The effect of whey protein denaturation on light backscatter and particle size of the casein micelle as a function of pH and heat-treatment temperature

Reconstituted low-heat skim milk with pH adjusted to 6.3, 6.7, and 7.1 was heated at 80 and 90 °C for 10 min to evaluate the relationship between the attachment of denatured whey proteins to the surface of the casein micelle and the intensity of optical light backscatter response. Both optical light backscatter intensity and casein particle size showed a significant negative correlation with pH and positive correlation with heat treatment temperature. When samples were analysed independently by respective pH, there was a significant correlation of both light backscatter and particle size with temperature for samples at a pH of 6.3, and between light backscatter and temperature at pH 7.1. These results show the potential for the use of optical light backscatter techniques as a measurement of changes in casein micelle particle size induced by heat treatment.