|Influence of acid tolerance responses on survival, growth, and thermal cross-production of Escherichia coli O157H7 in acidified media and fruit juices|
|Year of publication||2004년 이전|
|Author||Ryu, J.H., & L. R. Beuchat.|
|Publication in journal||International Journal of Food Microbiology 45 (1998) 185–193|
|Status of publication||Published|
A study was done to determine survival and growth characteristics of acid-adapted, acid-shocked, and control cells of Escherichia coli O157:H7 inoculated into tryptic soy broth (TSB) acidiﬁed with organic acids and three commercial brands of apple cider and orange juice. The three types of cells behaved similarly in TSB acidiﬁed with acetic acid; however, in TSB (pH 3.9) acidiﬁed with lactic acid, acid-adapted cells were more tolerant than acid-shocked cells which, in turn, were more tolerant than control cells. The ability of the three types of cells to grow after inoculation into acidiﬁed TSB, then plated on tryptic soy agar containing sodium chloride was determined. Tolerance of acid-adapted cells and, less markedly, acid-shocked cells to sodium chloride was diminished, compared to control cells. The pathogen showed extraordinary tolerance to the low pH of apple cider and orange juice held at 5 or 25°C for up to 42 days. Growth occurred in one brand of apple cider (pH 3.98) incubated at 25°C. Regardless of test parameters, there was no indication that cell types differed in tolerance to the acidic environment in apple cider or orange juice. Survival of control, acid-adapted, and acid-shocked cells heated in apple cider and orange juice was studied. Within each apple cider or orange juice, D52°C-values of acid-adapted cells were considerably higher than those of acid-shocked or control cells, which indicates that heat tolerance can be substantially enhanced by acid adaptation compared to acid shock.