Validation of Baking To Control Salmonella Serovars in Hamburger Bun Manufacturing, and Evaluation of Enterococcus faecium ATCC 8459 and Saccharomyces cerevisiae as Nonpathogenic Surrogate Indicators

Abstract

This study was conducted to validate a simulated commercial baking process for hamburger buns to destroy Salmonella serovars and to determine the appropriateness of using nonpathogenic surrogates (Enterococcus faecium ATCC 8459 or Saccharomyces cerevisiae) for in-plant process validation studies. Wheat flour was inoculated (∼6 log CFU/g) with three Salmonella serovars (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. Salmonella and E. faecium populations 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. faecium 8459 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. cerevisiae were 18.73, 5.67, and 1.03 min at 52, 55, and 58°C, respectivly. The z-values of Salmonella, E. faecium, and S. cerevisiae were 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 Salmonella cocktail; however, the lethality and microbial destruction kinetics should not be extrapolated to other bakery products without further research. E. faecium demonstrated greater thermal resistance compared with Salmonella during bun baking and could serve as a conservative surrogate to validate thermal process lethality in commercial bun baking operations. Low thermal tolerance of S. cerevisiae relative to Salmonella serovars limits its usefulness as a surrogate for process validations.

Validation of a Simulated Commercial Frying Process to ControlSalmonellain Donuts

“…The differences in the D- and z -values in the current study (proofed donut dough) and those generated by Channaiah et al (2016, 2017) for proofed bun dough and muffin batter could be attributed to differences in the Salmonella cocktails used in these studies. Moreover, the proximate compositions of hamburger bun dough (46.9% moisture, 8.5% protein, 3.8% fat, and 40.8% starch) and muffin batter (31.2% moisture, 6.3% protein, 8.9% fat, and 24.3% starch) in Channaiah et al (2016, 2017) studies were different than that of donut dough in the current study. The lower D-values of Salmonella cocktail in proofed donut dough compared to that in muffin batter (Channaiah et al , 2017) could also be attributed to the lower pH of proofed donut dough (4.82) than muffin batter (6.61) that would have facilitated thermal inactivation of Salmonella in donut dough.…”

“…The D-values of Salmonella cocktail in dough were 8.6, 2.9, and 2.1 min at 55°C, 58°C, and 61°C, respectively, with a z -value of 10°C. In similar studies, Channaiah et al (2016, 2017) determined that a 3-serovar Salmonella cocktail (Typhimurium, Newport, and Senftenberg) in proofed hamburger bun dough and plain muffin batter had D-values of 28.6 and 62.2, 7.6, and 40.1, and 3.1 and 16.5 min at 55°C, 58°C, and 61°C, respectively, and z -values of 6.6°C and 10.4°C, respectively. The differences in the D- and z -values in the current study (proofed donut dough) and those generated by Channaiah et al (2016, 2017) for proofed bun dough and muffin batter could be attributed to differences in the Salmonella cocktails used in these studies.…”

“…In similar studies, Channaiah et al (2016, 2017) determined that a 3-serovar Salmonella cocktail (Typhimurium, Newport, and Senftenberg) in proofed hamburger bun dough and plain muffin batter had D-values of 28.6 and 62.2, 7.6, and 40.1, and 3.1 and 16.5 min at 55°C, 58°C, and 61°C, respectively, and z -values of 6.6°C and 10.4°C, respectively. The differences in the D- and z -values in the current study (proofed donut dough) and those generated by Channaiah et al (2016, 2017) for proofed bun dough and muffin batter could be attributed to differences in the Salmonella cocktails used in these studies. Moreover, the proximate compositions of hamburger bun dough (46.9% moisture, 8.5% protein, 3.8% fat, and 40.8% starch) and muffin batter (31.2% moisture, 6.3% protein, 8.9% fat, and 24.3% starch) in Channaiah et al (2016, 2017) studies were different than that of donut dough in the current study.…”

“…The current study, along with similar validation studies conducted for various bakery products, can be used by the bakery industry to assess the pathogen control capabilities of their manufacturing processes. In similar validation studies, Channaiah et al (2016, 2017) validated commercially simulated baking processes as kill-steps against Salmonella in hamburger buns and plain muffins when contamination was introduced via contaminated flour.…”

“…In addition, the ability of Salmonella to survive under various environmental stress conditions, such as low water activity (a w ) and sublethal heat treatments, for lengthy periods of time makes it a challenging foodborne hazard for food manufacturers (Podolak et al , 2010; Van Doren et al , 2013). Although baking, cooking, roasting, frying, and boiling are generally considered effective kill-steps in controlling potential foodborne pathogens in food products, formal scientific evidence or validation of most of these processes for the inactivation of foodborne pathogens in bakery products has not been thoroughly investigated (Channaiah et al , 2016). The U.S. Food and Drug Administration's Food Safety Modernization Act (FSMA) shifted the main focus from reacting to food safety failures to proactively preventing these failures.…”