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Ultra-High Temperature Effects on Selected Bacillus Species¹

Department of Dairy Technology, The Ohio State University, Columbus

ABSTRACT

The effect of ultra-high temperatures of 104.5, 121, and 137.8 C for approximately 1 sec on bacterial spores added to milk was determined on the following Bacillus species. B. licheniformis, B. pumilus, B. circulans, B. sphaericus, B. coagulans, B. laterosporous, B. megaterium, B. cereus, and B. cereus var. mycoides.

The lower temperature (104.5 C) produced destruction percentages ranging from none for B. laterosporus to approximately 50% for B. pumilus, with values of 16% for B. licheniformis, 25% for B. cereus, and 45% for B. coagulans and B. sphaericus.

The temperatures of 121 and 137.8 C produced destruction percentages for the spores of all species greater than 97.7 and 99.99%, respectively. The outgrowth of all surviving spores was more rapid in the milk heat-treated at 121 and 137.8 than in the milk heat-treated at 104.5 C, as evidenced by increases in the number of new generations during 6 hr of incubation at 35 C. The percentage increase in outgrowth of spores heated at 121 C as compared to 104.5 C ranged from 27% for B. licheniformis to 400% for B. pumilus, with an average increase for all species of 110%. Increases in outgrowth of surviving spores heated at 137.8 C were 8, 24, 45, and 39% for B. sphaericus, B. circulans, B. Laterosporus, and B. megaterium, respectively, as compared to outgrowth of these spores after heating at 121 C. This effect was not evident with the other species studied.

¹ Article no. 1-66. This investigation was supported by Public Health Service Research Grant no. EF-00180-05 from the Division of Environmental Engineering and Food Protection, Bureau of State Service.