Author
 |
Novak, John |
|
YUAN, JAMES - AMERICAN AIR LIQUIDE |
|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/18/2002 Publication Date: 3/1/2003 Citation: NOVAK, J.S., YUAN, J.T. 2003. VIABILITY OF SELECT FOOD-BORNE PATHOGENS SURVIVING MILD HEAT OR AQUEOUS OZONE TREATMENT ON BEEF FOLLOWED BY IMPOSED HEAT, PH, OR SALT STRESS. JOURNAL OF FOOD PROTECTION. 66(3):382-389. Interpretive Summary: Following recent FDA approval of ozone as an antimicrobial agent for the treatment, storage, and processing of foods, research was initiated to further evaluate the technology. Since use of 3 parts per million of ozone resulted in a reduction of only 1 log of Listeria monocytogenes, Escherichia coli O157:H7 and Clostridium perfringens per gram of beef, the potential that bacteria surviving treatment may become more resistant or more sensitive to subsequent treatments such as heat, salt, or acid or alkaline conditions was investigated. Results showed that ozone treatment resulted in fewer stress adaptations with respect to exposure to heat, salt, or acid or alkaline conditions than sublethal heat treatments (55C for 30 minutes). Surviving Clostridium perfringens exposed to ozone, however, were more susceptible to heat treatment at 60C than non-treated bacteria indicating that a combination treatment of ozone and heat may be more effective in inactivating the bacterium than treatment with heat or ozone alone. These studies showed that preservation technologies require careful evaluation by the food industry to determine the effect of combination treatments and to ensure that surviving bacteria do not exhibit an increased potential for food-borne disease. Technical Abstract: The threat of pathogen survival following ozone treatment of meat necessitates careful evaluation of the surviving microorganisms for tolerance to subsequent heat, pH, and NaCl stress. Log reductions in CFU/g of 3-strain cocktails of Clostridium perfringens, Escherichia coli O157:H7, and Listeria monocytogenes on beef following a heat treatment of 55C for 30 min were 0.14, 0.77, and 1.47, respectively, whereas log reductions following ozone treatment of beef (3 ppm for 5 min) were 1.28, 0.85, and 1.09, respectively. C. perfringens cells exhibited elevated heat resistance at 60C (D-value of 17.76 min) following heat treatment of beef (55C for 30 min), but, exhibited reduced viability at 60C following ozone treatment of beef (D-value of 7.64 min) compared to untreated control cells washed from the beef surface (D-value of 13.84 min). No significant heat stress effects were recorded for L. monocytogenes or E. coli O157:H7 following the heat (55C for 30 min) or ozone (3 ppm for 5 min) exposures. C. perfringens cells that survived ozone treatment did not exhibit increased resistance to pH (6.0 to 12) when grown at 37C for 24 h as compared to non-ozone-treated cells grown at 37C for 24 h. The heat treatment (55C for 30 min) resulted in decreased numbers of surviving CFU above and below neutral pH values for both E. coli O157:H7 and L.monocytogenes as compared to non-heat-treated cells grown at 37C for 24 h. There were significant differences (P<0.05) in log CFU/g reductions of C. perfringens with increasing NaCl concentration from 0 to 6.0%. The NaCl effects were less apparent (less than a 2 log loss in viability) for E. coli O157:H7 and L. monocytogenes heat-treated and ozone-treated survivors. In conclusion, C. perfringens, E. coli O157:H7, and L. monocytogenes cells on beef surfaces that survived 3 ppm ozone for 5 min at 4C did not exhibit increased resistance to subsequent heat, pH, and NaCl stresses compared to non-ozone-treated cells, whereas heat treatment (55C for 30 min) resulted in increased resistance to heat and decreased resistance to pH and salt stress. |
