Effect of Combined Ultrasonication and Modified Atmosphere Packaging on Storage Quality of Pakchoi (Brassica chinensis L.)

Abstract

Feasible use of ultrasonic treatment (UT) in combination with modified atmosphere packaging (MAP) to preserve pakchoi was evaluated. Pakchoi was treated with ultrasound (30 kHz) for different periods of time (5 min, 10 min, and 15 min) prior to MAP (with 5% O2 + 10% CO2 + 85% N2); the treated vegetables were then stored at 4 °C for 30 days. UT in combination with MAP could retard an increase in the total number of colonies in pakchoi during the storage. UT-10 min decreased the initial total number of colonies in pakchoi from 7.11 to 6.01 log CFU/g and effectively slowed down the increase in mass loss, yellowing, cell membrane permeability, and malondialdehyde content of the stored vegetable; such a treatment also slowed down the decrease in total soluble solids and losses of ascorbic acid and chlorophylls. The synergistic effect of UT and MAP results in effective reduction of peroxidase and polyphenol oxidase activities. In conclusion, UT-10 min + MAP was the best method to preserve pakchoi for 30 days.