Search

•First scientific evidence that baking English muffins at 400°F for 18 min acts as an effective kill step by controlling Salmonellapopulation by >5 log CFU/g.•The D-values of 3 serovar cocktails of Salmonellaat 55, 58.5, and 62°C were 42.0 ± 5.68, 15.6 ± 0.73, and 3.0 ± 0.32, respectively; and z-value was 5.30 ± 0.51.•The Salmonella D−and z−values determined in the English muffin dough will help bakers optimize baking processes and achieve food safety.

AbstractThis study validated a typical commercial donut frying process as an effective kill-step against a 7-serovar Salmonellacocktail (Newport, Typhimurium, Senftenberg, Tennessee, and three dry food isolates) when contamination was introduced through inoculated flour. The bread and pastry flour mix (3:1) was inoculated with the Salmonellacocktail, and subsequently dried back to original preinoculation moisture content, achieving a Salmonellapopulation of 7.6 log CFU/g. Inoculated flour was used to prepare a typical commercial donut batter, which was fried using 375°F (190.6°C) oil temperature. No viable Salmonellawas detected using an enrichment plating protocol in the donuts after 2 min of frying, resulting in >7-log reduction in Salmonellapopulation. The internal donut temperature increased from ∼30°C to ∼119°C at the end of 2 min of frying. The water activities of the donut crumb and crust after 2 min of frying, followed by 30 min of ambient air cooling, were 0.944 and 0.852, respectively. The donut pH after ambient-air cooling was 5.51. The D- and z-values of the Salmonellacocktail in donut dough were determined using thermal-death-time disks and temperature-controlled water baths. The D-values of the cocktail were 8.6, 2.9, and 2.1 min at 55°C, 58°C, and 61°C, respectively, whereas the z-value was 10°C. This study validated that >7-log reduction could be achieved if donuts are fried for at least 2 min in the oil at 190.6°C, and calculated D- and z-values present the heat resistance of Salmonellain donut dough at the start of the frying processes. However, results from this study should not be extrapolated when donut composition and frying parameters are changed significantly.

This study was conducted to validate a simulated commercial baking process for hamburger buns to destroy Salmonellaserovars and to determine the appropriateness of using nonpathogenic surrogates (Enterococcus faeciumATCC 8459 or Saccharomyces cerevisiae) for in-plant process validation studies. Wheat flour was inoculated (~6 log CFU/g) with three Salmonellaserovars (Typhimurium, Newport, or Senftenberg 775W) or with E. faecium. Dough was formed, proofed, and baked to mimic commercial manufacturing conditions. Buns were baked for up to 13 min in a conventional oven (218.3°C), with internal crumb temperature increasing to ~100°C during the first 8 min of baking and remaining at this temperature until removal from the oven. Salmonellaand E. faeciumpopulations were undetectable by enrichment (>6-log CFU/g reductions) after 9.0 and 11.5 min of baking, respectively, and ≥5-log-cycle reductions were achieved by 6.0 and 7.75 min, respectively. D-values of Salmonella(three-serovar cocktail) and E. faecium8459 in dough were 28.64 and 133.33, 7.61 and 55.67, and 3.14 and 14.72 min at 55, 58, and 61°C, respectively, whereas D-values of S. cerevisiaewere 18.73, 5.67, and 1.03 min at 52, 55, and 58°C, respectivly. The z-values of Salmonella, E. faecium, and S. cerevisiaewere 6.58, 6.25, and 4.74°C, respectively. A high level of thermal lethality was observed for baking of typical hamburger bun dough, resulting in rapid elimination of high levels of the three-strain Salmonellacocktail; however, the lethality and microbial destruction kinetics should not be extrapolated to other bakery products without further research. E. faeciumdemonstrated greater thermal resistance compared with Salmonelladuring bun baking and could serve as a conservative surrogate to validate thermal process lethality in commercial bun baking operations. Low thermal tolerance of S. cerevisiaerelative to Salmonellaserovars limits its usefulness as a surrogate for process validations.

Laboratory experiments were designed to determine the survival of Enterococcus faecalisOG1RF:pCF10 in poultry and cattle feed and its acquisition and transmission by adults of the red flour beetle, Tribolium castaneum(Herbst), to sterile feed. Adult T. castaneumbeetles were introduced into poultry and cattle feed inoculated with E. faecalisOG1RF:pCF10 and incubated at 28°C with 65% relative humidity for 7 days in a growth chamber. E. faecalissurvived in both poultry and cattle feed during the 7-day test period. There was a logarithmic decrease in E. faecalisconcentration in poultry and cattle feed and in and on the insects. E. faecalispersisted on the surface and within T. castaneumadults for 7 days when adults were released on E. faecalis-inoculated poultry feed and for only 5 days on E.faecalis-inoculated cattle feed. The concentration of E. faecalisdecreased more slowly on poultry feed than on cattle feed, and this may explain why adult T. castaneuminsects were more successful in acquiring and transferring E. faecalisfrom inoculated poultry feed to sterile poultry feed during the 7-day test period. However, T. castaneumadults reared on inoculated cattle feed were unable to contaminate sterile cattle feed on day 7. To our knowledge, this is the first report documenting T. castaneumto successfully acquire antibiotic-resistant enterococci from animal feed and transfer them to sterile feed. Management of T. castaneumthrough effective integrated pest management program is therefore important to prevent the spread of antibiotic-resistant and virulent enterococci in animal feed and feed manufacturing environments