Characterization of Bacillus Species Isolated from Spoiled Ultrahigh Temperature Processed Milk

Abstract

Sixteen strains of Bacillus were isolated from a total of nine spoiled ultra high temperature processed milks. They closely resembled strains of Bacillus subtilis and Bacillus cereus. However, most were atypical in one or more biochemical or physiological traits. Spore crops were prepared from four of the isolates, and their thermoresistance was determined. The D100°C values (time at 100°C to destroy 90% of the population) obtained in water and reconstituted nonfat milk ranged from 3.10 to 7.68 min and z°C values (temperature change causing thermal death curve to traverse 1 log cycle) ranged from 5.6 to 8.8°C. All strains isolated were mesophilic with temperature optima between 37 and 45°C. Two strains could grow at 10°C, but none could grow at 5°C or 60°C. © 1981, American Dairy Science Association. All rights reserved.