Andrew F. Smith

Genetically Modified Foods: Overview: Biotechnology at the Supermarket

Appears in
Oxford Encyclopedia of Food and Drink in America
Oxford Encyclopedia of Food and Drink in America

By Andrew F. Smith

Published 2004

  • About
The average American supermarket contains many foods with ingredients of GM origin. Consumers may be unaware of what is or is not genetically modified, because such labeling is voluntary. The first product of genetic engineering in the U.S. food supply was Chy-Max chymosin, developed by Pfizer and approved by the FDA in 1990. It is a version of vegetarian rennet, used to make some kinds of cheese.

The presence of animal rennet (derived from the stomach tissue of calves) makes many cheeses undesirable for vegetarians and for those observing certain religious dietary bans. The gene for chymosin (the main molecule involved in rennet-induced milk coagulation) is either isolated from calf tissue or synthesized in a laboratory and inserted into bacteria or certain fungi. The chymosin produced is reliable in its clotting properties, making it cost effective for cheese makers. Approximately 60 percent of all U.S. cheeses are produced with GM chymosin from various companies. Some cheeses may be labeled “vegetarian,” but most supermarket hard cheeses are made with these chymosins. Those same cheeses may be made with milk from cows that have been given recombinant bovine somatotropin (rBST), sometimes called recombinant bovine growth hormone (rBGH), a protein hormone. Approximately one-third of U.S. dairy cattle are given rBST to increase milk production 10 to 15 percent. The rBST is indistinguishable from BST, or natural bovine somatotropin, and is mostly destroyed by pasteurization.