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Bleached kraft pulp of hardwood was pretreated in a NaOH-thiourea aqueous solution to modify the bulk and softness of the cellulose fibers with minimal reduction in paper strength. The effects of soaking time, fiber concentration, alkali dosage, and freezing time were evaluated through single factor experiments. The optimal conditions were determined to be a soaking time of 15 min, fiber concentration of 15%, alkali dosage of 9%, and freezing time of 75 min. Under the optimal conditions, the bulk and softness of the treated cellulose fibers were increased by 28.7% and 21.6%, respectively, compared with those of untreated cellulose fibers. The tensile and burst indices were only reduced by 1.2% and 5.1%, respectively, under these conditions. Also, there were almost no effects on the polymerization degree, the thermostability, and the structure of the functional groups or crystalline regions.

Aquaculture is a promising way of developing fisheries worldwide and in Ukraine. Aquaculture products should form the basis of a complete nutrition of the population of Ukraine in accordance with the world tendency. About 44 % of freshwater catches in 2015 were those of the silver carp. The range of food products from the silver carp is limited, which is due to the low activity of its enzyme system, which does not facilitate maturation in the production of salty fish products. Therefore, new kinds of silver carp products are suggested in jellylike marinade fillings of prolonged shelf life.The results of the statistical processing of complex organoleptic tests have determined the rational parameters of the hot smoked salty semi-finished product. It is proposed to conduct drying at a temperature of 60...70 °С for 25 minutes; evaporation is advised to be performed for 25 minutes at a temperature of 100...110 °С. The stage of the actual hot smoking should be carried out at a temperature of 90...100 °C for 45 minutes. The samples studied, which were smoked according to the above parameters, received the highest score. In order to provide stable structural and mechanical properties of the jelly during refrigeration, the formulation of the filling was substantiated. A combination of LEP and alginic acid in a ratio of 1:1 with a mass fraction of 1.5 % forms a jelly as strong as 112 g and with no synergetic changes. The developed technology helps obtain safe fish marinades in a jellylike filling with a shelf life of up to 90 days, Показана можливість виробництва гарячих маринадів з товстолобика. Особливістю м'язової тканини товстолобика є низька активність ферментативної системи і нездатність до дозрівання. Тому розроблена технологія гарячих маринадів з товстолобика з використанням гідроколоїдів рослинного походження для отримання драглеподібної заливки і поліпшення функціонально-технологічних властивостей готового продукту. Композиція прянощів і консервантів дає можливість збалансувати готовий продукт за органолептичними показниками і подовжити термін зберігання, Показана возможность производства горячих маринадов из толстолобика. Особенностью мышечной ткани толстолобика является низкая активность ферментативной системы и неспособность к созреванию. Поэтому разработана технология горячих маринадов из толстолобика с использованием гидроколоидов растительного происхождения для получения гелеобразной заливки и улучшения функционально-технологических свойств готового продукта. Композиция пряностей и консервантов дает возможность сбалансировать готовый продукт по органолептическим показателям и продлить срок хранения

Gastric digestion of food is the result of physical disintegration and enzymatic reactions leading to the release of nutrients. Depending on the gelation conditions, food protein networks with specific structural and rheological features can be formed. Several in vivo and in vitro studies have shown an influence of the macro- and microstructure on the kinetics of milk protein hydrolysis. Despite growing interest to modulate food structure to potentially control digestion rates, little is known concerning the fundamental mechanisms by which the structure of dairy gels affects the digestion kinetics.An original time-lapse synchrotron deep-UV microscopy method was developed using the natural tryptophan fluorescence of proteins. It allowed monitoring in situ the microstructural evolution of protein gels during simulated gastric digestion. Two dairy gels of identical composition but different coagulation modes (acid and rennet) were submitted to static in vitro digestion with the aim of decoupling the acidification process from the enzymatic action of pepsin. Automated analysis procedures of the collected images allowed to model the kinetics of disintegration of sub-millimetric gel pieces. Results confirmed the propensity of rennet gels, but not acid gels, to undergo large microstructural modifications and form compact protein aggregates (syneresis) under acidic conditions. Consequently, the kinetics of proteolysis was much slower for the rennet gel, reiterating the hypothesis of a pepsin accessibility reduced to the surface of solid casein substrates (Fig 1). Finally, the morphological shapes of particles were almost preserved during the full digestion process and the kinetics of disintegration could be fitted by a simple exponential model. Therefore, we concluded that the erosion mode is probably the predominant mechanism during the gastric digestion of dairy gels.

Food structure is an important factor in the nutritional quality of foods. With regard to dietary protein, it may have an impact on protein digestibility, proteolysis kinetics, gastric emptying and amino acid bioavailability, all with potential metabolic consequences. Egg white is an appropriate food model to investigate these issues, since very different structures and textures can be produced while keeping the chemical composition constant. Recently, we established that protein matrix structure impacts the extent of proteolysis and the nature ofthe peptides generated during in vitro digestion of egg white protein aggregates and gels. Our question here is “do such differences also exist in vivo, and do they have any biological consequences?” To address these questions, a smooth-rigid egg white gel, a granular-spongy gel and an intermediate gel were prepared. Each gel was fed to pigs (n=33) as a single meal, and gastric chyme samples were collected over a 6h-postprandial period in order to measure pH, proteolysis and particle size along digestion at 10 different stomach locations. Blood samples were also collected for plasma amino acid analyses.Acidification of the chyme started in the pylorus regin regardless of the type of gel, but acidification kinetics depended on the gel type, which suggested that gel structure impacts on HCl distribution in the chyme. In contrast, proteolysis commenced in the proximal region, consistent with the location of pepsinogen secretory cells. But from 1h-postprandial, proteolysis profiles greatly differed depending on the gels: the higher proteolysis was 2 observed in the pyloric region for the granular-spongy gel (acidity and proteolysis gradients were consistent), while maximum proteolysis was observed in the proximal region for the smooth-rigid and intermediate gels (acidity and proteolysis gradients were opposite), suggesting that pepsin diffusion profiles depend on the type of gel. Proteolysis kinetics weremore rapid with granular-spongy gel than with intermediate gel, while the smooth-rigid gel was the most resistant to proteolysis, which was consistent with the particle size observed during digestion. Finally, amino acid absorption was faster for the granular-spongy gel than for the two other gels.

This paper presents the possibility of real-time measurement of the diameter of pectin particles during their jellification using an optical correlation method based on the spatial averaging of data.

Проведена комплексная оценка свойств растительных пектиновых веществ и пектинметилэстераз, используемых для желированных овощных соусов при производстве рыбных продуктов. Установлено, что полученные биотехнологическим способом низкоэтерифицированные пектиновые вещества позволяют расширить ассортимент рыбной продукции с усиленными функциональными свойствами. Разработаны оптимальные условия биотехнологического способа получения желированного соуса и исследованы органолептические показатели рыбных консервов., Проведена комплексна оцінка властивостей рослинних пектинових речовині пектинметилестераз, які застосовувалися для жельованих овочевих со-усов при виробництві рибних продуктів. Встановлено, що отримані біотехнологічним способом низькоетерифіковані пектинові речовини дозволяють розширити асортимент рибної продукції з посиленими функціональними властивостями. Розроблені оптимальні умови біотехнологічного способу отримання жельованого соусу і досліджені органолептичні показники рибних консервів., Despite the well-known research and application of plant and microbial polysaccharides in food technology, including canned fish technology as thickeners and jelling agents for various fillings, there is a certain deficiency in this assortment, caused by the complexity of technological processes that would allow to obtain high-quality finished products.It was found that low-esterified pectin substances of plant raw materials, obtained by biotechnological method allow to make structured products, expanding the assortment of fish products with improved organoleptic and functional properties.A comprehensive evaluation of the properties of pectin substances and pectinmethylesterases used for jellied vegetable sauces in the manufacture of fish products was performed in the paper. The optimal conditions for the biotechnological sauce jellification method were obtained, and organoleptic characteristics of canned fish in the jelling sauce were investigated. The results of organoleptic evaluation showed that the analyzed canned products had identical high points on almost all counts. All samples had a pleasant taste and flavour, delicate texture of fish meat in a uniform structured sauce.

Maison de la Science en Bretagne Située sur le campus de Beaulieu de l'Université de Rennes 1, la Maison pour la science en Bretagne a ouvert ses portes en septembre 2014. Initiée par la Fondation "La main à la pâte" et par l’Académie des sciences, cette Maison est le fruit d’une collaboration exemplaire entre les universités, les grandes écoles bretonnes (dont AGROCAMPUS OUEST) et le rectorat d’académie. Elle propose à l’ensemble des professeurs des écoles et des collèges de l’académie de Rennes de participer à des actions de développement professionnel dans les domaines scientifiques. La 4 ième action de développement personnel, à destination des enseignants du collège, a eu lieu les 19 et 21 février avec l’intervention de plusieurs enseignants-chercheurs du dépt Productions animales, agroalimentaire, nutrition (PSAN). Romain Jeantet, Amélie Deglaire, Valérie Lechevalier, Françoise Nau et Catherine Guérin ont animé le module : « Les pieds dans le plat : transformer et conserver les aliments ». Infos : www.maisons-pour-la-science.orgContact : romain.jeantet@agrocampus-ouest.fr; L’OEuf dans tous ses états, modèle d’ingrédient culinaire. 4 iéme action de développement personnel, à destination des enseignants du collège: module : « Les pieds dans le plat : transformer et conserver les aliments ».

Calcium (Ca) concentrations are decreasing in softwater lakes across eastern North America and western Europe. Using long-term contemporary and palaeo-environmental field data, we show that this is precipitating a dramatic change in Canadian lakes: the replacement of previously dominant pelagic herbivores (Ca-rich Daphnia species) by Holopedium glacialis , a jelly-clad, Ca-poor competitor. In some lakes, this transformation is being facilitated by increases in macro-invertebrate predation, both from native ( Chaoborus spp . ) and introduced ( Bythotrephes longimanus ) zooplanktivores, to which Holopedium , with its jelly coat, is relatively invulnerable. Greater representation by Holopedium within cladoceran zooplankton communities will reduce nutrient transfer through food webs, given their lower phosphorus content relative to daphniids, and greater absolute abundances may pose long-term problems to water users. The dominance of jelly-clad zooplankton will likely persist while lakewater Ca levels remain low.

Micelle formation, gelation and adsorption of amphiphilic multiblock copolymers. Biopolymers 2013 : Biopolymer Assemblies for Material Design

Micelle formation, gelation and adsorption of amphiphilic multiblock copolymers: A Monte Carlo study. International soft matter conference (ISMC)

Ingénierie des nanoparticules protéiques et propriétés rhéologiques des gels acides laitiers. 5. Rencontres de Biologie-Physique du Grand Ouest

During the manufacture of dairy products, heat treatments of milk result in the conversion of whey proteins into protein aggregates. These heat-induced aggregates provide new functional properties to dairy products. A protein tailoring approach is developed at UMR-STLO to produce heat-induced aggregates with targeted physicochemical and structural properties, and then to introduce them in a recombined milk to test their functional properties for the formation of dairy acid gels, used as models of yoghurts. It is also well known that denaturation and heat treatments improve interfacial and foaming properties of proteins. The BIA research unit works on understanding the role of heat-induced aggregates in the formation and stability of foams. While non-aggregated proteins adsorb rapidly at the interface, the heat-induced aggregates present in the continuous phase build a protein network that stabilizes the foam. The objective of theses studies is to determine the properties of aggregates that promote the building of new interactions in products that will result in the improvement of custom properties of dairy products and to produce new functional ingredients.; formation de nouvelles entités protéiques ou agrégats thermo-induits. Ces agrégats confèrent des propriétés fonctionnelles aux produits laitiers. Une approche d’ingénierie des agrégats thermo-induits a été développée à l’UMR-STLO qui vise à produire par des moyens variés des agrégats thermo-induits de propriétés physico-chimiques et structurales ciblées, puis à les introduire dans un lait recombiné afin d’évaluer leur propriétés fonctionnelles pour la formation des gels acides, pris comme un modèle du yaourt. Il est connu que la dénaturation et les traitements thermiques améliorent également les propriétés interfaciales et moussantes des protéines. Le laboratoire BIA mène des recherches pour comprendre le rôle des agrégats thermo-induits dans la formation et la stabilisation des mousses. Alors que les protéines non agrégées s’adsorbent rapidement à l’interface, la présence d’agrégats thermoinduits stabilise la mousse par formation d’un réseau de type gel dans la phase continue. L’objectif de ces travaux est de déterminer les propriétés des agrégats qui sont favorables à l’établissement de nouvelles interactions dans les produits, ces dernières étant à l’origine de l’amélioration de leurs propriétés d’usage et de créer de nouveaux ingrédients techno-fonctionnels.

Tesis para obtener el grado de Doctor en el área de Química Industrial, de la Universidad de Buenos Aires, en 2011 El objetivo del presente trabajo fue analizar y caracterizar los factores involucrados en las transformaciones estructurales y físico-químicas de maíces argentinos de tipo colorado duro que determinan la calidad de productos obtenidos por procesos de gelatinización-laminación. Se estudiaron muestras tomadas de distintas etapas del proceso de producción industrial de copos de maíz comerciales que incluyeron desde la materia prima hasta el producto final. Además se analizaron sistemas modelo producidos en el laboratorio para estudiar la influencia de la formulación en el proceso de cocción. Se generó un mapa completo de los cambios de fase y estado que se produjeron a lo largo del proceso industrial mediante diagramas de estado suplementados y el estudio de la movilidad molecular. Se observó un efecto antiplastificante del agua, detectado al estudiar las propiedades mecánicas y los atributos sensoriales de los copos de maíz en función del contenido de agua. Los cambios más importantes en la textura producidos por la absorción de agua se observaron en el estado vítreo, indicando que el agua límite de hidratación es un mejor indicador de estabilidad que la Tg para estos sistemas. La correlación entre la generación de pigmentos y la apariencia visual de las muestras fue afectada por los procesos que afectan la transparencia como los cambios de forma y la generación y destrucción de interfases. Los diagramas de estado y las técnicas de medición no destructivas relacionadas a los marcadores químicos junto al modelado del efecto del agua en las propiedades texturales pueden utilizarse como herramientas para el diseño de procesos, desarrollo de productos y el control de su estabilidad. Se establecieron parámetros que podrían emplearse en e control de proceso o en el producto final para garantizar atributos de calidad. The objective of the present work was to analyze and characterize factors involved in structural and physicochemical transformations of argentine red flint corn which have impact on quality of food obtained by using gelatinization-lamination process. Samples from selected industrial process steps which included from raw materials to finished products were taken from cornflake production line. Model systems were cooked in the laboratory to study formulation effects on cooking process. Supplemented state diagrams generated and molecular mobility studies allowed to generate a complete map of phase and state changes that took place along the industrial process. Mechanical properties and sensory attributes of corn flakes were characterized as a function of water content. Antiplasticizing effect of water was detected both sensory and instrumentally. Important texture changes upon water absorption were observed when the samples were still in glassy state indicating that, for these samples, hydration limit is a better stability indicator than Tg. The correlation between pigment concentration and visual appearance was affected by shape and transparency changes, mainly due to generation or disappearance of inter-phases. Supplemented state diagrams and non destructive measurements techniques that correlate to chemical markers, along with water effect modeling on textural properties can be used as useful tools in process design, product development and stability control. EEA Pergamino Fil: Farroni, Abel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Laboratorio Calidad de Alimento, Suelos y Agua; Argentina

Designing the heat-induced whey protein complexes: a key to engineer the interactions in acid milk gels. IDF World Dairy Summit

Ingénierie des nanostructures protéiques et propriétés rhéologiques des gels acides de lait. 45 iéme colloque du GFR Rhéologie des matériaux nanostructurés

Zinc deficiency is a world wide problem, centred on the lower income population, though not restricted to it. Food supplementation with magnesium is also considered of interest for correcting deficiencies in this oligoelement. Highpressure partially gelatinised starch is proposed as a vehicle for inclusion of these metals in food products. While highpressure levels (and/or temperature) give rise to total gelatinisation, lower pressures, at temperatures close to ambient, yield partially-gelatinised products, where only a portion of the intramolecular bonds in the amylopectin double helix has been substituted by intermolecular bonds between the unfolded amylopectin and water, as it can be deduced by differential scanning calorimetry, while the resultant granular microstructure is strongly altered (observed by low temperature scanning electron microscopy). Production of this modified starch implies lower energy expense, compared to thermal gelatinisation, and it guarantees higher homogeneity in the final degree of gelatinisation. The effect of moderated high-pressure treatments (400 MPa, 25 deg C, 35 min) on potato and corn starches has been studied. The effect of pressure treatment, after alkaline treatment or the addition of another hydrocolloid (guar gum) has also been considered. The observed preferential binding of zinc and magnesium salts to these modified starches (after determination of metal content by atomic absorption spectrophotometry) is favourable to the use of these products as metal carriers., La deficiencia de cinc es una cuestión de alcance mundial, centrada en la población de menores recursos, aunque no restringido a ella. La suplementación de alimentos con magnesio también se considera de interés para corregir las carencias de este oligoelemento. Como vehículo para la inclusión de estos metales en productos alimenticios se propone el almidón parcialmente gelatinizado por alta presión. Mientras que altos niveles de presión (y/o temperatura) causan gelatinización total, menores presiones a temperaturas cercanas a la ambiente rinden productos parcialmente gelatinizados, en los que sólo una proporción de uniones intramoleculares de la doble hélice de amilopectina han sido sustituidas por enlaces intermoleculares entre la amilopectina desenrollada y agua, según se deriva de datos de calorimetría diferencial de barrido, mientras que la microestructura del gránulo resulta muy alterada (observada por microscopía electrónica de barrido de baja temperatura). La producción de este almidón modificado conlleva menor gasto energético, en comparación con la gelatinización térmica, así como garantiza mayor homogeneidad en el grado de gelatinización final. Se ha estudiado el efecto de tratamientos moderados de alta presión (400 MPa, 25 grados C, 35 min) sobre almidones de patata y de maíz. También se ha considerado el efecto de la presurización después de un tratamiento alcalino o de adición de otros hidrocoloides (goma guar). La observación de la unión preferencial de sales de cinc y de magnesio a estos almidones modificados (tras determinación del contenido en metales mediante espectrofotometría de absorción atómica) es favorable al empleo de estos productos como portadores de metales.

– In an attempt to improve the acid gelation properties of heated milk, or to reduce the heat load necessary to obtain significant acid gelation properties, skim milk adjusted at pH values ranging from 6.7 to 10.5 was heat-treated for 10 min at temperatures ranging from 25 to 95 °C then neutralised to pH 6.7. Protein composition of the serum and micellar phases of milk and separation of the protein particles present in the serum phase of milk indicated that formation of micelle-bound heat-induced whey protein/κ-casein aggregates was prevented from pH 7.5 upward, to the benefit of serum aggregates. Aggregates were formed in milk at pH 9.5 and 10.5 even at mild heating temperature (65–75 °C), while temperatures of 85 or 95 °C were necessary at lower pH values. Size of the aggregates decreased as pH of heat-treatment increased. Quality of the results was however reduced because of the extensive dissociation of caseins on alkaline treatment and of side mechanisms like Maillard reaction at high pH and temperature. However, some relationships could be found between the occurrence of aggregated whey protein and κ-casein and higher elastic modulus of the acid gels after heating at low temperature/high pH or high temperature/low alkaline pH values of skim milk.; Dans l'objectif d'améliorer l'aptitude à la gélification acide du lait traité thermiquement ou de réduire la charge thermique nécessaire à l'obtention d'une aptitude significative, du lait écrémé a été ajusté à des pH variant de 6,7 à 10,5, traité thermiquement pendant 10 min à des températures variant de 25 à 95 °C puis neutralisé. La composition en protéines des phases sérique et micellaire du lait et la séparation des particules présentes dans le sérum indiquaient que la formation d'agrégats thermo-induits de protéines sériques et de caséine k dans la fraction micellaire est inhibée à pH S 7,5 au profit des agrégats sériques. Des agrégats étaient formés à pH 9,5 et 10,5 dès 65 °C, tandis que des températures de 85 ou 95 °C étaient nécessaires à pH moins élevé. La taille des agrégats était inversement proportionnelle au pH de traitement thermique. La qualité des résultats était cependant médiocre du fait de la dissociation importante des caséines à pH alcalin et de la dégradation des protéines à pH et températures élevés (e.g. réaction de Maillard). Cependant, une relation entre la présence d'agrégats et les qualités rhéologiques des gels acides formés a pu être identifiée à basse température/pH élevé et à haute température/pH modéré.

Tesis (M. Sc) -- CATIE, Turrialba (Costa Rica), 2003 19 ilustraciones a color. 12 tablas Referencias de las páginas 82-90 El objetivo de la investigación fue determinar la variabilidad genética presente en líneas avanzadas de arroz, progenitores y variedades comerciales del proyecto de mejoramiento genético de arroz del IDIAP, a través de la caracterización morfológica, utilizando descriptores fenotípicos, y molecular mediante el uso de marcadores moleculares. La investigación, consistió de dos etapas, una de campo realizada en el IDIAP, Penonomé, Coclé, Panamá y la otra de laboratorio que se realizó en el CATIE, Turrialba, Cartago, Costa Rica. Las comparaciones realizadas entre los cultivares próximos a registro y sus progenitores, indican que existen características propias de cada línea que establecen diferencias con respecto a sus progenitores. Las distancias genéticas a nivel molecular presentaron valores bajos. El uso de descriptores morfológicos y marcadores moleculares AFLP's, permitió determinar la variabilidad genética presente en 48 líneas avanzadas de arroz, 5 progenitores y 4 variedades comerciales del proyecto de mejoramiento genético de arroz del IDIAP. The objective of this investigation was to determine the existing genetic variability in advanced rice breeding lines, progenies and commercial varieties of the rice breeding project of IDIAP through morphological and molecular characterization using phenotypic descriptors and molecular markers, respectively. The investigation consisted of two stages: one carried out in the field at the IDIAP Research Station in Penenome, Cocle, Panama, the other on in the Molecular Biology Lab of CATIE in Turrialba, Cartago, Costa Rica. The comparisons made between the new cultivars, which are close to registration and their progenies indicated that each line has characteristics of its own, which establish differences with its progenies. The genetic distances at the molecular level, however, are low. The use of morphological descriptors and AFLP markers allowed to determine the existing genetic variability in 48 advanced lines of rice of IDIAP's breeding project, five progenies and four commercial varieties, which served as control.

Physico-chemical changes during acidification by a yoghurt starter of heat-treated milk. 26 ème congrès international de laiterie

The structure of casein in heated suspensions affects the acid gelification of milk. FIL-IDF "Fermented milk"

Not available, La coagulation mixte du lait, induite par action conjuguée d'un agent acidifiant et d'une enzyme protéolytique, représente la phase initiale de la fabrication des fromages. Une légère variation physicochimique du lait, notamment l'ajustement à un pH donné, semble agir de façon prépondérante sur le type de fromage fabriqué. Les propriétés macroscopiques, soit les propriétés rhéologiques et sensorielles d'un gel de lait peuvent-elles être considérées comme gouvernées par l'état physicochimique initial des micelles de caséines ? Les mécanismes d'agrégation des micelles de caséines ont été étudiés par l'analyse de cinétiques spectrophotométriques et granulométriques. L’approche structurale de l'agrégation et de la gélification a été réalisée par application du concept de la géométrie fractale. Les propriétés mécaniques des gels ont été caractérisées par l'analyse de leurs modules viscoélastiques en oscillation dynamique. Dans une première partie, l'influence de la température et de la vitesse d'agrégation sur le mécanisme d'agrégation des micelles de caséines est montrée. Il s'avère que malgré un mode de déstabilisation des micelles de caséines différent, la structure des agrégats acides et enzymatiques ainsi formés évolue dans le même sens. Dans une deuxième et une troisième parties, les mécanismes d'agrégation-coagulation mixte du lait sont étudies et modélisés à partir des connaissances acquises sur l'agrégation-coagulation acide et enzymatique. Il apparait que la valeur du pH à l'emprésurage influence les étapes ultérieures de la coagulation du lait. Le comportement particulier de la voluminosité des micelles de caséines mis en évidence autour du pH 6,00 déterminerait la structure des agrégats et des gels ainsi que le comportement mécanique de ces derniers.

Not available, La coagulation mixte du lait, induite par action conjuguée d'un agent acidifiant et d'une enzyme protéolytique, représente la phase initiale de la fabrication des fromages. Une légère variation physicochimique du lait, notamment l'ajustement à un pH donné, semble agir de façon prépondérante sur le type de fromage fabriqué. Les propriétés macroscopiques, soit les propriétés rhéologiques et sensorielles d'un gel de lait peuvent-elles être considérées comme gouvernées par l'état physicochimique initial des micelles de caséines ? Les mécanismes d'agrégation des micelles de caséines ont été étudiés par l'analyse de cinétiques spectrophotométriques et granulométriques. L’approche structurale de l'agrégation et de la gélification a été réalisée par application du concept de la géométrie fractale. Les propriétés mécaniques des gels ont été caractérisées par l'analyse de leurs modules viscoélastiques en oscillation dynamique. Dans une première partie, l'influence de la température et de la vitesse d'agrégation sur le mécanisme d'agrégation des micelles de caséines est montrée. Il s'avère que malgré un mode de déstabilisation des micelles de caséines différent, la structure des agrégats acides et enzymatiques ainsi formés évolue dans le même sens. Dans une deuxième et une troisième parties, les mécanismes d'agrégation-coagulation mixte du lait sont étudies et modélisés à partir des connaissances acquises sur l'agrégation-coagulation acide et enzymatique. Il apparait que la valeur du pH à l'emprésurage influence les étapes ultérieures de la coagulation du lait. Le comportement particulier de la voluminosité des micelles de caséines mis en évidence autour du pH 6,00 déterminerait la structure des agrégats et des gels ainsi que le comportement mécanique de ces derniers.

Zinc deficiency is a world wide problem, centred on the lower income population, though not restricted to it. Food supplementation with magnesium is also considered of interest for correcting deficiencies in this oligoelement. Highpressure partially gelatinised starch is proposed as a vehicle for inclusion of these metals in food products. While highpressure levels (and/or temperature) give rise to total gelatinisation, lower pressures, at temperatures close to ambient, yield partially-gelatinised products, where only a portion of the intramolecular bonds in the amylopectin double helix has been substituted by intermolecular bonds between the unfolded amylopectin and water, as it can be deduced by differential scanning calorimetry, while the resultant granular microstructure is strongly altered (observed by low temperature scanning electron microscopy). Production of this modified starch implies lower energy expense, compared to thermal gelatinisation, and it guarantees higher homogeneity in the final degree of gelatinisation. The effect of moderated high-pressure treatments (400 MPa, 25 deg C, 35 min) on potato and corn starches has been studied. The effect of pressure treatment, after alkaline treatment or the addition of another hydrocolloid (guar gum) has also been considered. The observed preferential binding of zinc and magnesium salts to these modified starches (after determination of metal content by atomic absorption spectrophotometry) is favourable to the use of these products as metal carriers. La deficiencia de cinc es una cuestión de alcance mundial, centrada en la población de menores recursos, aunque no restringido a ella. La suplementación de alimentos con magnesio también se considera de interés para corregir las carencias de este oligoelemento. Como vehículo para la inclusión de estos metales en productos alimenticios se propone el almidón parcialmente gelatinizado por alta presión. Mientras que altos niveles de presión (y/o temperatura) causan gelatinización total, menores presiones a temperaturas cercanas a la ambiente rinden productos parcialmente gelatinizados, en los que sólo una proporción de uniones intramoleculares de la doble hélice de amilopectina han sido sustituidas por enlaces intermoleculares entre la amilopectina desenrollada y agua, según se deriva de datos de calorimetría diferencial de barrido, mientras que la microestructura del gránulo resulta muy alterada (observada por microscopía electrónica de barrido de baja temperatura). La producción de este almidón modificado conlleva menor gasto energético, en comparación con la gelatinización térmica, así como garantiza mayor homogeneidad en el grado de gelatinización final. Se ha estudiado el efecto de tratamientos moderados de alta presión (400 MPa, 25 grados C, 35 min) sobre almidones de patata y de maíz. También se ha considerado el efecto de la presurización después de un tratamiento alcalino o de adición de otros hidrocoloides (goma guar). La observación de la unión preferencial de sales de cinc y de magnesio a estos almidones modificados (tras determinación del contenido en metales mediante espectrofotometría de absorción atómica) es favorable al empleo de estos productos como portadores de metales.