Oregano and organic acids impede growth of C. perfringens.

C. perfringens is an anaerobic, Gram-positive bacterium widely found in soil and the intestinal tract of vertebrates. At least 12 toxins are produced by C. perfringens, including four lethal toxins, hemolysins, proteases, neuraminidase and enterotoxin. C. perfringens poisoning is one of the most common foodborne illnesses.

Heat treatments that are performed on minimally processed food products are not sufficient to kill spores of C. perfringens. The heat-resistant spores may survive, germinate, outgrow and multiply into high numbers of vegetative cells if the product is inadequately cooled.

There is a need to see if the time a product is refrigerated could be extended without posing a safety hazard caused by the growth by more than 1 [log.sub.10] of C. perfringens from spores of the bacterium. Kansas State University scientists conducted research to determine how combinations of a thermal treatment, organic acids and spices could control C. perfringens during 15-hour, 18-hour and 21-hour cooling processes.

The investigators inoculated 73% lean ground beef with a three-strain spore cocktail of C. perfringens ATCC 10388, NCTC 8238 and NCTC 8239 at approximately 2 [log.sub.10] spores per g. Researchers mixed 500 g of meat with water (10% w/w), sodium tri-phosphate (0.5% w/w) and sodium chloride (1.5% w/w). The treatments consisted of commercial solutions of sodium lactate or sodium citrate (2% w/w) alone or combined with powders of chili, garlic and herbs, curry, oregano or clove (1% w/w). The scientists cooked vacuum-packaged ground beef at 75 C for 20 min. The beef samples were exponentially cooled from 54.4 C to 7.2 C in 15 hours, 18 hours and 21 hours. All experiments were repeated twice.

The treatments containing sodium citrate altered the population of

C. perfringens from 0.38 [log.sub.10] to 1.14 [log.sub.10] cfu per g during 15 hours and 18 hours of cooling, respectively. Treatments with spices alone increased the population of C. perfringens by 0.98 [log.sub.10] to 4.3 [log.sub.10]. Combinations of oregano with sodium lactate resulted in less than a 1 [log.sub.10] cfu per g growth of C. perfringens under any cooling scenario.

Oregano used with organic acids can restrict the growth of C. perfringens when a product is cooled. These findings will help the meat industry meet the USDA standard of no more than a 1 [log.sub.10] increase in C. perfringens counts in beef. Further information. Daniel Fung, Department of Animal Sciences and Industry, Kansas State University, 202 Call Hall, Manhattan, KS; phone: [phone]; fax: [phone]; email: [e-mail].