Evaluation of Salmonella typhimurium, Yersinia enterocolitica and Staphylococcus aureus counts in apple juice with cinnamon, by conventional media and thin agar layer method

Abstract

Pasteurized apple juice (pH 3.64) with cinnamon (0% and 0.3%) was inoculated with Salmonella typhimurium, Yersinia enterocolitica or enterotoxigenic Staphylococcus aureus at 10 4 cfu ml −1, and stored at 5°C and 20°C. Counts on tryptic soy agar (TSA), selective medium and thin agar layer (TAL) were determined at 1 h and 1, 3, 7 and 14 days. The TAL method (selective medium overlaid with TSA) was for recovery of injured cells. In general, the sensitivity of pathogens to cinnamon in descending order was Staph. aureus, Y. enterocolitica and S. typhimurium. Staph. aureus (1.2 log cfu ml −1 at 3 days) and Y. enterocolitica (0.3 log cfu ml −1 at 1 day) were the most acid-sensitive at 5°C and 20°C, respectively. At some points of storage, the killing effect was significantly ( P<0.05) more pronounced at 20°C for the three pathogens, with c. 4 log cfu ml −1 reductions in 1 day in Y. enterocolitica-inoculated samples with and without cinnamon, and in Staph. aureus-inoculated samples with cinnamon. Counts on TSA and TAL did not differ significantly ( P>0.05) in any case. So, both media showed similar effectiveness in recovering damaged cells of the three pathogens. Cinnamon inactivates important foodborne pathogens in apple juice and thus enhances the safety of this product.