Alicyclobacillus acidoterrestris in fruit juices and its control by nisin

The acid-tolerant and heat-resistant bacterium Alicyclobacillus acidoterres tris is a spoilage problem in pasteurized and heat-treated fruit juices. In this study it was shown to grow in orange juice, grapefruit juice and appl e juice to produce detectable taint at levels of about 10(4)-10(5) c.f.u. m l(-1). Decimal reduction times were determined at 80 degrees, 90 degrees an d 95 degrees C in each juice and confirmed the heat-resistant nature of the spores under normal juice pasteurization conditions. They also confirmed t hat heat sensitivity increased with decreasing pH but that this effect was less pronounced at higher temperatures. The organism was, however, sensitiv e to the bacteriocin food preservative nisin. The presence of nisin during heating decreased the D value by up to 40% and the MIC for nisin against sp ores at 25 degrees C was only 5 International Units (IU) ml(-1). The result s indicate that use of nisin is a potentially useful way of controlling thi s organism in fruit juices and fruit juice-containing products.