Microstructure and Meltability of Model Process Cheese Made with Rennet and Acid Casein

Process cheese models were prepared by blending acid or rennet casein, milk fat, sodium chloride, 2.5% emulsifying salt, and water and heating to 80C. Four emulsifying salts (trisodium citrate, disodium phosphate, tetrasodium pyrophosphate, or sodium aluminum phosphate) were used. Undenatured or heatdenatured whey protein was added at 1.5, 3.0, or 4.5%. Microstructure and meltability of the models were examined. Emulsifying salts affected the degree of emulsification and meltability of the samples. Rennet casein models prepared with tetrasodium pyrophosphate or disodium phosphate were highly emulsified and had poor meltability. Samples prepared with trisodium citrate or sodium aluminum phosphate were not as emulsified and melted well. Acid casein models prepared with disodium phosphate were highly emulsified and melted very well. The remaining acid casein models had very open structure and melted well. Meltability decreased as whey protein concentration increased in both acid and rennet casein models. The highest whey protein concentration in the rennet casein model produced fibrous structures around the fat globules. Addition of whey protein to acid casein models did not affect emulsification. A relationship was noted between the fat emulsion and