Yersinia enterocolitica'nın FARKLI ISI İŞLEMLERİ KULLANILARAK ÜRETİLEN YOĞURTLARDA VARLIĞI VE GELİŞİMİ

Ozet Bu calismada, yogun uretimi icin kullanilacak sut numuneleri A. B ve C olmak uzere uc gru­ba ayrilmistir. Bunlardan A grubu: isi islemi Oncesinde, B grubu; isi islemine tabi tutulduktan sonra, C grubu ise mikrodalga firin ile isi islemi oncesinde. 2x10 7 kob/ml miktarinda Yersinia enterocolitica (0:3 P41797) saf kulturu ile inokule edilmistir. Sut orneklerinden, Streptecoccus thermophiius ve Lactobacillus hulgaricus star­ter kulturleri kullanilarak yogun yapilmis ve 5± 1 °C'de 7 gun depolanmistir. Her 24 saatte bir yogun ornek­lerinde Y. enterocolitica sayisina ve pH degerlerine bakilmistir. Uc grubun da pH degerleri baslangicta 6.4 iken, 7. gun sonunda sirasiyla 4.1. 4.0, 4.1 degerlerine dusmustur. A ve C grubu sutlerden hazirlanan yogun­larda depolama suresi boyunca hic Y. enterocolitica tespit edilememistir. Ancak, isi islemi sonrasi Y. enteroco­litica inokule edilmis sutten (B grubu) hazirlanan yogun Orneklerinde 1. gun 2x10 6 kob/ml, 2. gun 2x10 s kob/ml, 3. gun 1x10 4 kob/ml, 4. gun 2x 10 3 kob/mi, 5. gun 4x 10 2 kob/ml, 6.gun 1x10 2 kob/ml, Y. enterocoliti­ca izole edilirken, 7. gun ise hic izole edilememistir. Anahtar Kelimeler: Y. enterocolitica. isi islemi, yogurt. THE PRESENCE AND GROWTH OF YERSINIA ENTEROCOLITICA IN YOGURT PRODUCED WITH DIFFERENT HEAT TREATMENT Summary In this study, Yersinia enterocolitica (0:3 P41797) was inoculated in three different milk groups (A, B, C) about 2xl0 7 cfu/ml. Group A treated with heat method before inoculation, group B treated with heal method after inoculation and group C heated with microwave technique before inoculation. These three groups were fermented with Streptococcus thermophiius and Lactobacillus bulgaricus; and stored 5 ±1°C for 7 days. The count of Yersinia enterocolitica and pH value were determined every 24 hours. At the beginning, the pH value of these groups was 6.4. At the end of the 7 th day, this value decreased to 4.1, 4.0,4.1. During the storage Y. enterocolitica could not be found in the group A and group C. But, Y. enterocolitica was isolated from the group B at the 1 th day 2x 10 6 cfu/ml, 2 nd day 2x 10 5 cfu/ml. 3 rd day Ix 10 4 cfu/ml. 4' h day 2x I0 3 cfu/ml, 5 th day 4x I0 2 cfu/ml, 6 lh day 1x 10 2 cfu/ml, in this group, Y. enterocolitica could not isolated at the 7th day. Key Words: Yersinia enterocolitica. heat treatment, yogurt.