DETECTION OF RESIDUAL CHYMOSIN IN CHEESE BY AN ENZYME-LINKED-IMMUNOSORBENT-ASSAY

A simple and rapid competitive enzyme-linked immunosorbent assay metho d has been developed to detect the residual activity of chymosin in va rious types of cheese without extraction. In a cheese of the Saint-Pau lin type, concentrations of chymosin detected at the end of cheesemaki ng in curd and whey represented 22.5 and 73.5 % respectively of the to tal amount added to milk, so most of the chymosin was detected using t his method. In a cooked pressed cheese of the Comte type, only 14% of the chymosin added to milk was detected in curd and all the chymosin i n whey was inactivated. It was thus possible to demonstrate the presen ce of active residual chymosin in cooked pressed cheese. When measurem ents were carried out in 12 different cheeses, chymosin concentrations ranged between 384 ng/g in a Camembert cheese and 86 ng/g for an 8-mo nth old Comte cheese. Chymosin appeared to be highly stable during che ese ripening.