Literatura académica sobre el tema "Dimensional. rheological and complexation physico-Chemical properties"

Collagen hydrolysers are three-dimensional polymeric materials with limited cross-linking and high hydrophilicity, having multiple medical applications. The most used collagen is the one extracted from bovine skin, which is now the industrial source of collagen. Due to the outbreak of some threatening diseases such as BSE, transmissible spongiform encephalopathy, foot-and-mouth disease, researchers have sought a safer alternative to collagen. This was the marine resource, which offered multiple opportunities to capitalize on clean sea-water raw material. This paper presents a comparative study of the physico-chemical properties of collagen hydrogels derived from collagen obtained from calf and skin from the Black Sea. Physico-chemical and spectrophotometric analyzes were performed to determine the structure. Studies have been conducted to analyze rheological behavior, antioxidant activity and antimicrobial activity. The total antioxidant capacity (ACL) is higher for collagen mixtures with 40% ethyl alcohol and shows higher values for fish collagen compared to calf collagen. Antimicrobial analysis shows that all collagen hydrogels show antimicrobial activity, both gram-positive (Staphylococcus aureus ATCC 6538P) and gram-negative (Escherichia coli ATCC 10536), which increases with increasing collagen concentrations.

In the field of cultural heritage, the use of natural gels is rising for the application of active agents. Here, two natural polymers are assessed: agar, a pioneer hydrogel for conservation treatments, and chitosan, a rather novel and metal-binding gel. For chitosan, a state-of-the-art based formulation (CS–ItA–LCys) is evaluated as it was reported for silver-complexing properties. It is evaluated whether these polymers can withstand the addition of the chelating compound deferoxamine, which is a bacterial siderophore. This allows for the obtainment of completely bio-sourced gel systems. A Fourier-transformed (FT) infrared spectroscopy characterization is performed, completed with rheological measurements and Cryo-Scanning Electron Microscopy (cryo–SEM) to investigate the physico–chemical properties of the gels, as well as their interaction with deferoxamine. Both polymers are also tested for their inherent complexing ability on silver ions using FT–Raman spectroscopy. A multi-analytical comparison shows different microstructures, in particular, the presence of a thick membrane for chitosan and different mechanical behaviors, with agar being more brittle. Neither hydrogel seems affected by the addition of deferoxamine; this is shown by similar rheological behavior and molecular structures in the presence or absence of the chelator. The intrinsic abilities of the chitosan formulation to make silver complex are demonstrated with the observation of two peaks characteristic of Ag–S and Ag–O bonds. Agar and chitosan are both proven to be reliable gels to act as carriers for bio-based active agents. This paper confirms the potential asset of the chitosan formulation CS–ItA–LCys as a promising gel for the complexation of soluble silver.

Исследование структурообразования продуктов с промежуточной влажностью является важным элементом повышения качественных характеристик молочных консервов в странах, где данная категория пищевых продуктов широко внедрена в рацион питания населения. Определенную структуру консервированных продуктов, в том числе сгущенного молока с сахаром, обуславливают состав и свойства исходного сырья, технологический процесс производства и условия хранения. На всех этапах производства могут возникать пороки различного происхождения, ухудшающие комплексно показатели готового продукта. Для сгущенных молочных консервов с сахаром нерешенной проблемой является кристаллизация лактозы с образованием кристаллов размером более 15 мкм, детектируемых сенсорно. С начала века технологии производства существенно не изменились, для получения однородной консистенции в сгущенное молоко с сахаром принято вносить «затравку» лактозы. При этом не до конца изучено, как на процесс производства сгущенных молочных консервов будет влиять преобразование соотношения белковых компонентов в биосистеме. Одним из перспективных решений формирования заданных органолептических и физико-химических показателей сгущенных молочных систем, включая этап длительного хранения, является замена части традиционного белкового профиля нативными сывороточными белками, их концентратами или гидролизатами. В статье представлены результаты эксперимента по установлению влияния различных соотношений казеина и сывороточных белков на реологические характеристики сгущенного молока с сахаром в широком интервале рН. Самые высокие показатели динамической вязкости зафиксированы для всех экспериментальных образцов при рН 5,6, что объясняется интенсивным взаимодействием белковых частиц в концентрированных системах и гелеобразованием вследствие физико-химического воздействия. В 1,5-2 раза динамическая вязкость повышалась в системах с традиционным соотношением белковых фракций, где источником сывороточных белков выступали концентрат сывороточного белка и сыворотка подсырная сухая, что объясняется более интенсивным комплексообразованием k-казеина и b-лактоглобулина. Однако при доминировании в образце сывороточных белков из этих же источников наблюдалось снижение динамической вязкости во всем диапазоне рН. При введении в систему трансформированных в денатурирующих условиях сывороточных белков было зафиксировано повышение динамической вязкости в 1,5 раза при рН 5,6 и в 10-12 раз при рН 5,9 и 6,2. Полученные данные подтвердили потенциал детального изучения взаимодействий компонентов системы с целью получения необходимых показателей продукта, стабильных в процессе его хранения. This study of structure formation of products with intermediate moisture is important to improve the quality characteristics of canned milk in countries where this category of food products is widely introduced in the diet of the population. A certain structure of canned products, including sweetened condensed milk, is determined by the composition and properties of raw materials, technological production process and storage conditions. The defects of various origin can arise at all stages of manufacture, worsening indicators of a finished product in complex. Crystallization of lactose with formation of crystals larger than 15 microns by a sensory method is an open issue for canned condensed milk with sugar. Since the beginning of the century, production technology has not changed significantly; lactose «seed» is commonly added to condensed milk with sugar to obtain a homogeneous consistency. Thus, the influence of transformation of ratio of protein components in a biosystem on process of production of canned milk products is not studied up to the end. Replacement of a part of traditional protein profile by native whey proteins, their concentrates or hydrolysates is one of the most perspective solutions for forming of required organoleptic and physico-chemical parameters of condensed milk systems including the stage of long-term storage. The paper presents the results of the investigation of the influence of different ratios of casein and whey proteins on the rheological characteristics of condensed milk with sugar in a wide pH range. The highest values of dynamic viscosity were fixed for all experimental samples at рН 5.6, which can be explained by intensive interaction of protein particles in concentrated systems and gelation due to physical and chemical influence. Dynamic viscosity was 1.5-2 times higher in the systems with the traditional ratio of protein fractions, where whey protein concentrate and whey powder were the source of whey proteins. It can be explained by more intensive complexation of c-casein and b-lactoglobulin. However, a decrease in dynamic viscosity over the entire pH range was observed when whey proteins from the same sources dominated the sample. The introduction of whey proteins transformed under denaturing conditions recorded a 1.5-fold increase in dynamic viscosity at pH 5.6 and a 10-12-fold increase at pH 5.9 and 6.2. The obtained data confirmed the potential of a detailed investigation of the interactions of the system components in order to obtain the necessary product parameters stable during storage.

La connaissance des propriétés physico-chimiques des solutions de polymères utilisées en récupération assistée des hydrocarbures (RAH) est essentielle pour une bonne efficience du procédé. Ces travaux avaient pour but de conforter et enrichir un modèle de viscosité universelle dépendant du paramètre de recouvrement C[η] qui permet de prendre en compte l'occupation du milieu par les chaînes macromoléculaires (concentration d'enchevêtrement critique, C*, régimes dilué et semi-dilué). Les effets des microstructures, de la taille et de la composition des polymères ont été étudiés via la synthèse d'une librairie d'échantillons par polymérisation radicalaire contrôlée (RADT/MADIX) : polyacrylamides, copolymères statistiques et asymétriques acrylamide-acrylate de sodium, polyacrylamides post-hydrolysés. Chaque polymère a été caractérisé par chromatographie d'exclusion stérique et par rhéologie capillaire dont les protocoles et techniques ont été optimisées. Les effets de la microstructure sur les propriétés physico-chimiques dimensionnelles, rhéologiques et complexantes ont été déterminés. Mes travaux de thèse doivent répondre aux deux questions principales suivantes : Quel est l'effet de la microstructure et de la dispersité du polymère sur le modèle ? Quelle(s) est (sont) la(les) limite(s) du modèle en termes d'application ? Mes travaux incluent donc l'élaboration de polymères modèles couvrant une large gamme de masses molaires (de quelques dizaines de milliers à plusieurs millions de g/mol). Les polymères modèles sont de structures variées allant d'homopolymères aux copolymères statistiques et à blocs. Après leur caractérisation complète (composition chimique et structure), les propriétés rhéologiques des solutions sont étudiées. Pour cela, mes travaux comprennent le développement, au sein du laboratoire et spécifiquement pour cette étude, d'un rhéomètre capillaire. Les résultats expérimentaux sont alors comparés au modèle établi pour les polymères industriels pour accroître le potentiel du modèle
The knowledge of the physico-chemical properties of polymer solutions for enhanced oil recovery (EOR) is crucial to optimize the process. The purpose of this work was to consolidate and complete an universal viscosity model depending on C[η] parameter. The later allows taking into account the degree of interpenetration of polymer chains (critical concentration, C*, diluted and semi-diluted solutions). Various polymer parameters have been studied as the effects of microstructures, polymer size (molar mass and dispersity) as well as chemical composition. A library of polymer models was elaborated by controlled radical polymerization (RADT/MADIX). Series of polyacrylamides, statistical and asymmetric copolymers of acrylamide-sodium acrylate and post-hydrolyzed polyacrylamides were synthesized and characterized by steric exclusion chromatography and capillary rheology and the analytical protocols and techniques were optimized. The effects of the microstructure onto dimensional, rheological and complexation physico-chemical properties were determined

Etude de la gelification, la demixtion et des proprietes rheologiques de solutio nde galactomannane et d'alcool polyvinylique complexes par les ions borates. Etude des interactions polyol-borate par rmn du bore. Developpement d'un modele de type flory rendant compte des observations. Analogie entre la rheologie des gels reversibles (solution semidiluee de galactomannane) et celle de solution de polymere concentre