Survival of Escherichia coli O157:H7 in potato starch as affected by water activity, pH and temperature

A study was done to determine the survival characteristics of Escherichia coli O157:H7 in potato starch powder as affected by a(w) (0.24-0.26, 0.51-0.52 and 0.75-0.78), pH (4.1 and 6.7) and temperature (4, 20 and 37 degreesC) over a 33-week storage period. Survival was enhanced as the a(w) decreased. The rate of death was higher as the storage temperature increased. Survival did not appear to be affected by pH. Since the composition of foods greatly affects the viability of E. coli O157:H7 at reduced a(w), development of models to predict patterns of inactivation in a given food should be carried out using data generated from that food or one with very similar composition, a(w) and pH.