Effect of intermittent corona discharge plasma treatment for improving microbial quality and shelf life of kumquat (Citrus japonica) fruits

The effect of intermittent corona discharge plasma jet (ICDPJ) treatment in improving the microbiological quality and shelf life of kumquat fruits was evaluated. Kumquats were treated by ICDPJ generated using high-voltage power generator, with an output voltage of 8 kV DC and at current levels of 2.0-4.0 A. Aerobic bacteria and yeasts and molds were detected as contaminants in the fruits in the range of 3.00-3.46 log CFU/g. The plasma treatment for a cumulative period of 2 min induced a maximum fruit surface temperature of 35.6 °C and no alterations in the color and hardness of kumquats. Upon the plasma treatment, the initial microbial counts were reduced by 0.77-1.04 log CFU/g at 2.0 A current, by 1.08-1.57 log CFU/g at 3.0 A current, and by 1.51 log CFU/g to below detection limit at 4.0 A current. There was no significant difference in taste, flavor, color, texture, and total acceptance between the untreated and ICDPJ-treated samples at 2.0, 3.0, and 4.0 A currents. During storage at 25 °C for 15 days, the kumquats treated using ICDPJ generated at all currents tested exhibited extended shelf life compared to controls, without compromising their physicochemical and sensory properties.