Survival and Heat Resistance of Salmonella enterica and Escherichia coli O157:H7 in Peanut Butter

He, Yingshu; Guo, Deliang; Yang, Jingyun; Tortorello, Mary Lou; Zhang, Wei

doi:10.1128/aem.06270-11

Cited by 81 publications

(56 citation statements)

References 15 publications

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“…S1 in the supplemental material). This observation was consistent with our previous finding that S. enterica survived better in peanut butter with lower fat but higher carbohydrate content during an extended storage period (15).…”

supporting

confidence: 83%

“…Inoculated samples were stored at 25°C for 4 weeks, then serially diluted and plated on brain heart infusion (BHI) agar for calculating bacterial death rates. The storage simulated the stress that S. enterica may typically encounter during peanut butter processing (15). The bacterial population in low-fat formulation A (33% fat and 42% carbohydrate) decreased by an average of 0.6 to 0.8 log, compared to an average of 0.9 to 1.2 logs in the regular formulation, E (49% fat and 24% carbohydrate) (see Fig.…”

mentioning

confidence: 99%

“…When present in peanut butter, S. enterica becomes heat resistant, possibly due to adaptation to the desiccation stress and the protective effects of the fat content in the product (2,(4)(5)(6)(7)(10)(11)(12)(13)(14). We recently demonstrated that heat treatment at 72°C for 1 hour resulted in a less-than-2-log reduction of desiccationstressed S. enterica in artificially contaminated peanut butter with an a w of 0.4 (15). In this study, we evaluated the effects of desiccation and subsequent rehydration on the relative heat resistance of three S. enterica serotypes: S. Tennessee K4643 (a human isolate from the 2006 -2007 peanut butter outbreak in the United States) (1), S. Enteritidis BSS-1045 (an isolate from the 2000 -2001 raw almonds outbreak in the United States and Canada) (16)(17)(18), and S. Typhimurium LT2 (19,20).…”

mentioning

confidence: 99%

“…Bacterial cell suspensions were transferred to 500 g of peanut butter and vigorously stirred for 20 min by using a sampler spatula. Homogenous distribution of the cells was verified as previously described (15). Inoculated samples were stored at 25°C for 4 weeks, then serially diluted and plated on brain heart infusion (BHI) agar for calculating bacterial death rates.…”

mentioning

confidence: 99%

“…The come-up time to reach the final treatment temperature was less than 10 s. The heat-treated samples were taken at 30 s, 90 s, 5 min, 10 min, and 20 min and immediately cooled on ice for 1 min. Viable cell counts were determined as previously described (15). D values were calculated using the Bigelow model (23).…”

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confidence: 99%

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Increased Water Activity Reduces the Thermal Resistance of Salmonella enterica in Peanut Butter

Salazar

et al. 2013

Appl Environ Microbiol

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c Increased water activity in peanut butter significantly (P < 0.05) reduced the heat resistance of desiccation-stressed Salmonella enterica serotypes treated at 90°C. The difference in thermal resistance was less notable when strains were treated at 126°C. Using scanning electron microscopy, we observed minor morphological changes of S. enterica cells resulting from desiccation and rehydration processes in peanut oil. Salmonellosis outbreaks linked to contaminated peanut butter products have brought worldwide attention to the microbial safety of these popular food items. Salmonella enterica serotype Tennessee caused a salmonellosis outbreak in 2006 -2007 that was linked to peanut butter; it sickened 425 persons and resulted in 71 (20%) hospitalizations in 44 states in the United States (1). This and other food-borne outbreaks (2, 3) have highlighted the need for a reexamination of S. enterica behavior in low-water-activity (a w ) peanut butter products.The water activity of peanut butter is typically 0.35 or less (2, 4-9), which precludes the growth of spoilage and pathogenic microorganisms. When present in peanut butter, S. enterica becomes heat resistant, possibly due to adaptation to the desiccation stress and the protective effects of the fat content in the product (2,(4)(5)(6)(7)(10)(11)(12)(13)(14). We recently demonstrated that heat treatment at 72°C for 1 hour resulted in a less-than-2-log reduction of desiccationstressed S. enterica in artificially contaminated peanut butter with an a w of 0.4 (15). In this study, we evaluated the effects of desiccation and subsequent rehydration on the relative heat resistance of three S. enterica serotypes: S. Tennessee K4643 (a human isolate from the 2006 -2007 peanut butter outbreak in the United States) (1), S. Enteritidis BSS-1045 (an isolate from the 2000 -2001 raw almonds outbreak in the United States and Canada) (16-18), and S. Typhimurium LT2 (19,20). We compared two commercial peanut butter formulations (regular and low fat) to assess the influence of carbohydrate and fat contents on the heat resistance of S. enterica. Most published thermal challenge studies of S. enterica in peanut butter have focused on heat treatments at either 72°C or 90°C (11,21,22) and not at the higher temperatures commonly used in commercial peanut butter processing, such as dry roasting at 126°C (22). In this study, we thermally challenged S. enterica serotypes in artificially contaminated peanut butter at both 90°C and 126°C.Individual serotypes and a three-serotype cocktail were grown separately as previously described (15), followed by suspension in 5 ml of peanut oil prior to inoculation of peanut butter samples (a w , 0.2). Bacterial cell suspensions were transferred to 500 g of peanut butter and vigorously stirred for 20 min by using a sampler spatula. Homogenous distribution of the cells was verified as previously described (15). Inoculated samples were stored at 25°C for 4 weeks, then serially diluted and plated on brain heart infusion (BHI) agar for calculating bacterial d...

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supporting

confidence: 83%

mentioning

confidence: 99%