The gradient distribution of pigment metabolites provided insights into the uneven colouration of pulp in cold-stored blood orange.

Pigment accumulation is the material basis for colour formation in blood orange pulp. Regarding colour characterization during cold storage in this study, the red pigment intensity and the chlorophyll content of the fruit were lowest in the peduncle end and highest in the stylar end. Most of the carotenoids and anthocyanins in the peduncle end, equator and stylar end increased during cold storage. The highest carotenoid content was found at the equator, and the lowest carotenoid content was found at the stylar end. Regarding the two principal anthocyanins (C3,6 mg and C3G), the highest content was observed in the stylar end, and the lowest content was found in the peduncle end. The upregulated genes involved in pigment synthesis, such as CHLP, HemF, HemY, MgCh and DVR for chlorophyll synthesis; PDS, ZDS1/2/3, LCYb and CHY-β for carotenoid synthesis, and DFR, ANS, ANR, BZL, 3RT...