The most common method being used for coagulation is by the addition of enzymes. The physical properties of enzyme coagulated cheese are superior to the acid coagulated cheese. The most common source is rennet. Rennet is made from the lining of the fourth stomach of calves. The most common enzyme used to coagulate milk is rennet.
Rennet is made from the fourth stomach of calves.
The calves are milk fed and are usually less than 10 days old. Young calves are used because they stop making chymosin as they get older. The most important enzyme in rennet is chymosin. Rennet would therefore be a problem for the kosher consumer. Rennin is the name given to the enzyme fraction of rennet.