Inactivation of Alicyclobacillus contaminans in apple juice by dielectric barrier discharge plasma

Cold plasma (CP) has the potential for inactivating microorganisms; however, the deactivation effect of CP for Alicyclobacillus contaminans in apple juice is still rarely reported. In this study, dielectric barrier discharge plasma (DBDP) was applied to inactivate Alicyclobacillus contaminans vegetative cells and investigate the impact on the physicochemical properties of apple juice. After 65 V treatment for 4 min, the total viable bacterial count in sterilized saline and apple juice decreased by 6.4 log10 and 4.5 log10, respectively. And the initial cell concentrations had an insignificant effect on the inactivation of treatment. Inactivation kinetics models (Biphasic shoulder and double Weibull) fit well with the bactericidal curve of DBDP treatment. DBDP treatment caused the apple juice to darken and turn greenish and yellowish. The chroma, browning index, and chromatic aberration increased slightly. The pH value of apple juice was decreased after treatment. There were negligible changes in the total soluble solids, clarity, and turbidity; however, the antioxidant activity decreased slightly. The reactive oxygen species concentration, cell membrane peroxidation degree, protein content in the sample, and scanning electron microscopy and transmission electron microscopy measurements indicated that the cell membrane was damaged after DBDP treated, leading to cell leakage and death. DBDP is a promising method to reduce Alicyclobacillus contaminans in apple juice.