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A dry-inoculation method for nut kernels.
Tyann Blessington1, Christopher G Theofel, Linda J Harris
1Department of Food Science and Technology, University of California, Davis, Davis, CA 95616-8598, USA.
Food Microbiology
|December 4, 2012
Summary
A new dry-inoculation method for tree nuts was developed, simplifying Salmonella Enteritidis contamination studies. This method showed similar bacterial survival rates to traditional wet-inoculation, making it suitable for postharvest research.
Area of Science:
- Food safety microbiology
- Agricultural science
- Bacterial contamination studies
Background:
- Traditional wet-inoculation methods for studying bacterial contamination on tree nuts require a lengthy post-inoculation drying step.
- Investigating alternative inoculation methods is crucial for efficient and realistic contamination studies in food safety.
Purpose of the Study:
- To develop and evaluate a novel dry-inoculation method for almonds and walnuts.
- To compare the survival of Salmonella Enteritidis PT 30 on tree nuts using both dry- and wet-inoculation methods under ambient storage conditions.
Main Methods:
- Developed a dry-inoculation technique involving mixing liquid inoculum with sterilized sand, drying, and then transferring to nut kernels.
- Compared bacterial survival on wet- and dry-inoculated almond and walnut kernels stored at ambient conditions (23 °C; 41-47% RH) for 14 weeks.
- Optimized bacterial transfer from sand to kernel and evaluated Salmonella Enteritidis population levels (log CFU/g).
Main Results:
- The dry-inoculation method effectively transferred Salmonella Enteritidis to almond and walnut kernels, achieving comparable bacterial levels to wet inoculation.
- Salmonella Enteritidis populations declined similarly on both wet- and dry-inoculated kernels over 98 days of ambient storage.
- No significant differences in bacterial decline were observed between the two inoculation methods for either nut type.
Conclusions:
- The dry-inoculation method is a viable alternative to wet-inoculation for studying Salmonella Enteritidis contamination on tree nuts.
- This method eliminates the need for post-inoculation drying and mimics potential natural contamination routes.
- The dry-inoculation technique is suitable for postharvest challenge studies on tree nuts, enhancing research efficiency.
