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 (Al, Bl, Cl and Dl samples) or 5 (A2, B2, C2 and D2 samples) log cfu/mL of Listeria monocytogenes. So, eight different samples of Ayran were produced and stored at 4 degrees C (Group A and C) or 20 degrees C (Group B and D) for 21 days. According to the obtained results, there was no significant change in the number of viable cells of Listeria monocytogenes 1/2b in samples Al, A2, Cl and C2 after 21 days of the storage period. However, Listeria monocytogenes 1/2b cells of B1 and B2 samples were completely inhibited after 5 days of storage at 20 degrees C. Similarly to that, Listeria 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 10(3)-10(7) cfu/mL in all of the samples. Consequently, Ayran contaminated with Listeria 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 Listeria monocytogenes.