Whey protein isolate solubility

FIGURE 5.6 Solubility of texturized dairy protein products extruded at different temperatures, 25 (control), 50, 75, and 100 C Nonfat dried milk (NDM) whey protein concentrate (WPC80), containing 80% protein and whey protein isolate (WPl), containing 95% protein (Onwulata et at, 2003a). 

Steady cone-jet electrosprays in liquid insulator baths. ]. Colloid Interface Sci. 272,104—108. Bedie, G. K., Turgeon, S. L., and Makhlouf, J. (2008). Formation of native whey protein isolate—Low methoxyl pectin complexes as a matrix for hydro-soluble food ingredient entrapment in acidic foods. Food Hydrocolloids 22, 836-844. 

FIGURE 7.14 Solubility of protein preparations as a function of pH. (a) Turbidity (expressed as absorbancy) of solutions of a whey protein isolate, heated at 70°C for various times (indicated, minutes). (From results by S. Damodaran, see Bibliography), (b) Solubility (percentage of protein in supernatant after centrifuging) of various protein products sodium caseinate (C), peanut (P), and soya (S) proteins. (Approximate results after various sources.) (c) Solubility (as in b) of the protein in a potato juice extract (pH = 7.0, 7=0.2 molar) as a function of solvent volume (v, in ml). See text for lines 1 and 2. (After results by G. A. van Koningsveld. Ph.D. thesis, Wageningen University, 2001.)... 

Like the caseins, the whey proteins have been isolated from whey or whey concentrates and purified by differential solubilities, electrophoresis, or chromatography. 

Differential Solubility Methods. Many methods have been developed for isolating the major whey proteins based on their solubilities in different systems. Some of the methods have been employed to obtain only one protein others can be used to secure all of the major... 

This difference in solubility has been exploited to fractionate protein solutions. Polyacrylic acid was used to partially fractionate a mixture of four enzymes (2). Whey protein fractions have also been isolated by precipitation with CMC (3). 

While foaming is favored by increased viscosity, hydrophobicity, and solubility, the increase of net charge density caused by succinylation tends to decrease foam stability (FS), since it prevents optimum protein-protein interactions required in a continuous film around air bubbles. Therefore a number of succinylated proteins showed a drop of the FS with increasing degree of modification. This was reported for protein preparations from faba beans [86], peas [72], cottonseed [69], oat [66], and cheese whey protein concentrate [88] for instance. The unfavorable charge effect of succinylation can be overcome by foaming at sufficiently high protein concentration, as shown for faba bean protein isolates [86] and napin from rapeseed [84]. 

Milk from cows contains 3.2% protein, about 80% of which is casein. Casein is isolated by a precipitation process from milk, involving heating, rinsing to remove whey, and drying to a powder. The yield is about 3 kg/ 100 kg skim milk. Rennet casein is obtained when the casein is precipitated by chymosin enzyme, also known as rennet, and acid casein is produced when precipitation is accomplished by acidification. Acid casein is usually found in the form of sodium caseinate or calcium caseinate, which are water-soluble salts. Caseinates are made by reacting NaOH or CaOH with a slurry of casein curd or powder and then spray drying (Southward, 2010). 

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