Arginine treatment attenuates chilling injury of pomegranate fruit during cold storage by enhancing antioxidant system activity

In this study, the impacts of arginine treatment at 0, 0.5, 1 and 2 mM applied by preharvest spray in combination with postharvest immersion, on postharvest chilling injury and nutraceutical properties of pomegranate fruit during storage at 4 +/- 0.5 degrees C for 120 d was investigated. Pomegranate fruit treated with arginine at 1 mM, displayed significantly lower chilling injury symptom manifested by external husk browning. Lower husk browning in pomegranate fruit treated with arginine, caused by lower husk H2O2 accumulation, was partially due to higher antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities, leading to higher membrane integrity revealed by lower electrolyte leakage and malondialdehyde (MDA) accumulation. Also, lower husk browning in pomegranate fruit treated with arginine resulted from higher husk phenylalanine ammonia-lyase (PAL)/polyphenol oxidase (PPO) enzymes activity ratio. Moreover, pomegranate fruit treated with arginine displayed higher arils DPPH scavenging capacity, due to higher arils total phenols and anthocyanins accumulation. Also, higher arils PAL/PPO enzymes activity ratio together with lower arils H2O2 accumulation was partially due to higher antioxidant enzymes, SOD, CAT and APX activities which are crucial for higher arils DPPH scavenging capacity. In addition, higher arils ascorbic acid content in pomegranate fruit treated with arginine may be attributed to higher glutathione reductase (GR)/APX system activity or higher anthocyanin accumulation. The results of this study suggest that arginine treatment can be used as promising technology not only for attenuating chilling injury but also for maintaining nutraceutical properties of pomegranate fruit partially by promoting antioxidant system activity.