Дисертації з теми "Protéines sériques du lait"
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Geagea, Hany. "Contrôle des phages dans le lactosérum : étude de leur protection par les protéines sériques et identification d'un déterminant génétique responsable de leur résistance thermique." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/28377.
The incorporation of whey protein concentrates (WPC) into cheese is a risky process due to the potential contamination with thermo-resistant phages of lactic acid bacteria (LAB). Furthermore, whey proteins can protect phages during heat treatment, thereby increasing the above risk. The objectives of this work were to understand this protective effect and to identify genetic determinant(s) responsible for the thermal resistance of lactococcal phages. First, the effect of pH and time of heating on the inactivation of lactococcal thermo-resistant phage P1532 (Sk1virus/936 group) was measured, at 95 ºC, in WPC and in three individual major whey components. The molecular structure changes of the tested proteins were also monitored by Fourier transform infrared (FTIR) spectroscopy. Phage inactivation results indicated that acidic conditions of WPC favor the destruction of dairy phages by heat treatment. Moreover, it revealed that the protective effect of whey proteins was pH and time dependent and was not restricted to one component. FTIR spectra suggest that the protection is related to protein molecular structures and to the level of protein aggregates. Then, to further investigate this protection, we used lactoferrin (LF) as a whey protein model as a result of its unique physicochemical properties. We combined FTIR and circular dichroism (CD) spectroscopies to monitor the structural conformational changes of LF. Phage inactivation results revealed a strong protective effect of LF on P1532 phage at pH 5 but none at pH 7. Spectroscopic analysis showed that LF was unfolded after heating at pH 7, while it preserved its tertiary and secondary structures when heated at pH 5. In sum, there is a direct correlation between the thermal stability of whey proteins and their ability to protect P1532 phage from heat treatment. The results obtained in this respect offer new tools to minimize the impact of the protective effect on lactococcal phages. In order understand the thermal resistance of LAB phages, we aimed to identify genetic determinant(s) responsible for the thermal resistance of lactococcal phages. After challenging CB14 heat-sensitive phage (Sk1virus/936 group) to low and high temperatures, two phages with increased thermal resistance were selected. Sequencing of their genome revealed a 120 bp deletion in the gene coding for the tape measure protein (TMP). The TMP protein sequences of mutant phages were compared with their homologues in other wild-type L. lactis phages with a wide diversity in heat stability. Comparative analysis of TMP proteins of other lactococcal phages identified the same deletions in the extremely heat-stable phages P680 and P1532. We propose that the TMP is, in part, responsible for the heat stability of the highly predominant lactococcal phages of the Sk1virus group. Identifying this genetic determinant for Sk1virus heat stability is a first step to understand the emergence of this group of thermostable phages, and may lead to improved control strategies in the cheese industry
Pichard, Patrick. "Effets des protéines de différents produits laitiers sur les concentrations sériques du cholestérol et des lipoprotéines chez le rat : valeur nutritionnelle de ces protéines laitières." Paris 7, 1985. http://www.theses.fr/1985PA07F095.
Thill-Chardot, Valérie. "Étude de la dynamique de l'agrégation des micelles de caséines lors de l'acidification du lait : effet de la dénaturation thermique des protéines sériques." Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL023N.
Understanding mechanisms of acidic milk gelation implies the knowledge of casein micelles aggregation and of the different steps leading to gel formation. Small angle static light scattering and diffusing wave spectroscopy (DWS), which is based on light scattering in turbid medium, were used in this study. Static light scattering measurements permitted to follow micelles aggregation steps in diluted media and to calculate the fractal dimension of acidic aggreptes formed. Results showed the formation of four successive particle populations. The first population corresponds to casein micelles and the others populations correspond to casein aggregates with increasing size. The fractal dimension value, determined from double logarithmic plots of intensity versus scattering wave vector (q) resulted in value around 1. 8, which reflects a diffusion limited cluster aggregation mechanisms (DLCA). By static light scattering, casein/whey proteins ratio and heat treatment of milk were shown to influence the growth kinetics of aggregates, but only heat treatment of milk modified fractal dimension leading to more porous aggregates. The DWS results showed that acid gelation of unheated milk occurred via a single-stage aggregation. The aggregation pH was measured at pH 4. 9 and the gelation pH was estimated at pH 4. 8
Najib, Mustapha. "Étude du procédé de fabrication et caractérisation des interactions moléculaires lors de la fabrication de la Qishta et évaluation de la stabilité du produit alimentaire." Electronic Thesis or Diss., Université de Lille (2018-2021), 2020. http://www.theses.fr/2020LILUR057.
Qishta is a Lebanese dairy product obtained by heating whole milk for 2 to 3 hours in an open shallow vessel. During the process, milk is added to readjust its level and compensate the amount of evaporated water. The process consists of harvesting the coagulum formed at the milk surface. Our findings showed that these aggregates result from the denaturation of milk proteins and their interactions with the fat globules. This work has demonstrated that Qishta has almost the same amount of proteins and fat estimated at 12% and therefore the product has a composition similar to that of Ricotta cheese made from whole milk. The characterisation of Qishta using mass spectrometry has allowed to determine and quantify the proteins present in Qishta. These analyses have demonstrated also the presence of “Cross links” between proteins which are involved in the Qishta coagulum formation. Lanthionine and lysinoalanine were identified as neoformed amino acids during the heat treatment. These amino acids are involved in the cross links formed during the heat treatment of milk. These amino acids will establish covalent bonds between the proteins of Qishta coagulum. The confocal laser scanning microscopy analyses of Qishta samples previously treated with Fast Green and Nile red dyes have allowed to highlight the protein-fat interactions considered as the source of coagulum formation.Our findings showed the significant effect of the fat amount present in the initial milk on the process and the yield of Qishta. Increasing the amount of milk fat leads to an increase in the Qishta yield. A milk with 3.2% of fat has given the maximum yield. However, the use of skim milk in the production did not nor lead to any coagulum formation.The effect of ageing during Qishta storage for 20 days at 4 ℃ on the fat oxidation and therefore on the Qishta shelf life has been realized. The results of the primary and secondary indicators of oxidation analyses have showed the fat present in Qishta was not oxidized during the study period.In addition, the emission spectra of tryptophan, riboflavin and the excitation spectra of vitamin A were directly recorded using frontal fluorescence on Qishta stored at 4 ° C for 20 days.The analysis of these spectra by multidimensional statistical tools such as principal component analysis and discriminant factor analysis has allowed to significantly differentiate Qishta samples. Indeed, these analyses have allowed to significantly distinguish between the samples and subsequently predict their shelf life of the product
Tremblay-Marchand, Daniel. "Évaluation de l'impact de différents paramètres opératoires sur la performance de la membrane céramique à gradient de perméabilité pour la séparation des protéines sériques du lait par microfiltration." Master's thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/26669.
La microfiltration (MF) est un procédé membranaire permettant de séparer les micelles de caséines (CN) des protéines sériques (PS) du lait grâce à des pores ayant un diamètre de 0,1 μm. Le rétentat obtenu est enrichi en CN, tandis que le perméat contient des PS sous forme native. La membrane céramique à gradient de perméabilité (GP) a été développée récemment dans le but de réduire l’encrassement à long terme, ce qui permet des flux de perméation élevés et une meilleure séparation des protéines. À ce jour, les conditions opératoires les plus efficientes pour réaliser la MF du lait n’ont pas été déterminées pour ce type de membrane. L’objectif de cette étude était donc de caractériser l’effet de différentes pressions transmembranaires (PTM), différents facteurs de concentration volumique (FCV) et de la diafiltration (DF) sur l’efficience du procédé. Un bilan de matière a été réalisé à la suite du dosage des solides totaux, ainsi que de l’azote total, non caséique et non protéique. La consommation énergétique du système de MF a également été mesurée in situ. Les résultats obtenus démontrent qu’un FCV de 1,5X permet d’obtenir la meilleure séparation des protéines, tout en ayant un flux de perméation plus élevé et une plus faible consommation énergétique. Lorsque le FCV est plus élevé, les pertes totales de CN dans le perméat et la consommation énergétique deviennent plus importantes, ce qui réduit la rentabilité du procédé. Les étapes de DF réduisent l’efficience du procédé en augmentant la durée de filtration et la quantité de perméat généré de façon considérable, sans permettre d’obtenir une quantité satisfaisante de PS supplémentaires dans le perméat. Les résultats obtenus pourront bénéficier aux transformateurs laitiers lors de la prise de décision quant à la pertinence d’effectuer la MF du lait avec la membrane céramique GP.
Microfiltration (MF) is a membrane process used to separate casein (CN) micelles from serum proteins (SP) of milk using 0.1 μm pore diameter membranes. The resulting retentate is enriched in CN, while the permeate contains native SP. The graded permeability (GP) ceramic membrane has been recently developed to reduce long-term fouling, which improves permeation flux and protein separation. To date, the most efficient operating conditions to achieve MF of milk have not been determined for this type of membrane. The objective of this study was to characterize the effect of different transmembrane pressures (TMP), volumetric concentration factors (VCF) and diafiltration (DF) on the process efficiency. Mass balance measurements were carried out following the determination of total solids, total nitrogen, non-casein nitrogen and non-protein nitrogen. The in situ energy consumption of the MF system was also measured. Results obtained showed that a VCF of 1.5X provided the best separation of proteins, while allowing the highest permeation flux and the lowest energy consumption. When the VCF was higher, the total losses of CN in the permeate increased, as well as energy consumption, which reduces the process profitability. DF steps reduced the process efficiency by increasing the filtration time and the amount of permeate generated, without increasing significantly the transmission of additional SP in the permeate. Results will benefit dairy processors in decision making about the potential of MF of skim milk with GP membrane.
Ellouze, Maroua. "Les propriétés émulsifiantes du lait de chamelle et de ses fractions protéiques : étude physico-chimique et biochimique." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC052.
The emulsifying and interfacial properties of camel milk proteins were studied alone, in mixture or in their natural environment (in serum whey, as caseinates or directly in camel milk). The impact of certain physico-chemical conditions was studied, the impact of pH, heat treatment, concentration and homogenization at high pressures. This study was carried out in parallel on cow's milk, under identical conditions. The main results suggest that camel milk is more emulsifying than cow's milk regardless of the processing temperature, however, the stability of emulsions prepared by cow's milk is more important. The homogenizing effect at high pressures allows very stable emulsions compared to cow's milk. The effect of pH and temperature on the caseinic and serum fractions of camel milk is very significant on their behaviour at the oil-water interface and their ability to create emulsions. The coating of oil droplets by sodium caseinates protein of camel milk increases with incrising pH (from 3.0 to 9.0) regardless of the heat treatment (between 25°C and 95°C). This behaviour is the result of denaturation and loss of the micellar structure of sodium caseins at the oil-water interface, thus facilitating their adhesions and adsorption at the interface. However, the whey fraction of camel milk expressed significant emulsifying activity at acid pH as opposed to the sodium caseinate fraction and better emulsifying stability of the created oil droplets. Camel milk whey proteins are found to be less sensitive to the effect of temperature in emulsion creation than bovine milk whey (richer in β-lactoglobulin which are more sensitive to heat treatment). These aspects are due to the small molecular size of serum proteins relative to casein size, which allows them to adsorb quickly and efficiently at the interface of oil droplets and form a stable viscoelastic film all around which suggest that camel milk is more emulsifying active than cow's milk regardless of the processing temperature, however, the stability of emulsions prepared by cow's milk is found to be more important. The homogenizing effect at high pressures allows very stable emulsions compared to cow's milk. The main factor governing the stability of camel milk α-lactalbumin emulsions is its conformational flexibility at the oil-water interface. Structural rearrangements of camel milk α-lactalbumin as well as electrostatic repulsions between oil droplets stabilized by these proteins are the two key factors to explain the effect of pH variation and heat treatment. The surface properties of α-lactalbumin from camel milk are significantly improved after high heat treatments (95°C) which maintain potential emulsifying properties. As for the purified β-casein, its emulsifying activity is more important for camel milk than cow's milk. A micellar structure of caseins is formed from the critical micellar concentration (CMC) which maintains a compact structure close to pH 6.0 and is released at alkaline pH where electrostatic forces are at their highest. This induced a high stability of emulsions at pH 9.0 as well as a better emulsifying activity of β-caseins. The rheological behaviour of emulsions is non-Newtonian where viscosity is higher at low shear rates which depends strongly on the applied pH. Thus, stabilized emulsions at acid pH are the most viscous regardless of the heat treatment temperature applied for most of the studied fractions. This is mainly due to hydrophobic interactions between proteins of the different fractions and to high cohesion forces between larger droplets. However, the viscosity of emulsions stabilized by the protein fractions of cow's milk is often more viscous than camel milk as a result of their higher emulsifying stability. (...)
Granger-Delacroix, Manon. "Microfiltration tangentielle de lait écrémé : Impact des prétraitements du lait et de la conduite de la diafiltration sur les performances de la séparation et la qualité des fractions." Thesis, Rennes, Agrocampus Ouest, 2020. http://www.theses.fr/2020NSARB338.
Crossflow microfiltration of skimmed milk using 0.1 µm pore size is commonly used in dairy industry to separate casein micelles from serum proteins. However, the design and the conduct of this operation are not optimized. The objective of this thesis is to provide knowledge to improve the performance of 0.1µm-microfiltration skimmed milk. We considered both the characteristics of skimmed milk to be microfiltered and the operating conditions of the operation. This work shows that the duration of cold-storage and the method for microbiological stabilization performed prior microfiltration impact the performance of the operation. The decrease of performance (transmembrane pressure, serum protein recovery)is attributed to the cumulative effect of bacteria/bacterial fragments and modifications of serum proteins (denaturation and aggregation). Performance of microfiltration using polymeric membrane are considerably improved (increase of permeation flux and transmission of serum proteins) using diafiltration mode with reverse osmosis water realized on concentrated retentate and with low transmembrane pressure. The modifications observed can be explained by changes on the properties of the fluid (viscosity) and of the deposit of casein micelles accumulated at the membrane (swelling). These results and the analyses of composition and functionalities of fractions obtained with ceramic and polymeric membranes highlight the real necessity, in the futur, of multi-objective optimization of skimmed milk microfiltration
Kharlamova, Anna. "Texturization of dairy protein systems with whey protein isolate aggregates." Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1029/document.
The proteins of milk can be divided into whey proteins and caseins. Whey proteins are compact globular proteins that are found in the aqueous phase of milk. They are well-known for their exceptional functional properties. Upon heating, individual whey proteins denature and aggregate, forming aggregates of different morphologies and sizes, such as strands, fractal aggregates, microgels and fibrillar aggregates, depending on the heating conditions. On the other hand, the caseins in milk are organized in complex protein units with a diameter of 100-200 nm called casein micelles stabilized by colloidal calcium phosphate (CCP).The current work is an endeavor to understand how whey protein aggregates might be used in mixtures with other dairy proteins, such as casein micelles, in order to get a particular texture in a dairy product. We first extended the understanding of so-called “cold gelation” of pure WPI aggregates induced by calcium and acidification and then studied how the aggregates work in more complex mixtures of proteins and minerals. Interestingly, addition of small amounts of fractal aggregates to suspensions of casein micelles has been demonstrated to decrease the critical gelation temperature, increase the elastic modulus and decrease the syneresis of the gels.The aggregates are to be used to modify the viscosity of dairy products, as a gelling agent and for protein enrichment. The properties of strands, fractal aggregates and microgels have been studied and compared. WPI aggregates might be considered as “clean label” texturizing ingredients that do not require approval from the European Food Safety Authority (EFSA)
Karam, Marie-Céleste. "Réhydratation des protéines laitières dans un milieu complexe : influence de l'état d'hydratation sur les propriétés texturales des gels acides." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0132/document.
The main objectives of this work were to elucidate the rehydration mechanism of the two major milk proteins (micellar casein and whey protein) into a complex and opaque medium such as milk and to assess the influence of hydration state (defined as a function of rehydration length after 5,120,180,240,300, 480, 900 and 1440 minutes of rehydration) on the rheological, textural, physical properties and microstructure of the obtained acid milk gels. Whereas, micellar casein presented a long rehydration process into milk characterized by three stages: a wetting, swelling and dispersion phase, whey protein displayed a quick rehydration process characterized by an overlapping of wetting and dispersion phase. Furthermore, an extended rehydration time of micellar casein powder into the milk base was associated with a postponed onset of gelation and enhanced physical, textural as well as rheological properties of the obtained acid milk gels characterized by increases in gel firmness, strength, and decreases in syneresis susceptibility and grains formation. In contrast, acid milk gels prepared with whey protein powder exhibited comparable overall textural properties regardless the different rehydration times. Nevertheless, denaturation of whey protein powder (by dry heating) was associated with a deterioration of the textural properties of the acid milk gels. Finally, acid gels prepared with whey proteins displayed better overall textural quality than those prepared with micellar casein (except for grains formation)
Daynes, Aurélien. "Dosage de protéines sériques par la méthode d'agglutination magnétique." Paris 6, 2013. http://www.theses.fr/2013PA066307.
In vitro diagnostic is now a major actor in the domain of healthcare. There is a need for quick assays able to detect low concentrations of biomarker. Magnetic agglutination assay have been developed in that purpose. Antibodies grafted on superparamagnetic particles allow the formation of aggregates in a few minutes, thanks to the application of a magnetic field. Aggregates are generally observed by a turbidimetric method. First part of that work consisted in understanding the phenomena observed by turbidimetry. An agglutination model was developed, allowing predicting the number of aggregates formed, depending on the biomarker concentration. The model was confronted to experimental results. Experiments showed the effect of the way magnetic field was applied on aggregation, especially when important quantities of analyte were used. Concentrations around one picomolar were detected in less than one minute. In order to detect lower concentrations, an individual detection method, relying on the principles of flow cytometry, was then used. Decreasing of the background noise allowed reaching limits of detection of tens to hundreds of femtomolars. Parameters important to the assay, especially the size of the particles and the intensity of the magnetic field, were studied. This work make possible to detect a large variety of proteins, using the magnetic agglutination technique
Godard, Valérie. "Les protéines glyquées sériques : étude dans une population de diabétiques." Paris 5, 1989. http://www.theses.fr/1989PA05P072.
Espina, V. "Fractionnement de protéines du lait par filtration dynamique." Phd thesis, Université de Technologie de Compiègne, 2009. http://tel.archives-ouvertes.fr/tel-00433359.
Espina, Perez Valentina Soledad. "Fractionnement de protéines du lait par filtration dynamique." Compiègne, 2009. http://www.theses.fr/2009COMP1820.
This thesis focuses on milk proteins fractionation by dynamic filtration. A two-stage process has been proposed in order to separate milk proteins into three main fractions: casein micelles, A-Lactalbumin and A-Lactoglobulin. The first stage of the process consists in microfiltration of skim milk for separating casein micelles from whey proteins. The performances of two dynamic filtration modules: the Multi Shaft Disk (MSD) module and the rotating disk module have been compared. The results have shown that the MSD module presents high permeate flux, good whey proteins transmission and high casein micelles rejection. The second stage of the process is the separation of A-Lactalbumin from B-Lactoglobulin by ultrafiltration. The rotating disk module equipped with a disk with vanes and rotating at 2000 rpm, was used. The protein transmission and selectivity were constant during whey concentration. This is an advantage of dynamic filtration because in crossflow filtration protein transmission and selectivity decreased during whey concentration. The selectivities obtained with dynamic filtration, without changes in pH and ionic strength of the solution, were in the same range as those obtained with crossflow filtration after pH and ionic strength optimization
Saint-Eve, Anne. "Compréhension de la libération et de la perception des composés d'arôme en condition de consommation : cas du yaourt brassé aromatisé." Paris, Institut national d'agronomie de Paris Grignon, 2006. http://www.theses.fr/2006INAP0026.
Bonnefoy, Anne-Marie. "Etude de mécanismes homéostatiques intracellulaires et sériques des polyamines chez les eucaryotes." Lyon 1, 1985. http://www.theses.fr/1985LYO10015.
Matringe-Brunold, Elisabeth. "Propriétés fonctionnelles des protéines de lait et d'oeuf et de leurs mélanges." Dijon, 1993. http://www.theses.fr/1993DIJOS069.
Boutin, Chantal. "Propriétés émulsifiantes et gélifiantes des protéines sériques polymérisées, application dans la fabrication de yogourts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0030/MQ67430.pdf.
Zuñiga, de Lopez Raquel. "Étude structurale et texturale de laits acidifiés par hydrolyse de Glucono-Delta-Lactone et contenant des polysaccharides." Vandoeuvre-les-Nancy, INPL, 1999. http://www.theses.fr/1999INPL071N.
Saint-Sauveur, Diane. "Propriétés immunomodulantes des protéines et peptides du lactosérum." Thesis, Université Laval, 2009. http://www.theses.ulaval.ca/2009/26519/26519.pdf.
Chamoux, Muriel. "Étude des propriétés biologiques de l'angiogénine bovine et mise en évidence d'un récepteur sur les cellules endothéliales de capillaires." Lille 1, 1991. http://www.theses.fr/1991LIL10109.
Hélary, Mylène. "Caractérisation de l'effet satiétogène des protéines et macanismes impliqués : application aux protéines laitières." Paris, AgroParisTech, 2009. http://www.theses.fr/2009AGPT0073.
Goussard, Christophe. "Intolérance aux protéines du lait de vache (IPLV): une solution diététique, le lait hypoallergénique (exemple Nidal HAo)." Paris 5, 1990. http://www.theses.fr/1990PA05P047.
Andoyo, Robi. "Complexes thermo-induits de protéines de lactosérum : comment interagissent-ils avec la caséine dans les gels acides de lait ?" Rennes, Agrocampus Ouest, 2014. http://www.theses.fr/2014NSARB251.
In this project, we aimed at evaluating the role of physical factors, such as size and number of the denatured whey protein particles, on the acid gelation of skim milk model systems. To do that, two approaches were used, i. E. Varying the concentration, or the size of the particles using emulsification or microfluidics. Although concentration, size and number are somehow linked, our results showed that higher gel firmness is reached when connectivity is enhanced, i. E. When numerous particles are present; and in the case of mixtures with casein micelles, when enough particles are present to connect micelles together. The effect of size was less evident. Clearly, decreasing size leads to an increase in number and we indeed observed that small whey protein particles were forming gels with higher firmness. However, the effect was not linear, which suggested that a threshold value exists where the connectivity is not only low (due to a low number of particles) but maybe destroyed (due to hindrance of big particles in the gel). Although the denatured whey protein aggregates quantitatively affect the gel’s firmness and connectivity, the mechanism of gelation of model milk seemed to be essentially driven by the casein micelle, since the mixed gel had qualitatively the same scaling behavior than the pure casein. This is in agreement with the observation that whey protein aggregates preferably interact with the surface of the casein micelles, yielding “modified” casein micelles, with little or no side-interaction between the whey protein aggregates
Forkwa, Germaine Enyoh. "Boissons fermentées de type yogourt à boire enrichies en protéines de lactosérum et en probiotiques." Master's thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27736.
The aim of this project was to develop new fermented milk beverages from whey protein concentrates with attractive sensory properties. Other desired characteristics for these beverages were high protein concentration, high probiotic content and no use of additives (sugar, polysaccharides, colorants, artificial flavors). These drinks would have potential benefits on cardiovascular health, body weight and the well-being of consumers. Beverages containing 10% whey protein were obtained by fermenting whey protein concentrates (WPC) and/or whey protein isolates (WPI). Ten WPCs and two WPIs were evaluated for their ability to allow lactic fermentation by 2 types of mesophilic starter cultures. The medium with the best fermentation kinetics and the best organoleptic properties was selected. The impact of 7 thermophilic starter and 2 probiotic cultures on cell concentration and stability, post acidification and organoleptic properties was studied. The fermentations were adapted to generate products with at least 1 to 10 billion probiotics per serving. This project allowed the development of fermented beverages (drinking yogurt type) with 10% whey proteins and 2 billion probiotic bacteria per mL, exclusively from whey derivatives. Each 100 mL serving contained 200 billion probiotics and would be considered as a product with the highest probiotics counts on the Quebec market. These results could lead to the marketing of new products with high growth potential that respond to several market trends in the health food sector.
Marciniak, Alice. "Utilisation des hautes pressions hydrostatiques pour la modulation des interactions protéiques et la séparation des protéines sériques." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/33261.
Whey valorization through the better fractionation of highly valuable molecules is more than ever relevant in Quebec, as it is still used as a fertilizing residual material. Although whey protein concentrates have multiple nutritional and functional properties, the production of highly pure single proteins is more desired for their use in high quality product and in particular for infant formula. Usually, proteins separation is done using technologies with significant environmental and economic impacts as well as non-optimized effectiveness. For the major whey proteins such as alpha-lactalbumin (α-la) and beta-lactoglobulin (β-lg), the main problematic is their similar molecular weight. Consequently, the use of emerging and green technologies is crucial to improve the efficiency and productivity of existing processes. This thesis aims to demonstrate the potential of using a green and emerging technology known as high hydrostatic pressure (HHP) coupled with a ligand, caseins (CN) for the modulation of proteinprotein interactions to improve the fractionation of the two major whey proteins: α-la and β-lg with higher purity. In the first study, optimal pressurization parameters (duration and level of pressure) as well as ligand type (isoelectric CN – IC or micellar – MC) were determined. Broadly, HHP treatment induced specific aggregation of β-lg and CN, while maintaining α-la in its monomeric form. Subsequent acidification to pH 4.6 caused the precipitation of the β-lg/CN aggregates. Increase of pressure and process duration increased the β-lg/CN aggregation without significantly impacting α-la aggregation. Furthermore, the use of IC in comparison with MC improved the purification rate of α-la while decreasing its recovery rate. As part of a second study, the evaluation of concentration of CN as a ligand for the fractionation of α-la and β-lg was studied. The increase in CN concentration did not improve both the purification and recovery rates of α-la. Rather, at higher CN concentration, β-lg aggregation rate decreased, suggesting a chaperone-like effect of CN on the β-lg pressure-induced aggregation. In addition, pressurization of whey proteins in the absence of CN, resulted in a higher purification rate and recovery degree for both α-la and β-lg in soluble and insoluble fractions, respectively. Lastly, in the third study, the chaperone-like effect of β-CN on the pressure-induced aggregation of β-lg and α-la was investigated. Pressurization of single or combined whey proteins generated small globular aggregates with turbid solutions, whereas, the addition of β-CN decreased the turbidity in a concentration dependent manner. In parallel, limpidity was correlated with the presence of larger but amorphous aggregates with higher molecular weight. Furthermore, it was demonstrated that β-CN was not part of the aggregates formed, which is an important criterion of a chaperone-like protein. The present work has met all the objectives set in this thesis and contributed significantly to the advancement of knowledge concerning the application of HHP for the fractionation of α-la and β-lg with high purification and recovery rates, which is of great interest for the dairy processing industry.
Mahmoudi, Najet. "Impact de la structure sur les propriétés interfaciales d'agrégats de protéines globulaires du lactosérum." Nantes, 2007. http://www.theses.fr/2007NANT2102.
Whey proteins are widely used in the food industry for their emulsifying and foaming properties. The thermo-mechanical treatment during processing leads to aggregate formation whose role in the stabilization of dispersed systems is still poorly understood. In the present work, whey protein isolates have been subjected to thermal treatments, with or without shearing, in order to generate different types of aggregates. We have shown by light scattering and small angle neutron scattering as well as by cryo-transmission electron microscopy that aggregates formed without mechanical treatment have a fractal structure. The size and the fractal dimension of these aggregates depend on the ionic force and the protein concentration for neutral pH. Under shear, spherical structures of nanometric size have been observed. With dynamic drop tensiometry, Langmuir film balance studies and AFM the air-water interfacial layers have been characterized for the different aggregates types. It could be shown that the tension and dilatational elasticity properties depend on the presence of isolated proteins as well as on the size of the objects and their internal cohesion
Morand, Marion. "Des complexes protéiques thermo-induits fonctionnels : quelles interactions établissent-ils dans un gel acide laitier ?" Rennes, Agrocampus Ouest, 2011. http://www.theses.fr/2011NSARI063.
In the context of the acid gelation of milk, it is known that the heat treatment of milk at 85-95°C during several minutes increases the pH of gelation and yields more homogeneous, more elastic acid gels that also present less expulsion of serum than unheated milk. These new properties are attributed to the formation of heat-induced protein complexes. According to a recent hypothesis, these complexes interact with the casein micelle during heating or acidification. They functionalize the micelle, by modifying the colloidal interactions that account for its stability. However, these interactions are still not fully identified. The objective of this study was to evaluate the relationship between the physico-chemical properties of the complexes and the nature of the interactions that are established during acidification. The role of κ-casein involved in these complexes, as well as the role of hydrophobic or electrostatic interactions were tested. According to an original approach, each of these properties was widely modulated, without changes of the other properties. The consequences of these changes on the formation of the acid gel were measured using rheometry and confocal laser scanning microscopy. It was shown that the heat-induced complexes impose their functional properties of acid gelation to the casein micelle. During acidification, the reduction of the electrostatic repulsions between the complexes allows the particles to connect and to establish attractive interactions that induce destabilization of the milk and construction of the acid gel. Among these attractive interactions, hydrophobic interactions play a major role. These results shall participate to clarify the mechanisms of formation of acid milk gels
Queguiner, Claire. "Nouvelles propriétés fonctionnelles de protéines laitières obtenues par traitements thermomécaniques d'extrusion." Montpellier 2, 1992. http://www.theses.fr/1992MON20271.
Boutouili, Ghania. "Variations de la composition protéique et minérale du lait de vache : incidences sur les intéractions minéraux-protéines et la valeur technologique." Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPLA003.
Da, Silva Pinto Michele. "Chauffage et glycation des protéines du lait : agrégation et digestion in vitro." Rennes, Agrocampus Ouest, 2014. http://www.theses.fr/2013NSARB236.
Milk proteins are important for their nutritional value and for their functional properties. Heat treatment is commonly used in dairy technology and in some cases milk is submitted to cumulative heat treatments. However, behavior of protein during heating depends on the physico-chemical conditions and also on the presence of other molecules (sugar, protein and lipid). We hypothesized that in addition of the well- known β-lactoglobulin (β Lg) / κ-casein (κ-CN) complexes, other kind of aggregates occur in heated milk. To gain information of the occurrence of such species, the aim of this work was to study the effects of a strong heat treatment (90 ºC with different holding times) using following model systems: purified β Lg and β-casein (β-CN), in presence of a reducing sugar (glucose) at neutral pH heated up to 24 h; and β-Lg with other milk proteins: αS2 casein (αS2 CN) and κ-CN at neutral pH. Furthermore, we studied the consequences on the in vitro simulated digestion of the produced aggregates. To characterize aggregates formed during heat-treatment and their breakdown, we use a series of techniques: gel electrophoresis (LDS-PAGE), thioflavin T essay, transmission electron microscopy, size exclusion chromatography, fluorescence, dynamic light scattering and hydrolysis kinetics. Our results revealed that high temperatures have favored the formation of covalent bonds, others than disulphide. β Lg fibrils were produced at neutral pH and glucose decreased aggregate formation. On the other hand, glucose enhances β-casein aggregation. About digestion, when we consider only Maillard Reaction, we show that proteolysis was impaired by glycosylation. When β-Lg was heated with αS2-CN or κ-CN, we observed that homo- or hetero- aggregates were formed. Finally, the digestion of the mixed aggregates did not change when different proteins were heated together; even a slight increase of susceptibility to proteolysis was noted. These fundamentals studies highlighted some possible protein/sugar and protein/protein interactions during heat treatment, and give more details on the possible chemical transformations that occur during severe or cumulative heat treatments. Further, information about digestion of the aggregates may assist future studies about allergenicity or availability of milk proteins
Chevalier, Laura. "Étude des interactions entre les protéines de lactosérum et les fibres du bleuet dans la formulation d'aliments enrichis en fibres et en protéines." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/30958.
Fiber and protein are two nutrients highly desired by health-conscious consumers, however they cause texture and instability problems in the food products in which they are incorporated. In mixed systems, these two macromolecules may form complexes by electrostatic associative interactions under certain well-known conditions but far from food matrices and industrial reality. To date, there has been very little work on the application of protein-polysaccharide complexes in food products. In this thesis, interactions between whey proteins and blueberry puree, more specifically pectin, were studied in order to form protein-pectin complexes improving the functional properties of foods and beverages enriched in fiber and proteins. Firstly, purees of several blueberry cultivars were characterized, in particular in terms of fiber and pectin contents. Two cultivars were selected for the further work, namely Patriot for its larger production in Quebec and Polaris for its fiber richness. It was shown that the degree of methylation (DM) of their pectin can be decreased (< 50%) by applying a low-temperature blanching (LTB) onto the puree. A lower DM corresponds to a higher overall charge density, which may improve the pectin affinity toward proteins Then, whey protein isolate was added to non-heated and heated (LTB + pasteurization) purees. This time, blanching did not reduce DM and heating resulted in the solubilization of highly methylated pectin (DM > 70%). Regardless of the cultivar, insoluble protein-pectin complexes were formed at the acidic pH of blueberry (pH 3.5) in the non-heated puree and contributed to increase the viscosity of the resulting mixtures. In the heated puree, the high DM of pectin and the higher amount of soluble pectin probably decreased the pectin affinity toward proteins and increased the stability of the complexes. The non-heated mixtures that contained complexes were used to formulate smoothies and bars rich in fiber and protein. The final pasteurization of the smoothies enhanced complexation and reduced their particle size, which helped for reducing their viscosity, compared to the smoothies without whey proteins. For bars, complexes increased their initial hardness in particular because of a slower solubilization within the matrix, compared to bars without complexes. However, they contributed to slow kinetics of hardening over time, explained by a better stability of bar water activity and probably by a decrease in protein aggregation. All of this work demonstrated that a matrix composed of proteins added to blueberry puree is a functional ingredient that may be readily incorporated into formulations to produce foods and beverages rich in fiber and protein. These results show that the complexes formed between the proteins and the pectin in a puree have a significant impact on the textural and rheological properties of these products. They provide an original approach and new support for the industrial development of functional foods and beverages enriched with both fiber and protein.
Gentès, Marie-Claude. "Utilisation de complexes formés de pectine et d'isolat de protéines sériques dans la formulation de yogourts brassés." Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/25036/25036.pdf.
The aim of this work was to improve the rheological properties and whey retention of stirred yoghurts by the addition of whey protein isolate (WPI) and low methoxyl pectin complexes as stabilizing agent. The developed complexes were stabilized to a pH adjustment to 7.0 by the application of heat treatment. The level of incorporation to obtain adequate finish characteristics was determined. The stabilized complexes (heat treated) were unable to enhance the rheological properties of yoghurt despite of unheated complexes did. This effect could be due to the addition of WPI and pectin without complexe formation. Using a WPI and pectin solution without complexe formation led to increase the rheological properties. Varying the casein to total protein ratios gave different results: unheated complexes permitted to obtain greater rheological properties than WPI and pectin solution without complexe formation.
Canabady-Rochelle, Laëtitia. "Équilibre en calcium dans les systèmes lactés - Étude des interactions calcium-protéines." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL016N.
Ca equilibrium between soluble and colloidal phases was studied in milky systems (milk, Non Hydrolysed, NH, or Hydrolysed, H, soy milks). Calcium chloride supplementation (CC, 25 mmoles.kg-1) was followed by pH cycle (pHmin 5.5 or 3.5). pH, Ca2+, turbidity and apparent viscosity were recorded in situ. Ca equilibria were related to protein phase variations. Contrarily to milk, Ca2+ concentration was initially negligible in soy milks. Yet, whatever the milky system, Ca2+ increased upon CC addition and with acidification, and decreased during alkalinization. For reference milk, pH cycle to 5.5 was reversible neither on Ca2+ variations nor on protein phase contrarily to CC-milk. This could be due to the previous capture of Ca during supplementation, involving casein micelles reinforcement through Ca-protein interactions. For pH cycle to 5.5, acid-induced aggregation was partially and completely reversible upon alkalinization for NH and H-soy milks, respectively. Once CC addition, Ca-induced aggregation was irreversible and pH cycle had minor effects. Whatever the system, the irreversibility of phenomena was observed for pH cycle to 3.5. Ca-(milk or soy) protein interactions studied by ITC showed similar endothermic signals, probably due to the water release occurring upon interaction. Ca binding should rather be described as H+/Ca2+ exchange with respect to the electrostatic forces involved. Finally, Ca-binding sites were identified with FTIR spectroscopy. A decrease of the absorption energy in the amide I and II region and in the carboxylate region occurred upon CC-addition, with higher variations in soy milks
Nicodème, Muriel. "Identification d'une souche de Pseudomonas, bactérie psychrotrophe isolée de lait cru : Caractérisation de sa protéase extracellulaire et des sites d'hydrolyses sur les caséines bovines." Nancy 1, 2006. http://www.theses.fr/2006NAN10056.
Milk storage at refrigeration temperature permits the growth of psychrotrophic microorganisms, mainly belonging to the genus Pseudomonas that can generally produce heat-resistant extracellular proteases, causing milk proteolysis during storage. The proteolytic psychrotrophic strain isolated from raw milk, Pseudomonas sp. LBSA1 produces a unique caseinolytic extracellular protease with an apparent molecular mass of 49 kDa with milk addition. Different factors, such as temperature, agitation, and addition of many components can affect its production. A polyphasic taxonomic study of the LBSA1 strain reveals that it is phylogenetically related to the species P. Poae, but, it has an original siderovar and then it could belong to a new Pseudomonas species. The protease of the strain LBSA1 was purified, the corresponding gene was sequenced; the enzyme is identified as a zinc metalloprotease of the serralysin family (E. C. 3. 4. 24. 40). It is active under broad pH values and that optimal temperature for activity is nearly 40°C. The protease presented a low temperature inactivation around 45°C but it showed a greater stability around 60-80°C. The bovine caseins are rapidly hydrolysed by the enzyme without a real specificity but whey proteins are resistant to the action of the protease
Naveed, ul Haque Muhammad. "Production de protéines dans le lait en réponse à des profils en acides aminés intestinaux chez la vache laitière à différents niveaux d'apport de protéines digestibles dans l'intestin : Efficacité globale d'utilisation des protéines et des acides aminés." Rennes, Agrocampus Ouest, 2012. http://www.theses.fr/2013NSARB230.
Decreasing the supply of protein truly digestible in the small intestine (PDI) to dairy cows is a way to reduce nitrogen excretion in environment however it also decreases milk protein yield without increasing PDI supply. This is evident in the studies where Lysine (Lys) and Methonine (Met) were balanced n high PDI diets. Beyond Lys and Met, literature to see the effects of balancing other EAA on dairy cow’s performance is limited. Further, literature is inconsistent to conclude whether balancing the supply of EAA in low PDI diets could be equally effective as it proved to be in high PDI diets. Our objectives in this thesis were : 1) to refine the proposed ideal requirements of other EAA and to compare the increase in PDI efficiencies when diets were balanced with 2 (Lys, Met), 3 or all 9 EAA ; and 2) to see whether balancing EAA profile increase milk protein yield similarly at low vs. High PDI based diets and how mammary metabolism modifies with these changes. The results of these studies validate following requirements for EAA in dairy cows : 2. 5 % of PDI for Histidine 8. 9% of PDI for Leucine, 5. 2 % of PDI for Phenylalanine. PDI quality of diet based on corn-silage and soybean meal should account for Lys, Met, Histidine and Leucine concentrations. Balancing EAA profile increased PDI efficiency of conversion to milk by 7%-8% similarly in low vs. High PDI based diets. The increase in milk protein yield is a function of EAA uptake by mammary gland. In conclusion this research clearly demonstrate that balancing EAA profile of diet is an effective mean of decreasing PDI intake while maintaining milk protein yield at a similar level observed by providing high PDI based diets
Perreault, Véronique. "Contribution à la compréhension de la fonctionnalité des protéines du lactosérum dénaturées dans la matrice fromagère." Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27782.
La transformation du lactosérum de fromagerie en concentré de protéines du lactosérum dénaturées (CPLD), pour recyclage dans une production fromagère subséquente, est maintenant pratique courante dans l’industrie à grande échelle au Canada. Bien que les CPLD puissent être utilisés comme ingrédients de remplacement de la matière grasse, vu les coûts élevés de la protéine laitière dans le contexte canadien, l’emploi de CPLD vise parfois plutôt à substituer en partie la caséine du lait dans le fromage. Le CPLD ayant servi à réaliser le présent projet représente un CPLD conçu en milieu industriel dans cette optique. De façon générale, l’introduction de CPLD dans le lait de fromagerie est associée à une rétention d’eau accrue dans le fromage et à des changements de texture, mais les mécanismes responsables de ces phénomènes demeurent à clarifier. Cette thèse avait pour but d’étudier et expliquer les conséquences de l’addition de CPLD au lait de fromagerie sur les propriétés physico-chimiques des gels présure et mécaniques du fromage. Une première étude a permis d’évaluer l’effet combiné des niveaux de CPLD et de gras dans le lait de fromagerie sur ses propriétés de coagulation par la présure et la capacité de contraction du gel. L’augmentation du niveau de substitution des protéines du lait par des protéines du CPLD a résulté en une diminution du taux de coagulation et de la rigidité du gel (module d’élasticité - G), ainsi qu’en une diminution de la capacité de contraction du gel. Un effet direct du CPLD sur ces propriétés, au-delà d’un effet attribué à la dilution des caséines, a été mis en évidence. En outre, cette étude a permis de confronter l’effet des agrégats de protéines du lactosérum dénaturées, considérés comme éléments de remplissage des gels, à l’effet d’un autre type d’éléments de remplissage soient les gouttelettes de gras : à fractions volumiques équivalentes, les résultats ont montré des impacts distincts sur les propriétés mécaniques des gels. Une seconde étude a permis d’évaluer l’effet des différentes fractions du CPLD sur les propriétés de coagulation du lait par la présure et la capacité de contraction du gel. Le CPLD a été fractionné par centrifugation et dialyse en trois composantes : agrégats sédimentables, composante non sédimentable et composante diffusible. La composante diffusible (minéraux solubles) n'a pas affecté les paramètres de coagulation et de contraction. Les agrégats sédimentables de même que la composante non sédimentable ont influencé négativement les propriétés de coagulation ainsi que la capacité de contraction du gel. Les résultats ont notamment suggéré que des complexes protéiques solubles (non sédimentables et non diffusibles) retrouvés dans le CPLD puissent interagir avec les micelles de caséine emprésurées et limiter la formation et la contraction du gel. Une troisième étude a permis d’évaluer l'effet du CPLD et de ses fractions sur la composition et les propriétés mécaniques du fromage. La centrifugation a été utilisée pour induire un gradient d'humidité dans le fromage, afin d’isoler la contribution directe du CPLD et de ses fractions aux propriétés mécaniques du fromage. Le rendement et la teneur en humidité du fromage ont augmenté et la rigidité du fromage (module complexe - G*) a diminué avec l’augmentation du niveau de substitution des protéines du lait par des protéines du CPLD dans le lait de fromagerie. Cependant, pour des fromages ayant une même teneur en humidité, l’augmentation du niveau de CPLD n'a pas eu d'effet direct sur les paramètres rhéologiques. Les agrégats sédimentables ont été principalement responsables de l'augmentation du rendement fromager avec l’utilisation de CPLD. Dans l'ensemble, la teneur en humidité a expliqué en grande partie la variation des propriétés rhéologiques du fromage en fonction de la fraction de CPLD. Toutefois, en éliminant l'effet de l'humidité, l'addition des agrégats sédimentables du CPLD a conduit à une augmentation de la rigidité du fromage. Par la mise en évidence de l’effet distinct de chacune des fractions du CPLD, au cours de la transformation du lait en fromage, ces travaux ont conduit à l’identification de mécanismes d’action expliquant l’impact de l’introduction de CPLD dans le lait de fromagerie sur les propriétés des gels présure et du fromage : des connaissances en appui au développement de CPLD de haute performance en fromagerie et à l’amélioration de la qualité du fromage enrichi de CPLD.
Transformation of cheese whey into denatured whey protein concentrate (DWPC) for recycling into a subsequent cheese production is now common practice in large-scale industry in Canada. Although DWPC can be used as a fat replacer, considering the high cost of dairy protein in the Canadian context, DWPC is sometimes used as a substitute for milk casein in cheese. The DWPC used to carry out this project consists in a DWPC designed for this purpose in an industrial context. The introduction of DWPC into cheese milk is generally associated with increased water retention in cheese and changes in texture, but the mechanisms responsible for these phenomena remain to be clarified. This thesis was aimed at studying and explaining the consequences of the addition of DWPC to cheese milk on the physicochemical properties of rennet gels and mechanical properties of cheese. A first study evaluated the combined effect of DWPC and fat concentrations in milk on the rennet-induced coagulation properties and gel contraction capacity. The increase in the substitution level of DWPC proteins for milk proteins in cheese milk resulted in a decrease in coagulation rate and gel rigidity (elastic modulus - G), as well as a decrease in gel contraction capacity. A direct effect of the DWPC on these properties was demonstrated beyond an effect attributed to casein dilution. Moreover, this study allowed to compare the effect of denatured whey protein aggregates to that of fat globules, while both elements are considered to be fillers in rennet gels. For equivalent volume fractions, the results clearly showed different impacts of these fillers on gel mechanical properties. A second study evaluated the effect of different fractions from the DWPC on the rennet-induced coagulation properties and gel contraction capacity. The DWPC was fractionated by centrifugation and dialysis into three components: sedimentable aggregates, non-sedimentable component and diffusible component. The diffusible component (soluble minerals) did not affect coagulation and contraction parameters. The sedimentable aggregates and the non-sedimentable component both negatively influenced the coagulation properties as well as gel contraction capacity. The results suggested that beyond the effect of sedimentable whey protein aggregates, soluble proteinaceous complexes (non-sedimentable and non-diffusible) found in the DWPC could interact with the renneted casein micelles and limit gel formation and contraction. A third study evaluated the effect of DWPC and its fractions on the composition and mechanical properties of cheese. Centrifugation was used to induce a moisture gradient in the cheese to isolate the direct contribution of the DWPC and its fractions to the mechanical properties of cheese. Cheese yield and moisture content increased and cheese rigidity (complex modulus - G*) decreased when the DWPC was substituted for milk proteins in milk. However, for cheeses with the same moisture content, the substitution of DWPC proteins for milk proteins had no direct effect on rheological parameters. The sedimentable aggregates were primarily responsible for the increase in cheese yield with the use of DWPC. Overall, moisture content explained to a large extent the variation in cheese rheological properties depending on the DWPC fraction. However, when the effect of moisture was removed, the addition of the DWPC sedimentable aggregates to milk led to an increase in cheese rigidity. By demonstrating the distinct effect of each of the DWPC fractions during the processing of milk into cheese, this work led to the identification of mechanisms that explain the impact of introducing DWPC in cheese milk on the properties of rennet gels and cheese. These knowledges could support the development of high-performance ingredients that increase whey proteins recovery in cheese and could help to improve the quality of DWPC-fortified cheese.
Bouchard, Dominique. "Étude des fonctions d'une protéine à motif Whey Acidic Protein : la HE4 humaine." Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/23850/23850.pdf.
Casimir, Georges. "Contribution à l'étude de l'allergie aux protéines de lait de vache chez l'enfant." Doctoral thesis, Universite Libre de Bruxelles, 1990. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/213101.
Nabhan, Mohamad Ammar. "Protéolyse et redistribution des protéines entre différentes fractions azotées après traitement du lait par hautes pressions." Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL054N.
The thermal treatments induce frequently undesirable modifications in foods that could be avoided by the use of minimum treatment strategies. Among these treatments, high pressures are already commercialized by the alimentary industry. Pressure/temperature combination induced denaturation of beta-lactogiobulin and the formation of aggregates composed principally of beta-lactogiobulin, kappa-casein and of aipha-lactaibumin and of alphas1-casein at a lesser extent. The treatment reduce plasmin activity and induce an irreversible unfolding of alpha-lactaibumin at pH 7. 0 and a significant quantity was recovered in proteose-peptones fraction. To ensure the stability of natural microflora of milk during 21 days, milk must be treated at least 400 MPa and at comparatively extreme temperature. To eliminate completely the studied pathogen bacteria and ensure no surviving during 21 days, a treatment of at least 500 MPa and 55°C for 5 min minimum is necessary. Our results show that pressurized milks present an odor, a taste, a color and a texture different of pasteurized milk. Although different, the jury do not mark preference to any milk tested
Grandpierre, Catherine Bergonier. "Immunogénicité et antigénicité de produits de substitution dans les intolérances aux protéines de lait de vache." Toulouse 3, 1991. http://www.theses.fr/1991TOU30271.
Lajnaf, Roua. "Propriétés techno-fonctionnelles du lait de dromadaire." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT067.
Camel milk proteins isolates, prior to foaming properties, were studied as a function of pH and temperature of heat treatment. The purity of the extracted camel α-lactalbumin (α-La) and β-casein was estimated by combining different analytical methods such as high pressure liquid chromatography (HPLC) and SDS-PAGE electrophoresis.The increased temperature treatment changed the foaming properties of camel α-La solution and its ability to unfold at the air/water interface. At neutral pH, heat treatment was found to improve foamability, whereas at acid pH (4.3) this property decreased. Heat treatment caused changes in α-La surface charge and free thiol group concentration, which confirmed the pronounced aggregation of heated camel α-La solution. Otherwise, the foaming and interfacial properties of extracted bovine and camel β-casein showed that at neutral pH, maximum of foam volume was achieved by both camel and bovine β-caseins. This property decreased at acid pH because of the casein precipitation and the lower surface protein coverage. Findings indicated also that varying pH affected the physicochemical properties of the bovine and camel β-casein solutions by decreasing the surface negative charge and intrinsic fluorescence. These results were more pronounced on the bovine β-casein suggesting a higher acid-sensitivity of this protein when compared to its camel counterpart.The second part of this work investigated the foaming and adsorption behavior of camel proteins mixed systems compared to bovine systems including whey fraction, sodium caseinates (Na-cas) and α-La/β-casein mixed systems at different ratios. The results showed that, acid wheys gave better foams when compared to sweet whey for both milks, with higher values for the camel whey. This behavior was explained by the proximity of the isoelectric point (pI) of whey proteins (4.9–5.2), where proteins were found to carry the lowest negative charge as confirmed by the zeta potential measurements. Unlike whey fraction, camel and bovine Na-cas exhibited lowest foaming and interfacial properties near its pI because of the casein precipitation. Whereas, created foams were more stable at pH 5 than at pH 7 especially after a heat treatment. The heat treatment of 70 °C and 90 °C during 30 min affected also the physicochemical properties of the bovine and camel Na-cas by decreasing intrinsic fluorescence confirming also the pronounced caseins precipitation at pH 5 where caseins were found to carry the lowest negative charge as found by the zeta potential measurementsMixed solutions of the two isolated camel proteins (α-La and β-casein) at different ratios (100:0; 75:25; 50:50; 25:75; 0:100) give more foam with a higher β-casein amount in all camel and bovine mixtures. Good correlation was observed with the adsorption and the interfacial rheological properties of camel and bovine protein mixtures. Thus, the proteins adsorbed layers are mainly affected by the presence of β-casein molecules, which are suggested to be probably the most abundant protein at interface and the most efficient in reducing the interfacial properties. Whereas, globular proteins such as α-La and β-Lg are involved in the protein layer composition but could not compact well at the interface to ensure foams creation and stabilization because of their rigid molecular structure.This work therefore suggests new alternatives for the production of foam from proteins derived from dromedary milk, a dairy product characterized both by a high biological value but also by interesting functional properties of its proteins, in particular their surfactant power
Gaaloul, Sami. "Étude de la gélification et de l'incompatibilité thermodynamique de mélanges de protéines de lactosérum/kappa-carraghénane sous cisaillement." Thesis, Université Laval, 2009. http://www.theses.ulaval.ca/2009/26067/26067.pdf.
Lacroix, Magali. "Variations qualitatives & quantitatives de l’apport en protéines laitières chez l’animal & l’homme : implications métaboliques." Paris, AgroParisTech, 2008. http://pastel.paristech.org/5227/01/These-manuscrit.pdf.
Vidal, Véronique. "Influence des modifications chimiques des protéines du lait sur leur aptitude à la coagulation." Montpellier 2, 2000. http://www.theses.fr/2000MON20034.
Derisbourg, Pierre. "Etude des récepteurs entérocytaires de la lactotransferrine humaine : 1 - caractérisation des récepteurs des cellules entérocytaires humaines HT 29 : 2 - étude du mécanisme d'endocytose de la lactotransferrine." Lille 1, 1990. http://www.theses.fr/1990LIL1A002.
Colsenet, Roxane. "Étude par RMN de la diffusion moléculaire : influence de la structure des protéines laitières à l'état liquide et gélifié." Nantes, 2005. http://www.theses.fr/2005NANT2111.
Nasser, Sarah. "Evolution des propriétés structurales et fonctionnelles des poudres de PPCN en lien avec l’état initial et les conditions de vieillissement." Electronic Thesis or Diss., Lille 1, 2017. http://www.theses.fr/2017LIL10224.
During storage, the functional (rehydration) and sensory (color) properties of the milk protein powders can alter, especially when the casein content of the powder is high. Understanding the mechanisms of structural changes at the molecular level that are at the origin of those property changes of casein-concentrated powders represents an important challenge for the dairy industry and hence the objective of this thesis. For this purpose, powders of micellar casein (MC) with or without lactose were stored up to 12 months at 4, 20, 40 and 60 ° C. Evolutions of secondary structures, compound migrations, chemical modifications as well as the evolution of functional and sensory properties were determined experimentally.The analysis of the results demonstrated the possibility to predict i) the ageing trajectory of the MC powders stored at ambient temperature by applying accelerated aging conditions; ii) the total rehydration time using the experimental tests that we proposed.The secondary structural changes at the origin of protein destabilization as well as different chemical modifications (acetylation, deamidation, lactosylation, dephosphorylation) were identified according to the composition. It was established that the aggregation of the caseins on the particle surface slowed down their dispersion into the aqueous medium, resulting in an increase of rehydration time. Finally, it has been established that the absence of lactose does not prevent protein destabilization or formation of insoluble matter, but it does prevent browning
Gelebart, Perrine. "Modulation de la texture des gels acides laitiers par addition d'agrégats de protéines laitières." Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4018/document.
The texture of dairy products is a key parameter influencing consumer choices. In yogurt-type acid systems, the addition of milk protein aggregates would allow the development of products with innovative textures containing only dairy ingredients. The aim of this work is thus to highlight and understand the texturizing mechanisms of acidified models dairy emulsions through protein aggregates of different compositions, morphologies and sizes, by comparing them with conventional systems supplemented with whey proteins. For this purpose, fatty dairy gels acidified with GDL were manufactured by varying the concentration of different types of aggregates. The addition of whey proteins and fractal aggregates increases the strength of the gels and reduces their syneresis. Whereas the addition of compact spherical and mixed (casein-whey protein) aggregates does not modify the texture. Aggregates have a role in the continuous phase. The development of the interfacial surface by increasing the homogenization pressure and the fat fraction can allow the adsorption of aggregates at the interface of the fat droplets and increase the firmness. The nature of the aggregates influences interactions formed with the casein network during acidification. Among the interactions formed, disulphide bridges between whey proteins or fractal aggregates and the network were highlighted. The large variety of texture obtained in these systems demonstrates that it is possible to create innovative and specific products, especially protein-rich ones, to target certain types of population
Schong, Elise. "Assemblages microniques de protéines sériques produits par étuvage à pH 9,5 : mécanisme de formation et propriétés physico-chimiques et fonctionnelles." Thesis, Rennes, Agrocampus Ouest, 2017. http://www.theses.fr/2017NSARB302/document.
The dry heating of whey protein powder increases the functional properties of proteins such as their ability to form gels, foams or emulsions. The aim of this PhD thesis was to study the mechanism of formation and the physicochemical and rheological properties of protein assemblies of micrometer sizes that were produced by dry heating at 100 °C a whey protein powder isolate adjusted at pH 9.5 at a water activity of 0.2. Thus, morphological properties, protein denaturation, lactose conjugation and products of the Maillard reaction were studied during the time course of the dry heating. The role of each compound of the powder has also been studied by modification of the powder composition. Dry heating at pH 9.5 was able to form large assemblies of size and shape related to the size of the dry heated powder particles.In the first step, the glycation of proteins increased. Soluble aggregates formed and the powder browning progressed, while advanced glycated end products of the Maillard reaction were found. Then, the content in soluble aggregates decreased and large protein assemblies of micrometer sizes formed. These large assemblies were highly hydrated, and had very high viscosity values. Addition of lactose to the whey protein isolate powder allowed increasing the speed of formation of these large assemblies, increasing their density, and reaching higher yields of production. Caseins were able to join to whey proteins in the large assemblies, and had very poor effects on their structural properties and ability to retain the aqueous phase
Collard-Bovy, Christine. "Dosage des protéines du lait par immunonéphélémétrie sur supports microparticulaires : : Mise au point et applications." Nancy 1, 1988. http://www.theses.fr/1988NAN10491.