Дисертації з теми "Whey protein isolates"

Whey protein isolates (WPI) have been indicated to have potent cholesterol lowering and antioxidative properties. Such effects, however, are not consistently observed, which could be the result of major differences in the processing, isolation and composition of WPI. Moreover, the mechanisms of action or the bioactive component(s) in WPI are poorly understood although the relatively high cysteine content in WPI has been suggested to play an important role. Although high dietary cysteine has been shown to lower plasma homocysteine concentrations, the impact of WPI in this regard has not been investigated. The overall objective of this thesis was to examine the antioxidative and plasma cholesterol and homocysteine lowering properties of two WPI that were produced via different industrial processing and isolation techniques with the milk protein, casein, used as the control protein. We also examined for the mechanism(s) of action of WPI in terms of possible antioxidative, and plasma cholesterol and homocysteine lowering effects. In this regard, the intake of bovine serum albumin (BSA), a major cysteine-rich whey protein was also studied since this protein has been implicated as a key bioactive component for the antioxidant effects of WPI. Four studies were performed. The first involved the characterization of a variety of commercially prepared WPI by high performance capillary electrophoresis for identification of two WPI products that showed major differences in protein composition for subsequent feeding trials. Most of the WPI had similar characteristic electrophoretic profiles, however, significant differences in protein and macronutrient (Ca, Mg, P) composition were noted in two commercial WPI that were chosen as the test proteins in subsequent feeding trials. In the first two feeding studies, hamsters were fed different commercial WPI or milk protein (BSA or casein) containing diets that were either matched or unmatched in terms of macro

Hydrostatic pressure has been demonstrated to induce major changes in secondary structure of whey proteins resulting in an increased digestibility in vitro, and possibly an improvement of the glutathione (GSH) inducing effect of whey proteins in vivo. Micro filtration and ion-exchange, two commonly used processing techniques in whey protein manufacture, generate whey proteins with different compositions. Two animal studies were designed to compare the digestibility and GSH inducing effects of whey protein isolates (WPIs) treated with three repeated pulse cycling of pressure (3-cycle) or single pulse of high pressure (1-cycle) and pressurized microfiltrated and ion-exchange WPIs. The results indicate that special hydrostatic pressure treatment on the proteins improves its growth stimulating effect, but does not enhance the GSH-inducing effect of WPI in the healthy growing rats. Difference among commercial whey protein products is also an important factor that affects the biological properties of the pressurized whey proteins. In conclusion, both proper pressure treatment and product composition should be considered in order to find the most bio-effective whey protein preparation.

Early introduction of cow's-milk-based infant formulas, in particular the ABBOS epitope of bovine serum albumin (BSA), has been implicated as an autoimmune trigger in the pathogenesis of insulin dependent diabetes mellitus (IDDM). A direct enzyme-linked immunosorbant assay (ELISA), using polyclonal anti-BSA antibodies, was developed to determine the BSA content of cow's milk and 15 infant formulas. Powdered high-whey (60%) formulas averaged 41 mg BSA/100 ml; 2% milk contained 52 mg BSA/100 ml; and the high-casein formulas averaged 13 mg/100 ml. BSA content of powdered polymeric formulas and cow's milk varied directly with the whey protein concentration (correlation coefficient = 0.8445, Q = 0.008). BSA was not detected in any hydrolyzed powdered formula or commercially sterile liquid preparation regardless of protein composition. The absence of BSA was confirmed by polyacrylamide gel electrophoresis. It is unlikely that the ABBOS epitope is present in the formulas testing negative for BSA due to enzymatic hydrolysis and heat denaturation of these formula preparations. A laboratory technology was developed that could be upgraded to produce BSA free protein bases used in the manufacture of infant formula. Affinity chromatography, using paramagnetic beads with an immobilized antibody against BSA, was applied to extract BSA from cow's milk and whey isolates. Monoclonal and polyclonal antibody-activated beads were used to capture BSA from samples. The capture efficiency in milk was 11% and 19% for polyclonal beads, and 59% for monoclonal beads. Capture efficiency of monoclonal beads of 91% was significantly greater in both acid and sweet whey compared to the polyclonal beads exhibiting a capture efficiency 31% and 24% in acid and sweet whey, respectively. Capture efficiency of monoclonal and polyclonal beads did not differ significantly in milk, acid whey, or sweet whey. Removal of BSA from a known sample of 25ng of BSA treated with polyclonal beads was 70% effective with a capture efficiency of 35%. A net reduction of 99.9% of the BSA could be expected by coupling immunocapture with molecular sieving. Immunocapture was most effective in removing BSA when only small amounts were present in the sample.

Cystic fibrosis (CF) is a fatal inherited disease characterized by chronic, persistent and exaggerated inflammation. The airways of CF patients exhibit a sustained influx of neutrophils and interleukin (IL)-8, the major neutrophil chemoattractant. Anti-inflammatory therapy is a focus of CF treatment, with a clear need for novel, safe and effective therapies. Whey proteins have been attributed a number of biological activities, including antioxidant and anti-inflammatory effects. Previous research has suggested a suppression of the inflammatory response to tumor necrosis factor (TNF)alpha by whey protein hydrolysates (WPH) in respiratory epithelial cell lines. Furthermore, it is suggested that hyperbaric pressure (HP) treatment of whey proteins can potentiate their biological activities. The effect of HP treatment on the digestibility, anti-inflammatory and antioxidant activity of whey protein isolates (WPI) was explored in a series of mechanistic in vitro studies and in a clinical trial. Hydrolysates of pressurized (pWPH) and native (nWPH) whey protein isolates were generated using two differing in vitro digestion protocols that mimic human gastrointestinal digestion. Hyperbaric pressure pre-treatment resulted in enhanced in vitro digestibility and antioxidant activity of WPI regardless of major differences in enzymatic conditions and the resulting peptide profiles, signifying that pressure processing generates an enhanced release of bioactive peptides regardless of the proteolytic environment. The peptide profiles obtained from the hydrolysates of pWPH exhibited quantitative and qualitative differences from those of nWPH. To explore the possible mechanisms by which WPH may exert their anti-inflammatory effects, wild-type and cystic fibrosis (CF) conductance regulator-deficient cells were treated with either nWPH or pWPH and stimulated with TNFalpha, interleukin (IL)-1beta or lipopolysaccharide (LPS). Both nWPH and pWPH suppressed LPS-induced IL-8 secretion, although pWPH were more potent requiring lower doses to exert significant inhibition. pWPH increased the ferric-reducing antioxidant activity of cell culture supernatant in both cell lines. Neither type of hydrolysate suppressed TNFalpha- or IL-1beta-induced IL-8 secretion. Since LPS and IL-1beta, beyond the activation of their respective receptors, share a common intracellular pathway, further experiments were conducted on signalling events that occur prior to the convergence of the two pathways, at the level of Toll-like receptor (TLR)4. There was no effect of either nWPH or pWPH on the cell membrane expression of TLR4. Neither type of WPH exhibited direct binding and neutralization of LPS, but both significantly reduced the binding of LPS to cell surface receptors. It is therefore likely that the WPHs exerted the observed LPS-induced IL-8 suppression by suppressing the binding of LPS to its receptor with the consequent inhibited activation of TLR4. To explore the possible in vivo clinical effects of pressurized WPI, a one-month, open-label pilot study of supplementation with pressurized WPI in children and adults with CF was conducted. Nutritional status was enhanced in both children and adults. An improvement in lung function was observed in children, and C-reactive protein decreased in the majority of patients with initially high values. Overall, the thesis results provide a novel mechanism by which whey proteins and pressurized whey can exert anti-inflammatory effects and suggest new potential avenues for the use of pressurized whey protein isolate as a nutrition-based anti-inflammatory therapeutic or preventative agent.
La fibrose kystique (FK) est une maladie héréditaire fatale caractérisée par une inflammation chronique et exagérée. Les voies respiratoires des patients atteints de FK présentent un afflux soutenu de neutrophiles et d'interleukine (IL)-8, l'agent chimiotactique majeur des neutrophiles. La thérapie anti-inflammatoire est un focus du traitement de la FK et il existe un besoin évident de nouvelles thérapies sûres et efficaces. Des effets biologiques, incluant des effets antioxydants et anti-inflammatoires ont été attribués aux protéines de lactosérum. Des recherches antérieures ont suggéré une suppression de la réponse inflammatoire induite par le facteur de nécrose tumorale (TNF)alpha par des hydrolysats de protéines de lactosérum (WPH). De plus, il a été suggéré que le traitement par pression hyperbare (PH) des isolats de protéines de lactosérum (WPI) peut potentialiser leurs activités biologiques. Les effets d'un traitement PH sur la digestibilité et les activités anti-inflammatoires et antioxydants des WPI ont été explorés dans une série d'études mécanistes in vitro et dans un essai clinique. Des hydrolysats de protéines de lactosérum pressurisées (pWPH) et non pressurisées (nWPH) ont été générés par le moyen de deux différents protocoles de digestion in vitro imitant le processus de digestion gastro-intestinal humain. Le prétraitement HP a entrainé une augmentation de la digestibilité in vitro et de l'activité antioxydante des WPI, malgré les différences entre les deux protocoles de digestion et entre les profiles de peptides résultant des digestions, signifiant que la pression génère une augmentation des peptides bioactifs générés quel que soit l'environnement protéolytique. Les profiles des peptides des pWPH ont exhibé des différences qualitatives et quantitatives comparés aux nWPH. Pour explorer les mécanismes possibles par lesquels WPH pourraient exercer leurs effets anti-inflammatoires, des lignées cellulaires normales et déficientes du Régulateur de la Conductance Transmembranaire Mucoviscidose (CFTR) ont été traitées avec nWPH ou pWPH et stimulées avec TNFalpha, IL-1beta, ou lipopolysaccharide (LPS). Les nWPH et pWPH ont diminué la sécrétion d'IL-8 induite par LPS, bien que les pWPH aient été plus puissants, requérant de moindres doses pour exercer une inhibition significative. pWPH a augmenté l'activité antioxydante des surnageants des cultures des deux lignées cellulaires. Aucun type de WPH n'a inhibé la sécrétion d'IL-8 induite par TNFalpha ou IL-1beta. Puisque LPS et IL-1beta partagent une voie commune de signalisation suivant l'activation de leurs récepteurs respectifs, des expériences ont été menées sur des événements prenant place en amont de la convergence des deux voies de signalisation, au niveau du récepteur Toll-like receptor (TLR)4. Les nWPH ni les pWPH n'ont eu d'effet sur l'expression du TLR4, mais la liaison entre LPS et les récepteurs de surface a été réduite par les deux traitements. Aucun WPH n'a exhibé de liaison directe ou de neutralisation du LPS. Il est donc probable que les WPHs aient exercé la suppression d'IL-8 induite par LPS en inhibant la liaison du LPS avec son récepteur et par conséquent l'activation du TLR4. Pour explorer les effets cliniques in vivo des WPI pressurisés, un essai clinique pilote d'une durée d'un mois a été mené, où des enfants et adultes souffrant de FK ont été supplémentés avec des protéines pressurisées. Le statut nutritionnel des enfants et adultes a été amélioré. Une amélioration des fonctions pulmonaires chez les enfants a été observée et le taux sanguin de protéine C réactive a diminué chez la majorité des patients chez qui les taux étaient élevés au début de l'étude. Globalement, les résultats de cette dissertation fournissent un nouveau mécanisme par lequel les WPI pressurisés peuvent exercer des effets anti-inflammatoires et suggèrent de nouvelles avenues potentielles pour l'usage des WPI pressurisés en tant qu'agent nutritionnel thérapeutique ou préventif.

Dans le lait on peut distinguer les protéines sériques et les caséines. Les protéines sériques sont des protéines globulaires qui se trouvent dans le sérum du lait et elles sont connues pour leurs propriétés fonctionnelles exceptionnelles. Quand une solution de protéines sériques est chauffée, elles perdent leur structure native et peuvent s'agréger. Elles forment des agrégats de différentes formes, tailles et densités : des cylindres, des agrégats fractals, des microgels et des agrégats fibrillaires. De l'autre côté, les caséines sont organisées dans des micelles de caséine d'un rayon environ 100-200 nm stabilisées par du phosphate de calcium colloïdal.Au cours de ce travail, nous avons cherché à comprendre comment les agrégats de protéines sériques pouvaient être utilisés en mélange avec les micelles de caséine pour obtenir et contrôler la texture de produits laitiers. Dans un premier temps, nous avons étudié le processus de « cold gelation » induit par ajout de calcium et/ou acidification d'agrégats et de microgels de protéines sériques seuls. Dans une deuxième partie, nous nous sommes intéressés à la fonctionnalité des agrégats dans les mélanges plus complexes avec les autres protéines laitières et en présence de minéraux. L'addition de petites quantités d'agrégats fractals dans des suspensions de micelles diminuait leur température critique de gélification, augmentait le module élastique et diminuait la synérèse des gels.Les agrégats de protéines sériques peuvent être utilisés pour modifier la viscosité des mélanges, comme gélifiant ou pour enrichir la teneur en protéine du milieu sans en augmenter la viscosité
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)

Whey proteins are mainly a group of small globular proteins. Their structures can be modified by physical, chemical and other means to improve their functionality. The objectives of this study were to investigate the effect of radiation on protein-protein interaction, microstructure, and microbiological properties of whey protein-water solutions. Whey protein isolate (WPI) solutions (27-36% protein) were treated with different dosages (10-35 KGy) of gamma radiation. The protein solutions were analyzed for viscosity, turbidity, soluble nitrogen, total plate count, and yeast and mold counts. The interactions between whey proteins were also analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and scanning electron microscopy (SEM). The viscosity of protein solution (27%, w/w) was increased from 2.19 for the control to 4.78 mPa*s for the sample treated at 25 KGy, respectively, and viscosity also increased during storage at 23°C. The soluble nitrogen (10%, w/w) was decreased from 100% to 54.7% for control and the sample treated at 35 KGy. The effects of gamma radiation and storage time on viscosity of whey protein solutions were significant (p

The purpose of this study was to evaluate the effectiveness of a whey protein isolate (WPI), a reported glutathione (GSH) booster, on exercise performance, immune function, and antioxidant status during weight maintenance and energy restriction in humans. Twenty well-trained, college age, male cyclists performed a cycling exercise test for 45 min, the first 7 min at 70% of VO2peak and the remaining 38 min at 55% VO2peak immediately followed by a performance test set at 90% VO2peak until exhaustion. Blood samples were collected prior to the exercise test, after 45 min of exercise, within 5 min of exhaustion, and 1 h after exercise. Blood samples were analyzed for GSH, GSH/GSSG ratio, glutathione peroxidase (GPx), lipid hydroperoxides (LPO), phagocytosis, oxidative burst, peripheral blood mononuclear cell (PBMC) proliferation, and PBMC phenotyping. Subjects consumed 40g/day of WPI or casein placebo (P) along with their normal diet for 2 wk, repeated the exercise test, and then began a low energy period continuing the same supplementation for 4 d before the final exercise test. WPI was not associated with superior exercise performance or antioxidant status following exercise or weight loss. WPI supplementation did result in 33% greater lymphocyte proliferation capacity following exercise. Following exhaustive exercise for all trials, tGSH and GPx increased 7% and 11%, respectively, while WBCGSH decreased 13%. For WPI, GPx activity was 10% lower than P following exhaustive exercise for all trials combined. Weight loss (2.67 ± 0.26 kg) resulted in increases in phagocytosis (65%), white blood cell (WBC) GSH (40%), and GPx (35%) while decreasing the GSH/GSSG ratio (55%) and LPO (16%). Exhaustive exercise caused a 28% increase in CD8+ PBMCs and decreased CD4+ (34%), CD3+ (15%), the CD4+/8+ ratio (45%), and phagocytosis (8%) with all values returning to baseline after 1 h recovery. Supplementation with WPI did not enhance GSH status or exercise performance in trained cyclists, during weight maintenance or energy restriction. Following exercise, WPI is associated with greater lymphocyte proliferation of PBMCs which may help maintain an athleteâ s health during heavy training or competition.
Ph. D.

Master of Science
Department of Food Science
Karen A. Schmidt
Milk proteins are excellent sources of sulfur-containing amino acids methionine and cysteine, in particular whey proteins. Cysteine is synthesized from methionine by γ-cystathionase. However, cysteine has to be included in the diets of certain subpopulations due to diminished γ-cystathionase activity. Cysteine, a heat- liable amino acid, may lose bioavailability during thermal processing. The objective of this research was to enhance cysteine content in yogurt while maintaining its quality. First, yogurt mixes were formulated to a total solids content of 12.5% with nonfat dry milk (NDM) (N) or a combination of NDM (10%) and whey protein isolate (WPI) (2.5%) (W), and processed at 70°C (20 min) (70) or 90°C (7 min) (90). Yogurt was prepared and maintained at 4oC for 60 days. Three replications were performed and data were analyzed using SAS®. The W mixes had 65%, 32% and 190% more cysteine, true protein and whey protein contents respectively, compared to N mixes prior to processing. However in day 1 yogurt, the highest cysteine content (398.3 mg/L) was found in the W70 yogurt and its gel quality was comparable to the N90 yogurt except for firmness. During a 60 day storage period the W70 and N90 were similar in gel quality except for firmness. Secondly, a hedonic test was done on the W70 (HC) and N90 (LC) yogurts which had been reformulated to contain sugar and vanillin. One replication was performed and data were analyzed using SAS®. The LC and HC yogurts did not vary in liking of flavor (6.1), aftertaste (6.1) and overall acceptability (6.3) corresponding to the words of “like slightly” when compared. However, the appearance of the LC yogurt was liked more than the HC yogurt (6.7 vs. 6.1) whereas the thickness of HC yogurt was liked more than the LC yogurt (6.4 vs. 5.8). These results suggest that addition of WPI along with lower process treatment resulted in yogurt with enhanced cysteine; however, further studies may be needed to optimize the WPI addition to improve the visual characteristics of the yogurt for consumer acceptance.

Whey protein isolate (WPI) forms particulate, heat-induced gels under conditions of low electrostatic repulsion among proteins. Particulate gels appear opaque, release water when deformed, and can be formed by 1) adjusting the pH to near the isoelectric point (pI) of beta-lactoglobulin (?pH treatment?), and 2) addition of >200 mM NaCl at pH 7.0 (?NaCl treatment?). The objective of our research was to understand the electrostatic contribution to particulate gel formation, using large strain rheology and microstructural techniques to characterize gel properties.Gels of WPI (10% protein w/v) were formed by heating at 80 degrees C for 30 minutes. The large strain fracture properties of shear strain at fracture, shear stress at fracture, and slope ratio (R0.3) (indication of non-linear stress/strain behavior) were measured with a torsion gelometer. Gel microstructure was observed using scanning electron microscopy (SEM). Gel permeability (Bgel) was evaluated by measuring the flow of solvent through a fixed gel matrix and calculating the permeability coefficient based on Darcy's Law. Fracture properties for both treatments were determined from pH 5.2 to 5.8 and NaCl concentration from 0.2 to 0.6 M (pH 7). When fracture stress and fracture strain curves for pH and NaCl treatments were overlaid, there was a distinct overlap. Based on this, treatment pairs were formulated to match rheological properties. The "high stress" pair was matched at pH 5.47 and 0.25 M NaCl, pH 7.0 (fracture stress=23 kPa and fracture strain=1.86) and the "low stress" pair at pH 5.68 and 0.6 M NaCl, pH 7.0 (fracture stress=13 kPa and fracture strain=1.90). Each pair was not significantly different for fracture stress(p>0.05), and there was no significant difference among all treatment pair values for fracture strain (p>0.05). However, the R0.3 was treatment, not pair specific. The NaCl treatments (0.25 M NaCl, pH 7 and 0.6 M, pH 7) had R0.3 values of 1.23 and 1.26, respectively, which were not significantly different (p>0.05). The gels formed at pH 5.47 and 5.68 had R0.3 values of 1.05 and 1.11, respectively, which were significantly different (p1) have been related to the presence of more than one structural component in the gel network (Bot et al., 1996). The increased strain hardening for NaCl treatments may be largely due to intermolecular disulfide bond formation, which is preferred at pH 7 relative to isoelectric pH due to the pKa of the thiol group. Random coil structure may be the other structural component that contributes to strain hardening in WPI gels, but more research is needed in this area.With the fracture properties normalized, no relationships were observed with the permeability or the microstructure between treatments. Lower permeability values were found for the treatment values (0.25 M NaCl, pH 7 and pH 5.68) near the fine-stranded transition regions (~pH 6 and 0.2 M NaCl, pH 7). These networks had more of a stranded-type structure with smaller, less defined aggregates as observed in SEM. This further demonstrates that there is little relationship between fracture rheology and microstructure of particulate gels.

Orientador: Celio Kenji Miyasaka
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: As proteínas do soro de leite são consideradas de alto valor nutritivo. Elas têm escore químico superior às de outras proteínas de origem animal, possuem elevadas concentrações de aminoácidos de cadeia ramificada (BCAA), com excelente balanço e biodisponibilidade de aminoácidos essenciais. As proteínas de soro de leite vêm sendo largamente utilizadas pela indústria de alimentos como suplemento na alimentação de esportistas, devido às suas características fisiológicas e funcionais, destacando-se o uso dos hidrolisados, que tem sido recomendado para situações de estresse metabólico como o exercício físico em que a reposição de proteínas no organismo se torna necessária. O presente trabalho teve como objetivo avaliar alterações metabólicas induzidas pelo consumo de proteínas do soro de leite [isolado (ISL) e seu hidrolisado (HSL) com grau de hidrólise 10%] em comparação com a dieta padrão [caseína (CAS)], utilizadas como única fonte protéica em ratos submetidos ao exercício físico. Foram utilizados 96 ratos machos Wistar (~100g) divididos em grupos segundo o tipo de dieta (CAS, ISL e HSL) e a intensidade do exercício físico [treinados (T), treinados exaustos (TEX), sedentários (S) e sedentários exaustos (SEX)] durante 35 dias. Os seguintes parâmetros foram analisados: tempo de exaustão, concentração de lactato no sangue, glicogênio hepático (GH) e muscular (GM), atividade das enzimas marcadoras de lesão tecidual, incluindo lactato desidrogenase (LDH), creatina quinase (CK), alanina e aspartato aminotranferase (ALT e AST, respectivamente). Os animais alimentados com HSL nos grupos TEX e SEX conseguiram correr por muito mais tempo até atingir a exaustão em relação aos que receberam as dietas com CAS e ISL (p<0.05). O tempo de exaustão em relação à dieta CAS foi 72 min maior no grupo TEX e 44 min maior no grupo SEX. A diferença no tempo de exaustão entre os animais alimentados com as dietas de HSL e ISL foi de 40 min. no grupo TEX e de 13 min no grupo SEX. A concentração de lactato dos animais alimentados com ISL e HSL foi significativamente menor em relação aos alimentados com CAS nos grupos T e S (p<0,05). A concentração de glicogênio hepático dos animais que receberam as dietas com ISL e HSL foi estatisticamente superior em comparação com os que consumiram CAS nos grupos T(46%) e S (61%). A concentração de glicogênio muscular não apresentou diferenças significativas entre as três dietas nos diferentes grupos de treinamento (TEX, SEX, T e S). A atividade da ALT dos animais que consumiram HSL nos grupos SEX e S foi estatisticamente menor que os que receberam CAS. A atividade da AST dos animais alimentados com HSL foi significativamente menor que a dos que consumiram a dieta com CAS nos diferentes grupos de treinamento (TEX, SEX, T e S). A atividade da CK e LDH dos ratos que receberam a dieta com HSL foi estatisticamente menor que dos alimentados com CAS em todos os grupos de treinamento exceto no grupo S. Dos resultados obtidos neste trabalho pode-se concluir que o uso das proteínas do soro de leite [principalmente o hidrolisado (10% grau de hidrólise)] em relação à proteína padrão (CAS) como única fonte protéica em ratos submetidos a exercício físico, promoveu a) menor ganho de peso em todos os grupos, b) maior resistência à exaustão tanto no grupo TEX como no SEX, c) maior concentração de glicogênio hepático nos grupos T e S e d) maior proteção contra possíveis lesões hepáticas e musculares nos diferentes grupos estudados (TEX, SEX, T e S)
Abstract: The milk whey proteins are considered to be of high nutritive value and superior chemical score in comparison to other proteins of animal origin. They have high concentrations of branched-chain amino acids (BCAA) with excellent balance and bioavailability of essential amino acids. The milk whey proteins are widely used in the food industry as supplements for sportsmen due to their physiological and functional properties, and their hydrolysates are thought to be more efficient in the recovery of debilitated organisms under pronounced catabolic state because of their great stimulation to protein synthesis. In view of the energy value of proteins in exhaustive exercise, several studies on exercise and protein metabolism have been carried out in the attempt to elucidate the proper amount of protein that must be consumed by sportsmen. The present work had the objective of evaluating the metabolic changes induced by consumption of milk whey proteins [isolate (WPI) and its hydrolysate (WPH) with hydrolysis degree 10%] used as the only protein source in comparison to the standard diet [casein (CAS)] in rats submitted to physical exercise. 96 male Wistar rats (~100g) were divided in groups according to the type of diet (CAS, ISL and HSL) and the intensity of physical exercise [trained (T), trained taken to exhaustion (TEX), sedentary (S) and sedentary exhausted (SEX)] during 35 days. The following parameters were analyzed: time of exhaustion (min.), blood lactate concentration (mmol/L), liver glycogen (LG) and muscular glycogen (MG) (g/100g of tissue), activity of tissue injury marker enzymes (U/L) including lactate desidrogenase (LDH), creatine kinase (CK) and alanine and aspartate aminotranferase (ALT and AST respectively). The results showed that the animals fed with HSL in the groups TEX and SEX ran for much longer times until exhaustion in relation to the ones that received the diets with CAS and ISL (p<0.05). The exhaustion time in relation to the CAS diet was 72 min longer for the TEX group and 44 min longer for the SEX group. The difference in exhaustion time between the animals fed with the WPH and WPI diets was of 40 min for the group TEX and 13 min for the SEX group. The lactate concentration in the animals fed with WPI and WPH was statistically lower than in the ones fed with CAS in the groups T and S (p99<0,05). The concentration of liver glycogen in the animals that received the diets with WPI and WPH was statistically higher than in the animals that consumed CAS in the groups T (46%) and S (61%). The concentration of muscular glycogen did not have significant differences between the three types of diet in the different groups of training (TEX, SEX, T and S). The activity of the ALT of the animals that consumed WPH in the groups SEX and S was statistically lower than that of the animals that received CAS. The activity of the AST of the animals fed with WPH was significantly lower than that of the animals that consumed the diet with CAS in all of the groups of training (TEX, SEX, T and S). The activity of CK and LDH in the rats fed with HSL diet was statistical lower than in the ones fed with CAS in all of the groups of training except in the group S. From the results obtained in this work it can be concluded that the use of milk whey proteins [mainly the whey protein hydrolysate (10% hydrolysis degree)] in relation to the standard protein (CAS) as the only protein source in rats submitted to physical exercise promoted a) lesser weight gain in all of the groups, b) higher resistance to exhaustion in groups TEX and SEX, c) higher hepatic glycogen concentration in groups T and S and d) higher protection against possible hepatic and muscular injuries in all of the studied groups (TEX, SEX, T and S)
Doutorado
Nutrição Experimental e Aplicada à Tecnologia de Alimentos
Doutor em Alimentos e Nutrição

This study investigated the static and dynamic physical properties of protein foams and cake batters made from egg white protein and whey protein isolate. A method of rheological evaluation (vane method) initially employed in the study of soils was used to evaluate protein foam rheology. The method was shown to be a reliable method for determining large-scale rheological properties of protein foams. Egg white protein produced foams with higher yield stress at lower concentrations and shorter whip times than did whey protein isolate. Short lifetime decreases in yield stress were observed in foams of higher protein concentration of both types, which were both concentration and whip time dependent. This is considered to be the result of a restructuring of the system as opposed to collapse of the foam. Cakes made from foams of both types showed different performance properties as well. Cakes produced from egg white protein exhibited a minimum concentration of protein (between 5 and 10% w/w of foam) necessary to form a cake of satisfactory volume. Whey protein isolate was unable to form a satisfactory cake regardless of the concentration studied. Phase contrast microscopy, fluorescence microscopy and differential scanning calorimetry studies suggested that the difference in behaviors might be due to a high degree of phase separation between egg white protein and soluble starch that was not seen in whey protein containing systems. This phase separation appears to allow significant matrix development in egg white protein containing cakes that can support the volume of the final product.

Des solutions d'isolat de protéine de lactosérum (WPI) et d'isolat de protéine de soja (SPI) ont été chauffées à différentes concentrations en protéines conduisant à la formation d'agrégats fractals polydisperses de taille moyenne variable. Lastructure des solutions a été analysée par diffusion de la lumière en fonction de la concentration en protéine. La compressibilité osmotique et la longueur de corrélation dynamique diminuent quand la concentration augmente deviennent indépendantes de la taille initiale des agrégats pour les suspensions denses. Pour une taille d'agrégat donnée, la viscosité augmente initialement exponentiellement avec la concentration croissante puis diverge. Plus lesagrégats sont grands, plus l’augmentation de la viscosité apparaît à des concentrations faibles. La dépendance avec la concentration de la viscosité des solutions d'agrégats fractals est beaucoup plus forte que celle de microgels. Le comportement de mélanges de différents types d’agrégats (fractals/fractals ; fractals/microgels et WPI/SPI) a étéétudié principalement par rhéologie.Le recouvrement de fluorescence après photoblanchiment (FRAP) a été utilisé pour étudier la diffusion de chaînes de dextran marquées par des fluorophores dans des solutions d’agrégats et des gels de WPI. Une diffusion brownienne estobservée dans des suspensions d’agrégats et des gels faibles formés juste au-delà de Cg avec un coefficient de diffusion (D) qui diminue avec l'augmentation de la concentration mais, avec une dépendance plus faible que celle de la viscosité (). A des concentrations plus élevées, des gels densément réticulés sont formés, ce qui induit une forte diminution de la mobilité des chaînes de dextran. Pour ces systèmes, la recouvrance de la fluorescence est logarithmique avec le temps,suggérant une distribution exponentielle des coefficients de diffusion. La diffusion des chaînes de dextran a également été étudiée en fonction de la concentration en protéines pour les suspensions de trois types d'agrégats de WPI (petits et grands fractals et microgels)
Polydisperse fractal aggregates of varying average sizes were formed when solutions of whey protein isolate and soy protein isolate were heated at different protein concentrations and at neutral pH. The structure of these fractals aggregates solutions was analyzed by light scattering as a function of protein concentration. In dense suspension, the osmotic compressibility and the correlation length decreases with increasing concentration and become independent of the initial aggregate size. In this concentration regime, the aggregates are strongly interpenetrated and can be visualized as a set of "blobs". For a fixed aggregate size, the viscosity initially increases exponentially with increasing concentration and then diverges at the gel point. Larger fractal aggregates show a more important increase of the viscosity with increasing concentration than smaller aggregates, because they are less dense. The increase of the viscosity was much stronger for large fractal aggregates than for homogeneous microgels (microgels were formed by heating the WPI solution in present of CaCl2) of the same size.Dynamic light scattering, rheology and FRAP measurements were performed to investigate mixtures of different type of aggregates of WPI (fractals/fractals, fractals/microgels) and fractals of mixtures of WPI and SPI. Flow measurements were used to characterise the rheological properties of the aggregate suspension whereas Fluorescence recovery after Photobleaching (FRAP) was used to determine the self diffusion of fluorophore-labelled dextrans chains in mixtures over a wide range of concentrations. The results were compared to the concentration dependence of zero shear viscosity, gel stiffness, osmotic compressibility and correlation length. Brownian diffusion of the dextran chains was observed in aggregate suspensions and weak gels formed just above the gel point with a diffusion coefficient that decreased with increasing concentration, but the dependence was weaker than that of the viscosity. At higher concentrations, densely crosslinked gels were formed, which induced a sharp decrease in the mobility of the dextran chains. For these systems, the recovery of fluorescence was logarithmic over time, suggesting an exponential distribution of diffusion coefficients

The development of reduced fat foods is a continual challenge in the food industry. Among the many attributes fat contributes to food products is flavor. Fat replacers are used to regain some of these lost attributes as fat is removed from foods. These fat substitutes affect the rate and concentration at which flavor molecules are released during mastication. Whey is a source of protein for protein-based fat replacers. The effects this ingredient has on flavor intensity was studied utilizing 2,4-Dimethylbenzaldehyde (DMB) and Ethyl Butyrate (EB). The objective of this project was to develop a headspace gas chromatography method to measure the changes in volatility of these two flavor compounds in various concentrations of WPI solutions and to compare these results to sensory findings. There was a significant decrease in the volatility of DMB with increases of protein concentration from 0 to 2%. Aroma and taste intensity also decreased with increasing protein concentration. The volatility of EB and taste intensity showed no significant differences with successive increases in protein concentration. However, aroma shows significant decreases in intensity with increases in protein concentration at the 0 to 2% and 4 to 6% levels. There was significant positive correlations between volatility and sensory results.

Crispness is one of the most desirable textural characteristics of breaded fried foods. Consumers often judge the quality of breaded fried foods based on the perceived crispness of the product. Furthermore, today's consumers are showing increasing concern over fat intake. As a result, there is great interest in being able to enhance the crispness and reduce the fat uptake in breaded fried foods without sacrificing other quality attributes. To achieve these goals, modifications to both frying equipment and product formulation have been explored in this study. In this study, two edible film coatings, methylcellulose (MC) and whey protein isolate (WPI) were incorporated into the batter and pre-dust to determine their effect on the crispness of breaded fried chicken nuggets held under a heat lamp for varying time intervals. Crispness was evaluated by both objective (ultrasonic non-destructive evaluation system) and subjective methods. An untrained sensory panel was used to obtain subjective measurements of product crispness. Panelists rated product attributes such as crispness, juiciness, oiliness and flavor on a simple intensity scale. Additionally, panelists rated the liking of the products on a nine-point hedonic scale (1=dislike extremely, 9=like extremely). Two pressure sources (nitrogen gas and steam naturally released from the food material) were used to determine their effects on product crispness, texture, pressed juice, moisture content, fat content and color. Products fried with nitrogen gas as the pressurizing medium produced samples that were comparable to or exceeding the quality of products generated by frying with steam, as it relates to product crispness, texture, pressed juice, moisture content, fat content and color. As related to objective crispness, chicken nuggets fried with nitrogen were significantly crispier (p<0.05) than those fried with steam. Coating type and application also had a significant effect on product crispness. Samples coated with MC in the pre-dust were crispier than samples coated with WPI. However, no significant differences were found in product crispness, juiciness, oiliness or flavor, and overall liking among samples tested by the sensory panel. The results of this study demonstrated that applying an edible film coating to the pre-dust and using nitrogen gas as the pressurizing medium can enhance and maintain the crispness of breaded fried foods.
Master of Science

Lors de la production des poudres protéiques laitières, des précautions sont prises pour assurer des fonctions technologiques optimales selon leurs utilisations. Cependant, des évolutions structurales et fonctionnelles surviennent lors du stockage. Ce projet vise ainsi à comprendre les mécanismes de modification qui interviennent lors du stockage des poudres d’isolat de protéines solubles du lait (WPI). Pour ce faire, des poudres de WPI ont été stockées en conditions contrôlées (15 mois à 20°C, 40°C et 60°C), et leurs évolutions structurales et fonctionnelles après réhydratation ont été suivies expérimentalement à intervalles réguliers.Les résultats montrent que le vieillissement suit une trajectoire définie impliquant d’abord la lactosylation d’une partie des protéines, puis leur agrégation à l’état sec. De plus, cette trajectoire est caractérisée par un phénomène de rattrapage des modifications observées aux basses températures vers les plus hautes. L’impact des évolutions structurales sur les propriétés fonctionnelles est contrasté : les résultats montrent que les propriétés moussantes et interfaciales sont peu affectées, alors que les propriétés d’agrégation thermo-induites sont grandement modifiées. Pour minimiser ces modifications, deux pistes d’amélioration ont été suivies : 1. la granulométrie des poudres et 2. la teneur en lactose résiduel. La différence de granulométrie n’a pas eu d’influence sur le vieillissement alors que la diminution de la teneur en lactose a permis de limiter significativement l’étendue des modifications induites lors du stockage
During dairy powder manufacture, precautionary measures are taken to ensure optimal technological functionalities regarding their use requirements. However, changes in structural and functional properties appear during storage. This project aimed understand the mechanisms of changes that occur during storage of whey protein isolate (WPI) powders. To do this, WPI powders were stored under controlled conditions (20°C, 40°C and 60°C for 15 months), and their structural and functional changes after rehydration were experimentally monitored at regular intervals. The results showed that ageing follows a specific path involving first protein lactosylation and then their aggregation in the dry state. In addition, this path was characterized by a catching up behaviour from the changes obtained at lower temperatures to those at highest temperatures. The impact of these structural changes on the functional properties was mixed:the results showed that the foaming and interfacial properties were only slightly affected, while the heat-induced aggregation properties were greatly modified. To minimize these storage-induced changes, several areas for improvement were followed, playing on either the powder particle size, or on lactose content whose role appeared to be crucial for the development of the Maillard reaction. The study showed that the difference in powder particle size had no influence on their ageing path while lowering the lactose concentration allowed to significantly reduce the extent of the storage-induced changes

Inflammatory bowel disease (IBD) is a chronic debilitating disorder characterized by various forms of chronic mucosal and/or transmural intestinal inflammation, which increases the synthesis of the hepatic acute phase proteins contributing to muscle wasting and impaired growth. For the present thesis, in vitro and in vivo models of gut inflammation were used to study the antioxidant and anti-inflammatory effects of native and pressurized whey protein isolate (WPI) and polyphenols, as these nutritional supplements could be used to ameliorate complications of IBD. The antioxidant, anti-inflammatory and anabolic effects of WPI were examined in piglets with dextran sulfate sodium (DSS)-induced colitis that were fed a moderate protein deficiency diet that contained either native WPI (nWPI), pressurized WPI (pWPI) or skim milk (SM) as the protein source plus a well nourished SM control group. Although piglets receiving both forms of WPI diets gained less absolute weight than their SM counterparts, pWPI-fed piglets gained more lean mass than nWPI piglets, and were the only protein restricted group to gain a high lean/fat ratio comparable to well-nourished controls. Histopathology scores in descending colon (DC) were lowest in both WPI groups. The pWPI-fed piglets had the lowest myeloperoxidase activity in DC reflecting low neutrophil infiltration and also had the highest ferric reducing antioxidant power (FRAP) activity in DC and the highest serum peroxynitrite scavenging capacity. Pro-inflammatory cytokines in DC were most elevated in SM piglets, and lowest in pWPI. Control-, nWPI- and pWPI-fed piglets had the lowest caspase-3 abundance in DC signifying anti-apoptotic effects as compared to SM group. As an in vitro model of gut inflammation, Caco-2 cells were exposed with H2O2, that received either pre- or post-treatment with WPI hydrolysates. WPI hydrolysates were associated with decreased interleukin (IL)-8 secretion, lower intracellular reactive oxygen species (ROS) and increased FRAP activity; however, those parameters were all significantly improved when hydrolysates of pressurized WPI were used. In another study, polyphenolic-rich potato extracts were subjected to gut digestive enzymes and microbial metabolism in a simulated human gut model and the antioxidant and anti-inflammatory effects of the polyphenolic digests were tested in Caco-2 cells exposed to H2O2. Treatment of H2O2-stimulated Caco-2 cells with digests of polyphenolic-rich potato extracts was associated with decreased IL-8 release, lower ROS production and higher FRAP activity. Overall, the present thesis showed results regarding the antioxidant and anti-inflammatory effects of pressurized WPI and polyphenolic extracts that indicate the potential for these nutraceutical agents towards the treatment of IBD.
Les maladies inflammatoires de l'intestin (MII) sont des troubles chroniques et débilitants caractérisés par diverses formes d'inflammation chronique de la muqueuse et/ou transmurale, ce qui augmente la synthèse des protéines hépatiques de phase aigüe qui contribuent à l'atrophie musculaire et à l'altération de la croissance. Pour la présente dissertation, des modèles in vitro et in vivo d'inflammation intestinale ont été employés pour étudier les effets antioxydants et anti-inflammatoires de polyphénols et d'isolats de protéines de lactosérum (WPI) natives et pressurisées, puisque ces suppléments nutritionnels pourraient être utilisés afin d'améliorer les complications des MII. Les effets antioxydants, anti-inflammatoires et anaboliques des WPI ont été examinés dans un modèle de colite induite par administration de dextran sodium sulphate chez le porcelet. Des porcelets ont été soumis à une alimentation modérément déficiente en protéines contenant des WPI natives (nWPI), pressurisées (pWPI) ou du lait écrémé (SM) comme source de protéines; et un groupe de porcelets contrôle a été soumis à une alimentation suffisante contenant du lait écrémé. Bien que les porcelets recevant les deux formes d'alimentations WPI ont démontré un gain de poids absolu moindre que leurs homologues SM, les porcelets du groupe pWPI ont gagné plus de masse maigre que les porcelets nWPI et étaient le seul groupe sous restriction protéique à gagner un ratio de maigre/gras élevé et comparable aux contrôles bien nourris. Les résultats de l'histologie pathologique du côlon descendant (DC) ont été les plus bas chez les deux groupes WPI. Dans le DC, les porcelets nourris de pWPI ont eu les taux d'activité de myeloperoxidase les plus bas, reflétant un bas taux d'infiltration par les neutrophiles, ainsi que la puissance antioxydante réduisant les ions ferriques (FRAP) la plus élevée, et les taux sériques les plus élevés de capacité de balayage peroxynitrite. Les cytokines pro-inflammatoires dans le DC étaient le plus élevées chez les porcelets SM, et le moins élevées chez les pWPI. Les porcelets contrôles, nourris de nWPI et pWPI ont montrés la présence en abondance de caspase-3 la plus basse dans le DC, signifiant un effet anti-apoptotique comparativement au groupe SM. Dans un modèle in vitro d'inflammation intestinale, des cellules Caco-2 étaient exposées au H2O2 avant ou après être traitées avec des hydrolysats de WPI. Les hydrolysats de WPI étaient associés à une diminution de la sécrétion d'interleukine (IL)-8 et des taux intracellulaires d'espèces réactives de l'oxygène (ROS), ainsi qu'une augmentation de l'activité FRAP. De plus, ces paramètres étaient tous améliorés de façon significative quand les hydrolysats de WPI pressurisées étaient employés. Dans une autre expérimentation, des extraits de pomme de terre riches en polyphénols étaient soumis à l'action d'enzymes digestives intestinales et au métabolisme microbien dans un modèle intestinal humain simulé. Les effets antioxydants et anti-inflammatoires des produits digestifs phénoliques étaient administrés à des cellules Caco-2 exposées au H2O2. Le traitement des cellules stimulées au H2O2 par les produits digestifs des extraits de pommes de terre riches en polyphénols était associé à une diminution de la sécrétion d'interleukine (IL)-8 et des taux de ROS, ainsi qu'une augmentation de l'activité FRAP. Globalement, la présente dissertation démontre des résultats concernant les effets antioxydants et anti-inflammatoires des WPI pressurisées et des extraits polyphénoliques, indiquant un usage potentiel de ces agents nutraceutiques pour le traitement des MII.

This study compared the effects of whey and casein on plasma AA, nitrogen balance (NBAL), glutathione and performance in dieting athletes. Twenty cyclists consumed 40 g·d-1 whey (WHEY) or casein (CAS) for 3 wk. On d 18 – 21 subjects restricted intake to 20 kcal·kg-1·d-1 plus protein supplement. Apparent NBAL was estimated on d 18 – 21 while postabsorptive and 2 h postprandial plasma AA were measured on d 14 and 21. On d 1, 15 and 22 subjects performed an exercise performance test and provided blood for glutathione analysis. Both groups experienced similar negative NBAL (CAS = -19.7 ± 1.4 g, WHEY = -21.4 ± 2.7 g) during energy restriction. There were trends towards a reduction in performance during energy restriction (p = 0.073) and an interaction of group with day (p = 0.072). There were significant main effects of state (postabsorptive = 34.5 ± 2.4 µM, postprandial = 37.1 ± 3.0 µM; p = 0.038) and day (d 14 = 33.8 ± 2.2 µM, d 21 = 37.8 ± 3.2 µM; p = 0.008) on plasma cysteine. There was a significant interaction of state and day on glutamine (p = 0.002), as levels increased 1.3% from postabsorptive to postprandial measurements on d 14, but decreased 4.2% on d 21. The absolute change in postabsorptive cysteine from d 14 to d 21 was correlated with NBAL (r = 0.766, p = 0.01) in CAS but not in WHEY. Plasma glutamine did not correlate with NBAL in either group.
Master of Science

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.

[EN] Persimmon (Diospyros kaki L.) 'Rojo Brillante' is an astringent variety characterised by good growing conditions, excellent colour, size, sensory characteristics and good nutritional properties. In the last decade, its production has grown substantially in Spain given the application of high levels of CO2 to remove astringency while firmness is preserved. This technology has also increased its potential as a fresh-cut commodity. However, physical damage during processing result in degradation of the colour and firmness of the product and a higher susceptibility to microbial spoilage that significantly reduces the fruit's shelf life. The objective of the present thesis was to develop optimum procedures for processing and marketing 'Rojo Brillante' persimmon into a fresh-cut product with the maximum shelf life and best physicochemical, nutritional, sensory and microbiological quality. Firstly, the objective was to evaluate the effect of the maturity stage (MS) at harvest, storage time at 15 ºC before processing, and the application of different antioxidant treatments on enzymatic browning, sensory and nutritional quality of fresh-cut 'Rojo Brillante' persimmon during storage at 5 ºC. Concentrations of 10 g L-1 ascorbic acid (AA) or 10 g L-1 citric acid (CA) controlled tissue browning and maintained the visual quality of fresh-cut persimmon above the limit of marketability for 6-8 storage days at 5 ºC, depending on the MS. However, these acidic solutions reduced fruit firmness as compared to control samples. Further studies showed that the combination of these antioxidants with 10 g L-1 CaCl2 maintained firmness of the persimmon slices within the same range as the control samples. In another work, the application of 1-methylcyclopropene (1-MCP) allowed to process fruits after 45 days of storage at 1 ºC with commercial firmness and the antioxidant solution (10 g L-1 CA + 10 g L-1 CaCl2) extended the limit of marketability up to 9 days of storage at 5 ºC. Different controlled atmosphere conditions in combination with AA or CA dips were also evaluated as a first step to select optimum O2 and CO2 concentrations for modified atmosphere packaging (MAP) of fresh-cut 'Rojo Brillante' persimmons. Overall, the combination of antioxidant dips and a controlled atmosphere composed of 5 kPa O2 (balance N2) was proved to be the most effective combination to control enzymatic browning. This atmosphere maintained the visual quality of persimmon slices within the limit of marketability during 7- 9 days at 5 ºC. On the contrary, high CO2 concentrations (10 or 20 kPa) induced darkening in some tissue areas, associated with a flesh disorder known as 'internal flesh browning'. Later studies confirmed the beneficial effect of an active MAP in 5 kPa O2 compared to passive MAP to improve the visual quality of fresh-cut 'Rojo Brillante' persimmon, showing a synergic effect with the antioxidant dip (10 g L-1 CA + 10 g L-1 CaCl2). Antioxidant edible coatings were prepared from whey protein isolate (WPI), soy protein isolate (SPI), hydroxylpropyl methylcellulose (HPMC) and apple pectin as the polymeric matrix. All edible coatings were amended with the antioxidant combination selected (10 g L-1 CA + 10 g L-1 CaCl2). All the edible coatings tested proved effective to control enzymatic browning of persimmon slices. However, the samples treated with the HPMC- and pectin- based coatings were scored with a better visual quality that the rest of the treatments. In general, free radical scavenging activity and total carotenoid content increased in late-season persimmons; whereas, processing (cutting and storage at 5 ºC), antioxidant dips, controlled atmosphere storage or edible coatings had no clear effect on nutritional quality (vitamin C, free radical scavenging activity, total phenolic content, and carotenoids) of fresh-cut persimmons.
[ES] El caqui persimmon (Diospyros kaki L.) 'Rojo Brillante' es un cultivar astringente que presenta unas propiedades organolépticas y nutricionales excelentes. En la última década, su cultivo en el área mediterránea de España se ha incrementado de manera exponencial con el desarrollo de la tecnología que permite eliminar la astringencia, manteniendo la firmeza del mismo. Esta nueva forma de presentación, aporta numerosas ventajas, entre la que se incluye la posibilidad de ser comercializado como fruta fresca cortada. Sin embargo, el éxito comercial del producto está limitado por el pardeamiento enzimático, la pérdida de firmeza y al crecimiento microbiano. En este contexto, el objetivo de la Tesis ha sido el desarrollo de caqui 'Rojo Brillante' fresco cortado mediante un enfoque que integra el estudio de las características del producto en el momento del procesado y de distintas tecnologías que mantengan la calidad físico-química, sensorial, nutricional y microbiológica del producto durante un periodo que permita su comercialización. En primer lugar, se evaluó el efecto del estado de madurez (MS) en el momento de recolección, el tiempo de almacenamiento a 15 ºC antes del procesado y la aplicación de diferentes antioxidantes en el pardeamiento enzimático y la calidad sensorial y nutricional del caqui 'Rojo Brillante' cortado y almacenado a 5 ºC. La aplicación de 10 g L-1 de ácido ascórbico (AA) ó 10 g L-1 ácido cítrico (CA) controló el pardeamiento enzimático y mantuvo la calidad visual del caqui por encima del límite de comercialización entre 6 y 8 días de almacenamiento a 5 ºC, dependiendo del MS. Sin embrago, la aplicación de estos antioxidantes redujo de manera significativa la firmeza del fruto respecto al control. La combinación de estos antioxidantes con 10 g L-1 de CaCl2 permitió mantener la firmeza en el mismo rango que las muestras control. En un trabajo posterior, la aplicación de 1-metilciclopropeno (1-MCP) permitió procesar caqui almacenado 45 días a 1 ºC con una buena firmeza comercial y el tratamiento antioxidante (10 g L-1 CA + 10 g L-1 CaCl2) consiguió alcanzar un límite de comercialización del producto de 9 días a 5 ºC. La evaluación de distintas atmósferas controladas en combinación con tratamientos antioxidantes (AA o CA), como paso previo al envasado en atmósfera modificada (MAP) del caqui, mostró como más efectiva en el control del pardeamiento enzimático la atmósfera compuesta por 5 kPa O2 (balance N2). Esta atmósfera mantuvo la calidad visual del caqui cortado dentro del límite de comercialización durante 7-9 días a 5 ºC. Por el contrario, la aplicación de altas concentraciones de CO2 (10 ó 20 kPa) dio lugar a un pardeamiento en ciertas zonas de la pulpa que se conoce como 'internal flesh browning'. Estudios posteriores confirmaron el efecto beneficioso del envasado de caqui cortado y tratado con solución antioxidante (CA-CaCl2) en una MAP activa de 5 kPa O2 en la calidad visual del fruto frente a la aplicación de una MAP pasiva. El desarrollo de recubrimientos comestibles con capacidad antioxidante se realizó mediante la incorporación de antioxidantes (10 g L-1 CA + 10 g L-1 CaCl2) a formulaciones a base de proteína de suero lácteo (WPI), proteína de soja (SPI), hidroxipropilmetilcelulosa (HPMC) y pectina. Todos los recubrimientos fueron efectivos controlando el pardeamiento enzimático del caqui cortado, siendo las muestras recubiertas con HPMC y pectina las mejor evaluadas visualmente. En general, el procesado, la aplicación de antioxidantes, el envasado en atmósferas controladas y los distintos recubrimientos comestibles estudiados, si bien no mostraron un efecto claro en los parámetros de calidad nutricional evaluados, no tuvieron un efecto negativo en los mismos. Por otra parte, los frutos cosechados a final de campaña tuvieron mayor actividad antioxidante y contenido en carotenoides.
[CAT] El caqui persimmon (Diospyros kaki L.) 'Rojo Brillante' és un cultiu astringent que presenta unes propietats organolèptiques i nutricionals excel¿lents. En la última dècada, el seu cultiu en l'àrea mediterrània d'Espanya s'ha incrementat de manera exponencial amb el desenvolupament de la tecnologia que permet eliminar l'astringència, mantenint la fermesa del mateix. Esta nova forma de presentació, aporta un gran nombre d'avantatges, entre els quals s'inclou la possibilitat de comercialitzar-lo com fruita fresca processada. No obstant, l'èxit comercial del producte està limitat per pardetjament enzimàtic, la pèrdua de fermesa i el creixement microbià. L'objectiu de la Tesis ha estat en el desenvolupament de caqui 'Rojo Brillante' tallat en fresc mitjançant un enfocament que integra l'estudi de les característiques del producte en el moment del processat i de diferents tecnologies en el manteniment de la qualitat físico-química, sensorial, nutricional i microbiològica del producte durant un període que permeta la seua comercialització. En primer lloc, es va avaluar l'efecte de l'estat de maduresa (MS) en el moment de recol¿lecció, el temps d'emmagatzemament a 15ºC abans del processat i l'aplicació de diferents tractaments antioxidants en el pardetjament enzimàtic i la qualitat sensorial i nutricional del caqui 'Rojo Brillante' tallat i emmagatzemat a 5 ºC. L'aplicació de 10 g L-1 d'àcid ascòrbic (AA) o 10 g L-1 d'àcid cítric (CA) va controlar el pardetjament enzimàtic i va mantenir la qualitat visual del caqui per damunt del límit de comercialització entre 6-8 dies d'emmagatzemament a 5 ºC, depenent del MS. No obstant, l'aplicació d'antioxidants va reduir de manera significativa la fermesa del fruit comparat amb el control. La combinació d'aquestos antioxidants amb 10 g L-1 de CaCl2 va permetre mantenir la fermesa en el mateix rang que les mostres control. En un treball posterior, l'aplicació de 1-metilciclopropeno (1-MCP) va permetre processar caqui emmagatzemat 45 dies a 1 ºC amb una bona fermesa comercial i a més, el tractament antioxidant (10 g L-1 CA + 10 g L-1 CaCl2) va aconseguir un límit de comercialització del producte tallat de 9 dies a 5 ºC. L'avaluació de diferents atmosferes controlades en combinació amb tractaments antioxidants (AA o CA), com a pas previ a l'envasament en atmosfera modificada (MAP) del caqui 'Rojo Brillante, va mostrar com a més efectiva en el control del pardetjament enzimàtic l'atmosfera composta per 5 kPa O2 (balanç N2). Aquesta atmosfera va mantenir la qualitat visual del caqui tallat dins del límit de comercialització durant 7-9 dies a 5 ºC. Per contra, l'aplicació d'altes concentracions de CO2 (10 ó 20 kPa) va donar lloc a un pardetjament en certes zones de la polpa, el qual és conegut com 'internal flesh browning'. Estudis posteriors van confirmar l'efecte beneficiós de l'envasament de caqui tallat i tractat amb solució antioxidant (CA-CaCl2) en una MAP activa de 5 kPa O2 millorant la qualitat visual de la fruita front a l'aplicació de una MAP passiva. El desenvolupament de recobriments comestibles amb capacitat antioxidant es va realitzar mitjançant la incorporació d'antioxidants (CA-CaCl2) en formulacions a base de proteïna de sèrum làctic (WPI), proteïna de soia (SPI), hidroxipropilmetilcel-lulosa (HPMC) i pectina. Tots els recobriments van ser efectius controlant el pardetjament enzimàtic del caqui tallat. No obstant, les mostres recobertes amb HPMC i pectina van ser millor avaluades visualment que la resta de tractaments. En general, el processat, l'aplicació d'antioxidants, l'envasament en atmosferes controlades i els distints recobriments comestibles estudiats, si bé no van mostrar un efecte clar en els paràmetres de la qualitat nutricional avaluats, no van tindre un efecte negatiu en els mateixos. Per altra banda, els fruits recol¿lectats a final de temporada van tenir major activitat antioxidant i contingut en
Sanchís Soler, E. (2016). Effect of processing on the physicochemical, sensory, nutritional and microbiological quality of fresh-cut 'Rojo Brillante' persimmon [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62588
TESIS

Thesis (M.S.)--University of Georgia, 2002.
Directed by Milena Corredig. Includes articles submitted to The journal of dairy research, Food hydrocolloids, The journal of food science, and The journal of food quality. Includes bibliographical references.

It is well established that endurance exercise training leads to cardiovascular, skeletal muscle, and metabolic adaptations, with important implications for both athletic performance and health. While many studies have addressed the effects of endurance exercise training on such adaptations, very few have examined the role of post-exercise nutritional supplementation in facilitating or increasing the magnitude of the adaptive response. The beneficial effects of post exercise nutrition, in the form of carbohydrate and protein, following an acute bout of exercise has been the focus of many investigations. The results however remain equivocal due to methodological differences, such as the training status of participants, the treatment groups not being isocaloric, differing CHO contents, different protein sources, exercise modes and protocols, and outcome measurements all being different. The quality of the protein source used in post exercise supplementation may also affect training adaptations. Animal-source of proteins, such as milk and the constituent proteins of milk, casein and whey, are classified as being of high biological availability and quality. The types of proteins that are best for achieving muscle recovery and adaptations after endurance exercise are not defined. The significant aim of this PhD candidature was to determine the role of protein supplementation, when included in the training diet over an extended period, on endurance training adaptations. Along with investigating how different proteins affect the signalling pathways that regulate endurance training adaptations. As such the research presented in this thesis examines 8 weeks of supplementation, with and without an endurance training program, with micellar caseins or caseinates, whey protein isolates or a carbohydrate matched and isocaloric group in animal and human models. The first study demonstrated that after 8 weeks of supplementing with whey protein isolates, this group had lower body fat compared to the carbohydrate group at week 4 (P < 0.05) and week 8 (P < 0.05). The micellar caseins group had lower body fat compared to carbohydrate group only after 8 weeks (P < 0.05). A key finding in the second study was that despite matching all rodents across groups according to exercise performance, the carbohydrate supplemented animals were unable to perform for as long in the time to exhaustion test compared to both whey protein isolates and micellar caseins groups (P < 0.05); 14:19 ± 4 min, 29:81 ± 11 min and 25:51 ± 6 min.. There was no significant difference between protein groups in several measures including; enzyme activity of citrate synthase and β-hydroxyacyl-CoA dehydrogenase (βHAD), mitochondrial respiration or lean mass. The third study examined post-exercise supplementation with calcium caseinates compared to whey protein isolates in trained cyclists in a double-blind manner. Participants were provided all meals and snacks for the duration of the study. Endurance exercise performance, body composition and mitochondrial respiration, along with proteins involved in mitochondrial biogenesis showed no difference between protein groups after 8 weeks of supplementation and endurance training. This research has established that micellar caseins and whey protein isolates may have beneficial effects on body composition and mitochondrial function without exercise, however following exercise training these mitochondrial function differences are diminished. Despite this, animals supplemented with the different proteins and undertook an endurance training protocol for 8 weeks performed significantly better in the time to exhaustion test. Thus, it appears that this improved time to exhaustion is not related to improved mitochondrial function, but by some other, yet to be determined factor.

Poly(ethylene oxide) (PEO) is known for facilitating the electrospinning of biopolymer solutions, that are otherwise not electrospinnable. The objective of this study was to investigate the mechanism by which PEO enables the formation of whey protein isolate (WPI) electrospun fibers under different pH conditions. This investigation revealed that the addition of PEO increased the viscosity of WPI/PEO (10% w/w WPI; 0.4% w/w PEO) solutions. Difference in pH levels of the polymer solutions affected electrospinnability and fiber morphology. Acidic solutions resulted in smooth fibers (700 ± 105 nm) while neutral solutions produced spheres (2.0 ± 1.0 um) linked with ultrafine fibers (138 ± 32 nm). In comparison, alkaline solutions produced fibers (191 ± 38 nm) that were embedded with spindle-like beads (1.0 ± 0.5 um). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analyses revealed that the native globular configuration of WPI was not altered under neutral conditions. By contrast, the electrophoresis and spectrometry data indicated that WPI was denatured and hydrolyzed under acidic conditions, which facilitated the formation of smooth fibers. C13 nuclear magnetic resonance (NMR) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopies showed that the increase random coil and a-helix secondary structures in WPI contributed to the formation of bead-less electrospun fibers. Also, C13 NMR analysis showed no evidence of chemical interaction between WPI and PEO. Scanning transmission electron microscopy coupled with energy dispersive X-rays (STEM-EDAX) revealed that WPI was uniformly distributed within WPI/PEO electrospun fibers. Observations by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) indicated that fibers possessed a solid core. All these findings suggested that PEO enables the formation of WPI/PEO electrospun fibers by entanglement/entrapment/deposition. Preliminary studies were conducted on hydroxypropyl methyl cellulose (HPMC). In the absence of PEO, HPMC enabled the formation of WPI electrospun fibers under acidic conditions (124 ± 46 nm). FTIR analyses indicated that there was no interaction between HPMC and WPI, suggesting that HPMC aided in the electrospinning of WPI fibers, also by entanglement/entrapment/deposition. Hence, HPMC and PEO aid in the electrospinning of WPI fibers by entanglement/entrapment/deposition, which can be manipulated by alterations in the protein configuration and solution properties.
Natural Sciences and Engineering Research Council (NSERC) of Canada and the Dairy Farmers of Ontario (DFO)

Whey protein isolate (WPI) contains at least 90% protein and should ideally possess a bland flavor without typical dairy flavors including sweet aromatic and cooked/milky notes. However, its flavor may be highly variable due to factors including original whey source, processing and storage conditions. Novel technologies removing nonpolar compounds responsible for off-flavors and off-flavor formations are desirable. The major objective of this research was to evaluate impacts of supercritical carbon dioxide (scCO2) extraction, a known green process, on volatile profiles of WPI. A prior sub-objective was to establish an analytical technique for characterization of volatiles. Specifically, adsorption conditions in a well-established head-space solid-phase microextraction (SPME) method were used for quick and reliable assays of volatiles in WPI, using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber. The adsorption of volatiles on the SPME fiber was studied at 21, 40 or 50 °C, each with durations of 5, 15 and 20 min, and analyzed by GC/MS. Based on the number of GC/MS peaks and the corresponding peak areas, adsorption conditions of 50 °C for 20 min were selected for subsequent studies. In the second sub-objective, GC/MS profiles of WPI were characterized after scCO2 extraction using a continuous stream of CO2 at 50 g/min, controlled at various combinations of temperature (30-65°C), pressure (7.0-30.0 MPa), and duration (10-90 min). Extractions with a higher temperature and a higher pressure for a longer time were generally more effective in removing volatiles, and most peaks on the chromatogram of the unprocessed WPI sample disappeared or were reduced very significantly after all studied extraction conditions, even at subcritical conditions of 7.0 MPa and 30 °C for 1 hour. Our findings demonstrated that supercritical or subcritical CO2 may provide a green approach to reduce volatiles in whey protein preparations for novel food applications.

碩士
國立臺灣科技大學
化學工程系
105
Amyloids are aggregated proteins that self-assembled into fibrils. The proteins or polypeptides generally form β-sheet structure under a denaturation condition before aggregate into long fiber. β-Lactoglobulin is one of often used proteins for amyloid fibrils generation. Whey protein isolate (WPI) has rich content of β-Lactoglobulin was found in this study can be used directly for the preparation of amyloid fibrils under the condition of pH 2 and heating to 80°C for 20 h. The as-prepared fibrils have an averaged diameter of 15 nm and length of more than 2 μm as observed by AFM. The zeta potential of the fibrils was measured to be +12.9 mV at pH 2 and became zero charge at pH 5.2. The amyloid nanofibrils prepared from WPI could be easily fabricated into membrane by filtering the amyloids suspension using 0.2 μm cellulose acetate microfiltration membrane. Clitoria ternatea (butterfly pea flower) extract that has rich content of anthocyanin was easily concentrated by filtering through the WPI amyloid fibrils membrane. The anthocyanin collected on the membrane exhibited strong antioxidant activity as measured by DPPH assay. The WPI nanofibrils membrane could also work as a nanofiltration membrane for the recovery of silver nanoparticles. Silver nanoparticle (AgNP) prepared by citrate reduction method with particle size about 31 nm could be very effectively collected by the nonofibrils membrane that 96.8 % of AgNP was recovered.

碩士
國立嘉義大學
食品科學系研究所
106
In order to improve the performance of whey protein isolate (WPI) edible membrane, genipin (Gen) was as natural cross-linking agent. WPI edible films crosslinked with different concentrations of Gen (0, 0.4, 0.8, 1.2, 1.6, and 2.0 mg/g WPI and denoted as WPI-Gen 0, WPI-Gen 0.4, WPI-Gen 0.8, WPI-Gen 1.2, WPI-Gen 1.6 and WPI-Gen 2, respectively) were prepared and the physicochemical properties and mechanical properties of WPI-Gen edible films were investigated. The results showed that amount of genipin did not significantly affect the thickness and moisture content of WPI-Gen edible films. The water solubility and water vapor permeability (WVP) of the films decreased as the concentration of genipin increased. WPI-Gen 2 exerted the lowest water solubility of 25.72% and water vapor permeability 6.79±0.18 (×10-10 g m Pa-1s-1m-2), which were 15.5% and 20.2% lower than those in the control group, respectively. The L*, a*, whiteness index and light transmission of the films decreased and b* increased as the concentration of Gen increased. While the good transparency was maintained, the color of films changed from colorless to yellowish green. The occurrence of cross-linking by Gen was confirmed by FTIR-ATR spectra and swelling index. WPI-Gen 2 possessed the highest tensile strength and Young's modulus, which were significantly higher than those of control films. Furthermore, the break elongation also tended to increase with the increase of Gen concentration. From the results mentioned above, it was found that WPI cross-linked with Gen could improve the physicochemical properties and mechanical properties of WPI films. Since WPI-Gen 2 showed the best mechanical properties and barrier properties, this type of film was chosen for the following study. Different concentrations of gallic acid (GA, 0, 5, 10, 15 and 20 mg/g WPI) were incorporated into WPI-Gen films as antioxidants. The prepared films were denoted as WPI-Gen-GA 0, WPI-Gen-GA 5, WPI-Gen-GA 10, WPI-Gen-GA 15 and WPI-Gen-GA 20, respectively. The results showed that the addition of GA had no significant effect on the thickness and moisture content of the edible film, but slightly increased the water solubility of the film. Furthermore, the addition of GA significantly increased the water vapor permeability of the film. The lowest WVP of 7.37±0.21 (×10-10 g m Pa-1s-1m-2) was detected in WPI-Gen-GA 10 films. When the concentration of GA increased, the L* and b* of the films decreased, while the a* value changed from negative to positive. The results indicated that the color of the film gradually shifted to darker color. Moreover, the transparency of films significantly decreased. As for mechanical properties, when the concentration of GA exceeded 10 mg/g WPI, the tensile strength, elongation at break, and Young's modulus all increased. WPI-Gen-GA 20 exerted the best mechanical properties. During the 90-day storage period, all GA-added groups maintained stable antioxidant activity, and the antioxidant capacity increased with increasing gallic acid concentration. Although the addition of GA as natural antioxidant in the WPI edible films cross-linked with Gen reduced partial barrier property of the edible film, the mechanical characteristics of the films were not significantly affected. As films could maintain good antioxidant capacity for a certain period of time, these types of films possess the potential as antioxidant active packaging materials.

碩士
中山醫學大學
營養學系碩士班
104
People in the long-term care organization generally have malnutrition problem. Appropriate formula of enteral nutrition provides good sources of nutritional support to improve the nutritional status of residents and reduce the incidence of infection and mortality. The main objective of this study was to understand the effect of tube feeding formula containing soybean protein isolate and whey protein on the improvement of nutritional status of subjects with malnutrition. 30 subjects (14 males and 16 females, average age was 78 years old) of tube feeding with malnutrition were enrolled in this study. The experimental period was 12 weeks. Biochemical analyses, anthropometric factors, physiological symptoms and dietary condition were measured before and after 12 weeks of intervention. Results showed that the daily energy intake and the intake of carbohydrate, protein were significantly increased after using the formula (p<0.01). There were very significant difference in anthropometric measurements, including BMI, TSF, MAC and MAMC (p<0.01) and significant difference was found in body weight (p<0.05). Serum albumin, prealbumin, magnesium and triglyceride were very significantly increased (p<0.01). Serum cholesterol, calcium, phosphorus, sodium, potassium, iron and uric acid showed no difference. In conclusion, the intervention of this tube feeding formula could greatly improve the anthropometric data and nutritional status of the subjects.

A wide variety of food products exist in the form of oil-in-water emulsions. The bulk physicochemical properties and sensory properties of these products is largely determined by the type of emulsifier used to stabilize them. In this study the major factors which influence the properties of oil-in-water emulsions stabilized by whey protein isolate (WPI) are examined. WPI is a value-added ingredient derived from the waste water produced during cheese manufacturing. The properties of emulsions is influenced by the processing and environmental conditions they experience during production, storage and use, for example homogenization, heating, pH, and ingredient interactions. The aim of this study was to examine these factors in a systematic way. During this study it was found that WPI forms stable emulsions above 0.8 wt%, at pH values away from its isoelectric point (pH $<$ 4 or pH $>$ 6) and temperatures below its denaturation temperature (T $<$ 75$\sp\circ$C). The emulsion stability is influenced by the ionic strength, nature of surfactant (e.g. Tween 20, SDS) and polysaccharide (e.g. dextran sulfate) concentration. These changes are induced through modification of the colloidal interactions, interfacial characteristics and/or modification of the aqueous phase. Emulsion stability was monitored through creaming, rheological, light scattering, UV-visible absorption spectroscopic and ultrasonic techniques. The results were interpreted in terms of colloidal interactions, which act between the droplets. The knowledge gained from this research project will enable food manufacturers to improve product quality, reduce manufacturing costs and enhance energy efficiency, by providing a strong scientific foundation for understanding the properties of complex food products.

Naturally occurring food antimicrobials such as plant essential oils are receiving tremendous interest as intervention systems to enhance microbiological safety and quality. Poor water solubility of essential oils makes it difficult to incorporate them in foods, impacting visual appearance, antimicrobial effectiveness, and possibly organoleptic properties. Engineered nanoscale delivery systems can principally solve these challenges, but those based on low-cost food ingredients and inexpensive and scalable processes are currently scarce. This dissertation presents a simple and scalable two-step technology to prepare nano-delivery systems. The first encapsulation step, based on emulsion-evaporation, involves preparing emulsions composed of an oil phase with thymol or eugenol, major compounds in extracts from thyme and clove respectively, in hexane and an aqueous phase with conjugates of whey protein isolate and maltodextrin, followed by evaporation of hexane by spray drying. The second step is to hydrate spray dried capsules to enable the formation of nanoscale particles. The encapsulation performance and dispersion characteristics were affected by amounts and types of conjugates (ratio of protein: maltodextrin and maltodextrin chain length), volume fraction and composition of the oil phase. The optimal conditions corresponded to 55.8 % encapsulation efficiency and 12.6 % loading for thymol and 47.9 % encapsulation efficiency and 7.9 % loading for eugenol. Dispersions prepared from the identified capsules contained particles smaller than 100 nm and were transparent at pH 3.0-7.0 and 0-50 mM before and after heating at 80°C for 15 min. Nano-dispersions and free oil were tested for antimicrobial activity against Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, and Salmonella typhimurium. Nano-dispersed and free antimicrobials had similar effectiveness at various pH and temperatures in tryptic soy broth and apple cider, while in 2 % reduced fat milk, nano-dispersed antimicrobials were consistently more effective than unencapsulated ones. Therefore, the commercially viable nanoscale technology presented in this study enables the delivery of lipophilic antimicrobials for enhanced microbial safety and quality, without compromising visual appearance of foods, especially clear beverages.