Survival of E scherichia coli O 157: H 7 during the Manufacture and Storage of Fruit Yogurt

The objectives of the study were to assess the behavior of E scherichia coli   O 157: H 7 during the manufacture of fruit yogurt at different fermentation and storage temperatures. Reconstituted milk was fermented at 37, 40 or 45C; the resultant product was stored at 4, 10 or 15C for 7 days. Samples of milk and yogurt were analyzed. E . coli   O 157: H 7 and lactic acid bacteria ( LAB ) counts; pH of samples was recorded. During fermentation, E . coli   O 157: H 7 grew in the presence or absence of LAB regardless of temperature. E . coli   O 157: H 7 increased in presence of thermophilic LAB more than 2.75 log cfu/ mL . The growth of LAB in all samples showed the same trend. The pH values of milk containing E . coli   O 157: H 7 and LAB decreased gradually to reach 4.6 ± 0.1 at the end of fermentation period. During cooling, there was neither growth nor death of E . coli   O 157: H 7 at 4 and 10C, while a slight increase at 15C. All the experiments showed significant differences in the population of E . coli   O 157: H 7 in the presence or absence of LAB . During storage, E . coli   O 157: H 7 number declined for all experiments and approached undetectable levels at the end of storage. The sensitivity of E . coli   O 157: H 7 to acidity and lowered temperature was noticed during storage. Practical Applications E scherichia coli   O 157: H 7 has emerged as a major foodborne pathogen and has been implicated in several outbreaks involving milk and dairy products. The results of the present study indicate that E . coli cannot tolerate the acidity and storage temperature. Applying quality control systems in the processing line will ensure that the E .coli will not survive in the commercially prepared fruit yogurt.