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Dried and Tested: Inoculation Method Impacts Low-Moisture Food Persistent Bacterial Populations
Manita Adhikari1, Kavita Patil1, Jennifer C Acuff1
1Department of Food Science, University of Arkansas System Division of Agriculture Fayetteville Arkansas USA.
Journal of Food Protection
|January 29, 2025
Summary
Researchers developed a new method to create realistic low-moisture food persistent bacterial populations (LMF PBPs) for studying pathogen survival. Lawn-based cultures and specific food matrices, like silicon dioxide, improved Salmonella Tennessee survival in these models.
Area of Science:
- Food Safety and Microbiology
- Bacterial Persistence in Food Processing Environments
Background:
- Pathogen contamination in low-moisture food (LMF) processing is a significant public health concern, leading to outbreaks and recalls.
- Existing laboratory methods inadequately mimic real-world contamination and harborage in LMF environments, hindering the development of effective sanitation strategies.
Purpose of the Study:
- To compare different inoculation methods for creating low-moisture food persistent bacterial populations (LMF PBPs) that accurately represent environmental conditions.
- To evaluate the impact of culture preparation techniques and food matrices on the survival of Salmonella Tennessee within these established LMF PBPs.
Main Methods:
- A slurry method using 0.5 mL of culture and 0.4 g of non-fat dry milk (NFDM) was optimized for consistency and ease of use.
- Salmonella Tennessee was cultured using both lawn-based and broth-based methods and incorporated into various food matrices (NFDM, peanut butter powder, chicken powder, silicon dioxide).
- Inoculated stainless-steel coupons were stored under controlled conditions (22-25°C, 50% RH) and bacterial populations were enumerated over 7 days.
Main Results:
- Lawn-based cultures yielded significantly higher initial Salmonella Tennessee populations (10.1 log CFU/cm²) compared to broth-based cultures (8.2 log CFU/cm²).
- Lawn-prepared cultures exhibited lower bacterial reductions (0.3-2.7 log CFU/cm²) than broth-based cultures (1.0-5.1 log CFU/cm²) across all matrices.
- Salmonella in silicon dioxide (SiO₂) matrices showed significantly greater reductions (2.7-5.1 log CFU/cm²) compared to other food matrices or no matrix.
Conclusions:
- The optimized slurry method with lawn-based cultures provides a more realistic model for studying Salmonella persistence in LMF environments.
- Culture preparation and food matrix composition significantly influence bacterial survival, highlighting the need for context-specific sanitation research.
- Silicon dioxide demonstrates potential as a matrix for studying pathogen inactivation in LMF settings due to enhanced bacterial reduction.
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