The fate of Salmonella in ready to eat cereals.

Abstract

This study was intended to provide insight into the ability of Salmonella to survive in ready-to-eat (RTE) cereal during storage, contaminated post processing. Sweetened toasted oat cereal (STOC) and toasted oat cereal (TOC) were used to elucidate the ability of Salmonella to remain viable for 3 months and the effect of sucrose on its survival. To date, this is the first study to report survival of Salmonella in ready to eat cereal during storage. Commercial cereal samples were inoculated with approx. 106 CFU/g of five different Salmonella strains belonging to four serovars (Agona, Typhimurium, Tennessee and Senftenberg) and re-dried within 24 h. Inoculated cereal was periodically sampled after drying on 1, 3, 5, 7, 14, 30, 60, and 90 days of storage at room temperature. The viable Salmonella count was determined using complex differential media and standard microbiological techniques. The count of most serovars increased during the cereal re-drying step in TOC, but not in STOC. During storage the Salmonella count remained greater than 107 CFU/g in TOC for the entire experimental period with the exception of serovar Senftenberg. The level of Salmonella in STOC declined during the first week of storage, but their final counts were more than 103 CFU/g. These results indicated that Salmonella was able to survive for at least ninety days in either type of cereal. The relevance of this research to the cereal industry is that it confirms the unique ability of this microorganism to survive conditions of very low water activity and stresses the importance of further processing to minimize the risk of transmission of this pathogen by cereal foods.