The relationship between numbers of bacteria on surfaces and in deep tissues of mechanically tenderized beef

Inactivation of Escherichia coli O157:H7 in Minute Steaks Cooked under Selected Conditions

A national survey was conducted in Canada to determine consumer cooking practices for minute steaks (thin, mechanically tenderized beef cutlets). Results indicate that most Canadians prefer cooking minute steaks by pan frying and to a medium level of doneness. To identify safe cooking conditions, retail minute steaks (∼125 g), inoculated at three sites per steak with a five-strain cocktail of nontoxigenic Escherichia coli O157:H7 (6.1 log CFU per site), were cooked on a hot plate (200°C), mimicking a pan-frying scenario. The steaks (n = 5) were cooked for 4, 6, 8, or 10 min with turning over (flipping) up to four times at equal time intervals; or to 63 or 71°C at the thickest area with or without a tinfoil lid. When cooked for 4 min, E. coli O157:H7 was recovered from all inoculation sites, and the mean reductions at various sites (1.2 to 3.4 log CFU per site) were not different (P > 0.05), irrespective of the flipping frequency. When cooked for 6 min with flipping once or twice, or for 8 min with flipping once, E. coli O157:H7 was recovered from most sites; the mean reductions (3.8 to 5.3 log CFU per site) were not different (P > 0.05), but they were higher (P < 0.05) than those for steaks cooked for 4 min. When cooked for 10, 8, or 6 min with flipping once, twice, or three times, respectively, E. coli O157:H7 was eliminated from most sites, but sites with <5-log reductions were found. Reductions of E. coli O157:H7 by >5 log at all inoculation sites were attained when the steaks were cooked for 10 or 8 min with two or more or three or more flippings, respectively, or for 6 min with four flippings. When flipped twice during cooking to 63 or 71°C, E. coli O157:H7 was recovered from three or fewer sites; however, >5-log reductions throughout the steaks were only attained for the latter temperature, irrespective of whether the hot plate was covered with the tinfoil lid. Thus, turning over minute steaks twice during cooking to 71°C or flipping two, three, or four times with a cooking time of 10, 8, or 6 min could achieve 5-log reductions throughout the steaks.

Food Consumption and Handling Survey for Quantitative Microbiological Consumer Phase Risk Assessments

In the consumer phase of a typical quantitative microbiological risk assessment (QMRA), mathematical equations identify data gaps. To acquire useful data we designed a food consumption and food handling survey (2,226 respondents) for QMRA applications that is especially aimed at obtaining quantitative data. For a broad spectrum of food products, the survey covered the following topics: processing status at retail, consumer storage, preparation, and consumption. Questions were designed to facilitate distribution fitting. In the statistical analysis, special attention was given to the selection of the most adequate distribution to describe the data. Bootstrap procedures were used to describe uncertainty. The final result was a coherent quantitative consumer phase food survey and parameter estimates for food handling and consumption practices in The Netherlands, including variation over individuals and uncertainty estimates.