TY - JOUR
T1 - Influence of temperature and pH on survival of Escherichia coli O157:H7 in dry foods and growth in reconstituted infant rice cereal
AU - Deng, Yun
AU - Ryu, Jee Hoon
AU - Beuchat, Larry R.
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1998/12/22
Y1 - 1998/12/22
N2 - Factors affecting the ability of Escherichia coil O157:H7 to survive in foods with a(w) less than required for growth have not been fully defined. This study was undertaken to determine the ability of E. coli O157:H7 to survive in a commercial dry infant rice cereal as affected by a(w) (0.35±0.04, 0.52±0.03 and 0.73±0.03), pH (4.0 and 6.8), and temperature (5, 25, 35 and 45°C), and in nine other reduced-a(w) foods. Death of E. coli O157:H7 in cereal was enhanced with increased temperature and decreased pH during a 16- to 24-week storage period. Survival was enhanced at pH 6.8 compared to pH 4.0 in cereal at a(w) 0.34±0.04 during initial storage at 5 and 25°C. The effect of temperature (8, 15, 21 and 30°C) on survival and growth of acid-adapted cells of E. coli O157:H7 inoculated into cereal reconstituted with milk or apple juice at two inoculum levels (8.2-12.3 cfu/ml and 82-123 cfu/ml of slurry) was also studied. Growth occurred in cereal reconstituted with milk at all test temperatures and in cereal reconstituted with apple juice at 15, 21 and 30°C. Populations increased by > 1 log10 cfu/ml within 3-6 h at 21 and 30°C. Acid-adapted and unadapted cells had similar growth patterns. The effects of temperature and acid adaptation on survival of E. coli O157:H7 in nine commercial foods and food ingredients with pH 4.07-6.49 and a(w) 0.17-0.82 were determined. The pathogen survived in these foods for various lengths of time, depending the storage temperature, with an order of survival of 5°C > 21°C > 37°C. Survival appeared to be enhanced in foods with highest pH, and acid-adapted cells retained higher viability than unadapted cells in only two of the nine test foods. Of particular importance is the ability of E. coli O157:H7 to survive well in dry foods with a wide range in a(w) and pH, particularly at refrigeration temperature.
AB - Factors affecting the ability of Escherichia coil O157:H7 to survive in foods with a(w) less than required for growth have not been fully defined. This study was undertaken to determine the ability of E. coli O157:H7 to survive in a commercial dry infant rice cereal as affected by a(w) (0.35±0.04, 0.52±0.03 and 0.73±0.03), pH (4.0 and 6.8), and temperature (5, 25, 35 and 45°C), and in nine other reduced-a(w) foods. Death of E. coli O157:H7 in cereal was enhanced with increased temperature and decreased pH during a 16- to 24-week storage period. Survival was enhanced at pH 6.8 compared to pH 4.0 in cereal at a(w) 0.34±0.04 during initial storage at 5 and 25°C. The effect of temperature (8, 15, 21 and 30°C) on survival and growth of acid-adapted cells of E. coli O157:H7 inoculated into cereal reconstituted with milk or apple juice at two inoculum levels (8.2-12.3 cfu/ml and 82-123 cfu/ml of slurry) was also studied. Growth occurred in cereal reconstituted with milk at all test temperatures and in cereal reconstituted with apple juice at 15, 21 and 30°C. Populations increased by > 1 log10 cfu/ml within 3-6 h at 21 and 30°C. Acid-adapted and unadapted cells had similar growth patterns. The effects of temperature and acid adaptation on survival of E. coli O157:H7 in nine commercial foods and food ingredients with pH 4.07-6.49 and a(w) 0.17-0.82 were determined. The pathogen survived in these foods for various lengths of time, depending the storage temperature, with an order of survival of 5°C > 21°C > 37°C. Survival appeared to be enhanced in foods with highest pH, and acid-adapted cells retained higher viability than unadapted cells in only two of the nine test foods. Of particular importance is the ability of E. coli O157:H7 to survive well in dry foods with a wide range in a(w) and pH, particularly at refrigeration temperature.
KW - Dry foods
KW - Escherichia coli O157:H7
KW - Infant food
KW - Water activity
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U2 - 10.1016/S0168-1605(98)00161-5
DO - 10.1016/S0168-1605(98)00161-5
M3 - Article
C2 - 9926994
AN - SCOPUS:0032559022
VL - 45
SP - 173
EP - 184
JO - International Journal of Food Microbiology
JF - International Journal of Food Microbiology
SN - 0168-1605
IS - 3
ER -