Survival of Listeria monocytogenes in Ayran, a traditional Turkish fermented drink

Abstract

Ayran is a traditional fermented dairy product produced by mixing milk or yoghurt, water and salt. In this study, survival of Listeria monocytogenes 1/2b was investigated in Ayran samples. For that purpose, Ayran samples produced from yoghurt (Group A and B) or directly form milk (Group C and D) were contaminated with 1 % concentration of 7 (A1, B1, C1 and D1 samples) or 5 (A2, B2, C2 and D2 samples) log cfu/mL of L. monocytogenes. So, eight different samples of Ayran were produced and stored at 4 ºC (Group A and C) or 20 ºC (Group B and D) for 21 days. According to the obtained results, there was no significant change in the number of viable cells of L. monocytogenes 1/2b in samples A1, A2, C1 and C2 after 21 days of the storage period. However, L. monocytogenes 1/2b cells of B1 and B2 samples were completely inhibited after 5 days of storage at 20 ºC. Similarly to that, L. monocytogenes 1/2b cells in samples D1 and D2 were also completely inhibited after 3 days of the storage. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus viable cell counts were between 103-107 cfu/mL in all of the samples. Consequently, Ayran contaminated with L. monocytogenes may contribute to a risk for public health. But, due to low pH of approximately ≤3.90, Ayran is relatively safe from the risk of L. monocytogenes.