Effects of microwave treatment on physiology and quality of minimally processed bok choy ( Brassica campestris L.) during storage at 5 °C

The effects of microwave treatment (454 W for 5 s) on the physiology and quality of minimally processed bok choy were investigated for 9 days at 5 ± 0.5 °C. The treatment significantly reduced the respiration rate by 12% compared with that of untreated samples, although the rates increased during storage. Microwaving prevented incipient etiolation and transpiration, maintained relatively high − a/b value, chlorophyll content as well as low chlorophyllase activity and decay index during storage. The treatment also decreased the relative electrolyte leakage, superoxide anion radical (O2 ·−) production rate and malondialdehyde content compared with those of control. Furthermore, microwaving reduced the phenylalanine ammonia-lyase, peroxidase activities and total phenolic contents by 17, 20 and 15%, respectively, after 9 days of storage. In contrast to the soluble solid content, the ascorbic acid content in microwave-treated bok choy was slightly lower than that of control. These results suggested that the immediate microwave treatment (at 454 W for 5 s for example) could decrease respiration rate, retard etiolation and decay, improve cell membrane integrity, and therefore maintain a better quality of bok choy, which provides a sustainable alternative for thermal physical technologies and chemical agents.