Plant foods, such as fruits and vegetables, that have been dehydrated do not support the growth of pathogenic microorganisms. Recent... Show morePlant foods, such as fruits and vegetables, that have been dehydrated do not support the growth of pathogenic microorganisms. Recent listeriosis and salmonellosis outbreaks in the U.S. have been associated with imported specialty mushrooms. These mushrooms are commonly sold fresh or dehydrated. This study evaluated the survival and growth of two foodborne pathogens Listeria. monocytogenes and Salmonella. enterica on dehydrated mushrooms during both rehydration at 25 or 5℃ and storage at 5, 10, or 25℃. Fresh enoki and wood ear mushrooms were dehydrated for 24 h at 60°C. Dehydrated mushrooms were inoculated with a four-strain cocktail of S. enterica or L. monocytogenes at 4 log CFU/g. Mushrooms were dried for 1 h, followed by rehydration for 2 h with 5 or 25°C (water and air temperature). Rehydrated mushrooms were stored at 5, 10, or 25°C for up to 14 d. The pathogens were enumerated at 0, 1, 3, 6, 9 and 14 d. Three independent trials with triplicate samples at each time point were completed. Population differences were evaluated via Student’s t-test; p<0.05 was considered significant. The growth rates were determined by DMFit in Excel. Overall, the growth rates of L. monocytogenes and S. enterica on enoki mushrooms were significantly higher when the mushrooms were rehydrated at 25℃ and stored at 25℃ (P<0.05). The growth rates were 2.69 log CFU/g per day and 3.56 log CFU/g per day, for L. monocytogenes and S. enterica respectively. Since the growth of pathogens on wood ear mushrooms during rehydration and storage was considerably less and below the level of enumeration, enrichment of the pathogens was conducted. The pathogens could be suppressed during rehydration due to less nutrient contents and antimicrobial properties of wood ear. The result of this study outlines the importance of refrigerated storage temperature and time combination for safety during rehydration and subsequent storage of the mushrooms. Show less
