Alicyclobacillus, more conveniently known as ACB or TAB, is a gram-positive, non-pathogenic, thermophilic and acidophilic spore-forming bacteria. This strain is able to grow over a wide range of temperatures and pH  values, and spores are relatively heat-resistant.

Alicyclobacillus spp. possess several distinct characteristics, but the major one is their ability to survive to commercial pasteurization processes and produce off-flavors in fruit juices. Therefore, the fruit juice industry has acknowledged Alicyclobacillus spp. as a major quality control target microorganism.

Raw materials are a major source of contamination and should be controlled by both suppliers and beverage producers. However, a positive ACB test does not always imply spoilage. Instead, organoleptic spoiling — impacting odor and taste — occurs due to a metabolite called guaiacol, an unpleasant odorous compound in fruit juices produced from ACB.

Therefore, ACB represents a major challenge for the beverage industry, as pasteurization does not always kill ACB, strains do not always produce guaiacol and traditional ACB screening does not always identify spoilage.

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