Survival of E. coli O157:H7 and Listeria innocua in tahini (sesame paste)

Tahini is a traditional product in the Middle East and prepared by crushing roasted sesame seeds (Sesamum indicum). Many studies have reported that tahini or its products can be contaminated with several types of foodborne pathogens during processing and preparation. The objective of the current study was to evaluate the ability of Escherichia coli O157:H7 and Listeria innocua, a surrogate for L. monocytogenes, to survive in tahini before or after moisture addition (1:10 in water) during storage at 10 to 37°C. The viability of E. coli O157:H7 and L. innocua decreased faster during 28 d storage of tahini in the order 37°C > 21°C and > 10°C. In contrast, moisture-enhanced tahini supported significant growth of L. innocua at 21°C or 10°C and E. coli O157:H7 at all three temperatures. The results showed that if tahini is contaminated with E. coli O157:H7 or L. innocua, the contaminants can survive and grow during storage at most of the above temperatures. Prevention of pre- or post- processing contamination, along with the adoption of proper hygienic practices are essential to minimize the risk associated with foodborne pathogens in tahini or products containing tahini as an ingredient.