COMPRESSION STRENGTH OF DAIRY GELS AND MICROSTRUCTURAL INTERPRETATION

Contour plots were developed for the compression stress (at 20% deformation) of single-component, mixed and filled protein gels. Samples were made by heating and acidification from skim milk powder, SMP (0-20% TS), whey protein isolate, WPI (0-10% TS), and recombined cream, within pH 3.6-3.9, 4.6-4.8 and 5.1-5.3. At higher pH, WPI gels were stronger than SMP gels. WPI had a reinforcing effect on SMP gels, while small additions of SMP to WPI gels resulted in weaker mixed gels. Filled gels containing cream had higher compression strengths than mixed gels. Micrographs showed linking of casein chains by WPI strands in mixed gels and compatibility of fat globules with casein micelles in the protein network of filled gels.