Assessing postharvest food safety risks and identifying mitigation strategies for foodborne pathogens in pistachios

Assessing postharvest food safety risks and identifying mitigation strategies for foodborne pathogens in pistachios

Jan. 1, 2014 - Dec. 31, 2015

2014-35

$230,185.00

Linda J. Harris, Ph.D.
University of California, Davis

Final Report

In the past decade, nuts and nut products have been established as potential source of foodborne illness; outbreaks associated with consumption of raw almonds, inshell hazelnuts, peanut butter, pine nuts, and walnuts have been documented in the North America and Australia. Until recently, very little was known about the ecology of foodborne pathogens in nut production and processing environments impeding the development of targeted commodity-specific intervention programs. The proposed research builds on recent research in this laboratory pertaining to the survival of Salmonella in pistachios. Points during postharvest handling of pistachios where foodborne pathogens may be reduced, controlled or amplified will be identified. These data and industry expert opinion will be used to construct a pistachio risk model to estimate risks from harvest to storage; this model will allow the pistachio industry to develop harvest management strategies that reduce the potential for product contamination. Characterization of the heat resistance of foodborne pathogens in inoculated pistachios under dry and moist heat conditions will provide the scientific foundation for process validation in the pistachio industry. 

Technical Abstract

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. In the past decade, outbreaks of salmonellosis and E. coli O157:H7 gastroenteritis associated with consumption of a range of low moisture foods including several tree nuts have been documented in North America and Australia. The proposed research builds on previous research on the ecology of Salmonella in the pistachio postharvest environment. This proposal will, through laboratory studies, identify points during postharvest handling of pistachios where foodborne pathogens may be reduced, controlled or amplified. Emphasis will be placed on understanding the behavior of inoculated Salmonella, E. coli O157:H7, and L. monocytogenes during simulated postharvest holding (prehulling), post hulling holding, and drying. These data and industry expert opinion will be used to construct a pistachio risk model to estimate risks from harvest to storage; this model will allow the pistachio industry to develop harvest management strategies that reduce the potential for product contamination. Characterization of the heat resistance of Salmonella, E. coli O157:H7, L. monocytogenes, and E. faecium in inoculated pistachios under dry and moist heat conditions will provide the scientific foundation for process validation in the pistachio industry.