Thermophilic acidophilic spore-forming bacteria Alicyclobacillus can grow at low pH and at moderately high temperatures such as 40°C. Some of the species are known to cause spoilage of acidic beverages and produce medicinal odors. However, they do not produce gas or cause any change in the appearance of the beverage container, and therefore the spoilage is discovered only when the consumer opens and begins to consume the product. Fortunately, Alicyclobacillus are not pathogenic bacteria, but they are troublesome, not only for consumers but also for beverage producers, because no effective control methods have yet been developed. It is against this background and in recognition of the importance and urgency of the problem that International Life Sciences Institute (ILSI) Japan has published this book, bringing together new insights on the topic together with research published to date.