Color And Pigment Analysis Of Citrus Fruit During Development And Storage

The color of Citrus peel is different from cultivars to cultivars and closely related with the quantity and composition carotenoid and chlorophyll during its development. Many preservation methods which resulted in different flavor and color quality were applied in prolonging the period of harvesting and marketing after Citrus fruits maturation. Study was carried out on the relationship between color and pigment changes among different development stages in six varieties of Citrus fruit peel, including Skaggs Bonanza navel orange (Citrus sinensis Osbeck cv. Skaggs Bonanza), Newhall navel orange (Citrus sinensis Osbeck cv. Newhall), Chuanfuhongju (Citrus reticulata Blanco cv. Chuanfuhongju), Pinkmursh grapefruit (Citrus paradisi Macf. Pinkmursh), Guoqing 1 (Citrus unshiu Marc. cv. 'Guoqing 1'), Guoqing 4 (Citrus unshiu Marc. cv. 'Guoqing 4'). And the effect of on tree storage and cold storage on flavor and color quality in Newhall navel orange fruits were also analyzed. The main results were as follows:1. Degreening was firstly happened to Chuanfuhongju in early November which developed red color later on and had longer time to be fully colored. Approximately 10 days after Chuanfuhongju degreening, Navel orange (Newhall and Skaggs Bonanza) degreened, but mainly to develop the yellow background. There was no degreening process found in Guoqing 1 and Guoqing 4 until ripening. The process was also not obvious in Pinkmursh grapefruit.2. Composition of carotenoids within the peel of 6 varieties of different development stages was analyzed by using high performance liquid chromatography-photodiode array detector(HPLC-DAD). Totally 11 carotenoids were separated and identified.Navel orange At the earliest stage as late August, 6 carotenoids were detected. They were sequenced according to the content from the highest to the lowest as lutein,β-carotene, violaxanthin,α-carotene, (9Z)-violaxanthin and zeaxanthin. Later on, lutein,β-carotene andα-carotene gradually declined butβ-cryptoxanthin appeared and kept increasing. Zeaxanthin became a little lower, while violaxanthin and (9Z)-violaxanthin increased dramatically and the sum reached 95% of the total carotenoid, which contributed mainly to the background color of the peel.Guoqing 1 and Guoqing 4 The composition and content changes of carotenoid was similar to those of navel orange peel during fruit development. But it had the constantly higher level of lutein,β-carotene andα-carotene than in navel orange, although their contents were declining from late August to early November.β-cryptoxanthin increased noticeably from 21st Oct. to 1st Nov. by twice and three folds respectively in Guoqing 1 and Guoqing 4, only a little bit lower than (9Z)-violaxanthin, the highest one.Pinkmursh grapefruit Lycopene was found in albedo as the highest one of 7 carotenoids detected with an increase at the first stage followed by a decline. Lutein andβ-carotene run the second and third highest carotenoids, followed byα-carotene. The content of the last three pigments declined during ripening. Lutein andα-carotene disappeared in the end. The content variation tendencies of violaxanthin and (9Z)-violaxanthin were not evident.Chuanfuhongju In peels of the cultivar, contents of every carotenoid were found higher than other cultivars.β-Citraurin was detected only in the material in middle October (2.84μg/g FW), and accumulated abundantly later on.β-Citraurin, violaxanthin, 9Z-violaxanthin andβ-cryptoxanthin were the main coloration pigment in degreening.3. Chuanfuhongju had the highest total carotenoid upon ripening. It was three times as Guoqing 1 and Guoqing 4, 4 times as navel orange,11 times as grapefruit.4. The shift from theβ,ε-branch to theβ,β-branch of the carotenoid synthetic pathway was found during fruit coloration. The decrease in content ofβ-carotene was accompanied by increases in content ofβ-crytoxanthin and zeaxanthin during late stages of fruit development, indicating that the activities ofβ-BCH and ZEP increased. (9Z)-violaxanthin accumulated due to isomerization of all trans violaxanthin. It contributes mainly to the background color of orange fruit peel.β-Citraurin was responsible for the red-orange color of peel.5. The ratio of total soluble solids and total titratable acids of cold storage fruits were 4.28 less than control (21.36), whereas the ratio of the on tree storage fruits increased to 33.33 which were twice as cold storage fruits. Post harvest pigment synthesis was found in cold storage navel, especiallyβ-cryptoxanthin and zeaxanthin, indicating that light was not the necessary condition in carotenoid synthesis. Furthermore, the color of the peel on cold storage fruits turned to yellow. The total carotenoids level of the on tree storage fruits was 1.5 times as that of the cold storage fruits, and the peel color was smart orange, on account of large accumulation of violaxanthin and (9Z)-violaxanthin.