Validation of a Simulated Commercial Frying Process to ControlSalmonellain Donuts

Abstract

This study validated a typical commercial donut frying process as an effective kill-step against a 7-serovar Salmonella cocktail (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 Salmonella cocktail, and subsequently dried back to original preinoculation moisture content, achieving a Salmonella population 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 Salmonella was detected using an enrichment plating protocol in the donuts after 2 min of frying, resulting in >7-log reduction in Salmonella population. 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 Salmonella cocktail 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 Salmonella in 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.

Validation of brownie baking step for controlling Salmonella and Listeria monocytogenes

“…The differences in the D ‐values of Salmonella in the current study and that of Channaiah et al. (2016, 2017, 2018) can be attributed to the different Salmonella serovars used and the differences in the chemical/nutrient composition of the products used in these studies. In general, with the increase in fat, protein and sugar content of products, the thermal resistance of microorganisms also increases.…”

“…In another validation study, Channaiah et al. (2018) reported that frying donuts in oil at 190.6°C for 2 min (1 min on each side) resulted in >7 log reductions in 7‐serovar Salmonella cocktail population (Newport, Typhimurium, Senftenberg, Tennessee and three dry food isolates) and the internal donut temperature reached to ~119°C.…”

“…In a different study, Channaiah et al. (2018) determined the D ‐values of 7‐serovar Salmonella cocktail (Newport, Typhimurium, Senftenberg, Tennessee and three dry food isolates) in donut dough. They reported that the D ‐values of Salmonella cocktail were 8.6, 2.9, and 2.1 min at 55, 58, and 61°C, respectively, with the z ‐value of 10°C.…”

“…D ‐values were determined at 64, 68, 72, and 76°C following the method described by Channaiah et al. (2018) using temperature‐controlled water baths (18 L, Grant Instruments Ltd.) and sanitized aluminum thermal‐death‐time (TDT) disks (Engineering Shop, Washington State University). The TDT disks had internal height and diameter of 5 and 50 mm, respectively (Figure 3).…”

Properties and Application of Multifunctional Composite Polypropylene-Based Films Incorporating a Combination of BHT, BHA and Sorbic Acid in Extending Donut Shelf-Life

“…Most studies to date on the quality of the donuts are related to prevention of acrylamide formation during the frying process [26], reduction in oil absorption during the frying process [27], the effects of different process parameters (frying mode, temperature and time) [28], formulation [29] and type and quality of frying oil [30]. However, there are few studies focused on the direct incorporation of plant-based antioxidants in donut formulation to retard acrylamide formation during the frying process [26].…”