Effects of Microfluidizer® Technology on Bacillus licheniformis Spores in Ice Cream Mix

We studied the effect of Microfluidizer technology (sometimes referred to as "microfluidization"), a new ultra-high pressure homogenization process, on spores of Bacillus licheniformis in ice cream mix. Four batches of pasteurized ice cream mix were preheated to 33, 36, 44, or 50 degrees C, and spores of B. licheniformis were added to yield an inoculum of 2.0 x 10(4) spores/ ml of mix. Samples were treated at 50,000, 100,000, 150,000, and 200,000 kPa. Respective percentages of spore destruction ranged from 6 to 68%. As process pressure in the Microfluidizer system increased, the temperature of the product also increased. At the Microfluidizer system outlet, temperatures ranged from 46 to 88 degrees C. Therefore, a combination of forces, including high pressure and temperature, likely had a multiplier effect on spore destruction during Microfluidizer processing of ice cream mix. Data suggest that it might be possible to design a pasteurizer-Microfluidizer system that would inactivate most bacterial spores in dairy foods without the extreme heat treatment currently required in commercial processing operations.