Effect of water activity and storage of tahini on the viability of stressed Salmonella serovars

Abstract

Tahini (sesame seed paste) is a low water activity product that has been involved in several salmonellosis outbreaks. The objectives of the study were to examine over a year the impact of a w and storage temperature of tahini on the viability of Salmonella serovars previously stressed by drying or heat exposure. Tahini samples adjusted to a w values of 0.17, 0.35 and 0.50 were inoculated with a mixed culture containing 10 6-10 7 CFU/g of 4 serovars of unstressed, desiccation-or heat-stressed Salmonella and stored for up to 12 months at 10 and 25 °C. Generally, viability of stressed or unstressed Salmonella decreased as the storage temperature and time increased or the a w of tahini decreased. The survival of stressed or unstressed Salmonella in all samples decreased during storage for up to 12 months by ca. 6.0 and 3.3log 10 CFU/g, respectively. Exposing Salmonella to heat stress had no significant effect on survival in tahini, while desiccation stress significantly decreased survival during storage, especially at 25 °C in low a w tahini.

Inactivation of Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes in Tahini by Microwave Heating

“…Previous reports have shown that Salmonella can survive in tahini and its byproduct (halva) for up to a year [ 32 , 35 ]. Similarly, L. monocytogenes and E. coli O157:H7 were reported to grow well in tahini despite it being stored at 10 °C [ 36 ].…”

“…The a w was determined for a 5 g sample at 21 °C using a water activity meter (Hygrolab, Rotronic Instr. Crop, New York, NY, USA) [ 32 ].…”

Multi‐country outbreak of multiple Salmonella enterica serotypes linked to imported sesame‐based products

“…The intermittent occurrence of human cases and the identification of positive food samples containing isolates several months [2][3][4]. Moreover, the concerned products have a long shelf life and might still be stored in people's homes.…”

From chicken to salad: Cooking salt as a potential vehicle of Salmonella spp. and Listeria monocytogenes cross-contamination

“…Bacteria do not usually grow in low-water activity (a w ) foods, i.e food presenting an a w < 0.85 ( Young et al, 2015 ), such as flour, spices, nuts, nuts butters, dry powders, chocolate, etc.. Nevertheless, the survival of foodborne pathogens, such as Salmonella and L. monocytogenes , for long periods of time in this type of food products has been widely reported ( Santillana Farakos et al, 2014 ; Igo & Schaffner, 2021 ; Ly et al, 2019 ; Nummer et al, 2012 ; Osaili et al, 2020 ; Taylor et al, 2018 ; Tsai, et al, 2019 ).…”