Page Banner

United States Department of Agriculture

Agricultural Research Service

Proper Heat Treatment Kills Deadly E. coli Bacteria in Food / July 31, 1998 / News from the USDA Agricultural Research Service

Agricultural Research Service
U.S. Department of Agriculture
ARS News and Information Search News and Info Science for Kids Image Gallery Agricultural Research Magazine Publications and Newsletters News Archive News and Info home ARS News and Information
Latest news | Subscribe

Proper Heat Treatment Kills Deadly E. coli Bacteria in Food

By Doris Stanley
July 31, 1998

Cooking regimes designed to kill deadly Escherichia coli 0157:H7 must be based on the pathogen being in its most heat-resistant state, according to a microbiologist with USDA's Agricultural Research Service. Bacteria previously subjected to lower heating temperatures may be tougher to kill.

E. coli that have been subjected to only a sublethal dose of heat can be more heat-resistant than bacteria that have not been exposed to such heat. This is why it is so important to adequately cook food to kill foodborne pathogenic bacteria.

At the ARS Eastern Regional Research Center's Food Safety Research Unit in Wyndmoor, Pa, Vijay K. Juneja and colleagues heated beef gravy samples contaminated with E. coli 0157:H7 to 114.8·F for 15 to 30 minutes. The heat was not sufficient to kill the bacteria, but enough to stimulate it so that it could adapt to the stressful heating conditions. They then cooked the gravy to a final internal temperature of 140·F.

Pre-heated E. coli survived longer at the higher temperature—a 1.5-fold increase in heat resistance—than E. coli not subjected to sublethal temperatures. And, the increased heat tolerance lasted for at least 48 hours.

This research suggests to food processors that slowly heating foods to the final cooking temperatures normally used may not kill bacteria. Heat-shocking conditions may occur in refrigerated, cook-in-bag foods such as filled pasta, beef stew, roasts and soups. The slow heating rate and low heating temperatures widely used to prepare these foods may expose potential pathogens to heat shocking conditions, thereby making the microbes even more heat- resistant.

Adequate cooking is still the best way to kill pathogenic organisms in food.

A report on the E. coli research appears in the July issue of Agricultural Research magazine, the monthly publication of the Agricultural Research Service. The article can be viewed on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/jul98/coli0798.htm

Scientific contact: Vijay K. Juneja, Food Safety Research Unit, Eastern Regional Research Center, Wyndmoor, PA 19038; phone (215) 233-6500, fax (215) 233-6406, e-mail vjuneja@arserrc.gov

Top | News Staff | Photo Staff

E-mail the web team Privacy and other policies Site map About ARS Information Staff Bottom menu

Home | News | Pubs | Magazine | Photos | Sci4Kids | Search
About ARS Info | Site map | Policies | E-mail us

Last Modified: 1/3/2002
Footer Content Back to Top of Page