Abstract
In citrus fruit, citric acid is the predominant organic acid which influence fruit taste, flavor and quality. The effect of hot air treatment (HAT 40°C, 48 h) and 1.0% chitosan coating on the change of organic acids and the related gene expression of citric acid synthesis and degradation in ponkan (Citrus reticulata Blanco) fruit during cold storage have been studied. The results showed that citric acid was the main organic acid in fruit, the trend change of citric acid content was consistent with total organic acids and titratable acidity (TA) content, which decreased with the prolongation of storage time, hot air treatment significantly promoted but chitosan coating treatment significantly delayed citric acid degradation in Ponkan fruit. Hot air treatment could induced CitAco2/3, CitIDH2/3, CitGAD4, CitACLs, CitPEPCKs and CitFBPases expression during fruit storage period, but had no significant effect on CitGSs expression, The enhanced expression of degradation-related genes was closely related to the degradation of citric acid. The expressions of CitAco3, CitGAD4 CitACLα2/β, CitPEPCKs and CitFBPases were inhibited, which leading to the degradation rate of citric acid was slowed by chitosan coating during storage. These results showed that the degradation of citric acid in fruit was regulated by ATP citrate lyase (ACL) pathway and γ-aminobutyric acid (GABA) pathway.
Highlights
Acid is an important indicator of fruit quality
hot air treatment (HAT) significantly accelerated the decrease of citric acid content in Ponkan fruit, but chitosan coating significantly delay the decrease of citric acid
Quinic acid and tartaric acid content increased first and decreased in Ponkan fruit during storage, chitosan coating delay the decrease of quinic acid content in Ponkan fruit, HTA accelerated the decrease of tartaric acid content
Summary
Acid is an important indicator of fruit quality. Depending on the type of major organic in ripe fruit, the fruit can be divided into three types: citric acid type, malic acid type and tartaric acid type fruit. Citrus fruit is citric acid type fruit Main text paragraph [1]. Ponkan (Citrus reticulata Blanco) is one of the main mandarin citrus in China, the fruit are rich of organic acid [2]. Zhang et al [3] have demonstrated that citric acid was the major organic acid in Ponkan fruit, which accountings for 91.82% of the total content in single fruit. The content of organic acids in fruit affected fruit flavor and quality, and affected the storage characteristics of fruit [4]
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