Rapid Cooling Delays the Occurring of Core Browning in Postharvest 'Yali' Pear at Advanced Maturity by Inhibiting Ethylene Metabolism

During the storage and transportation processes, the occurrence of core browning in 'Yali' pear fruit due to adversity injury can be easily mitigated by implementing different cooling methods, especially in advanced maturity fruits. In this study, 'Yali' pears at an advanced maturity stage were subjected to slow cooling and rapid cooling treatment. The quality-related physiological percentage and severity, and the rate of good fruits were determined, and RNA-seq was used to explore the effects of different cooling methods on pathways related to core browning in advanced-maturity pears at the transcriptional level. The results indicated that, compared with slow cooling treatment, rapid cooling significantly inhibited core browning in advanced-maturity 'Yali' pears. Measurements of quality-related physiological indexes suggested that rapid cooling treatment led to higher SSC content, firmness, L* value, and b* value, indicating better brightness, coloration, and higher soluble solid content, which are desirable for commercial sale. Rapid cooling effectively suppressed the physiological metabolism of 'Yali' pears, delaying fruit senescence compared with slow-cooling treatment. Furthermore, the RNA-Seq sequencing results revealed that pathways related to browning are involved in hormone signal transduction pathways, which are associated with resistance and aging processes of pear fruit. In summary, rapid cooling treatment delayed the core browning of advanced maturity of 'Yali' pears, indicating that the core browning of 'Yali' pears is related to the cooling method, and the mechanism of rapid cooling in reducing the core browning of advanced maturity of 'Yali' pears was by delaying the aging process of the fruit. This provides a new perspective for alleviating the core browning of advanced-maturity 'Yali' pears during storage and transportation, and provides a theoretical reference for studying the mechanism of core browning of 'Yali' pears.