(西南大学 食品科学学院/食品贮藏与物流研究中心, 重庆 400715)
(College of Food Science/Research Center of Food Storage & Logistics, Southwest University, Chongqing 400715, China)
Temperature is one of the main environmental factors that regulate the coloration of citrus fruits after harvest. The effects of storage temperature of 5℃, 25℃ and 32℃ on the peel color, the plastid structure and the expression levels of related genes of early-ripening mandarin fruits (green ripening) produced in Chongqing Beibei were studied. The results showed that on the 9th day, the fruit showed significant coloring differences under different storage temperatures, and the color index of the fruits stored under 5℃ did not change significantly, and the color of peel was green. C* and a*/b* of the fruit stored at 25℃ increased significantly, H* decreased significantly, and the peel color changed from green to yellow. C* and a*/b* of the fruit stored at 32℃ increased slightly, and the peel remained green without significant change in H*. Ultrastructural analysis showed that the peel oil gland was oval when the fruit was harvested. The oil lumen, a complete plastid structure and the plasmid layer were clearly visible, and a small number of plastoglobulus were distributed in the plastid. Storaged at 5℃ delayed the change of the structure of peel oil gland, and the expression levels of plastid-related genes CcISPH1, CcISPH2, CcISPH3 and CcCRR22 were low, and the chloroplasts changed slowly. The peel oil gland morphology of fruits stored at 25℃ gradually disintegrated, and the up-regulated expression of CcISPH1, CcISPH3 and CcCRR22 promoted the development and differentiation of chloroplasts into chromoplast. The peel oil gland-layer structure of the 32℃ stored fruit disintegrated, showing a semi-vacuum state, and CcISPH3 and CcHSP17.6II were up-regulated on the 3rd and 6th day of storage, while the expression of CcCRR22 was down-regulated. And chloroplasts differentiated into chromoplast and then differentiated into chloroplasts. The experimental results aimed to provide some theoretical reference for well understanding the regulation mechanism of temperature on the coloration of postharvest citrus fruit.