Effects of low temperature conditioning on fruit quality and peel browning spot in 'Huangguan' pears during cold storage

'Huangguan' pears are susceptible to peel browning spots (PBS) during cold storage. In this study, the effects of low temperature conditioning (LTC) on fruit firmness, soluble solids content (SSC) and PBS incidence in 'Huangguan' pears were investigated. Fruit were directly stored at 0 degrees C (control) and conditioned at 10 degrees C for 3 d (LTC), respectively. Afterwards, all fruit were stored at 0 degrees C. Fruit firmness was unaffected by the LTC treatment. However, SSC was higher in the LTC-treated fruit than in control fruit on days 30 and 60. Compared with the control, LTC treatment effectively inhibited the development of PBS, reduced the activities of lipoxygenase (LOX) and polyphenol oxidase (PPO), reduced malondialdehyde (MDA) content in peel tissue, the decline in the phenolic content, and it showed higher praline content before the appearance of PBS. In addition, LTC treatment decreased the expression levels of LOX1, PPO1 and PPO5 genes, while it up-regulated the expression of the PPO4 gene in peel tissue. These results indicate that the alleviation effect of LTC on the development of PBS was closely related to reduced membrane lipid peroxidation, activities of LOX and PPO, and the expression of LOX1, PPO1 and PPO5 genes in peel tissue in 'Huangguan' pears.