Regulation of skin pigments in winter jujube fruit treated with elevated O2

Abstract

Color deterioration is one of the major symptoms of postharvest senescence in winter jujube fruit. Elevated O2 (60 %) was applied to winter jujube fruit during storage at 0 °C and 90 % relative humidity. The changes in three major skin pigments, chlorophyll, carotenoid, and anthocyanin, were quantified to explain changes in skin color. The results showed that elevated O2 maintained the contents of chlorophyll and carotenoid during the initial stages of storage, which were 25 % higher chlorophyll a, 34 % higher chlorophyll b, and 18 % higher carotenoid compared to the control on day 7. The maintenance of chlorophyll content under elevated O2 was due to the inhibition of chlorophyll catabolism. Additionally, elevated O2 treatment also maintained carotenoid content by activating its biosynthesis rather than inhibiting its degradation. During the later stages of storage, the accumulation of anthocyanin was enhanced by elevated O2, with a 1.3-fold increase in anthocyanin observed in elevated O2-treated fruit compared to the control fruit on day 21. Elevated O2 treatment effectively activated phenylpropanoid biosynthesis and flavonoid biosynthesis pathways, leading to the accumulation of anthocyanin. This study elucidated the mechanism by which elevated O2 regulated color deterioration in winter jujube fruit.