Academic literature on the topic 'Freeze-drying processes'

This study aimed to obtain encapsulated lycopene in a powder form, using either spray-drying or molecular inclusion with beta -cyclodextrin ( beta -CD) followed by freeze-drying. The encapsulation efficiency using spray-drying ranged from 94 to 96%, with an average yield of 51%, with microcapsules showing superficial indentations and lack of cracks and breakages. Lycopene- beta -CD complexes were only formed at a molar ratio of 1:4, and irregular structures of different sizes that eventually formed aggregates, similar to those of beta -CD, were observed after freeze-drying. About 50% of the initial lycopene did not form complexes with beta -CD. Lycopene purity increased from 96.4 to 98.1% after spray-drying, whereas lycopene purity decreased from 97.7 to 91.3% after complex formation and freeze-drying. Both the drying processes yielded pale-pink, dry, free-flowing powders.

The study investigated the effect of a combination of drying techniques: convection, microwave, and freeze-drying, on selected physical properties of the dried material (carrot) to determine which form of hybrid drying is the best alternative to traditional freeze-drying. Carrots were dried by freeze-drying, convection-drying, and microwave-drying as well as in hybrid methods: freeze-drying-convection, freeze-drying–microwave as well as convection–freeze-drying or microwave–freeze-drying. The color, porosity, shrinkage, water activity, dry matter content, and internal structure of carrots dried using various methods were examined. The dried samples obtained with the hybrid method were compared with those obtained with a single drying technique. Freeze-drying–microwave-drying (F-M) as an alternative drying method for freeze-drying allowed us to obtain dried material with a water activity similar (p < 0.05) to that of freeze-dried samples, at the same time reducing the duration of the process by 20 h. The combination of convection-drying methods with freeze-drying (K-F) and microwave-drying with freeze-drying (M-F) allowed us to obtain dried material with lower shrinkage than in the case of convection (K) or microwave (M) drying.

Freeze-drying has been implicated as a factor causing soil aggregate breakdown on the Canadian Prairies and northern Great Plains. Aggregates of a Dark Brown Chernozemic clay loam soil sampled in October 1993 and January and April 1994 were subjected to repeated cycles of wetting (to 0.1, 0.2 and 0.3 kg kg−1 water contents) freezing, and freeze-drying under laboratory conditions. The October 1993 samples showed less disruption when initially exposed to freeze-drying cycles compared to samples taken in January and April 1994. Using regression analysis, we predicted that 31 freeze-dry cycles were required for the 0.1 kg kg−1 water content aggregates to reach 60% erodible fraction (EF, % aggregates <0.86 mm), 9 cycles for the 0.2 kg kg−1 aggregates and 2 for 0.3 kg kg−1 aggregates. In a field study, conducted over the 1994–1995 winter on a similar clay loam soil, we estimated the number of freeze-drying cycles using large vapour pressure (VPL) and small vapour pressure (VPS) gradients between the soil surface (which had a mean winter water content of ~0.1 kg kg−1) and the atmosphere. With solar energy adjustments, we predicted that the number of freeze-dry cycles required for the soil to reach 60% EF was 60 for VPL and 37 for VPS conditions. The latter number was similar to the 31 cycles predicted in the laboratory study of aggregates at 0.1 water content. Our results demonstrate that freeze-drying is an important overwinter process in the breakdown of soil aggregates and hence wind erosion risk in the Canadian prairie region. Key words: Freeze-drying, wind erosion, erodible fraction

Freeze-drying is an important processing unit operation in food powder production. It offers dehydrated products with extended shelf life and high quality. Unfortunately, food quality attributes and grinding characteristics are affected significantly during the drying process due to the glass transition temperature (during drying operation) and stress generated (during grinding operation) in the food structure. However, it has been successfully applied to several biological materials ranging from animal products to plants products owning to its specific advantages. Recently, the market demands for freeze-dried and ground food products such as spices, vegetables, and fruits are on the increase. In this study, the effect of the freeze-drying process on quality attributes, such as structural changes, the influence of glass transition during grinding, together with the effect on grinding efficiency in terms of energy requirement, grinding yield, and morphological changes in the powder as a result of temperature, drying time were discussed. An overview of models for drying kinetics for freeze-dried food sample, and grinding characteristics developed to optimize the drying processes, and a prediction of the grinding characteristics are also provided. Some limitations of the drying process during grinding are also discussed together with innovative methods to improve the drying and grinding processes.

AbstractTransforming liquid smoke to powder form can provide convenience for use and storage. Liquid smoke was prepared by fast pyrolysis technology using a fluidised bed and converted to smoke powder by spray-drying or freeze-drying processes. Both drying processes effectively retained the bioactive compounds in the powder encapsulates with retention efficiencies up to 80%. The bioactive capacities were approximately two times higher than liquid smoke. Spray-drying did not induce thermal damage to the bioactive compounds, and the dominant compounds were retained in the powders. Gas chromatography–mass spectrometry and principal component analysis indicated that the chemical composition was not significantly changed after both drying methods, but small molecular carbonyls, furans and phenols were partially lost. The spray-dried particles had a spherical shape, while freeze-dried particles had irregular shapes because of different powder preparation methods. The particle size of spray-dried powders was in the range of 6.3 to 6.9 µm, while the value for freeze-dried powders was decreased from 580.4 to 134.7 µm by increasing the maltodextrin concentration. The freeze-dried powders performed better in terms of flowability and cohesiveness because of their relatively high density and large particle size. This study revealed that both encapsulation methods could efficiently prepare smoke powder. Spray-drying process would be suitable for large-scale production, while freeze-drying could be used to optimize the encapsulation efficiency of bioactive compounds.

The freeze-drying rate is essentially low, since it is controlled by internal moisture diffusion. In addition, the application of vacuum and low temperature during the process presents a higher energy demand. Therefore, the search for new strategies to improve water mobility during freeze-drying constitutes a topic of relevant research. The aim of this work was to evaluate the use of power ultrasound to improve freeze-drying characteristics of açai, quantifying the influence of the applied power on both the drying and rehydration kinetics of the material. Açai (Euterpe oleracea Martius) samples were sonicated with two different frequency levels, 20 kHz and 40 kHz, and two sonication times, 3 min and 10 min. Page’s equation considering internal and external resistances to mass transfer provided a good fit of freeze-drying kinetics, while the Peleg’s equation was found to be suitable for describing the rehydration kinetics of freeze-dried açai. Pretreatment of açai with ultrasound waves was not effective. Ultrasound-induced structural disruption in the açai skin hindered the mass transfer during both freeze-drying and rehydration processes.

Microencapsulation is widely used to minimize the oxidation of fish oil products. This study compared the effects of different drying methods, for example, spray drying (SD), freeze drying (FD), and spray freeze drying (SFD) on the microencapsulation of fish oil. Spray drying (SD) is the most common method for producing fish oil microcapsules, and it has low operation cost and short processing time, while the product yield and quality are poor. Freeze drying (FD) can be used to produce oil microcapsules with high quality, but it takes long time and high overall cost for drying. Spray freeze drying (SFD) is a new method for the preparation of microcapsules, which combines the SD and FD processes to obtain high quality powder. The yield of powder reached 95.07% along with porous structure by SFD. The stability and slow-release property of SFD products were better than those of SD and FD, which showed that SFD improved product storage stability and potential digestibility.

Abstract The effects of various drying techniques, such as air, oven, freeze, and spray drying, on the morphological, thermal, and structural behaviors of two different nanofibrillated cellulose (NFC) materials were investigated. Field emission scanning electron microscopy (FE-SEM) observations indicated an interlaced network formation of predominantly in-plane fibrillar orientation for air- and oven-dried samples, while freeze and spray drying resulted in the formation of coarse and fine powder fractions. Comparison of redispersed powders obtained by freeze and spray drying indicated that aggregation phenomena are significantly reduced in freeze-dried specimens. Rheological and sedimentation analysis revealed that the freeze-dried NFC powders are more stable than spray-dried NFC powders when redispersed in water. Aggressive dehydration processes, such as freezing or heating, significantly influence the thermal stability of the dried cellulose samples. On the contrary, the crystallinity properties of dried NFC materials are very similar regardless of the drying treatment.

Presently, over 300 proteins or peptide based therapeutic medicines have been approved by the FDA owing to advances in protein engineering and technology. However, majority of these protein-based medications are unstable or have limited shelf life when in aqueous form. During pre-formulation and manufacturing, various technological processes including mixing, dissolving, filling (through pipes) can produce strong mechanical stresses on proteins. These stresses may cause the protein molecule to unfold, denature or aggregate. To improve stability upon formulation, they may be manufactured as freeze dried cakes that requires reconstitution with a buffer or water prior to administration. Although it has been successful in improving the stability of protein-based formulations, the freeze drying process itself also contributes to protein aggregation. This process introduces other stresses such as freezing, thawing and drying. In addition to these stresses, the agitation processes used during reconstitution may also destabilize the protein’s native structure. Two key processes used in preparation of protein based formulations were studied in this work; mechanical agitation and freeze drying. The aim of this project was to explore the aggregation of proteins that occur due to the various technological processes typical in the production of protein based formulations. The project has two parts that relates to liquid and solid formulations. In the first part, the effect of different methods of mechanical agitations on BSA protein was investigated. In the second part, the focus was on the effect of formulation (i.e. the application of amino acids) on aggregation of protein (BSA) in freeze dried formulations. Arginine and lysine were added individually into protein-based freeze-dried formulation to study their potential of improving the stability of the proteins during manufacturing, storage and reconstitution. In the formulation development, additional excipients were added to prevent moisture uptake due to the hygroscopic properties of the amino acids and to provide lyo- and cryo- protection for the protein molecule during freeze drying. Without further purification, BSA solutions prepared by using sonication, low shear rotor mixer or high shear tube/pipe mixing were studied using dynamic light scattering (DLS). Thioflavin T assay and turbidimetry analysis were used as complementary studies. In protein-based freeze dried formulations, at accelerated storage conditions, the presence of aggregates were studied in samples containing arginine or lysine using ThT assay and turbidimetry analysis. Characterisation of the freeze dried cakes was performed relative to their moisture sorption, cake shrinkage, mechanical properties and morphology using various analytical techniques. iv In the BSA solution studies, particle size analysis indicated two distributions for non-agitated BSA solution that corresponds to the average particle sizes of BSA molecules and their aggregates. Under mechanical stresses (all types), the intensity of distribution centered ≈ 7.8 nm reduces and broadens as the agitation time increases, indicating a reduction in the amount of “free” BSA macromolecules. The second distribution, as a result of increasing agitation time or shear intensity, reveals a significant shift towards larger sizes, or even splits into two particle size populations. These particle size growths reflect the formation of aggregates due to intensive collisions and, as a result, partial unfolding followed by hydrophobic interactions of exposed non-polar amino acids. UV spectra showed that aggregation in both low shear and mechanical vibration agitations were lower compared to the high shear stress. When compared to non-agitated BSA solution, ThT assay recorded ≈15 times higher fluorescence emission from the high shear samples, ≈2 times fluorescence emission from low shear and ≈6 times fluorescence emission from mechanical vibrations. Thus all the three agitation methods showed a good correlation between the results. The second part of this project was performed in three stages. In the initial 2 stages, 2- and 3-excipients component system were investigated to develop an optimal preliminary formulations which will be used in the final protein based 4-components formulations. From the 1st stage (ArgHCl/LysHCl + sugar/polyol), among 4 tested excipients (polyol and sugar), mannitol was observed to have resisted moisture uptake by the highly hygroscopic ArgHCl/LysHCl amino acids. However, mannitol is considered a good cryoprotector but has poor lyoprotection properties. Therefore, in the following stage, a 3rd excipient (in a 3-excipients component system) sucrose or trehalose, was introduced into the formulation. The formulation was made up of 20% ArgHCl (LysHCl), and various ratios of mannitol and sugar were explored. The criteria for selecting the best systems were based on ideal physicochemical properties i.e. moisture uptake, shrinkage, mechanical properties, matrix structure and appearance, and thermal properties. The final stage was the formulation of a 4-components system comprising the three excipients and combinations selected from the stage 2 studies, and the addition of BSA as the model protein. To study aggregation in this system, a freeze dried 4-components excipient/protein system was reconstituted and incubated at accelerated storage conditions over time. Fluorescence spectroscopy and turbidimetry were used to study aggregation of proteins, moisture uptake kinetics with gravimetric balance, and thermal analytical techniques were used to characterise the freeze dried cakes with and without BSA protein. This study represented a systematic analysis of aggregation of proteins in both liquid and solid formulations. Some of the novel aspects of this study include: v 1. The new experimental results obtained for aggregation of proteins in solution subjected to mechanical agitations. The high shear stress created by syringe agitation, simulated the real situation in post manufacturing process during filling through narrow pipes, and has been shown here to strongly affect the aggregation of protein macromolecules. 2. The development of a methodical approach for optimization of multi component (up to 4 excipients) protein based formulations. 3. The unexpected non-linear behavior of the physicochemical properties of the 3-excipients component system as a function of composition. To the best of my knowledge, this novel aspect has not been previously reported in literature. 4. Application of amino acid in protein based formulations has shown the inhibition of aggregation of BSA, with the highest effect observed with ArgHCl. The results of this study coincide with the conclusions published previously for aggregation of proteins in solution.

Tesis por compendio
[ES] La industria alimentaria ha mostrado un enorme interés por desarrollar nuevos productos a base de fruta con el fin de satisfacer la demanda saludable y sostenible de productos alimentarios de los consumidores. En este sentido, un puré de naranja liofilizado podría representar una opción viable. La liofilización del puré da lugar a una torta que puede consumirse directamente como snack, o puede triturarse para obtener un polvo que puede utilizarse para una amplia gama de aplicaciones. Una optimización adecuada de las condiciones de liofilización podría ayudar a reducir su duración sin afectar a las características del producto final. Sin embargo, los alimentos deshidratados pueden presentar problemas de colapso estructural relacionados con su baja temperatura de transición vítrea. En este sentido, una técnica frecuente para la estabilización de estos productos deshidratados es la incorporación de biopolímeros de alto peso molecular. El objetivo de esta Tesis ha sido el diseño del proceso de liofilización para la obtención de un snack de naranja. Para ello se ha estudiado la influencia de diferentes combinaciones de biopolímeros en la estabilidad física del puré de naranja liofilizado (snack de naranja) y en la bioaccesibilidad in vitro de sus compuestos bioactivos. Asimismo, se ha evaluado su efecto en las propiedades de flujo en aire y de rehidratación del polvo de naranja. Se ha trabajado con diferentes combinaciones de goma Arábiga, maltodextrina, almidón sustituido por grupos octenil succínico, almidón nativo de maíz, fibras de guisante y de bambú. Los resultados mostraron la necesidad de incorporar estos biopolímeros para aumentar la actividad de agua crítica y el contenido de agua crítico para la transición vítrea, el cual se ha relacionado con la pérdida de la textura del snack. Si bien ninguna de las mezclas de biopolímeros fue mejor que las otras en higroscopicidad, carácter anti-plastificante, color y propiedades mecánicas del snack, la mezcla GA con FB fue la que mejoró la bioaccesibilidad de la vitamina C (VC) y de los compuestos fenólicos totales (TP). Además, esta misma combinación fue la que ofreció uno de los tiempos de mojado más cortos y una menor viscosidad del producto rehidratado, deseado para un producto tipo zumo. Por otra parte, se ha estudiado el impacto de las condiciones de liofilización en el consumo de energía del proceso y en la calidad del snack formulado con GA y FB. Las variables del proceso consideradas han sido la velocidad de congelación (convencional y abatidor), la temperatura de bandeja (30, 40, 50 ºC) y presión de trabajo (5, 100 Pa) durante el secado. Menor presión y mayor temperatura promovieron un ligero mayor secado de las muestras, obteniendo un producto más crujiente, con un color amarillo menos intenso, mejor preservación de VC y ß-caroteno (BC), y una reducción significativa, de hasta un 75%, en el consumo de energía total durante el secado, debido a la reducción del tiempo del proceso. La velocidad de congelación no tuvo impacto significativo sobre ninguna de las propiedades evaluadas. Por tanto, las condiciones recomendadas para el secado por liofilización son 5 Pa de presión y 50 ºC como temperatura de bandeja. Por último, se evaluó la estabilidad física y de los compuestos bioactivos y actividad antioxidante del snack almacenado en bolsas zip, a 4 y 20 ºC, durante 6 meses, simulando condiciones domésticas de almacenamiento. Como resultado, la muestra ganó cierta humedad, con la consecuente pérdida en porosidad y carácter crujiente a partir de los 2 meses. Asimismo, la luminosidad del snack almacenado a 20 ºC disminuyó pasados 2 meses, probablemente debido a las reacciones de pardeamiento, que incluyen la degradación de la VC (20%). BC sufrió una gran disminución, desde el inicio del almacenamiento y más cuanto mayor fue la temperatura. Por lo tanto, para este producto se recomienda un almacenamiento en refrigeración para una mejor preservación de los compuestos bioactivos.
[CA] La indústria alimentària ha mostrat un enorme interés per desenvolupar nous productes a base de fruita amb la finalitat de satisfer la demanda saludable i sostenible de productes alimentaris dels consumidors. En aquest sentit, un puré de taronja liofilitzat podria representar una opció viable. La liofilització del puré dona lloc a una coca que pot consumir-se directament com a snack, o pot triturar-se per a obtindre una pols que pot utilitzar-se per a una àmplia gamma d'aplicacions. Una optimització adequada de les condicions de liofilització podria ajudar a reduir la seua duració sense afectar les característiques del producte final. No obstant això, els aliments deshidratats poden presentar problemes de col·lapse estructural relacionats amb la seua baixa temperatura de transició vítria. En aquest sentit, una tècnica freqüent per a l'estabilització d'aquests productes deshidratats és la incorporació de biopolímers d'alt pes molecular. L'objectiu d'aquesta Tesi ha sigut el disseny del procés de liofilització per a l'obtenció d'un snack de taronja. Per a això s'ha estudiat la influència de diferents combinacions de biopolímers en l'estabilitat física del puré de taronja liofilitzat (snack de taronja) i en la bioaccessibilitat in vitro dels seus compostos bioactius. Així mateix, s'ha avaluat el seu efecte en les propietats de flux en aire i de rehidratació de la pols de taronja. S'ha treballat amb diferents combinacions de goma Aràbiga, maltodextrina, midó substituït per grups octenil succínic, midó natiu de dacsa, fibres de pésol i de bambú. Els resultats van mostrar la necessitat d'incorporar aquests biopolímers per a augmentar l'activitat d'aigua crítica i el contingut d'aigua crític per a la transició vítria, el qual s'ha relacionat amb la pèrdua de la textura del snack. Si bé cap de les mescles de biopolímers va ser millor que les altres en higroscopicitat, caràcter anti-plastificant, color i propietats mecàniques del snack, la mescla GA amb FB va ser la que va millorar la bioaccessibilitat de la vitamina C (VC) i dels compostos fenòlics totals (TP). A més, aquesta mateixa combinació va ser la que va oferir un dels temps de mullat més curts i una menor viscositat del producte rehidratat, desitjat per a un producte tipus suc. D'altra banda, s'ha estudiat l'impacte de les condicions de liofilització en el consum d'energia del procés i en la qualitat del snack formulat amb GA i FB. Les variables del procés considerades han sigut la velocitat de congelació (convencional i abatedor), la temperatura de safata (30, 40, 50 °C) i pressió de treball (5, 100 Pa) durant l'assecat. Menor pressió i major temperatura van promoure un lleuger major assecat de les mostres, obtenint un producte més cruixent, amb un color groc menys intens, millor preservació de VC i ß-caroté (BC), i una reducció significativa, de fins a un 75%, en el consum d'energia total durant l'assecat, a causa de la reducció del temps del procés. La velocitat de congelació no va tindre impacte significatiu sobre cap de les propietats avaluades. Per tant, les condicions recomanades per a l'assecat per liofilització són 5 Pa de pressió i 50 °C com a temperatura de safata. Finalment, es va avaluar l'estabilitat física i dels compostos bioactius i activitat antioxidant del snack emmagatzemat en bosses zip, a 4 i 20 °C, durant 6 mesos, simulant condicions domèstiques d'emmagatzematge. Com a resultat, la mostra va guanyar una certa humitat, amb la conseqüent pèrdua en porositat i caràcter cruixent a partir dels 2 mesos. Així mateix, la lluminositat del snack emmagatzemat a 20 °C va disminuir passats 2 mesos, probablement a causa de les reaccions de enfosquiment, que inclouen la degradació de la VC (20%). BC va patir una gran disminució, des de l'inici de l'emmagatzematge i més com més gran va ser la temperatura. Per tant, per a aquest producte es recomana un emmagatzematge en refrigeració per a una millor preservació dels compostos bioactius.
[EN] Food industries have showed a huge interest in developing new fruit-based products to satisfy the healthy and sustainable demand of food products by consumers. In this sense, offering a freeze-dried orange puree could represent a feasible option. Freeze-drying the puree results in a cake that can be consumed directly as a snack, or it can be crushed to obtain a powder that can be used for a wide range of applications. A suitable optimisation of the freeze-drying conditions could help to reduce its duration without affecting the characteristics of the final product. However, dehydrated foods may present problems of structural collapse related to its low glass transition temperature. In this sense, an approach for the stabilisation of dehydrated products is the incorporation of high molecular weight biopolymers. The aim of this Thesis has been the design of the freeze-drying process to obtain an orange snack. The influence of different combinations of biopolymers on the physical stability of the freeze-dried orange puree (orange snack) and on the in vitro bioaccessibility of its bioactive compounds has been studied. Their effect on the air flow and rehydration properties of an orange powder obtained after crushing the snack has also been evaluated. Different combinations of gum Arabic, maltodextrin, starch substituted with octenyl succinic groups, native corn starch, pea and bamboo fibres were used. The results showed the need to incorporate these biopolymers to increase the critical water activity and the critical water content for the glass transition, which has been related to the loss of snack texture. Although none of the biopolymer combinations was better than the others in terms of hygroscopicity, anti-plasticising character, colour, and mechanical properties of the snack, the GA mixed with FB was the one that improved the bioaccessibility of vitamin C (VC) and total phenolic compounds (TP). This same combination offered the shortest wetting times and a lower viscosity of the rehydrated product, which is desirable for a juice-type product. Also, the impact of the freeze-drying conditions on the energy consumption of the process and on the quality of the snack formulated with GA and FB has been studied. The process variables considered were freezing rate (conventional and blast freezer), shelf temperature (30, 40, 50 ºC) and working pressure (5, 100 Pa) during drying. Lower pressure and higher temperature promoted a slightly higher drying of the samples, which resulted in a crispier product, as well as a less intense yellow colour. However, at the sensory level, there was no significant preference for any of the samples processed under the different conditions studied. In addition, VC and ß-carotene (BC) were better preserved under these conditions, conditions which significantly reduced, up to 75%, the total energy consumption during drying, due to the reduction of the process time. The freezing rate had no significant impact on any of the properties evaluated. Therefore, the recommended conditions for freeze-drying to maximise the preservation of bioactive compounds, with a lower energy consumption, while providing a snack perceived as a crispy product by consumers, are 5 Pa pressure and 50 ºC as shelf temperature. Finally, the physical stability and the stability of bioactive compounds and antioxidant activity of the snack stored in zip bags at 4 and 20 ºC for 6 months, simulating domestic storage conditions, was evaluated. As a result, a certain moisture gain of the sample was observed, with a consequent loss in porosity and crispness after 2 months. Also, the luminosity of the snack stored at 20°C decreased after 2 months, probably due to browning reactions, including degradation of VC (20%). BC suffered a large decrease, from the beginning of storage and more so the higher the temperature. Therefore, refrigerated storage is recommended for better preservation of the bioactive compounds of this product.
Silva Espinoza, MA. (2021). Design of the process of obtaining a freeze-dried orange puree. Formulation, freeze-drying variables, and storage conditions [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/170354
TESIS
Compendio

This study aims to validate and develop applications for a novel impedance-based process analytical technology for monitoring the attributes of the product during the entire freeze-drying process (from pre-freezing and annealing to primary and then secondary drying). This measurement approach involves the application of foil electrodes, mounted externally to a conventional glass freeze-drying vial, and coupled to a high-impedance analyser. The location of the electrodes on the outside, rather than the inside of the vial, leads to a description of the technology as a through-vial impedance spectroscopy (TV-IS) technique. The principle observation from this approach is the interfacial-polarization process arising from the composite impedance of the glass wall and product interface. For a conventional glass vial (of wall thickness ~ 1 mm and cross sectional diameter ~ 22 mm) it was shown that the process is manifest within the frequency range 101 to 106 Hz, as a single, broad band peak which spans 2-3 decades of the imaginary part spectrum. Features of the interfacial-relaxation process, characterised by the peak amplitude, C″Peak, and peak frequency, fpeak, of the imaginary capacitance spectra and the equivalent circuit elements that model the impedance spectra (i.e. the solution resistance (R) and solution capacitance (C) were monitored along with the product temperature data during the cycle(s), for a variety of surrogate formulations comprising lactose, sucrose, mannitol or maltodextrin solutions, during the freezing, re-heating, annealing and primary drying stages of freeze drying). It was shown that the parameters, fpeak and R, are strongly coupled to each other and change as a function of the temperature of the solution and its phase state, whereas C″Peak is strongly coupled to the amount of ice that remains during the drying process. Both log fpeak and log R have a linear dependence on the temperature of the solution, provided there was no phase change in the solution. The crystallization process (ice onset, solidification and equilibration to shelf temperature) is characterized well by both log fpeak and log R, whereas the parameter R demonstrates most clearly the formation of eutectic crystallization during freezing. In contrast it was the parameter C which was most sensitive to the detection of the glass transition during re-heating. During primary drying, it was shown that C″peak, is dependent on the amount of ice remaining and therefore provides a convenient assessment of the rate of drying and primary drying end point. The impedance changes during annealing provide a mechanistic basis for the modifications in ice structure which result directly in the observed decrease in primary drying times. The principal observation on annealing of a 10% w/v solution of maltodextrin, was the minimal changes in the glass transition (recorded at ~−16 °C) during the re-heating and cooling step (post-annealing). This result alone appears to indicate that a maximum freeze concentration was achieved during first freezing with no further ice being formed on annealing. The phenomenon of devitrification (and the production of more ice, and hence larger ice crystals) was therefore discounted as the mechanism by which annealing impacts the drying time. Having excluded devitrification from the mechanism of annealing enhanced drying, it was then possible to conclude that the decrease in the electrical resistance (that was observed during the annealing hold time) must necessarily result from the simplified structure of the unfrozen fraction and the improved connectivity of ice crystals that may be the consequence of Ostwald ripening. The application of through vial impedance measurement approach provides a non-invasive, real time monitoring of critical process parameters which subsequently leads to an improved understanding of the mechanisms and effects of different parameters, providing a reliable basis for process optimization, along with improved risk management to ensure optimum quality of the formulation and optimization of the freeze drying process.

Orientador: Luis Vitor Silva do Sacramento
Banca: Marcia Luzia Rizzatto
Banca: Juliana Cristina Bassan
Resumo: Objetivo: quantificar teores de compostos fenólicos totais, carotenoides totais, ácido ascórbico e flavonoides totais, bem como avaliar a atividade antioxidante, pelos métodos de sequestro do radical DPPH e ABTS+, de duas espécies de pimentas: Dedo-de-Moça (Capsicum baccatum) e Biquinho (Capsicum chinense) em função de dois processos de manufatura (pasteurização e cozimento). Métodos: foram obtidas amostras de pimentas biquinho e dedo-de-moça em mercados de Matão-SP e Araraquara-SP, formando uma amostra composta de cada espécie, cuja homogeneidade foi obtida após quarteamento das amostras menores. Foram realizados os processos térmicos de cozimento (100ºC/5min) e pasteurização (65ºC/30min). Após resfriamento, as amostras foram liofilizadas (48h/-60ºC), realizando-se as extrações de acordo com as metodologias utilizadas. Realizaram-se análises de quantificação dos compostos fenólicos totais, flavonoides totais, vitamina C, carotenoides totais e capacidade antioxidante por DPPH˙ e ABTS⁺. Resultados: os processamentos térmicos não afetaram os teores de fenólicos totais em Capsicum chinense (pimenta biquinho); no entanto, para Capsicum baccatum (pimenta dedo-de-moça) houve diminuição no teor de fenólicos totais frente a pasteurização. Para o teor de flavonoides totais em ambas as variedades o processo de pasteurização demonstrou perdas significativas. A capacidade antioxidante em ambas as espécies foi favorecida devido ao cozimento, e o processo de pasteurização contrariamente de... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Objective: to quantify total phenolic compounds, total carotenoids, ascorbic acid and total flavonoids, as well as to evaluate the antioxidant activity, by the methods of scavenging of the DPPH˙ and Abts˙⁺ radical, of two species of peppers: finger-of-the-girl (Capsicum baccatum) and Biquinho (Capsicum chinense) as a function of two manufacturing processes (pasteurization and baking). Methods: samples of pout and finger-of-the-girl peppers were collected in the cities of Matão-SP and Araraquara-SP, composing a homogeneous sample of each pepper, the method of Quarteamente was performed in each of the varieties studied, so as to obtain a Best sampling. The thermal cooking processes (100ºC/5min) and pasteurization (65ºC/30min) were performed after the samples were freeze-dried (48h/ -20 º C). Aqueous and ethanolic extractions were performed to meet the methodologies used. Analysis of quantification of total phenolic compounds, total flavonoids, vitamin C, total carotenoids and antioxidant capacity by DPPH˙ and ABTS˙⁺ were performed. Results: the thermal processes did not affect the total phenolic contents in Capsicum chinense; however, for Capsicum baccatum (finger pepper) there was a decrease in the total phenolics content against pasteurization. For the total flavonoid content in both varieties the pasteurization process is the only one that has had significant losses. For the antioxidant capacity for both varieties the cooking process causes an increase of this capacity to oc... (Complete abstract click electronic access below)
Mestre

La présente étude concerne l'évaluation de l'impact du séchage par air chaud (HAD), lyophilisation (FD) et " swell drying " (SD), procédé couplant le séchage par air chaud avec le procédé de Détente Instantanée Contrôlée (DIC), sur les fraises (Fragaria var. Camarosa). Il s'agit de comparer et de contraster les performances des procédés et la qualité du produit fini séché en termes des cinétiques de séchage et de réhydratation, de contenus en molécules bioactives et activité antioxydante, et des paramètres caractéristiques de texture comme croquant et croustillant. Les résultats obtenus ont montré que le procédé de SD comparé aux procédés classiques de séchage et de lyophilisation, réduit d'une façon importante le temps de séchage ainsi que les coûts d'opération. D'autre part, SD conserve la qualité nutritionnelle des fraises en gardant leur contenu en composants bioactifs et en augmentant leur disponibilité. De plus, une corrélation importante entre la capacité antioxydante et le contenu total d'anthocyanes a été établie. D'autre part, les fraises séchées par SD ont montré une très intéressante macro et micro-structure. Les produits ont présenté une haute expansion et une croustillance significative due au phénomène de micro-alvéolation par décompression instantanée par DIC. D'ailleurs, il a été possible de mesurer les caractéristiques instrumentales de croustillance/croquance des échantillons finaux séchés. Grâce à la possibilité de modifier, contrôler et optimiser les paramètres opératoires du procédé DIC, il a été possible d'obtenir un produit du type " snack " croustillant avec une très haute valeur nutritionnelle.

L'obiettivo principale di questa tesi è stato quello di analizzare e riprogettare la logica di funzionamento delle macchine di carico / scarico di flaconi da un sistema di liofilizzazione. L’elaborato nasce durante il periodo di tirocinio trascorso all’interno di IMA Life, azienda del Bolognese che si occupa di realizzare linee di macchine automatiche per il confezionamento di prodotti farmaceutici liofilizzati in ambiente asettico. Dopo uno studio iniziale del funzionamento delle macchine e del processo di liofilizzazione, vengono descritte le applicazioni empiriche che sono state sviluppate, analizzando nel dettaglio le nuove funzioni e riportando l’intera fase di reingegnerizzazione del motion della macchina di carico / scarico compatta, in cui è stato introdotto l’utilizzo di camme elettriche per la sincronizzazione degli assi.

[EN] Dehydration is one of the most commonly used operations in the food industry, and although its aim is to extend the shelf life of foods by reducing their water activity, it could also involve quality degradation. Vacuum freeze-drying may be considered one of the best drying methods for the purposes of preserving the organoleptic and nutritional properties of the fresh product, but its high processing cost limits its use to high value-added products. Convective drying at low temperatures could be considered an alternative means of obtaining high quality products at lower cost. However, the low drying rates at low temperatures (T<20ºC) and atmospheric pressure makes its industrial application difficult. In this sense, high intensity ultrasound (US) has been used to intensify mass transfer phenomena in food processing. It could be of great interest to apply US in low temperature drying because the ultrasonic effects are mainly mechanical (non-thermal). In this context, the main aim of this thesis was to determine the feasibility of US application in low temperature drying, addressing the effect on both the drying kinetics and the quality of the obtained products. For this purpose, apple, eggplant and cod samples were dried at different temperatures (-10, -5, 0, 5 and 10ºC), air velocities (1, 2, 4 and 6 m/s) and applying different ultrasonic powers (0, 25, 50 and 75 W). Diffusion models were used to describe the drying kinetics and to quantify the influence of the process variables. Moreover, different quality parameters (rehydration capacity, texture, antioxidant capacity...) of the dried products were determined. The application of US significantly (p<0.05) shortened the drying time under every drying condition and with each product tested, reducing the drying time by up to 80, 87 and 60% in apple, eggplant and cod samples, respectively. Thus, the greater the ultrasonic power applied, the shorter the drying time. The drying temperature and air velocity influenced the US efficiency and the best performance was achieved at the lowest drying temperatures and air velocities. In general terms, the diffusion model adequately fitted the drying kinetics of the three products tested. Although, in the case of US assisted drying, a better fit of the experimental data was obtained when the external resistance to water transfer was considered. The URIF (Uniformly Retreating Ice Front) model successfully fitted the atmospheric freeze drying kinetics. This model was validated under different experimental conditions. As regards the effect of the process variables on the quality parameters, in overall terms, it was observed that neither the US application nor the air velocity greatly influenced the quality of the obtained products. However, the temperature affected some quality parameters, such as rehydration capacity and color, especially at temperatures below the samples' freezing point. Finally, as a technology employed for the purposes of obtaining porous food matrices to be used further in the development of functional foods, US-assisted low temperature drying could be considered of great potential. Thus, from dried apple samples impregnated with olive leaf extract, it was observed that US application during drying did not significantly (p<0.05) influence the infusion capacity but did increase the antioxidant capacity of the final product. Therefore, high intensity ultrasound could be considered an interesting technology with which to speed-up the low temperature drying processes without greatly affecting the quality of the dried product.
[ES] La deshidratación, una de las operaciones más utilizadas en la industria agroalimentaria, mejora la estabilidad de los alimentos al reducir su actividad de agua, aunque puede afectar a su calidad. Entre las diferentes técnicas de secado existentes, destaca la liofilización a vacío por ser una de las que mejor conservan las propiedades organolépticas y nutricionales de los productos. Sin embargo, esta operación resulta muy cara y sólo se utiliza en productos de alto valor añadido. El secado convectivo a baja temperatura (T<20ºC) representa una alternativa para obtener productos de alta calidad a menor coste aunque su baja velocidad de proceso dificulta su implementación a nivel industrial. En este sentido, los ultrasonidos de alta intensidad (US) se han aplicado para intensificar operaciones de transferencia de materia en diferentes procesos agroalimentarios. Sus efectos son principalmente mecánicos (no térmicos), por lo que su uso en el secado a baja temperatura resulta altamente interesante. En este contexto, el objetivo general de la presente tesis doctoral fue determinar la viabilidad de la aplicación de US en procesos de secado a baja temperatura, abordando tanto su efecto en la cinética como en la calidad de los productos obtenidos. Para ello, se deshidrataron muestras de manzana, berenjena y bacalao a diferentes temperaturas (-10, -5, 0, 5 y 10ºC) y velocidades de aire (1, 2, 4 y 6 m/s) y aplicando diferentes niveles de potencia acústica (0, 25, 50 y 75 W). Se utilizaron modelos difusivos para describir las cinéticas de secado y cuantificar la influencia de las variables de proceso. Además, se determinaron diferentes parámetros de calidad (capacidad de rehidratación, textura, capacidad antioxidante,¿) de los productos deshidratados. La aplicación de US permitió reducir significativamente (p<0.05) el tiempo de secado en todas las condiciones experimentales y productos analizados, obteniendo reducciones de tiempo de secado de hasta el 80, 87 y 60% en manzana, berenjena y bacalao, respectivamente. La reducción del tiempo de secado fue mayor cuanto mayor fue la potencia acústica aplicada. La temperatura y la velocidad del aire de secado influyeron en la efectividad de la aplicación de US, siendo mayor el efecto de los US a las temperaturas y velocidades más bajas. En general, la teoría difusional describió adecuadamente la cinética de secado de los tres productos estudiados. En las experiencias con aplicación de US se obtuvo un mejor ajuste a los datos experimentales cuando se consideró la resistencia externa en el modelo. Asimismo, en condiciones de liofilización a presión atmosférica, el modelo URIF (Uniformly Retreating Ice Front) se ajustó adecuadamente a los datos experimentales. Además, este modelo se validó en diferentes condiciones experimentales. Respecto al efecto de las variables de proceso en los parámetros de calidad, en general, se observó que ni la aplicación de US ni la velocidad de aire influyeron de manera importante en la calidad de los productos obtenidos. En cambio, la temperatura afectó de manera relevante a parámetros como la capacidad de rehidratación y el color, especialmente a temperaturas por debajo del punto de congelación de las muestras. Por otro lado, el secado a baja temperatura asistido con US tiene un alto potencial para la obtención de matrices porosas alimentarias para su posterior utilización en el desarrollo de alimentos funcionales. Así, en muestras de manzana deshidratada e impregnada con extracto de hoja de olivo, se observó que la aplicación de US durante el secado no afectó significativamente (p<0.05) a la capacidad de impregnación, pero sí incrementó la capacidad antioxidante del producto obtenido. Por lo tanto, los ultrasonidos de alta intensidad se pueden considerar como una tecnología interesante para acelerar los procesos de secado a baja temperatura sin afectar en gran medida a la calidad del producto obtenido.
[CAT] La deshidratació, una de les operacions més utilitzades en la indústria agroalimentària, millora l'estabilitat dels aliments en reduir la seua activitat d'aigua, encara que pot afectar-ne la qualitat. Entre les diferents tècniques d'assecatge que hi ha, destaca la liofilització al buit per ser una de les que millor conserven les propietats organolèptiques i nutricionals dels productes, però resulta molt cara i només s'utilitza en productes d'alt valor afegit. L'assecatge convectiu a baixa temperatura (T<20ºC) representa una alternativa per a obtenir productes d'alta qualitat a menor cost. No obstant això, la baixa velocitat d'assecatge dificulta la seua implementació a nivell industrial. En aquest sentit, els ultrasons d'alta intensitat (US) s'han aplicat per a intensificar operacions de transferència de matèria en diferents processos agroalimentaris. El seu ús en l'assecatge a baixa temperatura resulta altament interessant pel fet que els seus efectes són principalment mecànics (no tèrmics). En aquest context, l'objectiu general de la present tesi doctoral va ser determinar la viabilitat de l'aplicació d'US en processos d'assecatge a baixa temperatura, abordant tant l'efecte en la cinètica del procés com en la qualitat dels productes obtinguts. Amb aquesta finalitat, es van deshidratar mostres de poma, albergínia i bacallà a diferents temperatures (-10, -5, 0, 5 i 10ºC) i velocitats d'aire (1, 2, 4 i 6 m/s) i aplicant diferents nivells de potència acústica (0, 25, 50 i 75 W). Es van utilitzar models difusius per a descriure les cinètiques de l'assecatge i quantificar la influència de les variables del procés. A més, es van determinar diferents paràmetres de qualitat (capacitat de rehidratació, textura, capacitat antioxidant...) dels productes deshidratats. L'aplicació d'US va permetre reduir significativament (p<0.05) el temps d'assecatge en totes les condicions experimentals i tots els productes analitzats; es van obtenir reduccions de temps de fins al 80%, 87% i 60% en pomes, albergínies i bacallà, respectivament. La reducció del temps d'assecatge va ser més alta com més alta va ser la potència acústica aplicada. La temperatura i la velocitat de l'aire de l'assecatge van influir en l'efectivitat de l'aplicació d'US, sent major l'efecte dels US a les temperatures i velocitats més baixes. En general, la teoria difusional va descriure adequadament la cinètica de l'assecatge dels tres productes estudiats. En les experiències amb aplicació d'US es va obtenir un millor ajust a les dades experimentals quan es va considerar la resistència externa en el model. Així mateix, en condicions de liofilització a pressió atmosfèrica, el model URIF (Uniformly Retreating Ice Front) es va ajustar correctament a les dades experimentals. A més, aquest model es va validar en diferents condicions experimentals. Respecte a l'efecte de les variables del procés en els paràmetres de qualitat, en general, es va observar que ni l'aplicació d'US ni la velocitat de l'aire van influir de manera important en la qualitat dels productes obtinguts. En canvi, la temperatura va afectar de manera rellevant a paràmetres com la capacitat de rehidratació i el color, especialment a temperatures per davall del punt de congelació de les mostres. D'altra banda, l'assecatge a baixa temperatura assistit amb US presenta un alt potencial per a obtenir matrius poroses alimentàries per a la posterior utilització en el desenvolupament d'aliments funcionals. Així, en mostres de poma deshidratada i impregnada amb extracte de fulles d'olivera, es va observar que l'aplicació d'US durant l'assecatge no va afectar significativament (p<0.05) la capacitat d'impregnació, però sí que va incrementar la capacitat antioxidant del producte obtingut. Per tant, els ultrasons d'alta intensitat es poden considerar com una tecnologia interessant per a accelerar els processos d'assecatge a baixa temperatura sense afectar de manera re
Santacatalina Bonet, JV. (2016). Contribución al estudio de la aplicación de ultrasonidos de alta intensidad en procesos de secado a baja temperatura [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61484
TESIS

As the new paradigm of data collection enabled by the advancements in wireless technology and digital electronics, small sensing devices have started to be used in everyday life. These devices are capable of sensing, computing, communicating, and forming a wireless sensor network (WSN) which is necessary to provide sensing services and to monitor various conditions. In addition to WSNs, the idea of Internet of Things (IoT) has started to draw more attention. IoT is defined as an interconnection between identifiable devices within the internet for sensing and monitoring processes. This dissertation addresses the development of wireless network and process control for two challenging IoT applications, namely smart agriculture and industrial lyophilization.

AbstractFrom early dry-ice-based freezers and passive coolers, cryopreservation devices have come a long way. With increasing interest in the field of cryobiology from new scientific applications, the importance of reliable, traceable, and reproducible cold chain devices is sure to increase, ensuring more precise cryopreservation and enabling better post-thaw outcomes, both for the user and for biological samples. As with any cryopreservation process, it is important to optimize each part of the cold chain for each lab’s biological samples, cryocontainers used, and logistical restraints. In this chapter we describe how freezing technology can be used for cryopreservation of cells.

The complexity of biotherapeutics in development continues to increase as our capability in discovery and recombinant technology improves. While safety and efficacy remain the two critical aspects of all therapeutics, ensuring adequate stability is a challenge. Freeze-drying is a commonly-used processing technique to enhance the stability of biotherapeutic products, although the lengthy process time and low energy efficiency have led to the search for, and evaluation of, next-generation drying technologies, including spray freeze-drying and vaccum-foam drying. Both processes result in dosage forms that vary considerably from those produced by lyophilization and possess physical properties that may be deemed superior for their intended applications. Keywords: vacuum-foam drying; spray freeze-drying; lyophilization; biotherapeutics; stabilization

Fruit is a highly valuable food whose consumption should be encouraged. In addition, it would be desirable to design processes and products to channel the surplus and take advantage of the post-harvest losses that limit its fresh marketing. Freeze-drying is a known industrial process that permits the obtaining of high quality products, despite having always been labeled as very expensive. In this study, the economic feasibility of freeze-drying to obtain powdered fruit has been proven, as it yields a product more than twice as cheap as when obtained by spray-drying, recognized for its low cost. Keywords: freeze-drying; spray-drying; economic profitability; production costs

Freeze-drying is a low-pressure, low-temperature condensation pumping process widely used in the manufacture of pharmaceuticals for removal of solvents by sublimation. The performance of a freeze-dryer condenser is largely dependent on the vapor and ice dynamics in the low-pressure environment. The main objective of this work is to develop a modeling and computational framework for analysis of vapor flow and ice dynamics in such freeze-dryer condensers. The direct Simulation Monte Carlo (DSMC) technique is applied to model the relevant physical processes that accompany the vapor flow in the condenser chamber. Low-temperature water vapor and nitrogen molecular model is applied in the DSMC solver SMILE to simulate the bulk vapor transport. The developing ice front on the coils of the condenser is tracked based on the steady state mass flux computed at the nodes of the DSMC surface mesh. Verification of ice accretion simulations has been done by comparison with the solution for analytical free-molecular flow over a circular cylinder. The developed model has also been validated with measurements of ice growth in a laboratory and production scale freeze-dryer using time-lapse imaging. To illustrate the application of the ice accretion algorithm in the area of bio-pharmaceutical freeze-drying, the current work discusses the effect of the condenser geometry and non-condensable gas on non-uniformity of mass flux in a laboratory scale and production scale freeze-dryer condenser. In addition, the simulations are used to predict the ice formation on the coils of the condenser. It was found that in the laboratory scale dryer, the presence of a duct connecting the product chamber and condenser increased non-uniformity by 65% at a sublimation rate of 5 g/hr. The measured ice thickness on the coils of the condenser was found to increase non-linearly. This non-linearity was captured within an accuracy of 1% compared to the measurements towards the end of a 24 hour cycle using an unsteady icing model while that using a steady model was within 14%. In the production dryer, while the steady model predicted the iced coil diameter within an accuracy of 2–5% with respect to the measurements, the unsteady model captured this within an accuracy of 1–6%. The DSMC simulations demonstrate that by augmenting its capabilities with the icing model, it is possible to predict the performance of a freeze-dryer condenser with any arbitrary design.

The citrus industry in general has adapted to tremendous changes in the past 50 years. Consumers’ demand for ready to serve products have challenged processors to adopt new manufacturing techniques and processing skills. The Institute of Food Technologist reported the Top 10 innovations in 1991 as: 10. Ultra high temperature (UHT) short term sterilization of milk and other products 9. Food fortification 8. Understanding of water activity in foods 7. Frozen meals 6. Freeze drying 5. Atmosphere controlled packages for fresh fruits and vegetables 4. Frozen concentrated citrus juices 3. The microwave oven 2. Minimum safe canning processes for vegetables 1. Aseptic processing and packaging Paper published with permission.

Traditionally, sensors to be integrated into a structural component are attached to or mounted on the component after the component has been fabricated. This tends to result in unsecured sensor attachment and/or serious offset between the sensor reading and the actual status of the structure, leading to performance degradation of the host structure. This paper describes a novel extrusion-based additive manufacturing process that has been developed to enable embedment of sensors in ceramic components during the part fabrication. In this process, an aqueous paste of ceramic particles with a very low amount of binder content (< 1 vol%) is extruded through a moving nozzle to build the part layer-by-layer. In the case of sensor embedment, the fabrication process is halted after a certain number of layers have been deposited. The sensors are placed in their predetermined locations, and the remaining layers are deposited until the part fabrication is completed. Because the sensors are embedded during the fabrication process, they are fully integrated with the part and the aforementioned problems of traditional sensor embedment can be eliminated. The sensors used in this study were made of sapphire optical fibers of 125 and 250 micro-meters diameter and can withstand temperatures up to 1600 °C. After the parts were built, two different drying processes (freeze drying and humid drying) were investigated to dry the parts. The dried parts were then sintered to achieve near theoretical density. Scanning electron microscopy was used to observe the embedded sensors and to detect any possible flaws in the part or embedded sensor. Attenuation of the sensors was measured in near-infrared region (1500–1600 nm wavelength) with a tunable laser source. Raman spectroscopy was performed on the samples to measure the residual stresses caused by shrinkage of the part and its slippage on the fibers during sintering and mismatch between the coefficients of thermal expansion of the fiber and host material. Standard test methods were employed to examine the effect of embedded fibers on the strength and hardness of the parts. The result indicated that the sapphire fiber sensors with diameters smaller than 250 micrometers are able to endure the freeform extrusion fabrication process and also the post-processing without compromising the part properties.

Widespread use of advanced process control allows reduction of costs, by reducing drying time and energy consumption. The “control of the freezing stage” (by forced nucleation) also appears to be beneficial to process intensification, as it can impact the product structure and modify the product resistance to mass transfer. An alternative way to increase the drying rate is the use of organic solvents as they can lead to larger solvent crystals, hence lower product resistance to vapor flow. Atmospheric freeze-drying may be a good alternative to vacuum freeze-drying, as a way of increasing process efficiency. A further improvement can be obtained by combining atmospheric or vacuum freeze-drying with new technologies. A further step towards process intensification is given by continuous plants, as this allows a dramatic increase in throughput and product quality uniformity. Keywords: freeze-drying; process intensification; controlled nucleation; continuous process.

The freeze-drying kinetics and the superficial porosity development of grapefruit puree. The impact of biopolymers addition (gum Arabic and bamboo fiber) and to apply (40 ºC) or not shelf temperature (room temperature) was considered. To increase the shelves temperature during freeze-drying allowed to an important drying time reduction and doesn’t supposed a lower porosity related to the collapse development of the structure. Biopolymers do not affect the drying kinetics. From this results, biopolymers addition and to heat at least up to 40 ºC during grapefruit freeze-drying should be recommended. Keywords: freeze-drying; shelf temperature; drying kinetics; image analysis; pore size distribution.

In 3-D scaffold printing, it is critical to find a material that is suitable for your printing method, printing speed, and ease of use. For a biomaterial to best suit solid freeform fabrication techniques, it must: 1) be a low-viscous solution before being printed, 2) involve easily joined on-substrate mixing to form a homogenous gel, 3) have a short solution to gel transition time, 4) be a mechanically strong gel, and 5) have an irreversible gelation processes. Ionic crosslinkable, photocrosslinkable, and thermo-sensitive hydrogels have all been investigated and found to not fully satisfy our every requirement for SFF printing. Ionic crosslinking hydrogels can gel rapidly but tend to involve additional steps for crosslinking like freeze drying, stirring, and shaking, while some form beads, not homogenous gels. Some photocrosslinkable hydrogels would not work due to the concern for viability of cells in initial gel layers receiving copious amount of UV light. Thermosensitive hydrogels meet most of the requirements except that they are reversible gels. A new type of gel that obtains the qualities of a photocrosslinkable and thermosensitive hydrogel satisfies every requirement. A PEG-PLGA-PEG thermosensitive triblock copolymer additionally crosslinked with photocrosslinkable Irgacure 2959 allows for quick transition from solution to gel with a post-processing step utilizing UV light would add additional crosslinks to the gel structure resulting in an irreversible hydrogel.

The aim of the present study was to analyse and compare camel milk powder quality and functional properties produced with spray-drying and freeze-drying techniques. Freeze-drying is recognized as an advanced method for the production of high-quality dried products, but it has been a costly process for production of camel milk powder. Spray-drying and freeze-drying of camel’s milk demonstrated that the nutritional characteristics of this product basically remained unchanged compared to fresh milk. The differences were found analysing flowability, solubility and hygroscopicity of camel milk powder samples obtained with freeze-drying and spray-drying technique. Analysed quality indices of camel milk demonstrated that spray-drying has lower impact on camel milk powder physical properties in comparison with freeze-drying.