In the 1980s, it was found for the first time that thermophilic, acidophilic spore-forming bacteria caused the fruits to spoil; therefore, Alicyclobacillus bacteria were regarded to be adverse micro-organisms unwanted in the fruit juice industry, since they might incur economic losses. Those bacteria cause defects of microbiological origin. The spoilage of juices is mainly manifested through the formation of off flavours and odours resulting from the occurrence of chemical compounds, such as guaiacol and halophenols, produced by those bacteria. The spores of Alicyclobacillus spp. survive for long periods of time in fruit concentrates and similar environments; however, for their growth, environments containing more water are required. It is difficult to inactivate Alicyclobacillus spp. in fruit juices, because the spores thereof survive high temperatures and, after pasteurization, can germinate and grow under fitting conditions. A. acidoterrestris is the most commonly occurring species responsible for the spoilage of juices and similar products. Those strains grow in an environment showing pH between 2.5 and 6.0 and at a temperature above 20 °C.