Comprehensive analyses of the postharvest physiology and browning mechanism of pomegranate (Punica granatum L.) during cold storage

Abstract Pomegranate (Punica granatum L.) belongs to the Punicaceae family. Pomegranates are valued for their social, ecological, economic and aesthetic value and, more recently, for their health benefits. Tunisian pomegranate, which has soft seeds and large arils that can be easily swallowed, is particularly popular. In this study, soft seed pomegranate fruit was stored at chilling injury (CI) temperature (0 °C) and non-CI temperature (8 °C) after harvest to investigate the impacts of these temperatures on CI development and browning and the associated underlying mechanisms. Pomegranates are susceptible to CI when stored at temperatures below 7 °C. The results showed that at 0 °C, the CI index, browning degree, and chlorophyll content were greater than those at 8 °C. Furthermore, storage at 0 °C increased cell membrane permeability and increased polyphenol oxidase activity. These findings demonstrated that CI and browning in pomegranate were closely associated with the metabolism of membrane lipids and phenolics. The aim of this study was to explore environmental factors that affect fruit skin browning as well as the relationship between changes in enzyme activity and fruit skin browning. A temperature of 0 °C can cause low-temperature damage to pomegranates, while at 8 °C, the fruit hardly experiences cold damage. In the later stage of fruit storage, damage to cell membrane permeability, a gradual increase in the content of the membrane lipid peroxidation product malondialdehyde, oxidation and degradation of phenolic substances, slight ageing and browning of the fruit skin, and an acidic tissue pH were observed.