Evaluation and Application of Practices for Controlling Salmonella in Nuts and Nut Products

NON-TECHNICAL SUMMARY: This proposal is a collaboration among scientists from the University of California - Davis, University of Florida - Lake Alfred, and University of Georgia - Griffin and includes applied research and outreach aimed at reducing foodborne illness from consumption nuts and nut products. Once considered uncommon, outbreaks of salmonellosis from nuts and nut products have been recently recognized and may be underreported. Little is known about the ecology of Salmonella in nuts and their products. Our overall goal is to evaluate relative microbiological risk using three nut system models: peanuts, pecans, and pistachios selected for their distinct handling, lack of available data, broad applicability, and relevance to food safety. We propose to evaluate a range of commercial handling and treatment practices for their effects on infiltration, survival, growth, and inactivation of Salmonella in the model nuts. Factors affecting infiltration, survival during long-term storage, and inactivation during cleaning, conditioning, shelling, drying, and roasting will be studied. Results of these studies will be used for risk model development and for development of outreach training and publications. Information gained from this research will reveal the adequacy and appropriateness of practices currently used in the nut industry in terms of controlling and eliminating Salmonella in inshell nuts, nutmeats, and roasted nut products. This knowledge will form the scientific basis for the adequacy of or need to improve these practices. We will partner with the nut industry to disseminate this new information and to evaluate its application and implementation; ultimately improving the safety of these products.

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APPROACH: Methods: Lack of adequate survival and inactivation data in nuts under different processing conditions hinders the ability to evaluate the relative risks of industry processes. Materials collected from pecan, pistachio and peanut growers, hullers/shellers or processors will be used in laboratory-based studies designed to mimic processing parameters. Special attention will be given to the influence of environmental humidity and moisture in test materials. A range of handling and treatment practices will be evaluated for their effects on amplification, infiltration, survival, and inactivation of Salmonella during hulling and/or shelling, drying and thermal processing particularly under conditions where cross-contamination may occur. These data will be used to identify risk reduction strategies that can be practically applied. Longer-term studies will be established first. Studies that require materials available only during harvest (e.g., pistachio or pecan hulls) will be limited to the fall but others such as thermal processing may be carried out at other times of the year. Laboratory-based studies are planned for year 1 and 2 with concurrent development of risk models. Extension activities will be carried out throughout the 3-year project but activities in years 2 and 3 will incorporate data generated from the research. Data will be analyzed using the appropriate statistical measures (ANOVA, T-test, etc) using statistical software to determine if statistically significant differences exist between different treatments. We will collaborate with nut industry organizations to both disseminate information (through joint workshops or webinars, preparation of extension materials) obtained from the proposed research and to evaluate the use of the information by industry members. The long-term impact of strategies developed for the nut industry would be a reduction in risks associated with Salmonella in raw and roasted (processed) peanuts, pecans, and pistachios and food products containing these nuts. This would include reductions in outbreaks, sporadic illnesses, and recalls. This impact can be realized through modifications of current harvesting, storage, and processing practices with the objectives of preventing contamination of nuts with Salmonella, applying treatments that will kill Salmonella, and protecting raw and post-processed nuts and nut products against contamination i.e., adhering to Good Agricultural Pratices and Good Manufacturing Practices. Simultaneously, interventions to achieve this goal would likely reduce risks associated with other foodborne pathogens, e.g., E. coli O157:H7. We have proposed to evaluate behavior change of the nut industry in collaboration with industry organizations. Selected individuals will be contacted several months post exposure to the workshops and to educational materials to determine behavior and organizational changes that have been made as a result of exposure, including whether any of the materials they received were used. Indicators will include knowledge gained, behavior change, and implementation of new safety controls.