Calcium Chloride Affects Postharvest Color Change of ‘Xiaobai’ Apricots by Regulating Energy Metabolism Pathways

In order to investigate the regulatory mechanism of exogeneous calcium chloride (CaCl₂) on postharvest energy metabolism and ascertain the association between energy metabolism levels and color change in ‘Xiaobai’ apricots, ‘Xiaobai’apricots from Xinjiang were fumigated with 3 g/100 mL CaCl₂ solution or distilled water (control) before being stored at (10 ± 1.0) ℃ and relative humidity of (80 ± 5)%. Changes in chlorophyll, carotenoid, adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) contents and energy charge (EC) levels in the peel and pulp of apricots and changes in enzyme activities and gene expression related to energy metabolism were determined during the storage period. The results showed that compared with the control group, CaCl₂ treatment delayed chlorophyll degradation, inhibited carotenoid synthesis, maintained ATP and ADP contents and energy charge levels, enhanced the activities of H⁺-ATPase, Ca²⁺-ATPase, succinate dehydrogenase (SDH) and cytochrome c oxidase (CCO), and induced the expression of the PaH⁺-ATPase1, PaCa²⁺-ATPase10, PaSDH and PaCCO6 genes in both peel and pulp. Chlorophyll content in the peel and pulp was positively correlated with ATP, ADP and EC levels, but negatively correlated with carotenoid contents. There was a significantly positive correlation between chlorophyll and ADP levels in the peel and pulp (P < 0.01). It was suggested that exogenous CaCl₂ could delay postharvest color change and maintain high energy charge by regulating energy metabolism, therefore prolonging the shelf life of ‘Xiaobai’ apricots.