Survival of Yersinia enterocolitica during the Manufacture and Ripening of Mihalıç Cheese


Abstract: The survival of Yersinia enterocolitica strain 0:9 was investigated during the manufacturing and ripening of Mihalıç cheese produced from raw milk. Mihalıç cheese was produced after inoculating 10^5 cfu/ml of Y. enterocolitica strain 0:9 into raw milk. All cheese samples were ripened at + 4 °C for 30 days in 18 to 22% of brine. Samples taken from raw milk, scalded and strained curd, and cheese on days 1, 3, 5, 8, 15 and 21 of the ripening process were analyzed for Y. enterocolitica, pH values and salt content. In raw milk, where initial inoculated Y. enterocolitica counts were 10^5 cfu/ml, counts were 1.5 x 10^6-7.1 x 10^6 cfu/g in scalded curd, 4.2 x 10^6-3.0 x 10^7 cfu/g in strained curd, 2.4 x 10^4-3.4 x 10^6 cfu/g on day 1, 3.8 x 10^3-2.5 x 10^5 cfu/g on day 3, and 9.2 x 10^2-4.0 x 10^4 cfu/g on day 5. During the ripening process, due to the decrease in pH values and the increase in salt content, Y. enterocolitica was diminished in the 1^{st} batch on day 8, in the 3^{rd} and 4^{th} batches on day 15, and in the 2^{nd} batch on day 21.

Keywords: Yersinia enterocolitica, cheese, ripening, viability

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