Effects of N-ethylmaleimide and CaCl2 on cold gelation of whey protein isolate

Abstract

The combined effect of CaCl2 (10-120 mM) and N-ethylmaleimide [NEM] (0-5 mM) on colour and textural properties of Ca2+-induced cold-set whey protein isolate (WPI) gels was investigated. Raising [CaCl2] resulted in increasing gel opacity and hardness while reducing cohesiveness. In gels prepared by dialyzing against a 10mM CaCl2 solution, increasing [NEM] to 2 mM resulted in a slight increase in opacity and hardness. At > 2mM NEM, both parameters were reduced due to the lower degree of sulfhydryl-disulfide interchange reaction. Gels prepared by dialyzing against ≤30 mM CaCl2 showed an increase in opacity and a decrease in hardness as [NEM] was raised from 0 to 5 mM. These changes were likely to be related to the degree of WPI polymerization during the pre-heating stage, i.e. prior to calcium addition and gelation.