Proteolysis in Cheddar-type cheese made from goat's milk

Three batches of cheese were manufactured from pasteurised goat's milk using 3 levels of rennet, but otherwise following a standard recipe for Cheddar cheese. Composition was found generally to be in the normal range for Cheddar cheese (pH 4.9-5.0; 35.8-38.3% moisture; 1.0-1.2% NaCl; 49.8-54.8% fat-in-dry-matter; 21.3-21.9% protein). The levels of pH 4.6-soluble nitrogen as % of total nitrogen and free amino acids increased throughout ripening and were generally proportional to rennet levels. Urea-PAGE analysis of the pH 4.6-insoluble fraction of the cheese showed more degradation of α_s-than β-caseins throughout ripening, with proteolysis of the former protein being correlated with rennet level. Analysis of the 70% (v/v) ethanol-insoluble fraction by reversed-phase HPLC showed that higher levels of rennet produced the highest levels of peptides. However, as ripening progressed, fewer differences in peptide patterns were apparent, confirming the importance of the coagulant as an agent for primary proteolysis in cheese.