Detection of residual chymosin in cheese by an enzyme-linked immunosorbent assay

Summary A simple and rapid competitive enzyme-linked immunosorbent assay method has been developed to detect the residual activity of chymosin in various types of cheese without extraction. In a cheese of the Saint-Paulin type, concentrations of chymosin detected at the end of cheesemaking in curd and whey represented 22·5 and 73·5% respectively of the total amount added to milk, so most of the chymosin was detected using this method. In a cooked pressed cheese of the Comté type, only 14% of the chymosin added to milk was detected in curd and all the chymosin in whey was inactivated. It was thus possible to demonstrate the presence of active residual chymosin in cooked pressed cheese. When measurements 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-month old Comté cheese. Chymosin appeared to be highly stable during cheese ripening.