Effects of Nonthermal Processes on the Inactivation of Microorganisms and Antioxidants in Minimally Processed Vegetables

Abstract

Effects of several nonthermal disinfection processes, including high pressure carbon dioxide treatment (HCT), gaseous chlorine dioxide treatment (GCT) and pulsed xenon treatment (PXT), on the inactivation of microorganisms and antioxidants in ten cut vegetables (red paprika, green pepper, cucumber, cabbage, lettuce, mizuna, celery, onion, carrot, and bean sprout) were investigated. HCT (6 or 10 MPa, 10 min, 35°C) showed similar inactivation effects on microorganisms using conventional NaOCl treatment (100 ppm, 10 min) by controlling pressure. However, HCT caused a loss of more antioxidants such as vitamin C and phenolic compounds in cut vegetables under severe conditions. In addition, HCT softened the leaf vegetables, cabbage, lettuce, and mizuna. All samples after PXT (500 J, 10 times) had the same antioxidant contents and DPPH radical scavenging activities as the untreated intact samples, suggesting PXT could be a disinfection method that does not influence the antioxidants in cut vegetables. For inactivation of microorganism, PXT decreased the viable cell count by about 10-fold, but not significantly. On the other hand, GCT (10 ppm, 30 min) showed almost the same microorganism inactivation as NaOCl treatment. The loss of vitamin C and phenolic compounds due to GCT were negligible. These results suggest that GCT might be a promising nonthermal disinfection treatment for cut vegetables.