Effect of Lactococcus lactis ssp lactis inoculated in UHT skim milk on the proteo-lytic activity of psychrotrophic strains was studied. The titration of a purified non nitrogenous fraction from refrigerated UHT milk samples, previously... more
Effect of Lactococcus lactis ssp lactis inoculated in UHT skim milk on the proteo-lytic activity of psychrotrophic strains was studied. The titration of a purified non nitrogenous fraction from refrigerated UHT milk samples, previously inoculated by 10 6 psy-chrotrophic strains, showed that Pseudomonas fluorescens and P. putida were the most proteolytic species. This result has also been confirmed using polyacrylamide gel electrophoresis of casein fractions extracted from refrigerated and contaminated UHT milk samples. All extracellular proteases of the studied germs revealed a decreasing affinity towards κ, β, and α s1-caseins. This bacterial proteolysis of the UHT milk caseins samples, voluntarily contaminated by each of the studied psychrotrophic strains, was significantly reduced following the addition of 10 6 CFU/ml Lactococcus, which caused, after 9 days of refrigeration, an appreciable reduction of the number of psychrotrophic germs from a minimum of 100 to 1000 times, depend...
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En este trabajo se ha estudiado la interaccion de la alfa-lactalbumina humana y bovina, en sus formas nativas y apo, ocn los acidos grasos asi como el efecto que dicha interaccion tiene sobre el crecimiento de celulas en cultivo. Para... more
En este trabajo se ha estudiado la interaccion de la alfa-lactalbumina humana y bovina, en sus formas nativas y apo, ocn los acidos grasos asi como el efecto que dicha interaccion tiene sobre el crecimiento de celulas en cultivo. Para ello, la alfa-lactalbumina se aislo a partir de leche bovina o humana mediante tecnicas de ultrafiltracion y cromatograficas, utilizando condiciones no desnaturalizantes, con el objeto de mantener la estructura nativa de la proteina. La forma apo de la proteina se obtuvo mediante tratamiento con EDTA y se caracterizo por cromatografia de exclusion molecular, electroforesis, espectroscopia de fluorescencia y dicroismo circular. Los resultados obtenidos indican que la forma apo presenta una estructura secundaria similar a la forma nativa pero una estructura terciaria alterada con una conformacion parcialmente desplegada y una alta tendencia a formar agregados. La interaccion de las formas nativas y apo de la alfa-lactalbumica humana y bovina con los acid...
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α-Lactalbumin (α-LA) is a whey protein that has been extensively studied for its folding properties and its ability to bind several cations. An interesting property of α-LA is its ability to interact with fatty acids, although this... more
α-Lactalbumin (α-LA) is a whey protein that has been extensively studied for its folding properties and its ability to bind several cations. An interesting property of α-LA is its ability to interact with fatty acids, although this interaction requires the previous unfolding of the protein by removing the Ca bound. The main function of α-LA is to participate in lactose
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... as a thickener, micro-organism growth medium, food stabiliser, and has other applications in the textile, food, cosmetic and pharmaceutical industries (Calixto and Canella, 1982). ... This shear thinning behavior can be described by a... more
... as a thickener, micro-organism growth medium, food stabiliser, and has other applications in the textile, food, cosmetic and pharmaceutical industries (Calixto and Canella, 1982). ... This shear thinning behavior can be described by a Herschel-Bulkley model (Germain et al., 2006 ...
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The contamination of milk by spoilage bacteria is undesirable, particularly when Gram negative bacteria which produce thermo-resistant protease and lipase can grow. In this work, spoilage bacteria in refrigerated raw milk were identified,... more
The contamination of milk by spoilage bacteria is undesirable, particularly when Gram negative bacteria which produce thermo-resistant protease and lipase can grow. In this work, spoilage bacteria in refrigerated raw milk were identified, using API 20NE System. Five dominant species were found: Pseudomonas fluorescens (20%), Aeromonas hydrophila (16%), Pseudomonas cepacia (13%), Pseudomonas putida (6%) and Chryseomonas luteola (5%). On the basis of agar diffusion assays, five strains harbouring the strongest lipases activities were selected. It has been found that esterase activities are higher for each one. Effects of main environmental and nutritional factors on the esterase activity of those psychrotrophic strains were investigated. Biomass level, pH, lactose concentration and permanent agitation affected positively esterase activity of each strain. However, the ddition of Tween 20 influenced it negatively. Finally, and in order to extract information from the data sets, principa...
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En este trabajo se ha estudiado la interacción de la alfa-lactalbumina humana en sus formas nativa y apo con los ácidos grasos. La alfa-lactalbúmina nativa incubada con el ácido oleíco muestra un solo pico por filtración en gel, mientras... more
En este trabajo se ha estudiado la interacción de la alfa-lactalbumina humana en sus formas nativa y apo con los ácidos grasos. La alfa-lactalbúmina nativa incubada con el ácido oleíco muestra un solo pico por filtración en gel, mientras que la incubada con el ácido palmitico muestra dos picos, uno minoritario formado por agregados de proteína que interaccionan con el ácido graso y uno mayoritario de proteína monómera que no muestra dicha propiedad. El tratamiento de la proteína con EDTA para eliminar el calcio da lugar a la formación de numerosos agregados capaces de unir ácido graso. Utilizando la técnica de equilibrio de partición, la -lactalbúmina nativa no interacciona con los ácidos oleico y palmitico mientras que la forma apo es capaz de unirlos con unas constantes de afinidad aparentes del orden de 10-6 M-1 y 10-5 M-1 respectivamente.
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При помощи метода равновесного распределения исследовано взаимодействие холо и апоформ человечес кого α-лактальбумина с жирными кислотами. Апо-α-лактальбумин, полученный после обработки раство ром ЭДТА, содержит один участок связывания... more
При помощи метода равновесного распределения исследовано взаимодействие холо и апоформ человечес кого α-лактальбумина с жирными кислотами. Апо-α-лактальбумин, полученный после обработки раство ром ЭДТА, содержит один участок связывания жирных кислот с константами связывания олеиновой и пальмитиновой кислот соответственно 1,9 • 106 и 4,2 • 105 М–1. Тем же методом было показано, что холо α лактальбумин не способен связывать жирные кислоты. Анализ холо-α-лактальбумина, выделенного в неде натурирующих условиях методом газовой хроматографии, также не выявил присутствия жирных кислот. Сделан вывод, что конформационные изменения молекулы α-лактальбумина, индуцируемые удалением кальция, приводят к появлению способности связывать жирные кислоты.
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Research Interests: Biology, Medicine, Humans, Digestion, Flour, and 4 moreSeeds, Food Sciences, PLANT PROTEINS, and Food Function
The rheological properties of tomato concentrates produced by hot and cold break have been extensively studied by many authors. Only a few studies, however, focus specifically with the rheology of reconstituted concentrates from tomato... more
The rheological properties of tomato concentrates produced by hot and cold break have been extensively studied by many authors. Only a few studies, however, focus specifically with the rheology of reconstituted concentrates from tomato powders. In this study, the rheological properties of reconstituted tomato concentrate from lyophilized freeze-dried tomato juice were evaluated using rotational viscometer at temperatures 20 °C, 30 °C, 40 °C,
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α-Lactalbumin (α-LA) is a whey protein that has been extensively studied for its folding properties and its ability to bind several cations. An interesting property of α-LA is its ability to interact with fatty acids, although this... more
α-Lactalbumin (α-LA) is a whey protein that has been extensively studied for its folding properties and its ability to bind several cations. An interesting property of α-LA is its ability to interact with fatty acids, although this interaction requires the previous unfolding of the protein by removing the Ca bound. The main function of α-LA is to participate in lactose
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ABSTRACT The interaction of holo-and apo-forms of human α-lactalbumin with fatty acids was studied by a partition equilibrium method. Apo-α-lactalbumin, obtained by treatment with EDTA, displays one binding site for fatty acids, the... more
ABSTRACT The interaction of holo-and apo-forms of human α-lactalbumin with fatty acids was studied by a partition equilibrium method. Apo-α-lactalbumin, obtained by treatment with EDTA, displays one binding site for fatty acids, the association constants for oleic and palmitic acids being 1.9·106 and 4.2·105 M−1, respectively. However, holo-α-lactalbumin was unable to bind fatty acids as measured by this technique. Likewise, no fatty acids bound to holo-α-lactalbumin, isolated using nondenaturing conditions, were detected by gas chromatography. These results demonstrate that the conformational change induced in α-lactalbumin by the removal of calcium enables the protein to interact with fatty acids.
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The interaction of bovine holo- and apo- α-lactalbumin with fatty acids was studied using a partition equilibrium technique and fluorescence spectroscopy. Using there techniques, bovine holo- α-lactalbumin was found to be unable to bind... more
The interaction of bovine holo- and apo- α-lactalbumin with fatty acids was studied using a partition equilibrium technique and fluorescence spectroscopy. Using there techniques, bovine holo- α-lactalbumin was found to be unable to bind fatty acids. Gas chromatography analysis also did not reveal and fatty acids bound to bovine α-lactalbumin that had been isolated using non denaturing conditions. The partition
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Research Interests: Chemistry, Food, HPLC, ANOVA, Hydrolysate, and 15 moreDietary Supplements, CVD, Fermentation, AU, Biotransformation, Food Sciences, Food sciences and nutrition, Genistein, Bioactivity, Hydrolysis, Angiotensin Converting Enzyme Inhibitors, GIS, Bifidobacterium, Antihypertensive agents, and Angiotensin
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The effect of heat treatment on the denaturation of alpha-lactalbumin was studied, under different conditions, over a temperature range of 78-94 degrees C. The concentration of the residual immunoreactive protein after different... more
The effect of heat treatment on the denaturation of alpha-lactalbumin was studied, under different conditions, over a temperature range of 78-94 degrees C. The concentration of the residual immunoreactive protein after different treatments was determined by kinetic analysis, obtaining D and Z values. Thermodynamic parameters were also calculated. Denaturation of alpha-lactalbumin, measured by the loss of immunoreactivity, could be described as an order of reaction of n = 1.5. Results obtained indicated that alpha-lactalbumin was more heat-sensitive when treated in milk than in phosphate buffer. The protein was also denatured more rapidly in the apo form than in the calcium-saturated form. Besides, the thermal stability of apo-alpha-lactalbumin decreased with the binding of oleic acid.