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Resumo: Objetivo: O objetivo do estudo foi comparar os efeitos de uma dose-única de caseína micelar (MCa) com a ingestão de caseína micelar associada à proteína do soro do leite (whey protein) (1:1) sobre a resposta aminoacidêmica e a via de sinalização do alvo da rapamicina (mTOR) em músculos esqueléticos de ratos durante a fase de inatividade (período de luz ambiente). Métodos: Após 10h de jejum durante a fase ativa, os ratos foram alimentados com MCa ou PB (5,6g proteína por kg de massa corporal) por gavagem e a água foi usada como veículo (grupo controle, PLA). Em 30 e 450 min após a suplementação das proteínas, os animais foram sacrificados e as amostras de sangue e do músculo gastrocnêmio foram coletadas para análises bioquímicas. Resultados: Os níveis plasmáticos dos aminoácidos de cadeia ramificada (BCAA) aumentaram após as suplementações de MCa (3 vezes) e PB (3,2 vezes). Ainda mais relevante, os níveis estimulatórios da fosforilação da mTOR e do seu alvo downstream p70S6K foram maiores 30 min após MCa (2,6 e 2,9 vezes, respectivamente) e PB (2,8 e 3,8 vezes, respectivamente) quando comparado com PLA. As concentrações plasmáticas de leucina forma correlacionadas com a ativação da mTOR (r = 0,60; p < 0,05) e p70S6K (r = 0,77; p < 0,05) em 30 min. Não existiu diferença para as concentrações plasmáticas de BCAA e a via de sinalização da mTOR em 450 min. Conclusão: Nós concluímos que a suplementação de MCa e PB resultaram em um efeito anabólico semelhante no músculo esquelético ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Objective: The aim of the study was to compare the effects of single-dose supplementation of a protein blend (PB) composed of micellar casein and whey protein (1:1) with isolated micellar casein (MCa) on aminoacidemic response and the mammalian target of the rapamycin (mTOR) signaling pathway 30 and 450 min after the beginning of the inactive phase in Wistar rats. Methods: After 10h of fasting during the active phase, rats were fed with MCa or PB (5.6g protein per kg of body mass) by gavage and water was used as the vehicle (PLA, placebo group). At 30 and 450 min after protein supplementation, the animals were euthanized and blood and gastrocnemius muscle samples were collected for biochemical and immunoblot analysis. Results: Plasma BCAA levels increased after MCa (3-fold) and PB (3.2-fold) supplementations. More importantly, the stimulatory phosphorylation levels of mTOR and its downstream target ribosomal protein S6 kinase (p70S6K) were higher 30 min after MCa (2.6 and 2.9-fold, respectively) and PB (2.8 and 3.8-fold, respectively) when compared with PLA. Plasma leucine levels were correlated with activation of mTOR (r = 0.60, p < 0.05) and p70S6K (r = 0.77; p < 0.05) at 30 min. There were no differences for plasma amino acids levels and the mTOR signaling pathway at 450 min. Conclusions: MCa and PB supplementations resulted in a similar anabolic milieu in rat skeletal muscle by inducing a transient increase in BCAA plasma levels and activation of the mTOR/p70S6K axis. / Mestre

The Western Dairy Center at Utah State University funded this project to investigate cheese research using concentrated milks. Concentrated milk was provided by the South Dakota State University and starter culture for this study was prepared and donated by Vivolac Cultures Corporation, Greenfield, Indiana. The project initiated as a continuation of a previous study on effects of protein concentration, coagulum cut size and set temperature on curd moisture loss kinetics while stirring during cheesemaking. It was aimed at determining the extent to which pH drop prior to draining and final cheese moisture when using microfiltered concentrated milk. We performed twelve cheesemaking trials using recombined milk from micellar casein concentrate, cream and skim milk according to a modified cheddar cheese-make procedure. Four different levels of starter cultures were used to achieve different acidification rates for pH change during cheesemaking. The amount of starter culture added had significant effect on moisture of cheese at whey drainage, moisture and pH of cheese. Thus, it can be said that the pH drop that occurs during the cheesemaking increases rate and extent of whey expulsion.

L'objectif de la thèse a été d'élucider le processus de réhydratation des caséines micellaires et des protéines solubles dans un milieu complexe et opaque : le lait. L'influence de l'état d'hydratation de ces ingrédients laitiers en fonction du temps (5, 120, 180, 240, 300, 480, 900 et 1440 min de réhydratation) sur les propriétés rhéologiques, texturales, physiques ainsi que la microstructure des gels laitiers acides a également été étudiée. Il en résulte que le processus de réhydratation des caséines micellaires diffère de celui des protéines solubles, et est extrêmement long avec trois étapes : une étape de mouillage des particules, suivie d'une étape de gonflement caractérisée par une augmentation de la taille des particules et enfin une étape de dispersion marquée par la diminution de la taille des particules. La réhydratation des protéines solubles est caractérisée par une grande rapidité, avec deux phases : le mouillage et la phase de dispersion (superposée). D'autre part, l'allongement de la durée de réhydratation des caséines micellaires est associé à une augmentation du point de gélification ainsi qu'à une nette amélioration des propriétés physiques, texturales et rhéologiques des gels : augmentation de leur fermeté et de leur force, diminution de la synérèse et de la formation de grumeaux. La durée de réhydratation des protéines solubles n'a pas d'influence sur ces paramètres. En revanche, leur dénaturation (par chauffage à sec) est associée à une dégradation des propriétés texturales des gels acides. Finalement, il s'avère que les gels acides formulés à partir des protéines solubles sont de meilleure qualité texturale (à l'exception de la formation de grumeaux) que ceux préparés à partir des caséines micellaires / 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)