APPLICATION OF HIGH PRESSURE PASTEURIZATION TO INACTIVATE SPORES OF ALICYCLOBACILLUS ACIDOTERRESTRIS IN APPLE JUICE

Alicyclobacillus acidoterrestris (AAT), thermoacidophilic, and spore-forming bacteria cause fruits and vegetable juices to spoil. A pasteurization process does not completely destroy the spores of those bacteria, but it activates their germination and further growth. The objective of this study was to assess the usefulness of high pressure pasteurization applied to inactivate AAT spores in apple juice. There was described the effect of a 300 MPa and 500 MPa pressure at 50 degrees C on the survival of spores of eight AAT strains in the apple juice. When a 300 MPa pressure was applied for 10 min, the number of living spores was reduced to 1.27 - 3.46 log efu/ml of juice depending on the strain. When the pasteurization process was prolonged by 30 min. and applied to the two most resistant strains, it was possible to reduce the number of living spores to 2.06 and 2.64 log cfu/ml. The increasing of the pressure to 500 MPa did not cause the pasteurization process to become significantly more efficient. It was confirmed that the application of a pulsed high pressure was the most effective. There were applied six five-minute pressure cycles of 100 MPa, 300 MPa, and 500 MPa, at 50 degrees C. The highest reduction in the number of spores of the two AAT strains amounting to 2.40 and 3.11 log cfu/ml was achieved when a 300 MPa pressure was applied. The application of a pulsed high pressure (100 MPa at 50 degrees C), followed by one hour incubation at 50 degrees C, and the subsequent application of high pressure (500 MPa) resulted in the reduction in the number of the spores by more than 4 log cfu/ml. The AAT spores were resistant to the high hydrostatic pressure under the conditions as described in this study.