Use of fibre optics to study the transition from clear to opaque whey protein gels

Abstract

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 probe. The gels, formed by gradually increasing Na concentration, showed a progressive decrease in water holding capacity (WHC) which plateaued at 300 mM. The fibre optic probe was able to detect the differences in the gel's WHC ( r = 0.89; P ≤ 0.001); whereas, a regular surface colour meter was not as useful ( r = 0.72). The gel's ability 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 ≤ 0.001); the surface colour meter only provided r = 0.78. The specific design of the probe which made it sensitive to scattering light was used to explain the differences between the two light measuring systems. Overall, the probe will allow a rapid assessment of WPI gel quality in the transformation region.