Alicyclobacillus acidoterrestris in fruit juices and its control by nisin

Summary The acid-tolerant and heat-resistant bacterium Alicyclobacillus acidoterrestris 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 apple juice to produce detectable taint at levels of about 10⁴–10⁵ c.f.u. ml^?1. Decimal reduction times were determined at 80 °, 90 ° and 95 °C in each juice and confirmed the heat-resistant nature of the spores under normal juice pasteurization conditions. They also confirmed that heat sensitivity increased with decreasing pH but that this effect was less pronounced at higher temperatures. The organism was, however, sensitive 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 spores at 25 °C was only 5 International Units (IU) ml^?1. The results indicate that use of nisin is a potentially useful way of controlling this organism in fruit juices and fruit juice-containing products.