An Independent Evaluation of Alternative Rapid Methods for the Detection of Salmonella in Select Hydrocolloids (Gums)

Introduction: Low moisture foods are naturally low in moisture content or have been produced through a drying or dehydration process.  Their low water activity (a_w < 0.85) has led to the perception that they are low risk for contamination from a microbiological perspective.  However, in recent years, a number of foodborne illnesses resulting from ingestion of Salmonella has been linked to these commodities.  There is a need for industry to ensure that pathogen detection methods are fit for purpose.  

Purpose: To conduct an initial feasibility evaluation of the performance of AOAC OMA 2013.03 and 2003.09 for 9 gums using enrichment media modified with an enzyme or various enrichment media-to-sample-volume ratios.  A larger method validation study was conducted on one emulsifier upon completion of the feasibility study. 

Methods: Feasibility Study: For each matrix, 10 replicates at a high contamination level (5-10 CFU/test portion) were evaluated by the alternative RT-PCR methods. Method Validation: Thirty sample replicates (20 low level, 5 high level, 5 uninoculated control) were evaluated in a paired study by the alternative method and a modification of the FDA/BAM Chapter 5 reference method. 

Results: No issues were observed for the 9 matrices during the feasibility evaluation. GHB, a combination of two gums (LBG and Guar) evaluated in the feasibility study was selected for the full method validation.  Using the POD statistical model, no statistical significant difference was observed between the alternative and reference methods. 

Significance: The data generated in this evaluation indicates that the rapid alternative methods with modifications to the enrichment media are a suitable alternative for the detection and recovery of Salmonella in these select gum commodities.