Inactivation of Escherichia coli O157:H7, salmonellae, and Campylobacter jejuni in raw ground beef by gamma irradiation

Abstract

Raw ground beef patties inoculated with stationary-phase cells of Escherichia coli 0157:H7, salmonellae, or Campylobacterjejuni were subjected to gamma irradiation (60Co) treatment, with doses ranging from 0 to 2.52 kGy. The influence of two levels of fat (8 to 14% [low fat] and 27 to 28% [high fat]) and temperature (frozen [-17 to-15°C] and refrigerated [3 to 5°C]) on the inactivation of each pathogen by irradiation was investigated. In ascending order of irradiation resistance, the D1o values ranged from 0.175 to 0.235 kGy (C. jejuni), from 0.241 to 0.307 kGy (E. coli 0157:H7), and from 0.618 to 0.800 kGy (salmonellae). Statistical analysis revealed that E. coli 0157:H7 had a significantly (P < 0.05) higher DIo value when irradiated at-17 to-15°C than when irradiated at 3 to 5°C. Regardless of the temperature during irradiation, the level of fat did not have a significant effect on the D1o value. Salmonellae behaved like E. coli 0157:H7 in low-fat beef, but temperature did not have a significant effect when the pathogen was irradiated in high-fat ground beef. Significantly higher D1o values were calculated for C. jejuni irradiated in frozen than in refrigerated low-fat beef. C. jejuni was more resistant to irradiation in low-fat beef than in high-fat beef when treatment was at-17 to-15°C. Regardless of the fat level and temperature during inactivation, these pathogens were highly sensitive to gamma irradiation. An applied dose of 2.5 kGy would be sufficient to kill 108.1 E. coli 0157:H7, 103 ' salmonellae, and 1010.6 C. jejuni, resulting in a high probability of complete inactivation of populations much higher than those occasionally present in ground beef patties. Gamma irradiation has been used as a method of preserving foods in several countries, including Belgium, France, Japan, and the Netherlands (12). The process involves exposing the food to a specific dose of ionizing irradiation from, for example, 6"Co, a radioisotope of cobalt (21). Irradiation is

ELIMINATION OF BACTERIAL ISOLATES FROM JOLLOF RICE MEAL BY IRRADIATION AND CHILLED STORAGE

“…Although the calculated D 10 value of 0.173 kGy for E. coli in this study is fairly low, it is still within the reported range of 0.1-0.39 kGy for the isolate on beef and poultry meat (Patterson 1988;Thayer and Boyd 1993;Clavero et al 1994;Thayer et al 1995). Similarly, the D 10 value of 0.260 kGy for S. aureus in this study was within the reported range of 0.1 to 0.65 kGy for the isolate on meat, fish and poultry (Grecz et al 1983;Thayer and Boyd 1992;Thayer et al 1995;Loaharanu 1996).…”

Radiation inactivation of some food-borne pathogens in fish as influenced by fat levels

“…A lack of influence of fat content has been reported in L. monocytogenes , Salmonella spp. , Campylobacter jejuni and Escherichia coli (Maxcy and Tiwari 1973 ;Clavero et al 1994 ;Thayer et al 1995). Similarly, Thayer and Boyd (1994) found that endospores of six strains of B. cereus did not differ significantly in their gammaradiation resistance when irradiated in beef, pork and gravy with dissimilar fat levels.…”

Survival of Listeria monocytogenes, Yersinia enterocolitica and Escherichia coli O157:H7 and Quality Changes After Irradiation of Beef Steaks and Ground Beef

“…Research is required to demonstrate the benefits of irradiation in preventing outbreaks of foodborne illness from beef or beef products. Research (Clavero et al, 1994) has indicated that pathogens such as E. coli 0157:H7, salmonellae and Campylobacter jejuni are sensitive to gamma irradiation. A dose of 2.5 kGy was suggested as sufficient to kill large numbers of the pathogens in ground beef.…”