Changes In Phenolic Compounds And Antioxidant Capacity Of Mandarin Fruit During Storage

Citrus fruit are an important part of human diet due to their nutritional value. In addition to vitamin C, citrus fruit contain large amounts of phenolic compounds such as flavonoids and phenolic acids. Recently, many researches have reported the beneficial effects of these phenolic compounds to human health, such as antioxidant, anticancer, anti-inflammatory and prevention of cardiovascular diseases. Citrus fruit are often stored for a long time after harvest, and storage time as well as postharvest treatments may affect the content of bioactive compounds. However, studies on changes of phenolic compounds and antioxidant capacity of citrus fruit during storage are limited. Thus, this study aimed at evaluating the changes of standard quality parameters, ascorbic acid, individual phenolic compounds (flavonoids and phenolic acids) and antioxidant capacity of citrus fruit, and to discuss the impacts of fruit cultivars, different postharvest treatments and storage conditions on these bioactive compounds. The main contents and results are as follows:1、The changes of phenolic compounds and antioxidant capacity in the pulp and peel of Satsuma mandarin and Ponkan during storage were studied. The results showed that Satsuma mandarin maintained better nutritional quality and higher antioxidant capacity, while ascorbic acid and antioxidant capacity decreased fast in Ponkan during storage. Phenolic compounds were relatively stable. Flavonoids increased in Satsuma mandarin but changed slowly in Ponkan during storage. Phenolic acids increased after storage. Flavonoids in the peels of both cultivars increased after storage in different levels, especially polymethoxylated flavones.2、The effect of waxing and wrapping on phenolic compounds and antioxidant capacity of Satsuma mandarin was investigated. Waxing and wrapping significantly reduced fruit weight loss, retained fruit standard quality and maintained higher total phenolic content during the first15days of storage. Wrapping retained higher levels of flavonoids and phenolic compounds, while phenolic compounds were lower in waxed fruit, especially after30days. Antioxidant capacity was related to the changes of ascorbic acid and phenolic compounds.3、The effect of hot water dips (50,52and54℃for3min) on phenolic compounds and antioxidant capacity of Satsuma mandarin was investigated.50℃treatment did not influence fruit quality attributes and reduced fruit weight loss significantly. Flavanone glycosides were higher in hot water treated fruit as compared to control during the first15days of storage, and phenolic acids were not affected.50℃treatment increased total phenolic content and antioxidant capacity immediately after treatment and maintained similar levels with control during storage, while52and54℃treatments showed lower levels.4、The influence of storage temperature (4and10℃) and harvest time (November and December) on phenolic compounds and antioxidant capacity of Satsuma mandarin was investigated. Fruit harvested in November showed significant higher flavanone glycosides, total phenol contents and antioxidant capacity than fruit harvested in December, while ascorbic acid and major phenolic acids (ferulic acid and sinapic acid) were similar:Storage temperature exerted little effect on phenolic compounds, and ascorbic acid content and antioxidant capacity were higher in fruit stored at10℃.5、The effect of ultraviolet C (UV-C) treatments (0,0.75,1.5and3.0kJ/m2) on phenolic compounds and antioxidant capacity of Satsuma mandarin segments (minimally processed) was investigated. UV-C treatments had no adverse effects on fruit quality attributes, phenolic acids and antioxidant capacity of mandarin segments. Significant increases of flavonoids (11.75%-33.25%) and total phenolic content (5.73%and8.13%) were found in1.5and3.0kJ/m2UV-C treated fruit at3days of storage. Higer dose of UV-C (3.0kJ/m2) did not further improve the increase of flavonoids, and0.75kJ/m2was too low to have any effects on flavonoids.