Alicyclobacillus acidoterrestris, a thermoacidophilic, non-pathogenic and spore-forming bacteria, survive pasteurization and cause spoilage of fruit juices, inducing apple juice. In this study; the survival through pasteurization of seven chosen Alicyclobacillus acidoterrestris strains in medium of apple juice (total soluble solids content - 1 7,2%, pH 3,4) and concentrated apple juice (total soluble solids content - 70,0% pH 3,12) and heat resistance parameters of those strains were determined. The number of Alicyclobacillus acidoterrestris spores hold steady or decreased slightly during 60 minute of pasteurization in 85 °С, in both media. But after one hour of pasteurization in 90 °С, a drop in number of spores from 1,32 log cfu/ml to over 2,86 log cfu/ml in apple juice was observed, depending on strain. In concentrated apple juice after one hour a decrease from 0,48 log cfu/ml to over 3,04 log cfu/ml was observed. Pasteurization in 95 °С during 20 minute caused a substantial drop in number of spores: in apple juice from 2,32 log cfu/ml to 5,08 log cfu/ml and from 0,63 log cfu/ml to 3,08 log cfu/ml in concentrated apple juice. Values of D90 of examined strains were from 20,0 minute to 47,8 minute in apple juice and from 15,8 minute to 161,3 minute in concentrated apple juice. In temperature of 9 °С, D95 values ranged from 3,4 minute to 15,1 minute, depending on the strain. On the other hand in concentrated apple juice those values ranged from 5,3 minute to 29,8 minute, in the same temperature. Factor ,,z" valued from 5,4°C to 12,8 °С in apple juice and from 4,9 °С to 14,2 °С in concentrated apple juice. Obtained results proved the high heat resistance of Alicyclobacillus acidoterrestris spores. Direct dependence of heat resistance on soluble solids content in apple juices was not observed.
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