Prior to slaughter, the muscles of healthy food animals normally do not contain microorganisms that are toxic to humans. However, several species of these types of microorganisms can be found in the animal's gastrointestinal tract. An essential part of the slaughter process includes the cutting and removal of an animal's gastrointestinal tract and as a result the tract contents are often spilled and smeared onto the meat surface at this time. Another source of bacterial contamination occurs when the gastrointestinal tract contents are spreadfrom the surface of one animal to another due to the successive handling of carcasses by slaughterhouse workers. In addition, contamination can occur during successive machine-processing steps or when meat pieces are sequentially dipped in various liquid treatment baths.

A novel device has been conceived, built, success-fully tested and patented that selectively kills bacteria with steain on the surface of raw meat without cooking the surface. The device kills 99.99% of bacteria on the meat within 26 milliseconds by heating the meat surface very quickly with saturated steam. This is accomplished by first eliminating the air from around the meat, extremely brief exposure to the steam, then equally quick surface cooling by re-evaporating into a vacuum the steam condensate that had formed on the meat during the heating process.

When 138 degree C steam was used for 26 milliseconds, the device proved able to achieve four log reductions of bacteria applied to the surface of poultry meat, without cooking it. Because both the heating and cooling steps are finished within milliseconds there is not enough time for the meat to cook. This opportunity arises because of the higher activation energy of meat protein denaturation compared with the lower activation energy of disrupting the most vulnerable bacterial enzymes.

Since most contamination of intact meat is on the surface, this process gives promise of virtual elimination of this danger to meat consmers, provided that the resulting products are correctly handled. Consumers, producers, and exporters would benefit from use of the process in slaughter lines. In order to achieve the maximum benefit, the device must be adapted to the rates and conditions of slaughter lines. This appears possible because of the very short processing times required.

This technology has been patented and is available for licensing. The Eastern Regional Research Center is interested in entering into a Cooperative Research and Development Agreement to continue developmental studies.

Patent Status:
U.S. Patent 5,281,428 issued January 25, 1994.

Technology Transfer Contact:
Victor (Vic) Chavez
(215) 233-6610
e-mail: vic.chavez@ars.usda.gov