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Long-term survival of heat-stressed Salmonella Tennessee, Salmonella Typhimurium DTI 04, and Enterococcus faecium was evaluated in four model peanut paste formulations with a combination of two water activity (aw) levels (0.3 and 0.6) and two fat levels (47 and 56%) over 12 months at 20 ± 1°C. Prior to storage, the inoculated peanut paste formulations were heat treated at 75°C for up to 50 min to obtain an approximately 1.0-log reduction of each organism. The cell population of each organism in each formulation was monitored with tryptic soy agar plate counts, immediately after heat treatment, at 2 weeks for the first month, and then monthly for up to 1 year. The log reductions (log CFU per gram) following 12 months of storage were between 1.3 and 2.4 for Salmonella Tennessee, 1.8 and 2.8 for Salmonella Typhimurium, and 1.1 and 2.1 for E. faecium in four types of model peanut paste formulations. Enhanced survivability was observed in pastes with lower aw for all organisms, compared with those with higher aw (P < 0.05). In contrast, the effect of fat level (47 and 56%) on survival of all organisms was not statistically significant (P > 0.05). Whereas survivability of Salmonella Tennessee and Typhimurium DTI 04 did not differ significantly (P > 0.05), E. faecium demonstrated higher survivability than Salmonella (P < 0.05). Salmonella survived in the model peanut pastes well over 12 months, which is longer than the expected shelf life for peanut butter products. The information from this study can be used to design safer food processing and food safety plans for peanut butter processing. [ABSTRACT FROM AUTHOR]

Peanuts and peanut-containing products have been linked to at least seven salmonellosis outbreaks worldwide in the past two decades. In response, the Technical Committee on Food Microbiology of the North American Branch of the International Life Sciences Institute collaborated with the American Peanut Council to convene a workshop to develop a framework for managing risk in low-moisture food commodities where large data sets are unavailable (using peanuts as the example). Workshop attendees were charged with answering questions regarding the appropriate statistical and scientific methods for setting log reduction targets with limited pathogen prevalence and concentration data, suitable quantities of data needed for determining appropriate log reduction targets, whether the requirement of a 5-log reduction in the absence of data to establish a target log reduction is appropriate, and what targeted log reduction would protect public health. This report concludes that the judgment about sufficient data is not solely scientific, but is instead a science-informed policy decision that must weigh additional societal issues. The participants noted that modeling efforts should proceed with sampling efforts, allowing one to compare various assumptions about prevalence and concentration and how they are combined. The discussions made clear that data and risk models developed for other low-moisture foods like almonds and pistachios may be applicable to peanuts. Workshop participants were comfortable with the use of a 5-log reduction for controlling risk in products like peanuts when the level of contamination of the raw ingredients is low (<1 CFU/g) and the process well controlled, even when limited data are available. The relevant stakeholders from the food safety community may eventually conclude that as additional data, assumptions, and models are developed, alternatives to a 5-log reduction might also result in the desired level of protection for peanuts and peanut products. [ABSTRACT FROM AUTHOR]

Peanut butter and peanut paste products were implicated as the vehicle of contamination in an outbreak of Salmonella Typhimurium, which began in September 2008, and in the November 2006 outbreak of Salmonella Tennessee. Therefore, this study evaluated the effectiveness of electron beam (e-beam) radiation for the reduction of Salmonella serovars Tennessee (ATCC 10722) and Typhimurium (ATCC 14028) in creamy peanut butter. Each strain was studied independently. Peanut butter samples were inoculated with approximately 8.0 log CFU/g of Salmonella, and exposed to e-beam doses ranging from 0 to 3.1 kGy. Doses were confirmed with film dosimetry. Survivors were enumerated by standard spread plating on nonselective tryptic soy agar (TSA) and selective xylose-lysine-desoxycholate agar (XLD) media. Salmonella Tennessee was more susceptible to e-beam radiation, with 5.00- and 6.75-log reduction of cells on TSA and XLD, respectively, at the approximate e-beam dose of 3.0 kGy. Salmonella Typhimurium was reduced by 4.19 and 4.85 log on TSA and XLD, respectively, at the approximate e-beam dose of 3.0 kGy. D10-values show that Salmonella Typhimurium was more resistant (0.82 ±0.02 and 0.73 ± 0.01 kGy on TSA and XLD, respectively) than was Salmonella Tennessee (0.72 ± 0.02 and 0.60 ± 0.01 kGy on TSA and XLD, respectively) to e-beam radiation (P < 0.05). The recovery on growth and selective media were different (P < 0.05), indicating cell injury. The results of this study demonstrate that e-beam radiation may be an effective processing step for the nonthermal inactivation of Salmonella in peanut butter. [ABSTRACT FROM AUTHOR]

Partially defatted peanut flour was processed in a twin-screw extruder. Resulting extrudates were dried, ground, and incubated with simulated gastric fluid for various time periods. Soluble protein content of the resulting digesta was measured after 10% trichloroacetic acid treatment to evaluate the digestibility. In vitro digestion using pepsin increased the solubility of peanut protein in 10% trichloroacetic acid solution from 2 to 6% to 65 to 75%. Four strong IgE-binding subunits (65, 22, 17, and 14 kDa) were found with immunoblotting in peanut proteins extracted from unextruded peanut flour; no IgE-binding bands were observed in extrudates. The 65-kDa (putative Ara h 1) subunit was insolubilized during extrusion, and its IgE-binding property was susceptible to in vitro digestion. Following extrusion cooking, no IgE-binding bands were detected by immunoblotting, including the strongly IgE-binding 14-kDa fraction, a strong IgE-binding band from native peanut protein that is stable in pepsin. The 22- and 17-kDa (putative Ara h 2) subunits retained a small amount of IgE-binding potential and became susceptible to pepsin hydrolysis after extrusion. [ABSTRACT FROM AUTHOR]