Heat resistance of Alicyclobacillus acidocaldarius in water, various buffers, and orange juice

Abstract

The effect of the pH or the composition of the heating medium and of the sporulation temperature on the heat resistance of spores of a thermoacidophilic spore-forming microorganism isolated from a dairy beverage containing orange fruit concentrate was investigated. The species was identified as Alicyclobacillus acidocaldarius. The spores showed the same heat resistance in citrate-phosphate buffers of pH 4 and 7, in distilled water, and in orange juice at any of the temperatures tested (D(120°C) = 0.1 min and z = 7°C). A raise in 20°C in the sporulation temperature (from 45 to 65°C) increased the heat resistance eightfold (from D(110°C) = 0.48 min when sporulated at 45°C to 3.9 min when sporulated at 65°C). The z-values remained constant for all sporulation temperatures. The spores of this strain of A. acidocaldarius were very heat resistant and could easily survive any heat treatment currently applied to pasteurize fruit juices.