Purpose: The objective of this study was to optimize and validate application of alternative single-step enrichment to detect low levels of sub-lethally injured Salmonellawith a real time PCR assay in low-moisture ready-to-eat foods.
Methods: Peanut butter (25 g), raisin (25 g) and raw almond (375 g) samples were artificially contaminated with different sublethally injured by heating or desiccation Salmonella strains and stabilized for 14 days prior to testing. For each matrix, five uncontaminated, 20 low level and five high level contaminated samples were enriched at 35°C in 75-750 mL Actero™ Listeria Enrichment Media, and then processed with the DuPont™ BAX® System Real-Time PCR Assay for Salmonella to compare with the samples tested according to the US FDA BAM 5 reference method.
Additionally, efficacy of the alternative method was confirmed with various low-moisture ready-to-eat foods closely related to the validated matrices. A total of 505 samples of 25 g each, including dried or dehydrated fruits such as apricot, apple, date and cranberry; nuts such as cashew, walnut and pecan; and natural, crunchy and honey peanut butter were artificially contaminated with different levels (0.2-10 MPN/sample) of sublethally injured Salmonella and tested using the alternative method.
Results: According to the Probability of Detection, the alternative method showed equivalent performance to the reference method. No false positive or false negative results were observed.
Significance: The alternative method offers the capability of detecting Salmonella in low-moisture ready-to-eat foods after only 16 hours of enrichment, thereby significantly reducing presumptive reporting time in comparison with the reference method.