Survival of Escherichia coli O157 : H7 in yoghurt during preparation and storage at 4°C

Abstract

S . M AS S A, C. A LT IE R I, V. Q UA RA N TA AN D R. DE P AC E. 1997. Cow's milk was inoculated with ca 10 3 and 10 7 cfu ml −1 Escherichia coli O157 : H7. After fermentation at 42°C for 0-5 h, the yoghurt was stored at 4°C. Two kinds of yoghurt were used : traditional yoghurt (TY), made with Streptococcus thermophilus and Lactobacillus bulgaricus starter cultures, and 'bifido' yoghurt (BY), made with the two starter cultures plus Bifidobacterium bifidum. After 7 d E. coli O157 : H7 decreased from 3·52 to 2·72 log 10 cfu ml −1 and from 7·08 to 5·32 log 10 cfu ml −1 in TY, and from 3·49 to 2·73 log 10 cfu ml −1 and from 7·38 to 5·41 log 10 cfu ml −1 in BY. The pH values of yoghurt dropped from 6·6 to 4·5 and 4·4 in TY (for low and high pathogen inocula, respectively), and from 6·6 to 4·6 and 4·5 in BY (for low and high pathogen inocula, respectively).

Microbial, Physical and Sensory Properties of Three Novel Yogurt Flavors: Molasses, Mulberry and Amaretto

“…This suggested that the three yogurt flavors had no effect on the microbial counts. However, Massa, Altieri, Quaranta, & Pace (1997) and Ogwaro, Gibson, Whitehead, & Hill (2002) detected the counts of E.coli during storage. Benkerroum, Oubel, & Mimoun (2002) also detected the numbers of S. aureus in yogurt product.…”

The Inhibitory Effect of Lactic Starter Culture Against Food Borne Pathogenic Bacteria in Skim Milk

“…The pathogenic strains were reactivated twice using brain heart infusion (BHI) broth (Difco, 1984) at 37°C for 20-24 hrs before use in this study and were transferred weekly. These organisms were maintained on tryptic soy agar (Massa et al, 1997) and the activating inoculum was prepared after two successive 24-h cultures in tryptic soy broth (TSB) inoculated and incubated at 37°C for 48 hrs.…”

“…As regards to the results presented in Table 3 easily observed that, the pH was reduced slightly in the absence of lactic acid bacteria. Massa et al (1997) indicated that Escherichia coli 0157: H7 survived during the fermentation and storage of both traditional and bifido yoghurt and pH levels obtained during fermentation of the two products were within the range that has been demonstrated to allow the survival of Zero 20 19 23 24 17 15 28 30 32 30 12 26 14 29 11 20 3 31 13 51 11 24 32 11 33 7 27 2 37 3 70 5 36 37 7 38 1 32 1 45 1 91 3 48 40 2 44 0 44 1 51 0 113 2 72 41 0 50 0 55 0 70 0 140 0 A = control (SM incoulated with pathogens only), B = The incoculation of lactic acid bacteria and pathogenic organisms is in the same time at zero time. the pathogen.…”

Yoğurt Fermantasyonu Sirasinda Salmonella Enteritidis’i̇n Farkli İnokülasyon Koşullarinda Canli Kalma Durumunun Araştirilmasi

“…Salmonella üzerine s›n›rl› say›da çal›flma olsa da (23) patojen bakterilerin yo¤urdun fermantasyonu s›ras›ndaki canl› kalma durumu birçok araflt›rmac› taraf›ndan incelenmifltir. Çal›flmalar yo¤urdun fermantasyonu s›ras›ndaki pH'n›n patojen bakterilerin (Staphylococcus aureus, E. coli O157:H7) canl› kalmalar›na izin verdi¤ini ve fermantasyonun sonunda, kullan›lan yo¤urt kültürlerinin orijinlerinden ba¤›ms›z (5), son pH de¤erine ba¤l› olarak mikroorganizma say›s›nda sadece hafif bir azalman›n oldu¤unu belirtmifllerdir (7,8). Di¤er taraftan laktik asit bakterileri taraf›ndan üretilen, antimikrobiyel özellik gösteren bakteriyosinler, hidrojen peroksit, etanol, diasetil gibi bileflikler de fermente ürünlerde patojen geliflimi üzerine etki edebilmektedir (24).…”