The present study was aimed at extending our knowledge of the antioxidative properties of the milk protein products, whey protein isolate (WPI) and sodium caseinate (NaCas), in oil-in-water (O/W) emulsions rich in polyunsaturated fatty acids (PUFAs). In particular, the objective was to contribute to our understanding of the compositional and processing factors that influence the oxidative stability of protein-stabilised O/W emulsions. Linoleic acid (approximately 60 %) was used as the lipid for the oil phase (10.6 %). The emulsion samples were usually incubated at 50 °C to accelerate lipid oxidation. Lipid oxidation indicators were lipid hydroperoxides and headspace hexanal, determined by solid phase microextraction (SPME) combined with gas chromatography (GC). WPI- or NaCas-stabilised emulsions were prepared using a wide range of protein concentrations (0.5, 1.0, 2.0, 3.0, 4.0, 7.0 or 10.0 %) at two droplet sizes (d32 = 0.31 and 0.65 µm). In general, higher lipid oxidation levels were found for the larger droplet size. Increasing protein concentration led to a decrease in the lipid oxidation rate. The greatest decrease in lipid hydroperoxide levels (values after 4 h) occurred at up to 4.0 % protein concentration. The greatest decrease in hexanal levels (values after 24 h) occurred at up to 4.0 % protein concentration in WPI emulsions (0.31 µm). The hexanal levels were more independent of the protein concentration in the other emulsion types. The hexanal level decreased at protein concentrations > 4.0 % in NaCas emulsions (0.31 and 0.65 µm) and at protein concentrations > 7.0 % in WPI emulsions (0.65 µm). The difference between lipid hydroperoxide generation in emulsions with small and large droplet sizes decreased with increasing protein concentration. This effect was more pronounced in NaCas emulsions. In general, NaCas was a better inhibitor of lipid oxidation than WPI, but WPI appeared to be the better antioxidant at some droplet size/protein concentration combinations. The protein in the continuous phase, i.e. the unadsorbed protein, played an important role in lipid oxidation. In principal, the lipid hydroperoxide and hexanal levels showed the same development over the continuous phase protein concentration as over the protein concentration in WPI and NaCas emulsions (d32 = 0.31 µm). A low NaCas level in the continuous phase already led to a relatively low hexanal level, whereas a higher WPI level was required. When NaCas solution was added to a WPI emulsion or WPI solution was added to a NaCas emulsion, a synergistic antioxidative effect was observed. The high molecular weight fractions (molecular weight = 12000-14000) of WPI and NaCas contained pro-oxidative metal ions that contributed to lipid oxidation in the emulsions. An enrichment of NaCas emulsions with the low molecular weight fraction of NaCas (with a molecular weight = 12000-14000) notably inhibited lipid oxidation. An enrichment of WPI emulsions with the low molecular weight fraction of WPI (with a molecular weight = 12000-14000) also seemed to inhibit lipid oxidation, but the effect was not significant. The protein solutions were enriched with these fractions before emulsion preparation. Pure WPI solution or mixed WPI/NaCas (1:1, weight/weight) solution with 1.12 or 2.24 % protein concentration was heated at 84 °C for up to 40 min, cooled and then used to prepare emulsions. Lipid oxidation was generally not affected by the heat treatment or the degree of whey protein denaturation. However, at the lower WPI concentration, more hexanal was produced for the longer heating times (20, 30 and 40 min) and this appeared to be connected with the physical instability of the emulsions. Greater oxidative stability was found at the higher protein concentration and when the proteins were mixed, pointing to a possible synergistic antioxidative effect of WPI and NaCas. The addition of the free radical source 2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) greatly increased the oxygen uptake and the generation of lipid hydroperoxides in the emulsions. The oxidative stability increased with increasing protein concentration (1.0, 4.0 and 7.0 %). NaCas had a greater antioxidative effect than WPI. The inhibition of oxygen uptake appeared to be largely influenced by the free-radical-scavenging activity of the system, determined by the protein type and the protein concentration, as the radicals were produced linearly over time and oxygen was consumed linearly over time. It can therefore be concluded that free-radical-scavenging activity represents a major antioxidative mechanism of the milk proteins. Oxygen was consumed much faster in emulsions than in protein solutions when the same level of AAPH was incorporated. In a WPI (1.0 % protein) emulsion, much lower levels of protein hydroperoxides than of lipid hydroperoxides developed. This pointed to a much greater reactivity of linoleic acid than of the milk proteins with oxygen. In contrast, the exposure of WPI to oxidising linoleic acid in an emulsion (1.0 % protein) or to AAPH in aqueous solution led to oxidative damage of the whey proteins, indicated by the loss of amino acids. The loss of specific amino acids was different for proteins in the continuous phase or cream phase of an emulsion or in WPI solution. The present study confirms the antioxidative potential of WPI and NaCas and gives new insights into their functionality as oxidative stabilisers in O/W emulsions.

The present study was aimed at extending our knowledge of the antioxidative properties of the milk protein products, whey protein isolate (WPI) and sodium caseinate (NaCas), in oil-in-water (O/W) emulsions rich in polyunsaturated fatty acids (PUFAs). In particular, the objective was to contribute to our understanding of the compositional and processing factors that influence the oxidative stability of protein-stabilised O/W emulsions. Linoleic acid (approximately 60 %) was used as the lipid for the oil phase (10.6 %). The emulsion samples were usually incubated at 50 °C to accelerate lipid oxidation. Lipid oxidation indicators were lipid hydroperoxides and headspace hexanal, determined by solid phase microextraction (SPME) combined with gas chromatography (GC). WPI- or NaCas-stabilised emulsions were prepared using a wide range of protein concentrations (0.5, 1.0, 2.0, 3.0, 4.0, 7.0 or 10.0 %) at two droplet sizes (d32 = 0.31 and 0.65 µm). In general, higher lipid oxidation levels were found for the larger droplet size. Increasing protein concentration led to a decrease in the lipid oxidation rate. The greatest decrease in lipid hydroperoxide levels (values after 4 h) occurred at up to 4.0 % protein concentration. The greatest decrease in hexanal levels (values after 24 h) occurred at up to 4.0 % protein concentration in WPI emulsions (0.31 µm). The hexanal levels were more independent of the protein concentration in the other emulsion types. The hexanal level decreased at protein concentrations > 4.0 % in NaCas emulsions (0.31 and 0.65 µm) and at protein concentrations > 7.0 % in WPI emulsions (0.65 µm). The difference between lipid hydroperoxide generation in emulsions with small and large droplet sizes decreased with increasing protein concentration. This effect was more pronounced in NaCas emulsions. In general, NaCas was a better inhibitor of lipid oxidation than WPI, but WPI appeared to be the better antioxidant at some droplet size/protein concentration combinations. The protein in the continuous phase, i.e. the unadsorbed protein, played an important role in lipid oxidation. In principal, the lipid hydroperoxide and hexanal levels showed the same development over the continuous phase protein concentration as over the protein concentration in WPI and NaCas emulsions (d32 = 0.31 µm). A low NaCas level in the continuous phase already led to a relatively low hexanal level, whereas a higher WPI level was required. When NaCas solution was added to a WPI emulsion or WPI solution was added to a NaCas emulsion, a synergistic antioxidative effect was observed. The high molecular weight fractions (molecular weight = 12000-14000) of WPI and NaCas contained pro-oxidative metal ions that contributed to lipid oxidation in the emulsions. An enrichment of NaCas emulsions with the low molecular weight fraction of NaCas (with a molecular weight = 12000-14000) notably inhibited lipid oxidation. An enrichment of WPI emulsions with the low molecular weight fraction of WPI (with a molecular weight = 12000-14000) also seemed to inhibit lipid oxidation, but the effect was not significant. The protein solutions were enriched with these fractions before emulsion preparation. Pure WPI solution or mixed WPI/NaCas (1:1, weight/weight) solution with 1.12 or 2.24 % protein concentration was heated at 84 °C for up to 40 min, cooled and then used to prepare emulsions. Lipid oxidation was generally not affected by the heat treatment or the degree of whey protein denaturation. However, at the lower WPI concentration, more hexanal was produced for the longer heating times (20, 30 and 40 min) and this appeared to be connected with the physical instability of the emulsions. Greater oxidative stability was found at the higher protein concentration and when the proteins were mixed, pointing to a possible synergistic antioxidative effect of WPI and NaCas. The addition of the free radical source 2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) greatly increased the oxygen uptake and the generation of lipid hydroperoxides in the emulsions. The oxidative stability increased with increasing protein concentration (1.0, 4.0 and 7.0 %). NaCas had a greater antioxidative effect than WPI. The inhibition of oxygen uptake appeared to be largely influenced by the free-radical-scavenging activity of the system, determined by the protein type and the protein concentration, as the radicals were produced linearly over time and oxygen was consumed linearly over time. It can therefore be concluded that free-radical-scavenging activity represents a major antioxidative mechanism of the milk proteins. Oxygen was consumed much faster in emulsions than in protein solutions when the same level of AAPH was incorporated. In a WPI (1.0 % protein) emulsion, much lower levels of protein hydroperoxides than of lipid hydroperoxides developed. This pointed to a much greater reactivity of linoleic acid than of the milk proteins with oxygen. In contrast, the exposure of WPI to oxidising linoleic acid in an emulsion (1.0 % protein) or to AAPH in aqueous solution led to oxidative damage of the whey proteins, indicated by the loss of amino acids. The loss of specific amino acids was different for proteins in the continuous phase or cream phase of an emulsion or in WPI solution. The present study confirms the antioxidative potential of WPI and NaCas and gives new insights into their functionality as oxidative stabilisers in O/W emulsions.

The objective of this thesis was to test the environmental friendly additive substance, in particular sodium caseinate, which is not subject to designation "E" on the label of the product, which is unpopular among the consumers, and which would provide so-called a "higher value" to a product of economically important fish species in the Czech Republic, specifically the common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix) and the rainbow trout (Oncorhynchus mykiss).Determination of the influence of this additive on microbial and biochemical processes, and also on organoleptic properties of the selected smoked fish was another goal of the work. Three concentrations of this product were used for application in total, in particular 25, 50 and 100 g×kg-1. The results of this work confirmed that, due to caseinate (concentration of 100 g×kg-1) such losses of water were avoided, as observed in case of the control group, to which no additive product was applied, and which served for comparison with the groups treated with caseinate. General carp had an average loss of 12.9 % for the samples treated with sodium caseinate and 14 % for the control group. The silver carp white showed similar results. The group treated with caseinate lost 12.4 % in average, and the control group of approximately 14 %. The best results were recorded with the rainbow trout, which, due to caseinate withheld the largest amount of water, respectively, it did not lose so much of weight, in particular 15.9 % for sodium caseinate compared to 19.3 % measured in the control group, however these differences were not confirmed as statistically conclusive. As for the texture of the meat, tougher samples came out for the ones treated with sodium caseinate compared to the more brittle control group. In carp and trout no statistically noteworthy dissimilarity in stiffness of meat was proved between the control group and the group with the applied additive product. While these differences were significant in silver carp. While for silver carp were these differences significant. The control group showed clearly (p<0.05) lower stiffness compared to the group, to which the additive product was applied. Microbiological analysis was performed on the 7th day after smoking, and the values were in the range of 2×10 to 1.9×10^2 CFU×g-1. In the experiment, groups of test fish species did not show any statistically significant difference (p>0.05). Tests for the possible presence of Listeria monocytogenes in all of the smoked fish samples and the control group were negative. Nutrient composition was mainly focused on the basic nutrient components, which were the proteins, fats and carbohydrates. The control group did not show any significant differences compared to the group to which sodium caseinate was applied. The results from the consumers and sensory analysis by a panel of trained persons were very similar. No statistically significant differences between the group treated with caseinate sodium, and the untreated so called control group of smoked species of fish.

La mondialisation des marchés, les changements d’habitudes de consommation et les préoccupations croissantes concernant la sécurité alimentaire et l’environnement sont des éléments moteurs pour le développement des films d’emballage comestibles/biodégradables antimicrobiens. Une utilisation en masse de ce type de film est dépendante principalement des verrous technologiques car le mode de fabrication actuellement utilisé pour ce genre de film consiste à utiliser un procédé (voie solvant) qui n’est pas toujours adapté à une production importante et continue. L’étude présentée ici permet de montrer la possibilité d’obtenir des films comestibles antimicrobiens à partir de caséinate de sodium en utilisant les procédés traditionnels de la plasturgie : extrusion bi-vis et extrusion-gonflage. Grâce aux optimisations des paramètres d’élaboration tels que la température de transformation, le taux de cisaillement et le taux de plastifiant, les matériaux contenant un agent actif naturel : le lysozyme, la nisine ou la natamycine ont gardé en partie leurs activités antimicrobiennes. Par des caractérisations mécaniques et physico-chimiques des films thermoplastiques, il a été démontré que ces films ont des propriétés mécaniques et barrières similaires à ceux fabriqués par voie solvant. Ces propriétés dépendent principalement du taux de plastifiant. Ainsi, il est possible de fabriquer des films comestibles antimicrobiens de caséinate de sodium avec de bonnes propriétés mécaniques et barrières qui ne sont pas affectées par la transformation thermomécanique et qui peuvent être adaptées en fonctions des applications en variant le taux de plastifiant / Because food market becomes international, consumers are changing their habits and they are more concerned about food security and environmental issues, there are driving forces for the development of edible/biodegradable antimicrobial packaging films. However, fabrication process (solution-casting) of these kinds of films isn’t always suitable for a continuous industrial big production. The present study demonstrates the suitability of sodium caseinate based edible antimicrobial films to be fabricated by some conventional plastic transformation processes: twinscrew extrusion and blown-film extrusion. Thanks to the optimizations of elaboration parameters such as extrusion temperature, shear and plasticizer ratio, the materials incorporated with one of the following active agents: lysozyme, nisin or natamycin, partially kept their antimicrobial activity. Physical-chemical film characterization of films emphasized that the type of transformation process doesn’t have any influence on tensile or gas barrier properties. These properties are mainly affected by plasticizer type and content. Thus, sodium caseinate based edible antimicrobial films can be produced successfully by thermo-mechanical processes without losing good mechanical and gas barrier properties

L'objectif de ce travail était d'étudier l'influence qu'exerce la microstructure des caséines sur la diffusion moléculaire de petites sondes ayant des tailles et des déformabilités différentes. La mobilité de sondes moléculaires flexibles (''PEGs'') et rigides (dendrimères) de taille variée a été étudiée dans des suspensions et des gels de PPCN et de CaNa à différentes concentrations en protéines. Les mesures ont été réalisées par RMN qui permet de sonder des mobilités translationnelles sur une distance de 1,5 µm, mais également des mobilités locales à l'échelle moléculaire (quelques nanomètres) à travers les temps de relaxation T2. Un modèle cohérent a été utilisé et un mécanisme unique a été proposé pour décrire la diffusion de petites sondes dans les deux systèmes de caséine. C'est la combinaison de différents facteurs qui doivent être pris en considération : le rapport de la taille de la sonde à la distance entre les particules obstruantes ou les points d'enchevêtrement ainsi que la flexibilité de la sonde. La mobilité locale des sondes était beaucoup moins réduite que la mobilité translationnelle dans les deux systèmes de caséine. Différents comportements de relaxation ont été obtenus entre les deux systèmes de caséine et une diminution des T2 a été mesurée dans les gels. Ces résultats ont été liés à la mobilité intrinsèque de la matrice. L'ensemble des résultats obtenus ont permis d'avoir une meilleure compréhension de la mobilité des sondes dans les systèmes caséiques et de proposer un nouveau modèle qui contredit celui déjà proposé par Le Feunteun et al. pour expliquer la diffusion des sondes dans ces systèmes. / The aim of this study was to investigate the impact of the casein microstructure on the molecular diffusion of probes with different sizes and deformabilities. The mobility of molecular flexible (‘PEG’) and rigid (dendrimer) probes of various sizes was studied in suspensions and gels of NPC and SC at various protein concentrations. Measurements were carried out by NMR, which makes it possible to probe translational mobilities over a distance of 1.5 microns, as well as local mobilities at the molecular scale (several nanometers) through the relaxation times, T2. A coherent model was used and the same mechanism was proposed to describe the diffusion of small probes in both casein dispersions. It is the combination of different factors that should be considered: the ratio of the probe size to the distance between the obstructing particles or the entanglement points, as well as the flexibility of the probe. The rotational diffusion of PEG and dendrimer probes was less hindered than translational diffusion in both casein systems. Different relaxation behaviors were observed between the two casein systems and retardation in T2 relaxation times was highlighted in rennet and acid casein gels. These results are probably related to the local mobility of the matrix. The overall results of this project led to a better understanding of probe mobility in casein systems and made it possible to propose a new model that challenges the previous one proposed by Le Feunteun et al. to describe the diffusion of probes in casein systems.

Parmi les différentes méthodes de lutte contre les microorganismes pathogènes et/ou altérants en agroalimentaire, l’utilisation de bactéries lactiques (LAB) bioprotectrices s'avère être un outil prometteur pour la préservation des aliments. Ce travail de thèse collaboratif, entre l'équipe PAPC (AgroSup Dijon, Université de Bourgogne) et le laboratoire BioDyMIA (Université Lyon1-Isara Lyon), concerne l'étude de systèmes bioprotecteurs immobilisant des cellules entières de LAB dans une matrice polymérique d'alginate de sodium et de caséinate de sodium pour une activité ciblée contre Listeria spp. Dans un premier temps, la méthodologie mise en œuvre a consisté à sélectionner des souches de LAB bioprotectrices sur la base de leur activité antimicrobienne évaluée par la méthode de diffusion en milieu gélosé contre trois souches de Listeria spp. Quatre souches sur 19 ont ainsi été sélectionnées. Une caractérisation partielle des métabolites antimicrobiens produits par ces 4 souches a ensuite été réalisée en appliquant des traitements thermiques et enzymatiques aux surnageants de culture correspondants pour évaluer si ces traitements altéraient l’activité des métabolites antimicrobiens présents. Une purification et une identification partielle des actifs antimicrobiens de nature peptidique ont été réalisées uniquement pour la souche d'intérêt principale : Lactococcus lactis LAB3. Dans un second temps, une formulation de la matrice polymérique d’immobilisation des LAB sélectionnées a été choisie en réalisant le diagramme de phases du système aqueux alginate de sodium/caséinate de sodium : 1,5 % (m/m) d'alginate de sodium / 4 % (m/m) de caséinate de sodium / 20 % (m/m) bouillon MRS. Cette formulation a permis d'obtenir une matrice composée d’une phase continue riche en alginate et d’une phase dispersée riche en caséinate dans laquelle les cellules de LAB se localisent préférentiellement d’après les observations en microscopie de fluorescence confocale à balayage laser. Suite à l'inclusion des cellules de LAB dans ces matrices liquides et gélifiées d'alginate seul et d'alginate/caséinate, leur cultivabilité et leur activité anti-Listeria ont été suivies à 30°C pendant 12 jours. Ceci a révélé que la cultivabilité et l’activité antimicrobienne des cellules de LAB se maintiennent à des niveaux plus élevés dans les matrices d'alginate/caséinate que dans celles uniquement à base d’alginate. Ces matrices à base d’alginate et de caséinate apparaissent donc comme un système prometteur pour l'immobilisation de LAB bioprotectrices. Leur intérêt pour l’inclusion de LAB a pu être corrélé à leur viabilité et à la structure composite de cette matrice à base de protéines qui favoriserait la production et la libération des métabolites antimicrobiens / Among the various methods to control foodborne pathogenic and/or food spoilage microorganisms in food chain, bioprotective lactic acid bacteria (LAB) appear to be promising tools for food biopreservation. This collaborative study, between PAPC (Agrosup Dijon, University of Burgundy) and BioDyMIA (University Lyon1-Lyon Isara) laboratories, concerned the development of sodium alginate/sodium caseinate polymeric matrices intended to entrap LAB cells selected for their anti-Listeria spp. activity. First, 4 LAB strains from 19 LAB strains were selected for their anti-Listeria spp. activity: this screening was performed by the method of agar diffusion against three Listeria spp strains. Then, antimicrobial metabolites produced by the selected LAB strains were partially characterized by assessing the effect of various thermal and enzymatic treatments on the anti-Listeria spp. activity of their culture supernatants. A partial purification and identification of antimicrobial active peptides produced by the main strain of interest (Lactococcus lactis LAB3) was also performed. A composition of the polymer matrix has been selected by performing the phase diagram of sodium alginate/sodium caseinate system: 1.5% (w/w) sodium alginate / 4% (w/w) of caseinate sodium / 20% (w/w) MRS broth. This formulation provides a rich alginate continuous phase and a rich caseinate dispersed phase in which LAB cells localize according to the study by confocal microscopy. LAB cells were immobilized in liquid and gelled matrices of alginate and alginate/caseinate. Culturability and anti-Listeria activities were measured during a storage at 30°C for 12 days. The alginate/caseinate matrices were more effective in better maintaining LAB cells cultivability and their antimicrobial activity than alginate matrix. This effectiveness seemed correlated with cell viability and the dispersion-like structure of the protein-based system which enhance production and release of antimicrobial metabolites. Thus, this type of polymeric matrix appeared as a promising immobilization system of bioprotective LAB

Abstract Biodegradable starch-glycerol based films were obtained. The influence of lipid compounds (palmitic, stearic and oleic acid), other polymers (hydroxypropylmethylcellulose and sodium caseinate) and bioactive compounds (¿-tocoferol, D-limonene and orange essential oil) on film properties (oxygen and water vapour barrier, optical, mechanical, nano- and microstructural). Furthermore the effect of storage time on films¿ properties was also considered. Fatty acids addition did not improve the water vapour ability of films except for non-stored saturated fatty acids containing films. X-ray diffraction results showed that cristallinity of films increased with storage time, thus increasing the stiffness and decreasing the gloss of films. Furthermore, crystallinity affected the water sorption capacity of films as function of relative humidity and temperature. Glass transition temperature of starch films varied with saturated fatty acids addition. However, oleic acid did not affect this parameter. The presence of fatty acids promoted the formation of V-type structures, thus indicatin the formation of amylose-lipid complexes that inhibited the developmet of other crystalline structures. The effect of the incorporation of other biopolymers to improve the functionality of starch films was also studied. Hydroxypropylmethylcellulose (HPMC) addition inhibited starch retrogradation. However, obtained films were more permeable, specially in case of oxygen. HPMC addition produced phase separation as it was observed by scanning electron microscopy. On the contrary, sodium caseinate incorporation (NaCas) allowed to obtain homogeneous films and less permeable to oxygen. Obtained films showed less mechanical resistance in comparison with pure starch films but a greater flexibility without increasing the water vapour permeability. Rearrangement of polymers chains during storage reduced the mechanical resistance, the extensibility and the gloss of composite films. Regarding the obtained results, the film including a starch:protein ratio of 50:50 was choosen as the film with the most adequate properties. Composite film (starch:Nacas ratio = 50:50) was studied as a matrix for the incorporation o active compounds (¿-tocopherol, D-limonene and orange essential oil). The effect of ¿-tocopherol addition was compared with the incorporation of oleic acid and their mixture. Lipids addition promoted phase separation between starch and NaCas due to the different interactions between each polymer and the lipids. Furthermore, oleic acid addition increased significantly the oxygen permeability whereas ¿-tocopherol greatly improved the antioxidant capacity of films without affecting the oxygen permeability. D-limonene and orange essential oil incorporation was carried out by forming rapeseed and soy nanoliposomes, which acted as carriers of bioactive components. Nanoliposomes incorporation was performed directly in starch-NaCas dispersions without any homogenization, to avoid nanoliposomes damages. Bioactive compounds addition did not confer antimicrobial capacity to the films (except for soy-orange oil nanoliposomes containing film) probably due to the high stability of nanoliposomes and the low antibacterial activity of D-limonene and orange essential oil. / Se han desarrollado y caracterizado films biodegradables a base de almidón de maíz y glicerol como plastificante, evaluando al mismo tiempo el efecto de la adición de componentes lipídicos (ácido palmítico, esteárico y oleico), otros polímeros (hidroxipropilmetilcelulosa y caseinato de sodio) y compuestos bioactivos (¿-tocoferol, aceite esencial de naranja y D-limoneno) sobre las propiedades de los films (propiedades barrera al vapor de agua y al oxígeno, ópticas, mecánicas, micro y nanoestructurales). Asimismo se evaluó la influencia del tiempo de almacenamiento en las propiedades de los films. La adición de ácidos grasos no mejoró notablemente la permeabilidad al vapor de agua excepto en el caso de los films con ácidos grasos saturados y solo en films no almacenados. Los resultados de difracción de rayos X mostraron que la cristalinidad aumentó con el tiempo de almacenamiento, incrementándose la rigidez, y disminuyendo el brillo de los films. Del mismo modo, la cristalinidad afectó a la capacidad de sorción de agua de los films en función de la humedad relativa y la temperatura. La temperatura de transición vítrea de los films de almidón se vio afectada por la adición de ácidos grasos saturados pero no por la adición de ácido oleico. La presencia de dichos componentes promovió la formación de estructuras cristalinas tipo V, indicando la formación de complejos entre los lípidos y las cadenas de amilosa e inhibiendo la formación de otros tipos de formas cristalinas. Se analizó también el efecto de la incorporación de otros biopolímeros en la posible mejora de la funcionalidad de los films de almidón. En las mezclas con hidroxipropilmetilcelulosa (HPMC), se inhibió la retrogradación del almidón en los films composite, pero se observó un efecto negativo en las propiedades barrera de los mismos, que fueron más permeables, principalmente al oxígeno. La adición de HPMC produjo separación de fases en los films (observada por microscopía electrónica de barrido). Por el contrario, la incorporación de caseinato de sodio (NaCas) permitió formar films homogéneos y menos permeables al oxígeno. Los films presentaron una resistencia mecánica algo menor que los films de almidón puro pero una mayor flexibilidad sin incrementar los valores de permeabilidad al vapor de agua. La reorganización de las cadenas de los polímeros con el tiempo de almacenamiento provocó la disminución de la resistencia mecánica, la deformabilidad y el brillo de los films composite. Atendiendo a los efectos observados, se eligió como formulación más adecuada el film composite formado por almidón y NaCas con un ratio de polímeros del 50:50. El film composite de almidón y NaCas (50:50) se estudió como matriz para la incorporación de compuestos bioactivos como son el ¿-tocoferol y el aceite esencial de naranja o su principal componente, el D-limoneno. El efecto de la adición de ¿-tocoferol se comparó con la influencia de la adición de ácido oleico y también con la adición de ambos compuestos. La adición de lípidos provocó una separación de fases entre el almidón y el NaCas debido a la diferente interacción entre cada polímero y los lípidos. Asimismo la adición de ácido oleico incrementó significativamente la permeabilidad al oxígeno, al contrario que el ¿-tocoferol, que además impartió a los films una elevada capacidad antioxidante. La incorporación de aceite esencial de naranja y D-limoneno se realizó utilizando nanoliposomas de lecitina de soja y lecitina de colza que encapsularon los compuestos activos. La incorporación de nanoliposomas en los films se realizó directamente en las dispersiones acuosas sin posterior homogeneización para evitar su ruptura. La adición de los compuestos bioactivos en forma de nanoliposomas no confirió capacidad antimicrobiana a los films, salvo en el caso de los nanoliposomas de lecitina de soja con aceite esencial, debido probablemente a la dificultad de los compuestos encapsulados para difundir en el film por la gran estabilidad de los liposomas y a la baja actividad antilisteria del D-limoneno y el aceite esencial de naranja. / Jiménez Marco, A. (2013). Propiedades de films de almidón de maíz. Influencia de la incorporación de lípidos, biopolímeros y compuestos bioactivos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28214 / Premios Extraordinarios de tesis doctorales