Characterization of Bacillus Species Isolated from Spoiled Ultrahigh Temperature Processed Milk

Abstract

Sixteen strains of Bacillus were isolated from 9 spoiled ultra high temperature processed milks. They closely resembles strains of B. subtilis and B. cereus. Most were atypical in 1 or more biochemical or physiological traits. Spore crops were prepared from 4 of the isolates and their thermoresistance was determined. The D100.degree. C values (time at 100.degree. C to destroy 90% of the population) obtained in water and reconstituted nonfat milk ranged from 3.10-7.68 min and z.degree. C values (temperature change causing thermal death curve to traverse 1 log cycle) ranged from 5.6-8.8.degree. C. All strains isolated were mesophilic with temperature optima between 37-45.degree. C. Two strains could grow at 10.degree. C, but none could grow at 5 C or 60.degree. C.