Effect of low temperature-storage on the proteome of ‘Moro’ blood orange flesh

Abstract

Anthocyanins are a subclass of flavonoid pigments with important therapeutic properties beneficial to human health. Blood oranges are rich in these pigments, which present synergistic effects (i.e., anti-inflammatory and anti-obesity) with other orange juice phytonutrients. Anthocyanin biosynthesis is cold induced in blood citrus cultivars, requiring a broad day/night thermal range to get purple pigmentation in fruit. This cold-dependency limits geographically a reliable quality for commercial production to only a few regions worldwide. For example, cultivation of blood oranges under tropical/subtropical climates, as those of Brazil, yields fruit with very low level or lack of anthocyanins. A feasible alternative in tropical countries to enhance anthocyanin content is cold postharvest storage, as it has been shown that anthocyanin synthesis is induced when fruits are kept below 10°C for a few weeks after harvesting. Blood oranges kept at 9°C showed higher expression levels of anthocyanin biosynthetic genes, increased anthocyanin content and reached a darker purple coloration than those stored at 4°C. In order to gain insight on the effect of storage temperature on activation of anthocyanin biosynthesis and accumulation as well as on purple orange coloration, we have investigated the proteome of 'Moro' sweet orange [Citrus sinensis (L.) Osbeck] fruit stored either at 4°C (low temperature) or at 9°C (moderate temperature). Results on increased or reduced accumulation of specific proteins in the 'Moro' orange pulp upon storage at different temperatures reinforces that postharvest storage at 9°C could be better to enhance anthocyanin biosynthesis and accumulation on blood orange juices.