Gelation of reconstituted whey powders by heat

Whey protein preparations isolated from cheese whey form stable gels when their aqueous solutions are heated at 80°C. The gels consist of polypeptide chains crosslinked by disulphide bonds. They dissolve if a sulphydryl (‐SH) reagent is added after heating; their formation is retarded if compounds that react with ‐SH groups are added before heating. Opaque gels are formed from powders containing relatively large amounts of total ‐SH; clear gels form from those with low total ‐SH. Gels form faster on heating in N2 instead of air. Gels form more slowly at alkaline pH; it is suggested that this effect is caused by electrostatic repulsion between protein molecules with like charges.