Thermal Destruction Kinetics of Spores of Selected Bacillus Strains in Skimmilk and Skimmilk Concentrate

The thermal destruction of Bacillus spores was studied in skimmilk and 40% TS skimmilk concentrate. Spores of Bacillus licheniformis, Bacillus brevis and Bacillus coagulans were found to be more, and those of Bacillus stearothermophilus less, heat resistant in skimmilk concentrate than in skimmilk. Thus, B. licheniformis, B. brevis and B. coagulans showed a death rate that was influenced by product concentration in the same way as already found with the mesophilic mixed spore flora of milk, whereas B. stearothermophilus was influenced like the thermophilic mixed spore flora. Further, it was found that the spores of B. licheniformis seem to determine the product's state of sterility during mesophilic storage and those of B. stearothermophilus during thermophilic storage of heated milk and milk concentrates.