DISULFIDE-MEDIATED POLYMERIZATION REACTIONS AND PHYSICAL-PROPERTIES OF HEATED WPI-STABILIZED EMULSIONS

Heating a 19 wt% corn oil-in-water emulsion stabilized by 1 wt% whey p rotein isolate from 30 to 70 degrees C and then cooling to 25 degrees C for at least 15 hr, brought about minimal changes in droplet aggrega tion, apparent viscosity and susceptibility to creaming. At 75 degrees C, droplet aggregation occurred but this decreased on heating to 90 d egrees C. The apparent viscosity and susceptibility of droplets to cre aming increased as the degree of droplet aggregation increased. Inclus ion of the sulfhydryl blocking agent N-ethylmaleimide to inhibit thiol /disulfide interchange reaction did not affect droplet aggregation but resulted in higher apparent viscosity values and susceptibility to cr eaming at 85 and 90 degrees C and not at lower temperatures. The resul ts suggest that droplet aggregation results from noncovalent interacti ons between unfolded protein molecules adsorbed on different droplets and that the interactions are strengthened by disulfide bonds.