The kinetics of thermal inactivation of Bacillus stearothermophilus spores in water extracts of soybeans (“soymilk”) was studied using a pilot scale scraped-surface heat exchanger. Survivor curves followed typical first-order inactivation reactions, with D-values ranging from 21.9 sec at 259 F to 5.3 sec at 268 F. The z-value was 15 F, corresponding to an activation energy of 88.6 kcal/mole. Lethal effects in the heating and cooling cylinders accounted for more than 50% of the inactivation above a heater outlet (holding) temperature of 265 F.

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