Whey proteins bovine serum albumin

Chemical reactions Polymerization of casein and whey proteins are due to some kind of chemical reactions. The different proteins as found in the supernatant of milk after precipitation at pH 4.6 are collectively called whey proteins. These globular proteins are more water soluble than caseins and are subject to heat dena-turation. Denaturation increases their water-binding capacity. The principal fractions are P-lactoglobulin, a-lactalbumin, bovine serum albumin (BSA), and immunoglobulins (Ig). 

In contrast, the whey proteins are relatively small globular proteins. a-Lactalbumin represents about 20 % of the protein content of bovine whey (3.5 % of total bovine milk protein), and it is the principal protein in human milk (Brew and Grobler, 1992). Nanotube assembly has been discovered in some solutions containing a hydrolysed derivative of this protein. And it appears that the a-lactalbumin nanotube is unique in the sense that it is the only artificial nanotube that has so far been made from a food protein (Graveland-Bikker et al., 2004 Graveland-Bikker and de Kruif, 2006). As for p-lactoglobulin, it has the capacity under certain specific conditions to form nano-fibres in aqueous media (as can various other globular food proteins, such as ovalbumin, soy proteins, and bovine serum albumin) (van der Linden, 2006 Nicolai, 2007). 

Casein is synthesized in the mammary gland and is found nowhere else in nature. Some of the whey proteins (/Mactoglobulin and a-lactalbumin) are also synthesized in the mammary gland, while others (e.g. bovine serum albumin and the immunoglobulins) are derived from the blood. 

Bovine Serum Albumin. Since Polis et al. (1950) crystallized bovine serum albumin from whey and demonstrated that it was identical in all properties investigated to blood serum albumin, except in its electrophoretic behavior at pH 4.0, very little work has been done on this protein as isolated from milk. However, much work has been done on the protein isolated from bovine blood plasma. There is considerable evidence that serum albumin is heterogeneous. For example, Spencer and King (1971) have demonstrated several protein bands by electrophoretic focusing, with two major isoelectric components differing by one unit of charge. The chemical nature of this difference is not known. 

The effectiveness of surface and interfacial tension depressants can be compared by plots of concentration versus tension. Various dilution studies of milk, skim milk, wheys, and solutions of milk proteins reveal that casein and the proteins of the lactalbumin fraction (/3-lactoglobu-lin, a-lactalbumin, and bovine serum albumin) are powerful depressants, while the proteins of the immunoglobulin fraction are somewhat... 

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.)...

Whey proteins contain several major allergens, such as P-lg and a-la, and minor constituents, e.g., lactoferin, bovine serum albumin (BSA), and immunoglobulins. In this fraction, proteolytic fragments of casein and fat globule membrane proteins can occur during analysis. 

Because the proteins often studied are )6-lactoglobulin, bovine serum albumin, egg white ovalbumin, egg white (protein mixture) or whey protein isolate (protein mixture), it is of interest to note that their gels fall into one of the following types (Foegeding, 2006) ... 

Antibiotics, hormones, monoclonal antibodies, plasma proteins, insulin, vaccines, alkaloids Whey proteins, milk proteins, egg proteins, soy proteins, vitamins, amino acids, protein hydrolysates, yeast cells, yeast extract Glucose oxidase, peroxidase, hormones Detergent enzymes, insecticides Bovine serum albumin, ovalbumin, lysozyme Plant extracts, animal tissue extracts... 

Figure 15.14 Separation of milk proteins [reproduced with permission from B.B. Gupta, J. Chromatogr., 282, 463 (1983)]. Conditions sample, 100 pi of whey from raw skimmed milk (casein precipitated at pH 4.6) column, 60 cm x 7.5 mm i.d. stationary phase, TSK 3000 SW (silica, 10pm) mobile phase, 0.5 ml min buffer containing 0.1 M NaH2PO4, 0.05 M NaCl and 0.02% NaNa (pH 6.8) UV detector, 280 nm. Peaks (with molecular masses) 1 = high molecular weight proteins 2 = -y-globulin (150000) 3 — bovine serum albumin (69000) 4 = /3-lactoglobulin (35000) 5 = a-lactalbumin (16500) other components not identified.

From Hu et al. (2003a). Emulsion prepared with 5 wt% salmon oil, 0.2% protein, and 94.8% 5 mM acetate-imidazole buffer (pH 3.0). Sweet whey contained 12.1 wt% protein whey protein isolate contained 97.6 wt% protein consisting of 55-61% 8-lactoglobulin, 19-22% a-lactalbumin and 6-8% bovine serum albumin. 

The whipping properties of dried egg white can be improved by the addition of whey proteins, casein and bovine serum albumin. The foaming ability is also increased by weak proteolysis and partial hydrolysis of the oligosaccharides in the glycoproteins by treatment with amylases. 

The use of proteins as macromolecular amphiphiles was adopted long ago by scientists exploring the stability of multiple emulsions. Gelatin (Zhang et al., 1992), whey proteins (Comec et al, 1998), bovine serum albumin (BSA) (Dickinson et al., 1991 Fredrokumbaradzi and Simov, 1992), human serum albumin (HSA), caseins, and other proteins have been evaluated. In many cases the proteins were used in combination with other monomeric emulsifiers, especially when proteins were used in the internal phase. However, whether the adsorption is competitive or complementary remains a controversial question (Wilde and Clark, 1993 Kerstens et al., 2006). 

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