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By C. CLAIBORNE RAY
 heese and Vegetarians
Q. I no longer want to eat meat, but I hear that cheese making requires an enzyme from calves. Is this true?
A. Many cheeses, especially hard cheeses, are traditionally made from milk coagulated with an enzyme-rich substance called rennet that is obtained from the lining of the fourth stomach, or abomasum (pronounced ab-uh-MAY-sum), of calves. But there are cheeses made without rennet, with "vegetarian" rennet derived from plants, funguses or bacteria, or with genetically engineered rennet that never saw a calf.
The most important enzyme in rennet is called chymosin or rennin, and it inactivates a milk protein called kappa casein (KAY-see-in) that would otherwise keep the other forms of casein in milk in liquid form. The proteins then break out in clumps and combine with milk fat and water, forming the familiar curds.
Certain cheeses can be coagulated by lactic acid bacteria rather than rennet. They include cream cheese, cottage cheese, ricotta and some mozzarella, but check the label or ask the maker to find out if rennet is added.
Genetically engineered rennet, made by inserting a calf gene into the genome of bacteria or yeast, is becoming increasingly popular with cheese makers.
Labeling does not always make it clear which cheeses are made with which kinds of rennet, but some gourmet and health food stores and some manufacturers offer information. The New York Times. |
