preservatives for active food packaging applications, and an alternative to synthetic additives. The effect of the incorporation of the antimicrobial agents on relevant functional properties of the developed EVOH films was studied. In general, the polymer properties as materials for food packaging were not relevantly affected. In order to evaluate the potential of EVOH matrices as sustain release systems of active compounds, the release kinetics of the active compounds from the film to different media was evaluated; for that the agent release rate and extend into food simulants was monitored, and it was concluded that the agent concentration, release temperature, type of EVOH, interaction of EVOH with the food simulant, and the solubility of the active compound in the release media were the main controlling factors. EVOH matrices have also shown good properties to be used for the attachment of active molecules. In this regard, lysozyme was successfully immobilized on the film surface of EVOH. Several experiments were conducted to determine the antimicrobial properties of the resulting films in vitro against different microorganisms responsible for foodborne illness and in vivo with real foods –minimally-process salad, infant milk, surimi sticks and chicken stock- to enhance their preservation. All the materials presented a strong in vitro antimicrobial activity. Although the results obtained through in vivo tests showed activity reductions caused by food matrix effects, all materials presented significant microbial inhibition and, therefore, great potential to be used in the design of active food packaging. They can be applied as an inner coating of the packaging structure, releasing the active agent or acting by direct contact, producing a great protection against contamination with a prolongation of the microbiological food shelf life.
Muriel Galet, V. (2015). Novel antimicrobial films based on ethylene-vinyl alcohol copolymers for food packaging application [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48522
TESIS
Premiado

Titanium dioxide (TiO2) polymer nanocomposites improve barrier properties to gas and moisture and mechanical strength as well as providing active packaging functions. However, low compatibility between hydrophilic TiO2 nanoparticles and hydrophobic polymers such as polylactic acid (PLA) causes problems due to the tendency of TiO2 nanoparticles (TiO2) to agglomerate and form large clusters. A surface modification of TiO2 with long chain fatty acid may improve the compatibility between PLA and TiO2. The goal of this study was to enhance barrier properties of oxygen and water vapor, mechanical strength and add light protecting function to PLA composites by incorporation of oleic acid modified TiO2 nanoparticles (OA_TiO2). The objectives of this study were: 1) synthesize TiO2 and modify surface of TiO2 with oleic acid, 2) investigate dispersion stability of TiO2 and OA_TiO2 in hydrophobic media, 3) incorporate TiO2 and OA_TiO2 into a PLA matrix and to characterize properties of TiO2PLA (T-PLA) and OA_TiO2 PLA nanocomposite films (OT-PLA), and 4) to determine stability of green tea infusion in T-PLA and OT-PLA packaging model systems during refrigerated storage at 4 °C under florescent lightening. TiO2 was synthesized by using a sol-gel method and the surface of TiO2 was modified by oleic acid using a one-step method. T-PLA and OT-PLA were prepared by solvent casting. TiO2 and OA_TiO2 were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis and dynamic light scattering. The barrier properties to oxygen and water vapor, morphology, mechanical properties, thermal stability and light absorption properties of T-PLA and OT-PLA were characterized. Dispersion of TiO2 was improved in PLA matrix by the surface modification method with oleic acid. OT-PLA had more effective improvements in the barrier properties and flexibility than T-PLA and PLA, but toughness of the films based on Young's modules of OT-PLA was lower than the T-PLA and the PLA. The OT-PLA may have a potential to be used as transparent, functional and sustainable packaging films, but limited use for complete visible and UV-light protection for photosensitized foods.
Ph. D.

Oxygen scavengers are used in active packages to protect the food against deteriorative oxidation processes. The aim of this work was to investigate the possibilities to produce oxygen-scavenging packaging materials based on oxygen-reducing enzymes. The enzymes were incorporated into a dispersion coating formulation applied onto a food-packaging board using conventional laboratory coating techniques. Various enzymes were used: a glucose oxidase, an oxalate oxidase and three laccases originating from different organisms. All of the enzymes were successfully incorporated into a coating layer and could be reactivated after drying. For at least two of the enzymes, re-activation was possible not only by using liquid water but also by using water vapour. Re-activation of the glucose oxidase and a laccase required relative humidities of greater than 75% and greater than 92%, respectively. Catalytic reduction of oxygen gas by glucose oxidase was promoted by creating an open structure through addition of clay to the coating at a level above the critical pigment volume concentration. Migration of the enzyme and the substrate was reduced by adding an extrusion-coated liner of polypropylene on top of the coating. For the laccase-catalysed reduction of oxygen it was possible to use lignin derivatives as substrates for the enzymatic reaction. The laccase-catalysed reaction created a polymeric network by cross-linking of lignin-based entities, which resulted in increased stiffness and increased water-resistance of biopolymer films. The laccases were also investigated with regard to their potential to function as oxygen scavengers at low temperatures. At 7°C all three laccases retained more than 20% of the activity they had at room temperature (25°C), which suggests that the system is also useful for packaging of refrigerated food.

Capes; Fundação Araucária
Tendo em vista a crescente demanda por substituição de materiais de embalagens usuais por biodegradáveis bem como pela necessidade da manutenção de segurança dos alimentos durante seu armazenamento, o desenvolvimento de embalagens bioativas biodegradáveis torna-se importante. No presente trabalho foram produzidos laminados compostos por blendas de poli(L-ácido lático) (PLLA), amido termoplástico (TPS) e gelatina por extrusão e calandragem. O processo apresentou-se como uma forma viável para produzir blendas de PLLA / TPS / gelatina com propriedades funcionais interessantes e aspecto homogêneo. A adição de gelatina em diferentes proporções (1, 3 e 5% em relação ao TPS) apresentou diferença significativa nos resultados das análises de solubilidade, permeabilidade ao vapor de água (PVA) e isotermas de sorção de água devido à hidrofilicidade da mesma. Além disso, a incorporação de gelatina na blenda afetou significativamente as propriedades mecânicas através da redução da rigidez associada à incompatibilidade entre PLLA, amido e gelatina, como revelado pelas imagens de microscopia eletrônica de varredura (MEV). Nanopartículas de prata (AgNPs) foram sintetizadas para incorporação aos laminados pela técnica do polissacarídeo modificada, onde nitrato de prata foi reduzido a prata metálica por D-glicose. O diâmetro médio foi determinado através de três técnicas: Espalhamento Dinâmico de Luz (DLS, 63 nm), por Espectrofotômetria UV-Vis (100 nm) e por análise das imagens de MEV (145 nm). Com a análise de FTIR foi possível detectar interações entre os grupamento C=O dos subprodutos de oxidação da D-glicose, produto da reação com o nitrato de prata. As AgNPs apresentaram ação antimicrobiana eficaz contra os microrganismos Bacillus cereus, Staphylococcus aureus, Escherichia coli e Pseudomanas aeruginosa, sendo a Concentração Inibitória Mínima igual a 1,17 µg/ml para E. coli (menor resistência) e 37,50 µg/ml para S. aureus (maior resistência). Os laminados foram tratados superficialmente com a solução resultante da síntese das AgNPs por reticulação enzimática (transglutaminase). Nas imagens de MEV foi possível verificar que os laminados tratados apresentaram maior porosidade em função da umidade promovida pelo tratamento. Através da porosidade criada foram detectadas diferenças significativas nas análises de PVA e propriedades mecânicas. Houve aumento da PVA e redução em todas as propriedades mecânicas, principalmente no módulo de Young em função da criação de pontos de concentração de força. As isotermas apresentaram ajuste adequado ao modelo de GAB (R2>0,99). A atividade antimicrobiana dos laminados contendo AgNPs foi comprovada pela formação de halos de inibição contra os microorganismos descritos anteriormente. Finalmente, os laminados produzidos possuem potencial de aplicação como embalagens ativas com propriedades antimicrobianas e de biodegradação para alimentos.
Due to the growing demand for replacement of the usual packaging materials for biodegradable as well as the need to maintain food safety during storage, the development of bioactive biodegradable packaging becomes important. In this work sheets were produced by extrusion and calendaring process using blends of poly(L-lactic acid) (PLLA), thermoplastic starch (TPS) and gelatin . The process is presented as a viable way to produce blends of PLLA/TPS/gelatin with interesting functional properties and homogeneous appearance. The addition of gelatin in different proportions (1, 3 and 5% related to TPS) showed a significant difference in the solubility test results, the water vapor permeability (WVP) and water sorption isotherms due to gelatin hydrophilicity. Furthermore the incorporation of gelatin in the blend significantly affected the mechanical properties by reducing stiffness associated with incompatibility between PLLA, starch and gelatin, as shown by Scanning Electron Microscopy (SEM) micrographs. Silver nanoparticles (AgNPs) were synthesized for incorporation into the extruded sheets by the modified polysaccharide technique, where silver nitrate is reduced to metallic silver by D-glucose. The average diameter was determined by three techniques: Dynamic light scattering (DLS, 63 nm) by UV-Vis spectrophotometry (100 nm) and by analysis of SEM images (145 nm). With the analysis of FTIR was possible to detect interactions between the C = O groups of D-glucose oxidation byproducts, products of the reaction with silver nitrate. AgNPs presented effective antimicrobial action against the microorganisms: Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, and the Minimum Inhibitory Concentration equal to 1.17 µg/ml for E. coli (lower resistance) and 37.50 µg/ml for S. aureus (greater resistance). The extruded sheets were surface treated with the resulting solution from AgNPs synthesis and enzymatically crosslinked with transglutaminase. At the SEM images it was possible to verify that the treated laminates exhibited higher porosity due to moisture promoted by the treatment. The created porosity influenced significantly the results of the WVP and mechanical properties. There was an increase in vapor permeation and a reduction in all mechanical characteristics, particularly in Young's modulus due to the creation of tension concentration points. The isotherms showed adequate adjustment to GAB model (R2> 0.99). The antimicrobial activity of the laminates containing AgNPs was confirmed by the formation of inhibition zones against the microorganisms described above. Finally, the sheets produced have potential application as active packaging with antimicrobial and biodegradable properties for food.

Oxygen barrier coatings have the potential to greatly extend the lifetime of certain food products by incorporating them into existing food packaging. Present technologies face definite challenges of maintaining high performance, while attaining simple and inexpensive preparation methods. The oxygen barrier effect obtained with these coatings is also susceptible to a plasticization effect when exposed to high humidity, since water vapor molecules are readily soluble in typically hydrophilic resins. In this work, we demonstrate a 1 – 2 micron thick oxygen barrier coating, prepared on a 12 micron poly(ethylene terephthalate) substrate, that has oxygen transmission rates as low as 1.44 cc m-2 day-1 under standard conditions and can maintain similar oxygen barrier performance at high humidity. This degree of oxygen barrier meets the standard of 1 – 10 cc m-2 day-1 established for food packaging applications. The coating is prepared through use of sol-gel chemistry between poly(vinyl alcohol) and vinyltrimethoxsilane molecules, which form a strong network resin through hydrolysis and condensation reactions. The formulation of these oxygen barrier coatings allows for variability of solids percentage and viscosity without significant change in performance. The ability to scale up the preparation of these coated films was tested successfully on an industrial flexographic printing press.

This PhD dissertation focuses on the development of renewable and biodegradable active films based on chemically-modified wheat gliadin proteins endowed with antimicrobial capacity owing to the incorporation of naturally-occurring bioactive compounds, namely cinnamaldehyde, natamycin, and lysozyme. Gliadin proteins were treated with cinnamaldehyde at acidic pH and films were produced by casting. The resulting protein-based films presented improved functional properties (mechanical, barrier, and water resistance), and biochemical evidence of the formation of a more compact network whose degree of cross-linking increased with the amount of cinnamaldehyde incorporated into the gliadin-ethanolic solution. Free cinnamaldehyde not participating in the cross-linked reaction remained entrapped in the protein matrix at low relative humidity conditions. The sensitivity of the films to moisture owing to the hydrophilic character of gliadins provided a trigger and control mechanism for the release of cinnamaldehyde in moderate and high relative humidity environments, similar to conditions occurring in packaged food products. The antimicrobial properties of the films developed were tested in vitro by vapor diffusion assays against common food spoilage fungi (Penicillium expansum and Aspergillus niger), showing great effectiveness. Application of these active films to the preservation of two foodstuffs, sliced bread and cheese spread, gave promising results, lengthening fungal growth lag phase and minimizing fungal growth extension.
Balaguer Grimaldo, MDLP. (2015). Development of active bioplastics based on wheat proteins and natural antimicrobials for food packaging applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48520
TESIS
Premiado

[ES] El uso masivo de plásticos sintéticos y su impacto medioambiental obliga a buscar alternativas biodegradables para el envasado de los alimentos,etapa necesaria para su adecuada conservación.Así mismo,la necesidad de incrementar la vida útil de los alimentos ha despertado gran interés en el desarrollo de materiales activos(antimicrobianos y antioxidantes)que mantengan su calidad y seguridad por más tiempo,mediante el uso de compuestos de origen natural,seguros para el consumidor.En este sentido,el desarrollo de materiales biodegradables activos para el envasado de alimentos constituye hoy en día un reto importante para la industria alimentaria.En la presente Tesis Doctoral,se ha estudiado la encapsulación de carvacrol mediante el electroestirado o extensión y secado de diferentes disoluciones poliméricas con carvacrol.Se han utilizado polímeros biodegradables portadores de diferente polaridad(almidón termoplástico:TPS,polivinil-alcohol:PVA, policaprolactona:PCL o ácido poliláctico:PLA)disueltos en el solvente adecuado,con el fin de obtener capas activas.Estas capas se han combinado con otras de polímeros con propiedades complementarias,para obtener laminados activos adecuados para el envasado de alimentos.Los laminados combinaron polímeros polares(TPS o PVA)y poliésteres no polares(PCL o PLA)incorporando el carvacrol en una de las capas.Se evaluó la cinética de liberación del activo,así como la acción antimicrobiana de los materiales obtenidos.Los laminados se caracterizaron en su funcionalidad como material de envase(prop. de barrera,mecánicas u ópticas)así como en su estructura y comportamiento térmico.Los estudios de encapsulación revelaron un mayor potencial encapsulante del carvacrol para los polímeros no polares(PCL;PLA),aunque el PVA mostró también una buena afinidad con el compuesto activo.La matriz de PVA mostró una mayor retención de carvacrol mediante electroestirado de sus disoluciones acuosas que por extensión y secado,sin necesidad de adición de tensoactivos como el Tween85.Para la encapsulación en PLA,se usaron mezclas binarias de solventes aptos para contacto con los alimentos(acetato de etilo y DMSO).En este caso,se obtuvo una mayor eficiencia encapsulante del PLA en los materiales obtenidos por extensión y secado que en los electroestirados.La cinética de liberación del carvacrol de las fibras de PCL explicó el mayor efecto antibacteriano contra E.coli,y el escaso efecto antilisteria.La velocidad de liberación del activo aumentó cuando disminuyó la polaridad de los simulantes alimentarios, mostrando una liberación completa en los sistemas apolares,pero solo hasta 75% en los sistemas acuosos,que requerirían una mayor proporción del activo en el envase para potenciar su efectividad.La combinación de láminas de TPS con fibras de PCL cargadas con carvacrol dio lugar a materiales con una permeabilidad al vapor de agua mejorada,en comparación con los films de almidón,sin efectos relevantes sobre las otras propiedades funcionales estudiadas.Cuando los laminados se probaron in vitro contra cepas G(+) y G(-) mostraron un efecto antibacteriano similar al de las fibras de PCL con carvacrol,pero retrasado en el tiempo.Los estudios de desintegración-biodegradación de los laminados almidón-PCL revelaron que las películas con carvacrol afectaron la actividad del inóculo del compost,disminuyendo ligeramente la biodegradabilidad de las películas,pero alcanzando valores de desintegración similares(75-80%)a las muestras libres de carvacrol.Se obtuvieron también laminados de PLA y PVA mediante la extensión y secado de disoluciones acuosas de PVA con carvacrol.La superficie del PLA fue sometida a aminolización a fin de mejorar la extensibilidad de las disoluciones acuosas.A pesar del incremento de la componente polar de la energía superficial del PLA y su mejorada humectabilidad con las soluciones de PVA,estas bicapas no mostraron una mejora significativa en las propied
[CAT] L'ús massiu de plàstics sintètics i el seu impacte mediambiental obliga a buscar alternatives biodegradables per a l'envasament dels aliments necessari per a la seua conservació.Així mateix,la necessitat d'incrementar la vida útil dels aliments ha despertat gran interés en el desenvolupament de materials actius(antimicrobians i antioxidants)que mantinguen la seua qualitat i seguretat per més temps,per mitjà de l'ús de compostos d'origen natural,segurs per al consumidor.En este sentit,el desenvolupament de materials biodegradables actius per a l'envasament d'aliments constituïx un repte important per a la indústria alimentària.En la present Tesi Doctoral,s'ha estudiat l'encapsulació de carvacrol per mitjà de l'electroestirat o extensió i assecat de diferents dissolucions polimèriques amb carvacrol.S'han utilitzat polímers biodegradables portadors de diferent polaritat(midó termoplàstic:TPS, polivinil-alcohol:PVA, policaprolactona:PCL o àcid poliláctic:PLA)dissolts en el solvent adequat,a fi d'obtindre capes actives.Estes s'han combinat amb altres de polímers amb propietats complementàries,per a obtindre laminats actius adequats per a l'envasament d'aliments.Els laminats van combinar polímers polars(TPS o PVA)i poliésters no polars(PCL o PLA)incorporant el carvacrol en una de les capes.Es va avaluar la cinètica d'alliberament de l'actiu,així com l'acció antimicrobiana dels materials obtinguts.Els laminats es van caracteritzar en la seua funcionalitat com a material d'envàs(propietats de barrera, mecàniques o òptiques),així com en la seua estructura i comportament tèrmic.Els estudis d'encapsulació van revelar un major potencial encapsulant del carvacrol per als polímers no polars(PCL i PLA),encara que el PVA va mostrar també una bona afinitat amb el compost actiu.La matriu de PVA va mostrar una major retenció de carvacrol per mitjà d'electroestirat de les seues dissolucions aquoses que per extensió i assecat,sense necessitat d'addició de tensioactius com el Tween 85.Per a l'encapsulació en PLA,es van usar mescles binàries de solvents aptes per a contacte amb els aliments(acetat d'etil i DMSO).Es va obtindre una major eficiència encapsulant del PLA en els materials obtinguts per extensió i assecat que en els electroestirats.La cinètica d'alliberament del carvacrol de les fibres de PCL va explicar el major efecte antibacterià contra Escherichia coli,i l'escàs efecte antilisteria.La velocitat d'alliberament de l'actiu va augmentar quan va disminuir la polaritat dels simulants alimentaris,mostrant un alliberament complet en els sistemes no polars, però només fins a un 75% en els sistemes aquosos,que requeririen una major proporció de l'actiu en l'envàs per a potenciar la seua efectivitat.La combinació de làmines de TPS amb fibres de PCL carregades amb carvacrol va donar lloc a materials amb una permeabilitat al vapor d'aigua millorada,en comparació amb els films de midó, sense efectes rellevants sobre les altres propietats funcionals.Quan els laminats es van provar in vitro contra ceps Gram(+) i Gram(-) van mostrar un efecte antibacterià semblant al de les fibres de PCL amb carvacrol,però retardat en el temps.Els estudis de desintegració-biodegradació dels laminats midó-PCL van revelar que les pel·lícules amb carvacrol van afectar l'activitat de l'inocule del compost,disminuint lleugerament la biodegradabilitat,però aconseguint valors de desintegració semblants(75-80%)a les mostres lliures de carvacrol.Es van obtindre també laminats de PLA i PVA per mitjà de l'extensió i assecat de dissolucions aquoses de PVA amb carvacrol.La superfície del PLA va ser sotmesa a aminolizatció a fi de millorar l'extensibilitat de les dissolucions aquoses.A pesar de l'increment de la component polar de l'energia superficial del PLA i la seua millorada mullabilitat amb les solucions de PVA,estes bicapes no van mostrar una millora significativa en les propietats mecàniques i de barrera
[EN] The massive use of synthetic plastics and their environmental impact makes necessary the search for biodegradable alternatives for food packaging. Likewise, the need to increase the shelf life of food has aroused great interest in the development of active materials (antimicrobial and antioxidant) that maintain food quality and safety for longer periods of time through the use of compounds of natural origin, safe for the consumer. In this sense, the development of active biodegradable materials for food packaging is both a major imperative and challenge for the food industry today. In the present Doctoral Thesis, the encapsulation of carvacrol has been studied by means of the electrospinning or casting of different polymeric solutions with carvacrol. Biodegradable polymers with different polarities (thermoplastic starch: TPS, poly(vinyl-alcohol): PVA, poly-(¿-caprolactone): PCL or poly(lactic acid): PLA) dissolved in the appropriate solvent have been used to obtain active layers. These have been combined with other polymers with complementary properties, to obtain active laminates suitable for food packaging. The laminates combined polar polymers (TPS or PVA) and non-polar polyesters (PCL or PLA) incorporating carvacrol in one of the layers. The release kinetics of the active ingredient was evaluated, as well as the antimicrobial action of the materials obtained. The laminates were characterized in their functionality as a packaging material (barrier, mechanical or optical properties), as well as in their structure and thermal behaviour. Encapsulation studies revealed a higher encapsulating potential of carvacrol for non-polar polymers (PCL and PLA), although PVA also showed a good affinity with the active compound. The PVA matrix showed a higher retention of carvacrol by electrospinning of its aqueous solutions than by casting, without the need for addition of surfactants such as Tween 85. For the encapsulation in PLA, binary mixtures of solvents suitable for food contact (ethyl acetate and DMSO) were used. A higher encapsulation efficiency of PLA was obtained in the materials produced by casting than by electrospinning. The carvacrol release kinetics of PCL fibres explained the higher antibacterial effect against Escherichia coli and the lower antilisterial effect. The release ratio of the active ingredient increased when the polarity of the food simulants decreased, showing a complete release in non-polar systems and only up to 75% in aqueous systems that would require a higher proportion of the active ingredient in the packaging material to enhance its effectiveness. The combination of TPS films with carvacrol loaded PCL fibres resulted in materials with improved water vapour permeabilities, compared to starch films, with no relevant effects on the other functional properties. When the laminates were tested in vitro against Gram (+) and Gram (-) strains, they showed a similar antibacterial effect to that of PCL fibres with carvacrol, but delayed in time. Disintegration-biodegradation studies of PCL-starch laminates revealed that carvacrol films affected the activity of the compost inoculum, slightly decreasing the biodegradability of the laminates, but reaching similar disintegration values (75-80%) to the carvacrol-free samples. PLA and PVA laminates were also obtained by casting aqueous PVA solutions with carvacrol. The surface of PLA was submitted to aminolization in order to improve the extensibility of the aqueous solutions. Despite the increase in the polar component of the PLA surface energy and its improved wettability with PVA solutions, these bilayers did not show significant improvement in mechanical and barrier properties over the PLA monolayers.
The authors would like to thank the Ministerio de Economia y Competitividad of Spain, for funding this study as part of projects AGL2013-42989-R and AGL2016-76699-R and predoctoral research grant # BES-2014-068100.
Tampau, A. (2020). Carvacrol encapsulation by electrospinning or solvent casting to obtain biodegradable multilayer active films for food packaging applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/140313
TESIS

A busca por novos materiais de embalagem com o propÃsito de manter ou melhorar a qualidade dos alimentos e, ao mesmo tempo, reduzir a geraÃÃo de lixo nÃo biodegradÃvel, temVencorajado a exploraÃÃo de materiais comestÃveis e/ou biodegradÃveis à base de recursos renovÃveis. A formaÃÃo de filmes exige a presenÃa de um material que forme uma matriz contÃnua e coesa. O amido possui tal propriedade e, por ser abundante e de baixo custo, à uma matÃria-prima interessante para produÃÃo dos filmes. A goma de cajueiro à um polissacarÃdeo complexo, de propriedades filmogÃnicas ainda pouco exploradas. PolissacarÃdeos, como amido e goma de cajueiro, por sua alta polaridade, tÃm boa barreira a oxigÃnio (O2) e diÃxido de carbono (CO2), mas tÃm alta permeabilidade a vapor de Ãgua. A incorporaÃÃo de componentes hidrofÃbicos, como ceras, a filmes de polissacarÃdeos melhora a barreira ao vapor de Ãgua. O principal objetivo do estudo foi desenvolver filmes comestÃveis compÃsitos à base de amido, goma de cajueiro e cera de carnaÃba. Foram obtidos 10 tratamentos por meio de um delineamento de misturas (centroide simplex) com as seguintes proporÃÃes mÃssicas: amido, 15 - 30%; goma de cajueiro, 75 - 85%; e cera de carnaÃba, 0 - 15%. Com intuito de verificar se a temperatura utilizada seria suficiente para que ocorresse a gelatinizaÃÃo do amido, uma anÃlise de difraÃÃo de raio - x (DR-X) foi realizada. A caracterizaÃÃo dos filmes foi realizada por meio das seguintes anÃlises; propriedades mecÃnicas (resistÃncia à traÃÃo - TR, elongaÃÃo na ruptura - ER, mÃdulo elÃstico - ME), opacidade (OP), solubilidade em Ãgua (SOL), permeabilidade ao vapor de Ãgua (PVA) e temperatura de transiÃÃo vÃtrea (Tg). A DR-X comprovou que a temperatura de gelatinizaÃÃo utilizada foi suficiente para provocar a ruptura dos grÃnulos de amido. As proporÃÃes relativas de amido e goma de cajueiro nÃo afetaram muito as propriedades dos filmes formados. A incorporaÃÃo de cera de carnaÃba, por minimizar o teor hidrofÃlico da matriz filmogÃnica, reduziu a solubilidade em Ãgua e a permeabilidade ao vapor de Ãgua. Por outro lado, a cera de carnaÃba aumentou a opacidade dos filmes, e reduziu a resistÃncia à traÃÃo e o mÃdulo elÃstico. Para a elongaÃÃo na ruptura o comportamento foi oposto, ou seja, a cera de carnaÃba favoreceu a elongaÃÃo. A presenÃa de cera nos filmes promoveu o aparecimento de picos endotÃrmicos na curva de fluxo de calor. Entretanto, nos filmes, sem o conteÃdo hidrofÃbico, picos endotÃrmicos nÃo foram observados, com isto pode-se concluir que houve uma interaÃÃo entre os materiais utilizados.
The search for new packaging materials to keep or even improve food quality, at the same time reducing generation of nonbiodegradable waste, has motivated the exploitation of edible and/or biodegradable materials based on renewable resources. Film formation requires the presence of a component which forms a continuous and cohesive matrix. Starch has such a property and, being abundant and relatively cheap, is an interesting material for film formation. Cashew tree gum is a complex polysaccharide whose film forming properties are still poorly exploited. Polysaccharides such as starch and cashew tree gum, due to their high polarity, have good barrier to oxygen (O2) and carbon dioxide (CO2), but high water vapor permeability. The incorporation of hydrophobic components such as waxes to polysaccharide-based films improves their barrier to water vapor. The main objective of this study was to develop composite edible films based on starch, cashew tree gum and carnauba wax. A mixture (simplex centroid) design generated 10 treatments with the following proportions (on a weight basis): starch, 15 to 30%; cashew tree gum, 75 to 85%; and carnauba wax, 0 to 15%. In order to check the temperature used is sufficient had occurred to starch gelatinization, one ray diffraction analysis - x (X-DR) were performed. The film characterization was based on the following analyses: tensile properties (tensile strength - TS, elongation at break - EB, elastic modulus- EM), opacity (OP), water solubility (SOL), water vapor permeability (WVP) and glass transition temperature (Tg). The relative starch:cashew tree gum proportions did not significantly affect the overall film properties. Incorporation of carnauba wax reduced water solubility and water vapor permeability, since it decreased the hydrophilic content of the films. On the other hand, carnauba wax increased the film opacity and reduced their tensile strength and elastic modulus. For elongation at break, the influence of carnauba wax was the opposite, i.e., the property was favored by the wax. The presence of wax in the film promoted the onset of endothermic peaks in the curve of heat flow. However, the films without hydrophobic content, endothermic peaks were not observed, thus we can conclude that there was an interaction between the materials used.

The demand for biodegradable packaging materials as an alternative to synthetic ones to reduce environmental cost has seen an increase in recent years. In addition, functionalizing the packaging film to provide specific advantages like antimicrobial properties has yet to be explored thoroughly. This study considers adding antimicrobial agents to improve the quality and safety of actively packaged fresh produce using an antimicrobial enzyme (lysozyme) immobilized on a biopolymer based packaging film (corn-zein). The developed packaging material is aimed as an active biodegradable packaging to reduce bacterial contamination on the surface of fresh organic produce, specifically tomatoes. The study uses glutaraldehyde and glyoxal as binding agents to immobilize the enzyme on the packaging film. The effect of concentration of glutaraldehyde and glyoxal on the controlled release of the enzyme was studied. Concentrations of 0.1 and 0.2 g/g lysozyme: cross linking agent had controlled release properties. However, concentrations of 0 or 0.05 are about 20-30% more effective at inactivating bacteria. Antimicrobial activity in the constructed zein films are also tested against selected pathogens (Salmonella Newport and Listeria monocytogenes). Developed zein based film is tested against inoculated tomatoes to determine the efficacy of the films in reducing the pathogen population. The inoculated tomatoes are stored at room temperature over a storage period of one week. The film was able to reduce Listeria monocytogenes population by three logs but was unable to reduce the population of Salmonella Newport.
Master of Science

Afin de protéger les denrées alimentaires, l’industrie d’emballage enduit sur un film une couche très fine de polymère pour augmenter ses propriétés barrière aux gaz. Le problème majeur de ces enduits, généralement faits de poly (chlorure de vinylidène), vient de leur production de gaz toxiques à l’incinération. Les restrictions environnementales mondiales évoluent rapidement et sont de plus en plus strictes. De ce fait, des bioplastiques sont envisagés comme alternative. Dans ce contexte, l’objectif de la présente thèse est d'étudier le revêtement de films poly(téréphtalate d’éthylène) avec un polysaccharide, le chitosane. Ce dernier possède de bonnes propriétés barrières au gaz à sec. Cependant, son application dans l’emballage est limitée à cause de son caractère hydrophile. Le but de notre étude est donc d'améliorer les propriétés barrières à sec du chitosane par l’ajout de nano-charges d’argile et sa résistance à l’humidité par greffage de l’acide palmitique à la chaine du chitosane. L'efficacité d'incorporation de la vermiculite a été confirmée par DLS, DVS et DRX. Un facteur d'amélioration de la barrière (BiF) d’environ 100 pour l'hélium et de plus de 10 pour le dioxygène avec l'addition de 50% de vermiculite a été obtenu à sec. Le greffage de l’acide palmitique a été confirmé par spectroscopie IR-TF, ATG, DSC et RMN. Les résultats de mesures de la perméabilité hélium montrent une amélioration de facteur de la barrière (BIF) de 2 d’une couche de chitosane-g-acide palmitique et vermiculite à 60% en poids par rapport au PET non revêtu à 98% HR
In order to protect food, the packaging industry performs a film coating with a very thin polymer layer to increase its gas barrier properties. The major problem of these coatings is that they are generally made of poly(vinylidene chloride) which leads to a toxic gas production during incineration. In view of the rapid change of the global environmental restrictions that become quite stringent, bioplastics seem promising alternatives. In this context, this thesis deals with a fundamental study of poly(ethylene terephthalate) films coated with a polysaccharide: chitosan. Chitosan offers good barrier properties in dry conditions. However, its application in the packaging is limited because of its hydrophilic character. Therefore, the main goal of our work is on one hand to enhance the dry barrier properties of the material through adding nanoclays and on the other hand to improve its resistance to moisture by incorporating palmitic acid by grafting it to the chitosane backbone. The incorporation efficiency of vermiculite was confirmed by DLS, DVS and XRD. A barrier improvement factor (BiF) of about 100 for helium and more than 10 for dioxygen with the addition of 50% vermiculite was obtained under dry conditions. The grafting of palmitic acid has been confirmed by FTIR spectroscopy, ATG, DSC and RMN. The results of helium permeability measurements showed an improvement of the barrier factor (BIF) of 2 in the case of a chitosan-grafted-palmitic acid layer with 60 weight% of vermiculite compared to the uncoated PET at 98% RH

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
O objetivo desse trabalho foi desenvolver filmes biodegradÃveis à base de amido e goma de cajueiro, acrescidos ou nÃo de montmorilonita. Em uma primeira etapa, foi feito um delineamento experimental composto central a partir de misturas entre amido e goma de cajueiro (1:1, m:m) adicionadas de diferentes concentraÃÃes da argila montmorilonita (0 a 15% - MMT) e tempos de ultrassom (0 a 5 min), onde foi realizado um estudo das variaÃÃes de desempenho de filmes produzidos por deposiÃÃo (casting), em funÃÃo das variÃveis. Os filmes foram avaliados em termos de propriedades Ãticas, mecÃnicas, de barreira e tÃrmicas e analisados por Microscopia eletrÃnica de varredura (MEV) e Ãngulo de contato. Em uma segunda etapa do trabalho, as formulaÃÃes dos filmes amido e goma de cajueiro (AGC) e os de amido, goma de cajueiro e montmorilonita AGC-MMT foram testadas como revestimentos para amÃndoas de castanhas de caju. As amÃndoas revestidas com AGC e AGC-MMT, assim como um controle (amÃndoas sem revestimento), foram acondicionadas em sacos plÃsticos de polietileno de baixa densidade, estocadas em temperatura e umidade ambiente e tiveram sua estabilidade avaliada. Os testes de estabilidade realizados foram baseados em medidas de absorÃÃo de umidade, atividade de Ãgua e do grau de oxidaÃÃo das amÃndoas (determinado por Ãndice de perÃxido e Ãndice de acidez). O incremento de MMT interferiu nas propriedades Ãticas dos filmes, aumentando sua opacidade. A permeabilidade ao vapor de Ãgua dos filmes produzidos foi significativamente (p < 0,05) reduzida pela MMT. A resistÃncia à traÃÃo e o mÃdulo elÃstico apresentaram valores mÃximos em uma faixa intermediÃria de concentraÃÃo de MMT. O tempo de ultrassom favoreceu a dispersÃo da argila em concentraÃÃes baixas de MMT, porÃm em concentraÃÃes maiores favorece a formaÃÃo de aglomerados, o que tambÃm à visualizado nas micrografias obtidas por MEV. Com o aumento do tempo de ultrassom, a resistÃncia à traÃÃo e o mÃdulo tenderam a aumentar. As curvas de DSC do amido, goma de cajueiro e do filme produzido sem MMT apresentaram picos endotÃrmicos similares em torno de 110ÂC, que podem estar relacionados à superposiÃÃo de eventos como vaporizaÃÃo da Ãgua e fusÃo da fase cristalina dos componentes. A medida do Ãngulo de contato comprovou que os filmes produzidos sÃo altamente hidrofÃlicos. Os testes de estabilidade realizados mostram que os revestimentos AGC e AGC-MMT conferem menor acidez e Ãndice de perÃxidos quando comparados a um controle podendo ser uma alternativa para aumento da vida de prateleira das amÃndoas de castanhas de caju, servindo como embalagem primÃria.
The purpose of this study was to develop biodegradable films based on starch and cashew gum, added or not with montmorillonite. At a first stage, a central composite experimental design was carried out from mixtures of starch and cashew gum (1:1, m: m) added with different concentrations of montmorillonite (0-15% - MMT) and submitted to variable ultrasound times (0-5 min), In a study of variations in the performance of films produced by casting. The films were evaluated in terms of optical properties, mechanical, barrier and thermal. As well as scanning electron microscopy (SEM) and contact angle. In a second stage of the work, the formulations of the films based on starch and cashew tree gum (SCG) and starch cashew tree gum and montmorillonite (SCG-MMT) were tested as coatings for cashew kernels. The kernels coated with SCG and SCG-MMT, as a control (uncoated kernels) were placed in plastic bags of low density polyethylene, stored at room temperature and relative humidity and their stability were evaluated. Stability tests were based on measurements of moisture absorption, water activity and the degree of oxidation of almonds (determined by peroxide value and acid value). The increase of MMT concentration interfered with the optical properties of the films, increasing its opacity. The water vapor permeability of films was significantly (p <0.05) reduced by the MMT. The tensile strength and elastic modulus showed a peak in an intermediate range of concentration of MMT. The time of ultrasound favors the dispersion of clay in low concentrations of MMT, but at higher concentrations et led to formation of agglomerates, which also appeared in SEM micrographs. With the increase of ultrasound times tensile strength and modulus tended to increase. DSC curves of starch, cashew gum and the film produced without MMT the endothermic peaks had similar MMT about 110 Â C, that may be related superposition events such as the vaporization of water and melting of the crystalline phase of the components. The contact angle measurement showed that the films are highly hydrophilic. Stability tests performed show that the coatings AG and AG-MMT give less acidity and peroxide value when compared to a control, may be an alternative of the use to increase the shelf life of almonds cashew nuts serving as primary packaging.

The dairy food industry is continuously striving towards products with higher quality and longer shelf-life available to the customer at low prices. Arla Foods in Linköping, Sweden, is currently investigating the possibilities of changing the material in yogurt packaging containers by replacing the currently used carton with a different and cheaper alternative. A successful switch will give the company an economical advantage without affecting the sensory attributes (smell, taste, sight, and consistency), aroma profile or other important trademarks of the yogurt. This study is designed to examine and compare yogurt that has been stored in different packaging cartons, one coated with a single-layered low-density polyethylene (LDPE) and one coated with a currently used multi-layered ethylene-vinyl alcohol (EVOH). The study was based on the analysis and measurement of sensory attributes performed by experts, physical properties in laboratory and chemical composition in GC-FID/MS together with a discriminative test where a group of people would identify any difference between the yogurts. Together, these analyses would provide an explanation about any differences between the packaging materials by connecting physical, chemical and/or sensory characteristics. The collected results would give a better and more comprehensive picture than each analysis would do separately. The results from the study show that there is a difference between yogurts stored in LDPE-based containers and yogurts stored in EVOH-based containers and that the product was chemically affected, mainly by the level of oxygen in contact with the food. The overall assessment is that the largest difference was discovered in the taste.

Neste trabalho, ingredientes naturais antimicrobianos foram adicionados em filme biodegradável (biofilme) à base de fécula de mandioca tendo como plastificantes sacarose e açúcar invertido. A seleção dos ingredientes antimicrobianos (cravo em pó, canela em pó, pimenta vermelha em pó, óleo essencial de laranja, café em pó, mel e extrato de própolis) foi conduzida por meio de um delineamento experimental (fatorial fracionado 27-3) e os biofilmes foram analisados quanto às suas propriedades de barreira (permeabilidade ao vapor de água e taxa de permeabilidade ao vapor de água) e propriedades mecânicas (resistência máxima à tração e porcentagem de alongamento na ruptura). Os biofilmes apresentaram valores inferiores aos apresentados pelo biofilme controle quanto às propriedades mecânicas. Em geral, a taxa de permeabilidade ao vapor de água nos biofilmes antimicrobianos manteve-se estatisticamente igual ao do controle. Na segunda etapa do trabalho, a otimização dos ingredientes selecionados foi realizada através de delineamento experimental, com somente adição de cravo e canela em pó, que apresentaram resultados mais promissores na etapa anterior. Foi constatado que a adição de cravo e canela em pó alterou as propriedades mecânicas, porém as alterações foram menos intensas com a adição da canela em pó do que com o cravo em pó, o que pode ser justificado pela diferença de granulometria entre eles. A taxa de permeabilidade diminuiu até certa concentração dos ingredientes (0,34% para a canela em pó e 0,20% para o cravo em pó). O efeito antimicrobiano dos biofilmes foi investigado como embalagem de fatias de pão tipo forma e foi constatado que a atividade de água dos biofilmes aumentou após 7 dias de contato. É provável que os biofilmes tenham se tornado meios propícios para o desenvolvimento de bolores e leveduras visto que estes microrganismos cresceram de forma similar ou mais intensa nas fatias de pão na presença do que na ausência dos biofilmes. A partir dos resultados obtidos, não é possível avaliar de forma clara, o efeito antimicrobiano dos ingredientes incorporados na matriz dos biofilmes contra o crescimento de bolores e leveduras em fatias de pão tipo forma.
In this work, natural antimicrobial ingredients were added to biodegradable film (biofilm) based on cassava starch with sucrose and inverted sugar as plasticizers. The selection of the antimicrobial ingredients (clove powder, cinnamon powder, red pepper powder, orange essencial oil, coffee powder, honey and propolis extract) was carried out applying an experimental design (incomplete factorial 27-3) and the barrier properties (water vapour permeability and water vapour permeability rate) and mechanical properties (tensile strength and elongation at break) of the biofilms were determined. The biofilms presented lower data regarding mechanical properties when compared to biofilm control. In general, the water vapour permeability rate of the antimicrobial biofilms was statistically equal to the control. In the second phase of the work, the optimization of the selected ingredients was carried out applying an experimental design, with the addition of only clove and cinnamon powder due to the fact that they showed the most promissing results at the previous phase. The addition of clove and cinnamon powder modified the mechanical properties but the modifications resulted by the addition of cinnamon powder were less intense tha n the ones resulted by the addition of clove powder, which can be justified by the particle size differences between them. The water vapour permeability rate decreased by specific ingredients concentration (0.34% for the cinnamon in powder and 0.20% for the clove in powder). The biofilms antimicrobial effect was investigated as packaging of pan bread slices and it was verified that the biofilms water activity increased after 7 days of contact. Probably, the biofilms became suitable substrates for yeast and mold development due to the fact that these microorganisms grew equally or more intensely in the pan bread slices when the biofilms were present in comparison to the cases of its absence. According to the results, it is not possible to evaluate clearly the antimicrobial effect of the added ingredients to the biofilm matrix against yeast and mold development in pan bread slices.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

No presente trabalho foram estudadas as propriedades mecâncias (resistência à tração e porcentagem de alongamento na ruptura e resistência à perfuração), propriedades ópticas, permeabilidade ao gás oxigênio e ao vapor d\'água, migração total em simulante aquoso (ácido acético 3%) e gorduroso (n- heptano), e a formação de produtos voláteis da radiólise, com vistas à avaliar o efeito da radiação ionizante (raios gama e feixe de elétrons) em filmes flexíveis mono e multicamadas comerciais, fabricados no Brasil para a indústria de produtos cárneos. Os filmes estudados foram: um monocamada de polietileno de baixa densidade (LDPE) e um multicamadas coextrusado composto de polietileno de baixa densidade (LDPE), copolímero de etileno e álcool vinílico (EVOH) e poliamida (PA), ou seja, a estrutura: LDPE/EVOH/PA. As irradiações foram realizadas em uma fonte de 60Co do tipo Gammacell e em um acelerador de elétrons do tipo eletrostático (l,5MeV), com doses de até 30 kGy, na temperatura ambiente e presença de ar. As alterações nas propriedades foram avaliadas de acordo com a dose de radiação aplicada, oito dias após a irradiação e novamente, dois a três meses após a irradiação. Os resultados mostraram que as reações de cisão predominaram sobre as reações de reticulação para ambos os filmes estudados, irradiados com raios gama ou com feixe de elétrons. As variações observadas em função da irradiação, nas propriedades avaliadas não limitam a aplicação final desses filmes, uma vez que não ultrapassaram o limite de segurança especificado pelo fabricante em nenhuma dose e período em que foram estudadas. Concluiu-se que os filmes estudados podem ser utilizados, sob o ponto de vista das propriedades avaliadas, como embalagens para produtos pasteurizáveis por radiação e radioesterilizáveis usando irradiadores gama ou aceleradores de elétrons, nas doses de radiação estudadas.
In this study the mechanical properties (tensile strength and percentage elongation at break and penetration resistance), optical properties, gas oxygen and water vapor permeability, the overall migration tests into aqueous food simulant (3% aqueous acetic acid) and fatty food simulant (n-heptane), as well as the formation of volatile radiation product tests were used to evaluate the effects of ionizing radiation (gamma irradiation or electron-beam irradiation) on commercial monolayer and multilayer flexible plastics packaging materials. These films are two typical materials produced in Brazil for industrial meat packaging, one of them is a monolayer low-density polyethylene (LDPE) and other is a multilayer co extruded low-density polyethylene (LDPE), ethylene vinyl alcohol (EVOH), polyamide (PA) based film (LDPE/EVOH/PA). Film samples were irradiated with doses up to 30 kGy, at room temperature and in the presence of air with gamma rays using a 60Co facility and electron beam from 1.5 MeV electrostatic accelerator. Alterations of these properties were detected according to the dose applied initially eight day after irradiation took place and new alterations of these values when the properties were evaluate two to three months after irradiation process. The results showed that scission reactions are higher than cross-linking process for both studied films, irradiated with gamma rays and electron beam. The evaluated properties of the irradiated films were not affected significantly with the dose range and period studied. The monolayer Unipac PE-60 and the multilayer Lovaflex CH 130 films can be used as food packaging materials for food pasteurization and in the sterilization process of by ionizing radiation using a gamma facilities and electron beam accelerators in commercial scale.

The integration of antimicrobial (AM) agents into packaging materials is aimed at killing or inhibiting the spoilage and pathogenic microorganisms that may contaminate packaged food products. Over the years there has been an increased emphasis on naturally derived AM agents and polymer films containing AM agents derived from basil, for example, exhibit an AM effect against a wide spectrum of microorganisms. Due to the relatively high temperatures involved in manufacturing such films, however, there is a considerable evaporation loss of AM agent during the film blowing process. The present study aims at developing effective AM films and subsequently reducing the loss of active AM agents. The effect of polyethylene glycol (PEG) and ethylene vinyl acetate (EVA) in minimising the loss of active AM agent during the manufacturing of low-density polyethylene (LDPE) film is explored by measuring the release of AM agent into food simulants. The release of AM agents from the film is satisfactorily and consistently described by short-term and long-term migration equations and by first order kinetics. Furthermore, the polymer additives PEG and EVA play a role in controlling the release of the AM agents. The incorporation of AM agent does not adversely affect the mechanical or optical properties of the extruded LDPE/EVA film and the films retain ca. 75% of AM agents after extrusion.

Research Doctorate - Doctor of Philosophy (PhD)
The continuous increase of consumer interest in higher quality food, in combination with the ecological and economic requirements to decrease disposal of post-user waste, has induced increasing attention to research into edible films and coatings. As a replacement to more traditional recycling procedures, edible and biodegradable polymers, that can be reverted to the biological cycle after use, have emerged. Consequently, the use of biodegradable agricultural polymers would not only resolve the environmental problems, but also present a potential new use for extra farm produce. Such films can mechanically protect foods, inhibit the contamination from microorganisms, and preserve quality loss of foods caused by mass transfer (e.g. moisture, gases, flavors, etc.). Additionally, edible films and coatings can be applied as a carrier for incorporating natural or chemical antimicrobial agents, antioxidants, enzymes or functional components such as probiotics, minerals and vitamins. The application of edible films and coatings has been studied as a good alternative for the conservation of intact, and fresh fruit and vegetables. Fruit and vegetables consist of living tissue which undergoes many physical and chemical changes due to deteriorative and synthetic biochemical processes, such as enhanced ethylene production and respiration rate, as well as consumption of sugars, lipids and organic acids accelerating the ripening process. Therefore the quality of products can be affected including flavor, textural, nutritional, and pigmentation changes during storage. The major purpose of employing edible films and coatings is to act as a semipermeable membrane against gases and vapor that preserves the produce and reduces the rate of physiological postharvest degradation; however, they can also carry additives, for example texture enhancers, antimicrobials, and antioxidants to extend the shelf life of produce after harvest. Edible films can be prepared from proteins, polysaccharides, lipids or a combination of these constituents. Starch can be used for edible films production because it can be obtained from a large number of raw materials and is a renewable and biodegradable biopolymer. Pea starch has been demonstrated to produce the films with improved physical and mechanical properties in comparison with films prepared from other starches due to high amount of amylose. The development of pea starch film with improved functions affects its application. Hypothesis and Aims: In the current study, we hypothesized that development of novel edible films made of pea starch will be an improved alternative to substitute the common commercial waxes used for coating in the citrus industry for extending the orange fruit shelf-life. The optimized formulations of pea starch and other ingredients used to improve the physical, mechanical and barrier properties of films will maintain physical, sensorial and quality properties of the fruit during simulated commercial storage conditions. Overall, the aims of this study were: Aim 1: To develop pea starch films: (A) To determine the moisture barrier, color, mechanical, and structural properties of pea starch film affected by different concentrations of glycerol as plasticizer and environmental relative humidity (RH). (B) To develop a new type of edible film made of pea starch and guar gum in the presence of glycerol, and to examine the mechanical and water barrier properties of the resulting composite films as a function of guar gum and glycerol concentrations using a mixture experimental design. (C) To study the influence of different plasticizers (glycols, sugars and polyols) on the moisture sorption, mechanical, physical, optical, and microstructure characteristics of pea starch-guar gum (PSGG) film. (D) To investigate the alteration of physical, barrier and mechanical properties of PSGG films resulting from the incorporation of hydrophobic compounds such as shellac, emulsifier, and surfactant using response surface methodology. Aim 2: To evaluate the potential of application of films obtained from Aim 1 on ‘Valencia’ orange fruit: (A) To determine whether films have the potential to be used as an edible coating for increasing the shelf life of ‘Valencia’ orange whilst maintaining the quality of fruit during storage. The effectiveness of the best coatings formulation on gas exchange, vitamin C, total phenolic compounds, antioxidant capacity, and sensory quality of fruit were evaluated. Results: The results showed that increasing the concentration of glycerol led to improvement of the tensile strength of the pea starch films at RH < 43 %, the percent elongation as well as the deformation at break at RH < 84 %. Increasing plasticizer content and RH also resulted in films with lower Young’s modulus, lower puncture force, but higher puncture deformation. Furthermore, increasing plasticizer content led to the films with a more opaque appearance. Pea starch films prepared with 15 and 25 % glycerol had lower water vapor permeability in comparison with un-plasticized film indicating its potential application as edible films in the food and pharmaceutical industries. The physical, optical, mechanical and barrier properties of pea starch edible films were improved by optimizing concentrations of pea starch (2-3 g), guar gum (0.1-0.5 g) and glycerol (15-35%) by using Box–Behnken response surface design (BBD). The results revealed that increasing pea starch and guar gum content favored formation of a more resistant polymeric structure. The optimized conditions with the goal of maximizing optical and mechanical properties and minimizing water vapor permeability, moisture content, solubility and color were 2.5 g pea starch, 0.3 g guar gum and 25 % (w/w) glycerol based on the dry film matter in 100 mL of distilled water. The addition of various plasticizers to the PSGG film showed that the films containing plasticizers with higher functional groups had lower equilibrium moisture content at a_w < 0.4. In general, a reduction in tensile strength and Young's modulus and an increase in elongation at break were detected when the molecular weight of plasticizers and relative humidity increased in all film formulations. Films plasticized with monosaccharide showed similar mechanical properties to those with sorbitol, but lower solubility and water vapor permeability (WVP), higher transparency and moisture content than the sorbitol-plasticized films. The most noticeable plasticization effect was exerted in the following order: glycerol > EG > PG > xylitol > fructose > sorbitol > mannitol > galactose > glucose > sucrose > maltitol. The incorporation of shellac as the hydrophobic compound in the PSGG film plasticized with glycerol led to a slightly increased film thickness. However, the addition of higher concentrations of shellac did not improve the moisture barrier of PSGG film owing to the poor distribution of shellac in the film structure. Film formulated with 40 % shellac, 1 % SA, and 0.3 % Tween-20 exhibited optimal functional properties. Moreover, films containing oleic acid (OA) showed not only lower thickness, WVP, moisture content, and water solubility, but also higher percentage of elongation (E), tensile strength (TS), and transparency compared with other fatty acids tested. Biocomposite pea starch-guar gum-shellac (PSGG-Sh) film containing OA was considered for the coating of oranges. The incorporation of lipid compounds into the PSGG coatings (PSGG-Sh) generally resulted in the best performance in reducing fruit respiration rate, ethylene production, weight and firmness loss, peel pitting, and fruit decay rate of the coated oranges. Fruit coated with PSGG-Sh and a single layer of PSGG coatings generally resulted in higher scores for overall flavor and freshness after four weeks at 5 °C followed by one week at 20 °C, than uncoated fruit, as assessed by a sensory panel. Overall results suggested that PSGG-based edible coatings could be a beneficial substitute to common commercial waxes for maintaining quality and storability, as well as extending shelf life of citrus fruit and potentially other fresh horticultural produce. Conclusions: In conclusion, the hypothesis was supported and the aims were addressed. This study revealed that pea starch can be used to produce films with appropriate physical and mechanical properties in the presence of guar gum, various plasticizers (polyols, glycols and sugars), and hydrophobic compounds. Application of PSGG edible coatings incorporated with shellac showed great potential for preservation quality, storability and improved shelf life of ‘Valencia’ oranges at 5 °C and 20 °C. The results of this study can be further utilized for formation of biodegradable films or edible coatings and better understanding of using pea starch in the food packaging industry. The results also suggested that PSGG-based edible coatings could be a beneficial substitute to common commercial waxes for maintaining quality and extending shelf life of citrus fruit and potentially other fresh horticultural produce.

碩士
萬能科技大學
材料科技研究所
100
We used polyurethane, ethyl acetate, and commonly used food packing films to prepare lamination films. After laminating, the lamination film was dried and cured in a oven at 50℃ for aging. The lamination films possessed thermal, mechanical, and anti-moisture-penetrability properties, which is suitable for food packing materials. The structure of the films was characterized by FTIR. The thermal properties of the film were measured by TGA and DSC. The anti-penetration strength was used by an Instron. The water vapor transmission rate of the films was measured with a water vapor transmission machine. Mechanical analysis showed that the lamination films have different properties, due to the composition and the lamination order in the films. The lamination films have good thermal properties, due to the addition of polyurethane and the combination of various films. PET and ALOPET showed different thermal properties, due to the different component in the film. The hydrophobic property of the single film was measured by contact angle. Surface treatment on the film showed the improved hydrophilic properties, which is favor for printing and combination. For water vapor transmission rate analysis, the lamination films can reduce the rate of water vapor transmission. These studies revealed that the lamination films improve the anti-penetration strength, water vapor penetration rate, and thermal properties.

The overuse of synthetic non-biodegradable plastic packaging in the last decades turned into a serious global environmental problem, once recycling and energy recovery are not perfect solutions. To overcome this problem, efforts have been done by researchers around the world to use biodegradable biopolymers from renewable resources as food packaging materials. In this thesis, FucoPol, a microbial exopolysaccharide has been studied as a sustainable alternative and the following questions were raised: • Is it possible to produce films of FucoPol and which properties should be improved? • Which strategies may be applied to improve their behaviour, specially their barrier properties to gases and water vapour? • Is it possible to use FucoPol films as an alternative to synthetic plastics aiming their use as packaging material? This study shows that, FucoPol films offer good barrier properties to gases and biodegradability. Their weaker properties, low barrier properties to water, have been improved along the work, using two distinct strategies: formulation of bilayer films of FucoPol and chitosan and use of different coatings techniques in FucoPol films. The results have shown that, it is possible to improve FucoPol films properties, namely the barrier properties to gases and water vapour, and resistance to liquid water. FucoPol combined with chitosan as a bilayer film was used for walnuts packaging and it was possible to verify that it can protect food susceptible to lipid oxidation as effectively as synthetic materials.

In the last decades, the overuse of synthetic polymers in the plastic packaging industry has become a serious global environmental problem due to their non-biodegradability. To overcome this issue, industries and researchers have joined efforts to decrease the amount of synthetic materials used by exploring alternatives from renewable resources, aiming at developing biodegradable and biocompatible packaging materials. In this context, edible films and coatings based on biodegradable biopolymers have been gaining a significant importance as they present a promising solution for the issue at hand. In this thesis, the polysaccharide arabinoxylan, extracted from corn fibre by alkaline hydrolysis, was used to produce composite and multilayer edible films. The composite films were produced through an oil-in-water emulsion with different quantities of oleic acid or limonene, while the multilayer films were manufactured by submerging the arabinoxylan films in a beeswax solution. Both films, along with the pure arabinoxylan film, were later characterised in terms of their antioxidant activity, optical and mechanical properties, surface hydrophobicity, and barrier properties against water vapour and Ultraviolet-Visible (UV-Vis) radiation. The emulsified films were found to be heterogeneous and thick, presenting worse water vapour permeability and surface hydrophobicity properties, and a lower antioxidant activity than the pure arabinoxylan films. On the other hand, the multilayer films revealed a smooth and uniform beeswax coating, which enhanced the films’ barrier properties against water vapour and UV-Vis radiation. Moreover, these films showed higher values of water contact angle, tensile stress and Young’s modulus, but lower elongation at break than the composite films. The results suggest that the multilayer films are more advantageous than the emulsified films. Therefore, the production of the developed biopolymeric films will have a positive outcome, contributing to improve sustainability practices in the food packaging sector.
Nas últimas décadas, o uso excessivo de polímeros sintéticos na indústria das embalagens de plástico, tornou-se um grave problema ambiental a nível global devido à sua falta de biodegradabilidade. Para ultrapassar este problema, as indústrias e os investigadores têm vindo a unir esforços para diminuir a quantidade de materiais sintéticos usados, explorando alternativas obtidas a partir de fontes renováveis, de modo a desenvolver embalagens biodegradáveis e biocompatíveis. Neste contexto, filmes e revestimentos comestíveis baseados em biopolímeros biodegradáveis têm ganho uma importância significativa por apresentarem uma solução promissora para o problema que enfrentamos. Nesta tese, o polissacárido arabinoxilano, extraído da fibra do milho por hidrólise alcalina, foi usado para produzir filmes comestíveis compósito e multicamada. Os filmes compósito foram produzidos através de uma emulsão óleo-em-água com diferentes quantidades de ácido oleico ou limoneno, enquanto que os filmes multicamada resultaram da submersão dos filmes de arabinoxilano numa solução de cera de abelha. Ambos, em conjunto com os filmes de arabinoxilano puros, foram de seguida caraterizados em termos da sua atividade antioxidante, das suas propriedades óticas e mecânicas, hidrofobicidade superficial, e propriedades de barreira contra o vapor de água e radiação Ultravioleta-Visível (UV-Vis). Os filmes produzidos a partir de emulsões resultantes eram heterogéneos e espessos, apresentando piores resultados ao nível de permeabilidade ao vapor de água e de hidrofobicidade de superfície, além de menor atividade antioxidante em comparação com os filmes de arabinoxilano puros. Por outro lado, os filmes multicamada revelaram um revestimento de cera de abelha liso e uniforme, melhorando as suas propriedades de barreira contra o vapor de água e a radiação UV-Vis. Adicionalmente, estes filmes demonstraram valores mais elevados de ângulo de contacto com a água, tensão de stress e módulo de Young, mas valores de deformação mais baixos, em comparação com os filmes compósito. Os resultados sugerem que os filmes multicamada são mais vantajosos do que os filmes produzidos a partir de emulsões. Sendo assim, a produção dos filmes biopoliméricos desenvolvidos irá ter um resultado positivo, contribuindo para melhorar as práticas sustentáveis no setor das embalagens para alimentos.

The integration of antimicrobial (AM) agents into packaging materials is aimed at killing or inhibiting the spoilage and pathogenic microorganisms that may contaminate packaged food products. Over the years there has been an increased emphasis on naturally derived AM agents and polymer films containing AM agents derived from basil, for example, exhibit an AM effect against a wide spectrum of microorganisms. Due to the relatively high temperatures involved in manufacturing such films, however, there is a considerable evaporation loss of AM agent during the film blowing process. The present study aims at developing effective AM films and subsequently reducing the loss of active AM agents. The effect of polyethylene glycol (PEG) and ethylene vinyl acetate (EVA) in minimising the loss of active AM agent during the manufacturing of low-density polyethylene (LDPE) film is explored by measuring the release of AM agent into food simulants. The release of AM agents from the film is satisfactorily and consistently described by short-term and long-term migration equations and by first order kinetics. Furthermore, the polymer additives PEG and EVA play a role in controlling the release of the AM agents. The incorporation of AM agent does not adversely affect the mechanical or optical properties of the extruded LDPE/EVA film and the films retain ca. 75% of AM agents after extrusion.

Equipment and procedures for the rapid measurement of the water vapor permeability of polymer films and food coatings has been evaluated. The method uses an electronic sensor to measure the concentration increase in water vapor diffusing through a film into a chamber of known volume. Air of known humidity is passed over each side of the film to establish a desired equilibrium relative humidity differential prior to each test. Experimental results showed that moisture vapor transmission rates of polymer packaging films and edible coatings could be determined in a range from 0.25 to 12 hours instead of the usual 24 hour period required by existing tests. Permeance values for Teflon, high density polyethylene (HDPE), polyethylene terephtalate (PET) and three coating materials were measured at relative humidity differentials between 0 - 100% and temperatures between 5 and 30°C. Results were found to be similar to values reported in the literature using standard measurement methods. This method allows the measurement of film and coating permeance values at temperature and relative humidity values close to actual food storage conditions.
Graduation date: 1994

The quality and safety of foods may deteriorate due to the surface growth of microorganisms. The integration of antimicrobial (AM) agents in polymeric packaging films to enhance microbial stability of foods may have a crucial effect on extending the shelf life of packaged food products or on maintaining food safety. Linalool and methylchavicol are the principal constituents of basil and exhibit an AM effect against a wide spectrum of bacteria, yeasts and mould. These compounds are generally recognized as safe (i.e. possess GRAS status) and are stable at the high temperatures that prevail during the extrusion film blowing process. Therefore, films containing these substances might have a potential use as AM packages. The present study generally aimed at investigating AM polymeric packaging films containing the principal constituents of basil.

Corn fiber is a by-product of the starch industry, currently used as animal feed. It contains in its composition arabinoxylan, with film-forming properties, thus this material has a great interest in being valorized. Arabinoxylan was extracted with an alkaline solution and centrifuged. The resulting extract was purified with an ultrafiltration membrane hollow-fiber unit, in a continuous diafiltration process, at two different Reynolds number at the feed side (129 and 267), under controlled temperature and permeate flux conditions. At the final diavolume of 10, rejections were higher at Reynolds number 267, (91±2)% of NaCl equivalents, NaCleq, and (97±1)% of ferulic acid equivalents, FAeq, than at Reynolds number 129, where rejections were (87±3)% and (95±1)% of NaCleq and of FAeq, respectively. At both Reynolds numbers, the removal of small compounds was similar (97.0±0.3)% in NaCleq and (91±1)% in FAeq, meaning that the final extracts had a similar quality. The discoloration of the purified extract was then evaluated with activated charcoal and hydrogen peroxide treatments, in which only the latter resulted in a lighter colored solution. Various formulations were applied to the decolorized extract: glycerol was used as a plasticizer and different non-hazardous diacids (succinic, malonic and citric acids) were used as cross-linkers. The resulting films were characterized in terms of their antioxidant properties, solubility in water and mechanical properties. It was found that a decolorized film formulated with glycerol and citric acid had a lower antioxidant activity (0.053±0.001)μmol Trolox/mg film than a pure arabinoxylan film (0.091±0.002)μmol Trolox/mg film. Films were still very soluble in water, with the minimum solubility being around 70%. The decolorized film with glycerol and citric acid showed the highest tension of perforation (1.28±0.14)MPa and deformation (6.4±1.7)%.

碩士
大葉大學
食品工程研究所
86
Development and use of biodegradable food packaging films insubstitution of petroleum plastic films is an urgent issue attracting theworldwide concern based on the consideration of environmental protec-tion.In general, cellulose-based films are hydrophilic and hygroscopic, whilezein films are hydrophobic and fragile. In this study, a goal was pursued tocombine the beneficial properties of cellulose and zein to comprise asuitable formulation to prepare biodegradable packaging films.Hydroxylpropyl me thyl cellulose （ HPMC ）, methyl cellulose （ MC ） andzein were used. The plasticizer effect of polyethylene glycol （ PEG ） wasintensively investigated. A dynamic mechanical analyzer （ DMA ） wasmonitored to analyze the mechanical properties of the prepared films.Elongation （ or strain ）, toughness and tensile strength （ or stress ）of HPMC and HPMC/MC films decreased while hardness （ modulus ） increasedwith the increase of zein concentration. On the same basis of zeinconcentration, elongation and hardness of H PMC/MC films are higher thanHPMC films while tan d of HPMC/MC films increased with the increase of zeinconcentration. In comparison, HPMC films were more elastic than HPMC/MCfilms. As a general trend, both HPMC and HPMC/MC films increased theirhard-ness and brittleness as zein concentraion increased. When PEG wasadded, elongation of HPMC and HPMC/MC films increased while hardnessdecreased with increase of PEG addition. The toughness of HPMC films alsoincreased as the concentration of the added PEG in -creased. Tan d and Tg ofHPMC and HPMC/MC films decreased with increase of PEG addition and thisindicates that elasticity of the films increased with increase of PEGaddition. Water vapor permeability （ WVP ） of HPMC and HPMC/MC filmsdecreased as the concentration of zein increased. On the same basis of zeinconcentration, WVP of HPMC films decreased with an increase of PEG addition.When PEG was added at 1.0 % for HPMC/MC films, the lowest WVP was obtained.In the aspect of oxygen barrier of the films in relation to peanut oiloxi-dation, oxidation retardation of the HPMC and HPMC/MC films in-creasedwith increase of zein concentration. When PEG was added, the most effectiveoxygen barrier in prevention of oil oxidation was ob-tained at 1.0 % PEG forHPMC films containing 2.0 % zein and 0.5 % PEG for HPMC/MC films containing1.0 % zein.

The inherent volatility and/or heat sensitivity of many natural antimicrobial (AM) additives can be detrimental to their widespread use in commodity polymer packaging film formulations. In this study, beta-cyclodextrin (β-CD) inclusion complexes with naturally-derived AM agents: thymol, carvacrol, and linalool were prepared using a co-precipitation technique. The complexes were optimised and then characterised by techniques including thermal analysis. They were then incorporated into low-density polyethylene (LDPE) films with AM agents added directly for comparison. The subsequent release of the AM agents into food simulants was studied followed by an investigation of the efficacy of the films in vitro against selected bacteria. The films were later tested on real foods to assess their potential for controlling microbial growth and lipid oxidation. In the initial experiments, conditions for synthesising the β-CD/AM agent complex including solvent composition, temperature, reaction time, and total solvent volume were investigated to optimise the inclusion efficiency (IE) and yield. Electrospray ionization mass spectrometry and gas chromatography were used to confirm the formation and quantify the amount AM agents that were encapsulated, absorbed onto the surface, or remaining in the filtered solvent. The systematic optimisation of the conditions improved both the yield of the complex and the IE of the AM agents. Using a 1:1 mole ratio of the AM agent to β-CD, the optimised parameters resulted in maximum yields of 87, 84 and 86% (w/w) for thymol, carvacrol and linalool respectively with IE’s close to 100% (w/w) for each agent. The kinetics of the thermal decomposition of the optimised β-CD and complexes of the three AM agents were then investigated using thermogravimetric analysis. Under a linear temperature ramp and in the degree of conversion, α, domain: 0.1 ≤ α ≤ 0.8, the major decomposition steps of the β-CD, and complexes with carvacrol, linalool and thymol occurred at ca. 300°C and followed Avrami-Erofeev kinetics with apparent activation energies, Ea, of: 156 ± 6, 107 ± 7, 96 ± 3 and 110 ± 3 kJ mol-1 respectively. Below ca. 300°C there were staged mass losses from each of the complexes that were not observed for the neat β-CD. These were attributed to lower energy binding interactions and accounted for a little over half of the available guest species in the complex in each case. Lower temperature mass losses for β-CD complexes with carvacrol (ca. 140 to 230°C) and linalool (ca. 95 to 150°C) were analysed and found to be adequately fitted by second-order kinetics with apparent Ea values of: 37 ± 1 and 69 ± 6 kJ mol-1 respectively. The results suggest the optimized complexes are generally thermally stable and would potentially be suitable for high-temperature extrusion processes with acceptably low losses. The next experiments involved the incorporation of the AM agents into LDPE films either directly or encapsulated in β-CD. Quantification of the AM agents was performed immediately following thermal processing, then six and thirty days after the film samples were stored in an open atmosphere. After six days, no AM agent was detected in the films where the agent was added directly to the film whereas the films containing encapsulated agents showed only small decreases in the concentrations of the agents up to 30 days. The migration of AM agents from LDPE films into 95% (v/v) ethanol/water mixtures food simulants at 4℃ was adequately described using first-order kinetics and Fick’s second law of diffusion. For the AM agents added directly to the film, the initial release rates were between four and eight times greater than those of the encapsulated agents. Similarly, the diffusion coefficients of the free agents were ca. four to five times greater than the encapsulated agents. The free and encapsulated natural AM agents incorporated into LDPE film were tested against Escherichia coli (ATCC 25922) in order to assess the potential of the AM inclusion complexes for use in food packaging films. The direct incorporation of the complexes in the film formulations resulted in little inhibition of the target bacterium as assessed by the agar diffusion method even with AM levels as high as 5% (w/w). In comparison, levels of 2% (w/w) of free thymol and carvacrol added directly to the film demonstrated inhibition. The addition of glycerol to the film formulations was investigated as a means of facilitating the AM agent from the complex. A concentration of 1% (w/w) of glycerol in the film formulation was found to result in microbial inhibition which increased with additional glycerol. The use of 2% (w/w) glycerol resulted in a more pronounced inhibition of targeted microorganism. Upon the addition of glycerol, all of the films showed AM activity against the target bacterium with the exception of those containing linalool in either the free or encapsulated forms. Upon the addition of 2% (w/w) of glycerol to the film formulation, encapsulated thymol at a concentration of 2% (w/w) was more effective than encapsulated carvacrol at a concentration of 3% (w/w) against E. coli with zones of inhibition of 30.70 ± 0.72 and 29.61 ± 0.86 mm respectively. In the final experiments, the LDPE films containing encapsulated thymol were tested on real food systems. The level of thymol was 1 to 3% (w/w) relative to the LDPE and glycerol was added in order to obtain the optimum controlled release. In the case of packaged minced beef inoculated with E. coli, no inhibition was observed when the concentration of encapsulated thymol was 3% (w/w) with 2% (w/w) glycerol, however, the same film reduced E. coli growth by 0.7 log10 CFU g-1 on chicken breast fillets compared with the control during storage at 4℃ for 12 days. The growth of E. coli was found to be affected by the temperature at 4℃ whereby the bacterial counts remained relatively low with slow growth over the test period under refrigeration. However, when the temperature increased to 10℃ it was also found that the presence of coliforms interfered with growth of E. coli and, in general, the films containing encapsulated thymol effectively reduced coliform growth. Analysis of the antioxidant (AO) activity of films using the diphenyl-picrylhydrazyl (DPPH) radical assay showed a 71% reduction in DPPH concentration for the LDPE/thymol/β-CD films containing 3% (w/w) thymol. Furthermore, a film comprised of 1% (w/w) thymol with glycerol stored at room temperature for 20 months showed a reduction by 23% in DPPH concentration confirming that the films are suitable for extended storage. Analysis of the formation of thiobarbituric acid reactive substances on packaged minced beef showed decreases in lipid oxidation of 60 and 75% for films containing 1% and 3% (w/w) thymol in the film respectively. The films therefore show promise for the dual purpose of AO and AM activity in order to prolong the shelf-life of selected food products.

Carrageenan-based films exhibit some desirable properties for food packaging applications, but the high cost of source materials has been a considerable constraint for commercial development. This thesis presents a series of investigations designed to develop novel composite films for food packaging purposes utilizing a more economical and renewable raw material resource, namely semi-refined carrageenan (SRC). Additionally, the development and use of SRC as a biodegradable film-forming alternative to the current and commonly utilized refined carrageenan (RC) will also bring about benefits to the environment. Reinforcing the SRC with nanoclay and/or nanocellulose, lamination with poly(caprolactone), and surface photo-crosslinking are among the approaches used to enhance the SRC film properties. In the initial investigation, the preparation and characterization of SRC films plasticized with up to 50% (w/w) glycerol was performed using a solution casting method. The resultant film color and opacity increased with increasing levels of glycerol along with the moisture content, whereas the water vapor permeability decreased. The tensile properties of the SRC films improved significantly, particularly at glycerol additions greater than 30% (w/w). Moreover, the addition of glycerol improved the thermal stability and altered the surface morphology of the films. In general, the properties of the plasticized SRC films were comparable to those of refined carrageenan film counterparts. To overcome inherently poor water sensitivity and barrier properties of the SRC, film samples were reinforced with nanocellulose fibrils (NCF) and were benchmarked against similar films made from refined carrageenan (RC) with regard to the water sensitivity, physicomechanical and thermal properties. The level of NCF was varied from 1% to 7% (w/w) and, in general, the NCF reinforcement improved the overall properties of both the SRC and RC films including the water sensitivity and moisture barrier properties. Nonetheless, NCF inclusion in SRC film was less effective with regard to the mechanical and thermal properties enhancement compared with NCF inclusion in RC film. The enhancement in properties was attributed to the greater cohesiveness of the reinforced polymer structure and the crystalline regions formed in the structures of SRC and RC films by NCF incorporation. Semi-refined carrageenan film was also reinforced with nanoclay (NC) in combination with surface lamination using a thin layer of poly(caprolactone) (PCL) with a view to improving the barrier properties and hydrophobicity of the film and concurrently improving the mechanical properties. The water vapor permeability, moisture uptake, and water solubility decreased by 20%, 24% and 11%, respectively and the water contact angle increased from ca. 72° to 95° upon inclusion of the NC in the formulation. The tensile strength and elongation at break increased by 17.9% and 2.8% respectively, and the thermal stability also increased slightly. The PCL lamination was the main contributor to the enhanced barrier and mechanical properties of the films, whereas the NC inclusion contributed more to the enhanced thermal properties. In a further study, the surface regions of SRC film samples were photo-crosslinked with UV light of 0.46 W m-2 intensity using 6% (w/v) sodium benzoate solution as a photosensitizer. The surfaces were coated with the photosensitizer and exposed to the light source for 5, 10, 20 and 40 min. The effects of the surface crosslinking on the overall properties of the SRC films were investigated and related to the possible changes in the morphology of the substrate. The UV exposure and crosslinking were found to increase the crystallinity and the thermal stability of the films but with minimal colour changes. The mechanical properties were improved relative to the control sample with a ca. 42–55% increase in the tensile strength, ca. 142–144% increase in the modulus but with a concomitant ca. 50−52% decrease in the elongation at break. The crosslinking decreased the inherent moisture content in the films by ca. 50–52% and decreased the water vapour transmission rate by ca. 16–21% relative to the control. Changes in water sensitivity were observed with increases of ca. 35–44%, 18–22% and 21–22% in the water solubility, moisture uptake and water contact angle respectively. The latter increases were attributed to possible photodegradation products and the presence of residual photosensitizer that rendered the samples more hydrophilic. Under the conditions of the experiment, a UV exposure time of ca. 10– 20 min was found to be optimal in enhancing the mechanical and water barrier properties. These overall findings of the research have provided a most promising step towards the production of an economical food packaging material from SRC that has a minimal impact on the land environment.

Packaging is one of the most important technological steps of food preservation. Microbial growth and oxidation reactions occurring on food surface are two of the main causes of deterioration of fresh and processed food products. Traditional food packaging generally protect foodstuff from external influences. Whereas active packaging systems interact with the food permitting the extension of their shelf-life and the maintenance, or even the improvement of their quality and sensorial features. The main objective of this thesis is the attainment of knowledge related to the development of new material formulations for food packaging by using suitably modified inorganic nanoparticles in order to obtain a controlled release system of active substances and to improve active film physical and gas barrier performances. As far as antioxidant active films is concerned, the aim of the work is the development of innovative films containing natural -tocopherol adsorbed onto functionalised and not functionalised mesoporous silica particles (SBA-15; SBA-15+APTES) in order to protect it during LDPE film manufacture and to be able to control its release rate. The synthesized mesoporous powders were characterized by means of X-ray diffraction and N2 adsorption/desorption at 77 K. Powders loaded with tocopherol were characterized by infrared spectroscopy and thermogravimetric analysis. Results show that the maximum of the pore size distribution reduces from 90 Å for purely siliceous SBA-15 to 73 Å for amino-functionalized SBA-15. Infrared analysis shows that tocopherol interacts with the amino groups of functionalized SBA-15. It has been also proven that circa 40% and 30% of tocopherol is loaded into SBA-15 and SBA-15+APTES respectively. Release tests performed using 96% v/v ethanol as fatty food stimulant show that the tocopherol diffusivity of films containing functionalized mesoporous silica decreased of about 50% with respect to films containing free tocopherol, as. This is due to the decrease in the pore size and to the increase in diffusion resistance caused by the functionalization of the internal pore walls with the amino groups. Moreover, the oxygen radical absorbing capacity (ORAC) assay of the produced active polymer films proved the antioxidant effectiveness of tocopherol released from samples after manufacturing process. As far as antimicrobial activity is concerned, silver montmorillonite clays have been increasingly investigated as germicidal, bactericidal, antifungal, and antiseptic components in different food packaging formulation. The aim of this thesis is the development of a new class of antimicrobial systems in which the inorganic phyllosilicate clays (MMT) have been used as support for silver nanoparticles (AgNPs) . The Ag-MMT filler consists of nanometric metallic silver and oxides particles (size in the range 2-40nm) preferentially located on the surface of MMT single lamellae as the UV adsorption and FT-IR spectra showed. Antimicrobial bionanocomposites have been obtained by solution casting of AgMMT particles into chitosan, one of the most interesting biopolymers obtained from natural sources. The combined effect of glycerol and AgMMT particles on the thermal, structural and barrier properties of the obtained bionanocomposites was investigated. In fact, the plasticizer and the silver ions as well as the surface of metallic particles exert a combined effect which allows a reduction of the liquid water uptake and water permeability with respect to neat chitosan. Indeed, X.Ray results revealed that Ag-MMT particles result partially intercalated by chitosan macromolecules although it cannot be excluded in such an extent the exfoliation due to the collapse of MMT structure during the preparation of the active filler. Moreover, considering that the antibacterial mechanism of silver is mainly related to the action of silver ions and metallic AgNPs, the silver release kinetics from bionanocomposites in water at 25°C were also investigated. In conclusion, samples of purely siliceous and amino-functionalized SBA-15 mesoporous silica were successfully used as α-tocopherol carriers for the production of active LDPE polymer films. In fact, active polymer films containing the functionalized carrier showed a slower tocopherol release when compared to samples containing free tocopherol and tocopherol loaded onto purely siliceous substrate. Whereas, for antimicrobial active film,. the silver supporting nanoparticles, Ag-MMT, contribute to modulate the release kinetics of silver ions from bionanocomposite films over a longer time interval (up to 20 days). This is of paramount importance for the production of active films to be used as food packaging materials or potentially as biomaterials.