COMPOSITION, MICROSTRUCTURE AND MATURATION OF SEMIHARD CHEESES FROM HIGH-PROTEIN ULTRAFILTERED MILK RETENTATES WITH DIFFERENT LEVELS OF DENATURED WHEY-PROTEIN

Standardized milks, heated at 72-100 degrees C to denature similar to 5-63% of the whey protein, were ultrafiltered to yield retentates with protein and fat levels of similar to 18.5 and 14%, respectively. Retentates were converted into semi-hard cheeses using specialized coagulation and gel-cutting equipment, with scalding and further syneresis being carried out in conventional cheese vats. High heat treatment of milk necessitated an increase in set temperature, a reduction in set pH and higher scalding temperatures in the cheese vat. Cheese from milk heated at 72 degrees C for 15 s had a mean composition of similar to 39.8% moisture, 28% protein, 45.1% fat-in-dry matter, 3.5% salt-in-moisture (S/M) and an ex-brine (1 day) pH of 5.27. Increasing levels of whey protein denaturation (WPD) resulted in cheeses having higher moisture, S/M, and whey protein levels, lower ex-brine pH values and lower rates of pH increase during a 182-day ripening period. Cheeses with high levels of WPD also showed poorer curd fusion and lower yield (fracture) values during ripening. Higher levels of denatured whey protein in cheeses were associated with a higher degree of primary proteolysis. However, the levels of small peptides (<1000 Da) and amino acids were higher in the control cheese and generally decreased with increasing level of denatured whey protein in the cheese. The concentrations of most free fatty acids, especially butyric, were higher in control cheese.