Salmonella Detection in Cocoa and Chocolate by Motility Enrichment on Modified Semi-Solid Rappaport-Vassiliadis Medium: Collaborative Study

Abstract

A collaborative study was performed in 13 laboratories (including the authors' laboratories) to validate motility enrichment on modified semi-solid Rappaport-Vassiliadis (MSRV) medium for rapid detection of motile Salmonella in cocoa powder and chocolate. The MSRV method was compared with the AOAC standard culture method for detection of Salmonella in cocoa powder, milk chocolate, sweet chocolate, and dark chocolate. Chocolate samples were artificially inoculated with Salmonella at 2 levels of contamination. Cocoa powder was inoculated at 2 levels with naturally contaminated dust from cocoa beans. Uninoculated control samples were also included for each type of product. The sensitivity rate was 98.1% for the MSRV method and 94.9% for the AOAC culture method. The specificity rate was 100.0% for both methods. There was no significant difference in the proportion of samples positive by MSRV and the AOAC culture methods for any of the food types. The MSRV method has been adopted first action by AOAC INTERNATIONAL.