Adaptation of Escherichia coli O157:H7 to acid in traditional and commercial goat milk amasi.
Acid resistance of Escherichia coli O157:H7 strains UT 10 and UT 15 were determined in traditional Amasi fermented for 3 days at ambient temperature (ca 30 degrees C) and commercial Amasi fermented at 30 degrees C for 24h and stored at 7 degrees C for 2 days. Escherichia coli O157:H7 counts in commercial Amasi were detected at 2.7 log(10)cfu/ml after 3 days while those in traditional Amasi could not be detected after the same period. There was no significant difference (p< or =0.05) in the survival of acid adapted (AA) and non-adapted (NA) E. coli O157:H7 in traditional Amasi, while in commercial Amasi, the NA strain survived significantly (p< or =0.05) better than its AA counterpart. Regardless of prior adaptation to acid, E. coli O157:H7 can survive during fermentation and storage of fermented goat milk Amasi. Also, the fermentation time, pH and storage temperature affects the survival of E. coli O157:H7 in the fermented milk.
Dlamini
Bhekisisa C
BC
Department of Food Science, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa.
Buys
Elna M
EM
D000222:Adaptation, Physiological; D000818:Animals; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D019453:Escherichia coli O157 / Q000254:growth & development / Q000502:physiology*; D005285:Fermentation; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D006041:Goats; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000382:microbiology*; D013696:Temperature; D013997:Time Factors