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Title: THE FATE OF CLOSTRIDIUM PERFRINGENS SPORES EXPOSED TO OZONE AND/OR MILD HEAT PRETREATMENT ON BEEF SURFACES FOLLOWED BY MODIFIED ATMOSPHERE PACKAGING

Author
item Novak, John
item YUAN, JAMES - AMERICAN AIR LIQUIDE

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2004
Publication Date: 7/1/2004
Citation: Novak, J.S., Yuan, J.T. 2004. The fate of clostridium perfringens spores exposed to ozone and/or mild heat pretreatment on beef surfaces followed by atmosphere modification. Food Microbiology. 21:667-673.

Interpretive Summary: Clostridium perfringens is a very common cause of illness associated with consumption of beef that has not been properly refrigerated. The organism produces spores that are resistant to numerous processing technologies including cooking and ozone treatment. This study examined the survival of spores from C. perfringens when attached to raw beef surfaces following pretreatments with 60C for 30 min and/or 5ppm of aqueous ozone for 5 min in combination with increasing carbon dioxide levels and vacuum packaged storage for up to 10 days. The results suggested that heat treatments create a greater concern through adaptations of C. perfringens to stress that were not observed in the ozone-treated bacteria. Pretreatment of beef at temperatures that do not result in spore inactivation may actually increase the microbial risk for illness due to C. perfringens as compared to ozone treatment of beef. The study also showed that refrigeration and storage in atmospheres containing greater than 30% carbon dioxide played important roles in increasing the shelf-life of beef and preventing growth of C. perfringens. The overall recommendation is to limit heat exposure to beef prior to final meal preparation to prevent germination of C. perfringens spores.

Technical Abstract: Clostridium perfringens is a common contaminant of raw beef products that can proliferate to dangerous levels under conditions of temperature abuse. Spores of the bacterium were inoculated onto irradiated subprimal cut beef surfaces at levels of 3 log spores/g beef. Samples of beef (7.5 x 10.0 x 1.0 cm) were treated with aqueous ozone (5 ppm O3 for 5 min), or heat (60C for 30 min), or both and then vacuum-packaged to 2 kPa and stored up to 10 d at 37C, 25C, or 4C. Storage at 37C resulted in increases in viable counts after 1 d to over 7 log CFU/g beef, whereas storage at 4C prevented spore germination and growth for all treatments. At 25C, heat-treated beef samples reached 6 log CFU/g viable counts in 2 d, and spores/vegetative cells on control or ozone-treated samples did not germinate or grow through the first day of vacuum-packaged storage. Modified atmospheres with increasing CO2 concentration were also compared with regard to the effect on bacterial survival during beef storage at 25C. Only control and ozone-treated spores of C. perfringens on beef were inhibited during a 10-d storage at 25C. Pretreatment with heat increased germination during storage of beef, whereas ozone treatment and no treatment controls were effective in inhibiting spore germination and outgrowth in combination with increasing CO2 concentrations above 30% or refrigeration. These data support the avoidance of heat in the pretreatment of raw beef.