Inactivation of Alicyclobacillus spp. in apple juice by pulsed light and the analysis of its mechanisms

This study investigated the effect of pulsed light (PL) treatment on the inactivation of Alicyclobacillus spp. in apple juice and its mechanisms. The results indicated that five kinds of bacterial strains (including A. acidoterrestris, A. acidiphilus, A. cycloheptanicus and A. acidocaldarius) in apple juice (8–20 °Brix) can be completely inactivated by the total fluence of 23.52–35.28 J/cm2 and a total processing time of less than 8 min, which depended on the types of bacterial strains. The treatment of PL can change the permeability of cell membrane and destroy the cell parietal structure, with the leakages of intracellular electrolytes. Moreover, the PL treatment can increase the leakage of intracellular protein and reduce the levels of cellular adenosine triphosphate. Also, compared with the untreated bacteria, the levels of intracellular reactive oxygen species were increased more than 1.4-fold after the PL treatment, indicating the antioxidant defense system was disrupted and then the bacteria were inactivated by certain oxidative damage. These results displayed that the PL treatment can effectively inactivate Alicyclobacillus spp. in the apple juice. The established method provides an effective technology for the control of bacteria in fruit juices. •Alicyclobacillus spp. can be effectively inactivated by PL treatment.•The inactivation efficiency was affected by pulse numbers, SSC, and bacterial concentration.•PL treatment changes cell membrane permeability and destroys cell parietal structure.•PL treatment can cause protein leakage and reduce cellular adenosine triphosphate.•SD-4, SD-19, DSM-4006 were more sensitive to PL treatment.