Alicyclobacillus acidoterrestris is a gram-positive, spore-forming bacillus that occurs widely in nature. This specie has been studied substantially after the incident of turbidity of transparent apple juice in 1984. The Alicyclobacillus genus bacteria, which peculiarly grows under relatively high temperatures and acid conditions, is called Thermo-acidophilic Bacilli (TAB) [1, 2, 3].

TAB are not destroyed by pasteurization and may remain in final products of fabricated food and beverages. TAB are not known to be harmful to health but are known to degrade the quality of juices and other products by producing guaiacol, causing off-flavor. Even without the off-flavor problem, product values may be degraded by slight deterioration during distribution.

It is very difficult to avoid contamination of TAB, which are common in soil. Fortunately, A. acidocaldarius and other main species that cause contamination are known to be harmless, and damage caused by TAB can be minimized by monitoring the contamination of A. acidoterrestris, which is known to be harmful. These species, however, cannot be detected by usual isolation culture methods as they grow only under acidic and relatively high temperature conditions.

Because of frequent occurrence of fruit juice deterioration incidents in Europe and other regions, Japan Fruit Juice Association developed and publicized a unified test method for TAB in March 2003 [4]. To allow easy performance of this test, we developed a kit that differentiates A. acidoterrestris in terms of productivity of guaiacol, which causes off-flavor.