Dried fruits and nuts make up a significant portion of the commodities traded globally, and the presence of yeasts and molds on dried fruits and nuts can be a public health risk because of the potential for exposure to toxigenic fungi. Since current postharvest treatment technologies are rather limited for dried fruits and nuts, electron beam (E-beam) radiation experiments were performed to determine the doses required to reduce the yeast and mold bioburden of raisins, walnuts, and dates. The indigenous yeast and mold bioburden on a select number of commodities sold at retail ranged from 10(2) to 10(3) CFU/g. E-beam inactivation kinetics based on the linear model suggest that the decimal reduction dose required to eliminate 90% of the microbial population (D10-value) of these indigenous fungal populations ranges from 1.09 to 1.59 kGy. Some samples, however, exhibited inactivation kinetics that were better modeled by a quadratic model. The results indicate that different commodities can contain molds and yeasts of varying resistance to ionizing radiation. It is thus essential for the dried fruit and nut industry to determine empirically the minimum E-beam dose that is capable of reducing or eliminating the bioburden of yeasts and molds in their specific commodities.
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.
Clostridium botulinum may be of concern in prepared refrigerated meals, for which strict cold chain management cannot be guaranteed. This study evaluated the effect of temperature, product composition, and cultured celery juice powder (CCJP) as a source of nitrite on the inhibition of botulinum toxin formation in two experimental (meat- and vegetable-based) prepared meals. Data obtained from the challenge study were compared with a published mathematical model to determine whether the model is fail-safe with regard to the tested meals. Treatments were inoculated with proteolytic C. botulinum, vacuum packaged, cooked at 90°C for 10 min, and assayed for botulinum toxin at appropriate intervals in samples stored at 10, 15, or 20°C for up to 8 weeks. None of the treatments stored at 10°C for 8 weeks supported toxin production by proteolytic C. botulinum. The addition of CCJP delayed toxin production by 1 and 3 weeks in cauliflower potatoes and in Dijon pork, respectively, stored at 15°C. Toxin production was delayed by 1 week at 20°C when CCJP was added to the cauliflower potatoes. This study found that the predictive model was fail-safe but was overly conservative for the experimental meals described. Finally, this study confirms that product composition, the addition of nitrite via CCJP, storage time, and temperature play important roles in the inhibition of toxin formation by proteolytic C. botulinum.
Clostridium botulinum is a foreseeable biological hazard in prepared refrigerated meals that needs to be addressed in food safety plans. The objective of this study was to evaluate the effect of product composition and storage temperature on the inhibition of botulinum toxin formation in nine experimental meals (meat, vegetable, or carbohydrate based). Treatments were inoculated with proteolytic C. botulinum, vacuum packaged, cooked at 90°C for 10 min, and assayed for botulinum toxin in samples stored at 25°C for up to 96 h for phase 1, or at 25°C for 12 h and then transferred to 12.5°C for up to 12 and 6 weeks in phases 1 and 2, respectively. For phase 1, none of the treatments (equilibrated pH 5.8) supported toxin production when stored at 25°C for 48 h, but toxin production was observed in all treatments at 72 h. For the remaining experiments with storage at 12.5°C, toxin production was dependent on equilibrated pH, storage time, and growth of indigenous spoilage microorganisms. In phase 1, no gross spoilage and no botulinum toxin was detected for any treatment (pH ≤5.8) stored at 12.5°C for 12 weeks. In phase 2, gross spoilage varied by commodity, with the brussels sprouts meal with pH 6.5 showing the most rapid spoilage within 2 weeks and botulinum toxin detected at 5 and 6 weeks for the control and cultured celery juice treatments, respectively. In contrast, spoilage microbes decreased the pH of a pH 5.9 beef treatment by 1.0 unit, potentially inhibiting C. botulinum through 6 weeks at 12.5°C. None of the other treatments with pH 5.8 or below supported toxin production or spoilage. This study provides validation for preventive controls in refrigerated meals. These include equilibrated product pH and storage temperature and time to inhibit toxin formation by proteolytic C. botulinum, but the impact of indigenous microflora on safety and interpretation of challenge studies is also highlighted.
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