Combination of TiO2-UV Photocatalysis and High Hydrostatic Pressure to Inactivate Bacterial Pathogens and Yeast in Commercial Apple Juice

초록

The purpose of this study was to investigate the effect of combined treatments using TiO2-UV photocatalysis (TUVP) and high hydrostatic pressure (HHP) on inactivation of microorganisms in commercial apple juice as model liquid food. A synergistic effect was observed for combined treatments to inactivate microorganisms. Gram-positive bacteria, Listeria monocytogenes and Staphylococcus aureus, were completely inactivated from initial loads of 7.1 and 6.7 log CFU/mL, respectively, when treated with a combination of TUVP (8.45 J/cm(2)) and HHP (500 MPa). In contrast, reductions of only 4.8 log CFU/mL (L. monocytogenes) and 2.4 log CFU/mL (S. aureus) were achieved with 500 MPa HHP alone. Gram-negative bacteria, Escherichia coli O157:H7 and Salmonella Typhimurium, were reduced by 7.1 and 7.2 log CFU/mL, respectively, after a combined treatment using 8.45 J/cm(2) TUVP and 600 MPa (E. coli) or 400 MPa (S. Typhimurium) HHP which were significantly higher than the effects of HHP alone. A 6.2 log CFU/mL reduction in Saccharomyces cerevisiae count was monitored after treatment with a combination of 8.45 J/cm(2) TUVP and 500 MPa HHP whereas even 600 MPa alone could not achieve complete S. cerevisiae inactivation. Combined treatments (TUVP + HHP) were more effective for microbial inactivation than alone treatments. Scanning electron microscopic images of microorganisms showed highly deformed morphologies after TUVP + HHP treatment. In conclusion, pretreatment of commercial apple juice using TUVP before HHP processing results in better disinfection and may assure complete disinfection.

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