Assessing Postharvest Risks for Salmonella in Pistachios

Nuts and other low-moisture foods have generally been considered low-risks for foodborne illness because they are consumed in a dry state where water activity (available moisture) is too low to support microbial growth. However, it is increasingly recognized that many foodborne pathogens can cause illness at very low concentrations, such that microbial growth is not required. <P>
In the past decade, outbreaks associated with consumption of raw almonds and peanut butter have been documented in the U.S. In 2009 there was a large recall of pistachios when Salmonella was isolated from commercial products. <P>With the exception of almonds, very little is known about the ecology of Salmonella in nut production and processing environments impeding the development of targeted commodity-specific intervention programs. Quantitative microbial risk assessment (QMRA) provides a framework for identifying critical data gaps and evaluating the overall effectiveness of risk-reduction strategies. <P>This proposal will, through laboratory studies, identify points during post-harvest handling of pistachios where Salmonella may be reduced, controlled or amplified. Emphasis will be placed on understanding the behavior of inoculated Salmonella during hulling, drying and long-term storage. Building upon a previously generated raw almond QMRA these laboratory data, industry prevalence data and expert opinion will be used to construct a pistachio QMRA. <P>The overall goal of this research is to use the laboratory data and risk model to develop scientifically-based food safety risk-reduction strategies for the pistachio industry.