DETERMINATION OF KINETICS OF GELATION OF WHEY-PROTEIN AND CASSAVA STARCH BY OSCILLATORY RHEOMETRY

Kinetics of heat-induced gelation of cassava starch (CS) suspensions, whey protein isolate (WPI) solutions and mixed blends at 10% total sol ids (TS) were followed by small deformation oscillatory shear rheometr y in the temperature range 70-90 degrees C. Storage moduli (G') of WPI solutions (4-14% TS) increased steadily following simple first order kinetics. G' of CS suspensions (8-14% TS) increased rapidly to a peak and decayed steadily later. A model consisting of a two-step reaction with a reversible step was proposed for gelation of CS. G' of WPI gels were two orders of magnitude higher than those of CS. Mixed gels havi ng a starch fraction = 0.2 had G' similar to those of pure WPI gels. ( C) 1998 Canadian Institute of Food Science and Technology. Published b y Elsevier Science Ltd.