Structure and visco-elastic properties of set yoghurt with altered casein to whey protein ratios
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Keywords:
Milk protein
Beta-lactoglobulin
Whey protein isolate
The model in vitro protein digestion technique has received greater attention due to providing significant advantages compared to in vivo experiments. This research employed an in vitro infant digestive static model to examine the protein digestibility of whey proteins isolate–lactose (WPI–Lac). The polyacrylamide gel electrophoresis (PAGE) pattern for alpha-lactalbumin of WPI at 60 min showed no detectable bands, while the alpha-lactalbumin of the WPI–Lac was completely digested after 5 min of gastric digestion. The beta-lactoglobulin of the WPI–Lac was found to be similar to the beta-lactoglobulin of the WPI, being insignificant at pH 3.0. The alpha-lactalbumin of the WPI decreased after 100 min of duodenal digestion at pH 6.5, and the WPI–Lac was completely digested after 60 min. The peptides were identified as ~2 kilodalton (kDa) in conjugated protein, which indicated that the level of degradation of the protein was high, due to the hydrolysis progress. The conjugated protein increased the responsiveness to digestive proteolysis, potentially leading to the release of immunogenic protein by lactose, and to the creation of hypoallergenic protein.
Whey protein isolate
Alpha-lactalbumin
Digestion
Proteolysis
Beta-lactoglobulin
Hypoallergenic
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Whey protein isolate
Denaturation (fissile materials)
Beta-lactoglobulin
Gel permeation chromatography
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Whey protein isolate solutions (8.00 g protein/100 g; pH 6.8) were treated for 2 min at 72, 85 or 85 °C with 2.2 mM added calcium Ca to produce four whey protein systems: unheated control ( WPI ‐ UH ), heated at 72 °C ( WPI ‐H72), heated at 85 °C ( WPI ‐H85) or heated at 85 °C with added Ca ( WPI ‐H85Ca). Total levels of whey protein denaturation increased with increasing temperature, while the extent of aggregation increased with the addition of Ca, contributing to differences in viscosity. Significant changes in Ca ion concentration, turbidity and colour on heating of WPI ‐H85Ca, compared to WPI ‐ UH , demonstrated the role of Ca in whey protein aggregation.
Whey protein isolate
Denaturation (fissile materials)
Turbidity
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The effects of whey protein hydrolysis on film oxygen permeability (OP) and mechanical properties at several glycerol−plasticizer levels were studied. Both 5.5% and 10% degree of hydrolysis (DH) whey protein isolate (WPI) had significant effect (p ≤ 0.05) on film tensile properties compared to unhydrolyzed WPI. Hydrolyzed WPI required less glycerol to achieve the same mechanical properties compared to those of unhydrolyzed WPI. Little or no significant difference (p > 0.05) occurred for film OP between unhydrolyzed WPI, 5.5% DH WPI, and 10% DH WPI films at the same glycerol content. Hydrolyzed WPI films of mechanical properties similar to those of WPI films had better oxygen barrier. Therefore, use of hydrolyzed WPI allowed achievement of desired film flexibility with less glycerol and with smaller increase in OP. Keywords: Hydrolyzed whey protein; oxygen permeability; mechanical properties
Whey protein isolate
Oxygen permeability
Plasticizer
Enzymatic Hydrolysis
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As public concerns grow over the quality, shelf-life of food products and the environmental impact of food producing process, more and more research have been devoted to developing edible or biodegradable films. This study aims to determine the influence of whey protein concentration, heating temperature, and glycerol:whey protein ratio on the characteristics of WPI edible films. Our results reveal that the whey solution turns into gel when heated at the concentration over 12%. As the concentration of WPI increases from 8% to 12%, thickness of whey protein films also increases. Glycerol, used as a plasticizer, affects the formation of films. The formation time, thickness and softness of films increase as the glycerol:whey protein ratio increases. There is no significant difference between heating at 80 ℃and 90 ℃ in film formation. Optimum conditions for film formation and physical properties are at WPI concentration of 10%, glycerol/WPI ratio(v/v) is 1∶1, heating at 80 ℃ for 30 min.
Whey protein isolate
Plasticizer
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Pasteurization
Modified milk ingredients
Milk protein
Beta-lactoglobulin
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Whey protein isolate
Ultrafiltration (renal)
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Water activity
Whey protein isolate
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The ability of alphas1/beta-casein and micellar casein to protect whey proteins from heat-induced aggregation/precipitation reactions and therefore control their functional behavior was examined. Complete suppression (>99%) of heat-induced aggregation of 0.5% (w/w) whey protein isolate (pH 6.0, 85 degrees C, 10 min) was achieved at a ratio of 1:0.1 (w/w) of whey protein isolate (WPI) to alphas1/beta-casein, giving an effective molar ratio of 1:0.15, at 50% whey protein denaturation. However, in the presence of 100 mM NaCl, heating of the WPI/alphas1/beta-casein dispersions to 85 degrees C for 10 min resulted in precipitation between pH 6 and 5.35. WPI heated with micellar casein in simulated milk ultrafiltrate was stable to precipitation at pH>5.4. Protein particle size and turbidity significantly (P
Whey protein isolate
Denaturation (fissile materials)
Beta-lactoglobulin
Turbidimetry
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Whey protein isolate
Supercritical Carbon Dioxide
Enzymatic Hydrolysis
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