Modified-atmosphere packaging maintains the quality of postharvest whole lettuce (Lactuca sativa L. Grand Rapid) by mediating the dynamic equilibrium of the electron transport chain and protecting mitochondrial structure and function

The mechanism by which modified-atmosphere packaging (MAP) protects the quality of whole lettuce (Lactuca sativa L. Grand Rapid) was investigated in this study. MAP-treated lettuce exhibited a low respiration rate, weight loss, chlorophyll loss, and relative conductivity, together with improved overall quality. Transmission electronic microscopy (TEM) was used to reveal the integrated mitochondrial morphology in MAP-treated lettuce, and a further analysis found that MAP treatment could increase the calcium (Ca2+) content and Ca2+ pump activity. MAP-treated lettuce also displayed low levels of the superoxide anion and hydroxyl radical, which was explained by a stable electron transport chain (ETC), as evidenced by high succinate dehydrogenase and cytochrome c oxidase activity. It was further found that MAP could increase superoxide dismutase and ascorbate peroxidase activity, as well as the ascorbic acid and glutathione content. These findings suggest that MAP maintains the quality of postharvest whole lettuce by protecting the mitochondrial structure and maintaining the ETC balance.