Whey protein strength

WPI Whey protein isolates. Properties of nonextmded WPI moisture 1.94%, gel strength 52.3 (N), foam volume 288%, and foam stability 28.7%. Value not reported. Means with different letters within a column are significantly (p < 0.05) different. 

We turn now to the other major whey protein, p-lactoglobulin. This is an acidic globular protein (p/= 5.1) with a molar mass of 18.4 kDa and a radius of about 2 nm (Aymard et al., 1999). The protein can form long semi-flexible fibrils when heated in solution at around or above its dena-turation temperature (60-80 °C) at pH = 2 and low ionic strength (Durand et al., 2002 Veerman et al., 2002, 2003a,b). (An example of the... 

Table IV. The pH effect on gel strength of whey protein concen-...

The strength of the rennet-induced gel is also adversely affected by heat treatment of the milk, again presumably because the whey protein-coated micelles are unable to participate properly in the gel network. Gels from severely heat-treated milk have poor syneresis properties, resulting in high-moisture cheese which does not ripen properly. Syneresis is undesirable in fermented milks, e.g. yoghurt, the milk for which is severely heat-treated (e.g. 90°C x 10 min) to reduce the risk of syneresis. 

Electrophoresis on cellulose acetate strips has also been used for the rapid resolution of whey proteins (Bell and Stone 1979). Samples of a 10 1 concentrate of whey are applied to cellulose acetate strips which have been saturated with Tris-barbiturate buffer, pH 8.6, ionic strength 0.097, and the electrophoresis is performed at 225 V for 1 hr. This procedure separates not only the major whey proteins but also their genetic variants. 

Fig. 1 Ion-exchange chromatography of whey proteins on a Mono Q column using different buffer systems (A) a 100-/rl sample of total whey protein dissolved in 0.05 M sodium acetate buffer, pH 6.3, was injected into the column and eluted with a 0.05-0.7 M sodium acetate linear ionic-strength gradient for (B) and (C) the sample was dissolved in 0.02 M Tris-HCl, pH 7 (B) or pH 8 (C), and a 0-0.35 M NaCl linear gradient was applied. Key 1 immunoglobulins, 2 a-lactalbumin, 3 bovine serum albumin, 4 /3-lac-toglobulin B, 5 /3-lactoglobulin A. (From Ref. 37.)...

Enzymatic gelation of partially heat-denatured whey proteins by trypsin, papain, pronase, pepsin, and a preparation of Streptomyces griseus has been studied (Sato et al., 1995). Only peptic hydrolysate did not form a gel. The strength of the gel depended on the enzyme used and increased with increasing DH. Hydrolysis of whey protein concentrate with a glutamic acid specific protease from Bacillus licheniformis at pH 8 and 8% protein concentration has been shown to produce plastein aggregates (Budtz and Nielsen, 1992). The viscosity of the solution increased dramatically during hydrolysis and reached a maximum at 6% DH. Incubation of sodium caseinate with pepsin or papain resulted in a 55-77% reduction in the apparent viscosity (Hooker et al., 1982). 

The WPC (0.2 - 7 stabilized emulsions have the lowest protein load ( 1.5 mg/nr) at fat surface areas between 1.0 and 3.0 nr/ml, whereas at larger surface areas, the soy protein (0 - 7) stabilized emulsions have as low values as those stabilized with WPC (0.2 - 7). It is interesting to note that an increase in ionic strength to 0.2 M NaCl does not increase the amount of protein adsorbed in the case of the whey proteins. In fact the opposite is observed, in contrast to the behavior of the other two proteins. 

The interfacial and emulsifying behavior of three food proteins, a soy protein isolate, a sodium caseinate and a whey protein concentrate (WPC) have been studied. A kinetic analysis of the interfacial tension decay of the proteins indicates the following characteristics. The soy proteins diffuse slowly to the interface compared to the other proteins, probably with the quaternary structure intact, which disintegrates when adsorbed at the interface. Both the whey proteins and the caseinates diffuse quickly to the interface, where for the caseinates the diffusion--controlled occupation of the interface is very evident, especially at an ionic strength of 0.2. 

Proteins in homogenized dairy products Symmetrical Separation of whey proteins from fat globules fractionation of whey proteins and casein micelles effect of carrier ionic strength, cross-flow rate, pH, and membrane type on retention and size distribution of micelles [M. A. Jussila, G. Yohannes, and M.-L. Riekkola, J. Microcol. Separ. 9 601-609 (1997)]... 

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