Survival of E. coli O157:H7 in yogurt incubated until two different pH values and stored at $4^ oC $

Bu çalışmada iki farklı başlangıç pH’sı ile üretilen yoğurtlarda Escherichia coli O157:H7’nin canlı kalma durumu araştırılmıştır. Örnekler iki farklı dozda E. coli O157:H7 ($10^ 3$ cfu/mL ve $10^ 5$ cfu/mL) ile kontamine edilmiştir. Yoğurt örneklerinin inkübasyonları pH 4.0 ve 4.6’da sonlandırılmış ve örnekler $4^ oC $’de 14 gün depolanmıştır. Örneklerde depolamanın başlangıcında ve 1, 2, 4, 6, 8 ve 14. günlerinde E. coli O157:H7 sayılar, pH ve asitlik değerleri belirlenmiştir. E. coli O157:H7 pH 4.0 ve 4.6 başlangıç pH’sı ile üretilen her iki örnek grubunda da canlı kalmıştır. Ancak E. coli O157:H7 canlılığı 4.0 başlangıç pH’lı örneklerde, 4.6 pH’lı olanlara göre ve $10^ 3$ cfu/mL kontaminasyonlu örneklerde $10^ 5$ cfu/mL kontaminasyonlu olanlardan çok önemli derecede (P

Anahtar Kelimeler:

uygulama yöntemleri, yoğurt, pH, gıda mikrobiyolojisi, Escherichia coli

İki farklı pH değerine kadar inkübe edilen ve 4oC’de depolanan yoğurtlarda E. coli O157:H7’nin canlı kalma durumu

In the present study the survival of Escherichia coli O157:H7 in yoghurt produced at two different initial pH levels was investigated. Samples were contaminated with two different doses of E. coli O157:H7 ($10^ 3$ cfu/mL and $10^ 5$ cfu/mL). Yoghurt samples were taken from incubation at pH 4.0 and 4.6. Incubated samples were stored at $4^ oC $ for 14 days. In the samples, viable counts of E. coli O157:H7, pH and titratable acidity were determined on day 0 and the $1^ {st}, 2^ {nd}, 4^ {th}, 6^ {th}, 8^ {th} and 14^ {th}$ days of storage. E. coli O157:H7 survived in yoghurt produced at pH 4.0 and 4.6 in the both contamination level. The survival of E. coli O157:H7 was significantly lower at pH 4.00 than at pH 4.60 (P<0.001) and at $10^ 3$ cfu/mL than at $10^ 5$ cfu/mL contamination level (P<0.001).

Keywords:

application methods, yoghurt, pH, food microbiology, Escherichia coli,

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