High-voltage electrostatic field-assisted modified atmosphere packaging for long-term storage of pakchoi and avoidance of off-flavors

Abstract

Pakchoi is an important source of many essential nutrients for humans, but the leaves are prone to yellowing and rotting. This study aimed to maintain the quality of post-harvest pakchoi by using non-thermal high-voltage electrostatic field (HVEF) treatment in combination with modified atmosphere packaging (MAP) to compensate for each other's technical shortcomings and extend the shelf life of pakchoi. After 40 days of storage, HVEF at 4 kV/cm effectively degraded the volatile flavor components within the package, maintaining the chlorophyll and ascorbic acid content. It also reduced the microbial count by 1.82 ± log CFU g−1 (at 25 days) compared to the single MAP treatment (p < 0.05). The combined treatment of pakchoi has been verified by low-field nuclear magnetic resonance to have relatively low water mobility as well as lower electrolyte permeability and better texture than the single treatment. So, it has a higher sensory score. The HVEF assisted treatment resulted in lower respiration rates in the modified atmosphere packed pakchoi and changes in polyphenol oxidase (PPO) and superoxide dismutase (SOD) activities by affecting metal ion valence and enzyme conformation in favor of long-term storage. Principal component analysis (PCA) showed that the sensory and nutritional qualities of pakchoi treated with MAP and HVEF at 4 kV/cm in concert were closest to those of fresh samples. As a result, the shelf life of the pakchoi was successfully extended to 40 days while the pakchoi with a single MAP treatment lost its edible value at 25 days. HVEF assisted modified atmosphere packaging is expected to be an environmentally friendly, efficient and promising preservation technology. Industrial relevanceThis research provides new ideas for reducing the production of off-flavors vegetables in modified atmosphere packaging and extending the shelf life of vegetables. After modified atmosphere packaging the vegetables receive a high-voltage electrostatic field treatment at five-day intervals. This intermittent post-treatment is both low energy and efficient; and the antibiotic effect on microorganisms is unmatched by other integrated treatments. This opens up new possibilities for the transportation of fresh vegetables by fleets on long sea voyages and for the marketing of off seasonable fruit and vegetables in extreme weather.