Influence of salt content on ripening of semi-hard round-eyed cheese of Danbo-type

Semi-hard cheese of Danbo-type was manufactured and brine-salted at 4 diffe rent levels. Salting for 0, 24, 48 and 96 h resulted in successively decrea sing moisture content and in 0.06, 2.6, 4.3 and 6.4% salt-in-moisture, resp ectively. The proteolysis was followed during 10 weeks of ripening at 16 de grees C by Kjeldahl analysis of N contents in the pH 4.6-soluble fraction ( pH 4.6-SN) and the phosphotungstic acid-soluble fraction (PTA-SN), by capil lary zone electrophoresis (CZE) and reverse-phase (RP)-HPLC. Increasing NaC l contents decreased the formation of pH 4.6-SN and PTA-SN in the cheeses. The CZE results showed no salt effect on the hydrolysis of alpha(s1)-casein (alpha(s1)-CN) and alpha(s1)-CN (f24-199), while hydrolysis of beta-CN but not the accumulation of gamma-caseins was retarded by increasing NaCl cont ent. The primary breakdown products of beta-CN by chymosin in aqueous solut ions, beta-CN (f1-192) and beta-CN (f193-209) were not found, not even in t he unsalted cheese during the first weeks of ripening. Analysis by RP-HPLC of the pH 4.6 soluble fraction showed that several peptides eluting early f rom the column as well as the amounts of the free amino acids Tyr, Phe and Trp decreased with increasing salt content indicating an influence of the s alt content on bacterial activity.