USE OF FIBER OPTICS TO STUDY THE TRANSITION FROM CLEAR TO OPAQUE WHEY-PROTEIN GELS

The transition from a clear whey protein isolate gel (25 mM Na) to an opaque gel (500 mM Na) was studied by a fast responding fibre optic pr obe. The gels, formed by gradually increasing Na concentration, showed a progressive decrease in water holding capacity (WHC) which plateaue d at 300 mM. The fibre optic probe was able to detect the differences in the gel's WHC (r=0.89; P less than or equal to 0.001); whereas, a r egular surface colour meter was not as useful (r=0.72). The gel's abil ity to deform (spread out during compression) also decreased with the increase in [Na] and was highly correlated with the probe readings (r= 0.92; P less than or equal to 0.001); the surface colour meter only pr ovided r=0.78. The specific design of the probe which made it sensitiv e to scattering light was used to explain the differences between the two light measuring systems. Overall, the probe will allow a rapid ass essment of WPI gel quality in the transformation region. Copyright (C) 1996 Canadian Institute of Food Science and Technology.