Survival and inhibition of Staphylococcus aureus in commercial and hydrated tahini using acetic and citric acids

Tahini (sesame paste) is a low-moisture ready-to-eat food that has been linked to foodborne outbreaks and recalls. The objectives of this study were to investigate the behavior of Staphylococcus aureus in commercial and hydrated tahini at 10, 21 and 37 °C and to inhibit S. aureus in these products by 0.1, 0.3 and 0.5% acetic or citric acid. S. aureus was able to survive in commercial tahini with reductions of 3.3, 1.6 and 0.7 log₁₀ CFU/g at 37, 21 and 10 °C, respectively; while it grew in hydrated tahini with an increase of 3.9, 3.0 and 1.8 log₁₀ CFU/ml at 37, 21 and 10 °C, respectively, by 28d. Citric or acetic acid at ≤ 0.5% reduced S. aureus in commercial tahini by ≤ 2.3 log₁₀ CFU/ml by 28d compared to control at all of the tested temperatures. However, acetic and citric acid were more inhibitory at 37 and 10 °C, respectively. In hydrated tahini, viable S. aureus cells were not detected in the presence of 0.5 or 0.3% acetic acid after 7 and 14d, respectively, at both 21 and 37 °C; and after 14 and 28d, respectively at 10 °C. Acetic acid at 0.1% also reduced S. aureus numbers to undetectable levels after 14 and 28d at 21 and 37 °C, respectively. S. aureus cells were also not detected in the presence of 0.5% citric acid by 21d at all of the tested temperatures, or 0.1 and 0.3% citric acid by 28 and 21d, respectively at 21 °C. Acetic and citric acids could be used in tahini or tahini-based products to reduce the potential risk associated with S. aureus.