Influence of composition and concentration of milk proteins on whey protein denaturation and gel forming characteristics.
1993
Kessler H.G. | Plock J. | Beyer H.J.
The denaturation of beta-lactoglobulin in solutions of whey protein isolates ranging in concentration from 1.7 to 24.0 mg per ml could be described as a reaction of the second order. With increasing casein content at constant beta-lactoglobulin concentration (0.58 per cent) the reaction order changes from 2.0 to 1.5, accompanied by an increasing degree of denaturation for comparable heating conditions. For these solutions the rate constant kn of the denaturation reaction obtained over a range of temperatures was found to be independent of the initial whey protein concentration. Further experiments were carried out to investigate the effect of the concentration and the degree of denaturation of whey proteins on the apparent viscosity for lower protein concentrations and the gel strength for higher protein concentrations. The results confirm the strong effect of a degree of denaturation of more than 80 per cent. In presence of casein, similar viscosities could be obtained already at a lower degree of denaturation than without casein. For gel formation, however, a whey protein concentration of more than 5 per cent is necessary. Changing the casein/whey protein ratio at constant total protein content (10 per cent) for totally gelled systems, maximum gel strength could be observed at a casein portion of approximately 30 per cent, indicating the ability of casein to interact as active ingredient in heat induced structures. The strength of milk protein gels then was strongly dependent on the calcium concentration of the solutions.
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