Fate of Salmonella during sesame seeds roasting and storage of tahini

Abstract

Tahini is usually consumed without further heat treatment, and roasting of sesame seeds is the only Salmonella inactivation step in its traditional production process. This study examined the efficiency of the roasting process in the elimination of Salmonella from sesame seeds and the survival of Salmonella in tahini during storage. Sesame seed and tahini samples were inoculated with a cocktail of three serotypes of Salmonella (S. Typhimurium, S. Newport and S. Montevideo). Complete inactivation of Salmonella in sesame seeds, inoculated with 5.9log cfu/g, was achieved by roasting at 110°C for 60min, 130°C for 50min, or 150°C for 30min. Salmonella levels in tahini (aw=0.17) inoculated with 5.6log cfu/g and stored for 16weeks at 22 or 4°C decreased by 4.5 and 3.3 log, respectively. Results of this study demonstrated that the standard roasting process is sufficient to inactivate Salmonella in sesame seeds and low water activity of tahini prevents microbial growth, but its composition allows Salmonella to survive for at least 16weeks. Therefore, prevention of cross-contamination after roasting is crucial for food safety.