THE EFFECT OF DIALYSIS ON HEAT-INDUCED GELATION OF WHEY PROTEIN CONCENTRATE

Abstract

Time required for gelation of 10% protein dispersions of commercial whey protein concentrate (WPC) heated at 100°C was influenced by preparation technique. Gel times ranged from 1.25 to greater than 30 min. Dialysis of a rapid gelling WPC resulted in the formation of stronger, more cohesive, less springy, more gummy, more chewy and more translucent gels with heating (100° C for 15 min) at 10% protein than did non-dialyzed WPC. Addition of CaCl2 or NaCl to the dialyzed WPC increased gel strength more dramatically than did salt addition to non-dialyzed WPC. Resistance to penetration and hardness of dialyzed whey protein gels maximized with CaCl2 addition from 5.0 to 20 mM and decreased with 25 mM CaCl2 addition. In non-dialyzed whey protein gels, resistance to penetration maximized at 25 mM added CaCl2 while hardness values maximized at 5.0 mM CaCl2. Addition of 0.2 to 0.5 M NaCl increased resistance to penetration of both whey protein gel systems. Hardness values for dialyzed WPC gels maximized at 0.1 to 0.3 M NaCl and decreased at 0.4 M or greater added NaCl. Hardness values of non-dialyzed WPC were only slightly affected by NaCl addition. Addition of CaCl2 at 5 mM or greater or NaCl at 0.1 Af or greater decreased cohesiveness and springiness of dialyzed WPC gels. Cohesiveness of non-dialyzed WPC gel systems was maximal at 10 mM CaCl2 or 0.2M NaCl. Salt had no apparent effect on springiness of the non-dialyzed WPC gels. Gumminess data followed similar trends to those observed for hardness with respect to salt effects in WPCgel systems. Maximum chewiness values for both WPC gel systems were apparent with addition of 5.0 to 10 mM CaC12 or with addition of0.1 to 0.3 M NaCl.