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Wolverhampton Intellectual Repository and E-Theses > Research Institutes > Research Institute in Healthcare Science > Food Biology, Medical Microbiology and Disinfection Research Group > Survival of Escherichia coli O157:H7 in traditional African yoghurt fermentation.

Please use this identifier to cite or link to this item: http://hdl.handle.net/2436/29458
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Title: Survival of Escherichia coli O157:H7 in traditional African yoghurt fermentation.
Authors: Ogwaro, B.A.
Gibson, Hazel
Whitehead, Michael P.
Hill, David J.
Citation: International Journal of Food Microbiology, 79(1-2): 105-112
Publisher: Elsevier Science Direct
Journal: International Journal of Food Microbiology
Issue Date: 2002
URI: http://hdl.handle.net/2436/29458
DOI: 10.1016/S0168-1605(02)00184-8
PubMed ID: 12382690
Additional Links: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T7K-461XHYP-1&_user=1644469&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000054077&_version=1&_urlVersion=0&_userid=1644469&md5=e5ce33b14b4bde88083ea91a1034f261
http://www.ingentaconnect.com/content/els/01681605/2002/00000079/00000001/art00184
Abstract: Growth and survival of a nontoxigenic strain of Escherichia coli O157:H7 (ATCC 43888) was determined in traditionally fermented pasteurized milk. Preheated milk was inoculated with 1% (v/v) of a mixed culture of Lactobacillus delbrueckii ssp. bulgaricus (NCIMB 11778) and Streptococcus salivarius ssp. thermophilus (NCIMB 110368) and incubated at 25, 30, 37 or 43 degrees C for 24 h. E. coli O157:H7 (10(5) CFU/ml) were introduced into the milk pre- and post-fermentation. Fermented milk samples were subsequently stored at either 4 degrees C (refrigerator temperature) or 25 degrees C (to mimic African ambient temperature) for 5 days. After 24 h of fermentation, the pH of the samples fermented at the higher temperatures of 37-43 degrees C decreased from 6.8 to 4.4-4.0 ( +/- 0.2) whereas at the lower temperature of 25 degrees C, the pH decreased to pH 5.0 +/- 0.1. During this period, viable counts for E. coli O157:H7 increased from 10(5) to 10(8) - 10(9) CFU/ml except in milk fermented at 43 degrees C wherein viability declined to 10(4) CFU/ml. In fermented (25-30 degrees C) milk stored at 4 degrees C for 5 days, E. coli O157:H7 viability decreased from 10(8-9) to 10(6-7) CFU/ml whereas milk fermented at 43 degrees C resulted in loss of detectable cells. In contrast, storage of fermented milk samples at 25 degrees C for 5 days eventually resulted in complete loss of viability irrespective of fermentation temperature. Stationary phase E. coli O157:H7 inoculated post-fermentation (25 and 43 degrees C) survived during 4 degrees C storage, but not 25 degrees C storage. Fermentation temperature and subsequent storage temperature are critical to the growth and survival of E. coli O157:H7 in traditional fermented products involving yoghurt starter cultures.
Type: Article
Language: en
Keywords: Escherichia coli O157:H7
Lactobacillus delbrueckii ssp. bulgaricus
Streptococcus salivarius ssp. thermophilus
pH
Temperature
Fermentation
Acid
MeSH: Colony Count, Microbial
Escherichia coli O157
Fermentation
Food Contamination
Food Handling
Food Microbiology
Hydrogen-Ion Concentration
Lactobacillus
Streptococcus
Temperature
Yogurt
ISSN: 0168-1605
Appears in Collections: Food Biology, Medical Microbiology and Disinfection Research Group

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