PROTEOLYSIS IN THE IRISH FARMHOUSE BLUE CHEESE, CHETWYND

Chetwynd blue is an Irish farmhouse cheese produced from pasteurised, homogenised cows' milk. Proteolysis in two samples of this cheese was studied over a 71-day ripening period. The concentrations of pH 4.6-, trichloroacetic acid- and phosphotungstic acid-soluble N increased sub stantially during ripening, especially after 15 days, concomitant,vith mould growth and sporulation. The pH of the cheese increased from sim ilar to 4.8 at day 1 to similar to 5.9 by day 71. High concentrations of amino acids had accumulated by the end of ripening, particularly gl utamic acid, leucine, valine and lysine. Urea-polyacrylamide gel elect rophoresis of the cheeses showed that considerable degradation of the major caseins had occurred at the end of ripening. During the early st ages of ripening, proteolysis was due mainly to chymosin (rennet) but during the later stages, the fungal endo- and exo-peptidases became do minant and the cheese proteins were hydrolysed extensively. Reverse-ph ase HPLC showed an increase in the total concentration of pH 4.6-solub le peptides during ripening. Chromatograms of the ethanol-soluble frac tion were similar to those of the pH 4.6-soluble fraction.