Abstract: ‘Lanfeng’ blueberries were used to explore the mechanism by which blueberry skin turns red during chilling storage. Meanwhile, the effect of programmed chilling treatment on controlling this phenomenon was also investigated. The results showed that the skin of only a minority of blueberries turned red during chilling storage. During the shelf life at room temperature after 30 days of chilling storage, there were significantly more blueberries whose skin turned red. At this time, the brightness of fruits decreased, and the a* value increased rapidly. These changes became more pronounced with extended storage time. Polyphenol oxidase (PPO) activity was significantly enhanced after long-term refrigeration, leading to a considerable reduction of anthocyanin and total phenols in the skin of blueberries. Programmed chilling treatment could effectively hinder blueberries from turning red and significantly inhibit the increase in a* value and the reduction in anthocyanin. Thus, the degradation of the pigments anthocyanins may explain why blueberry skin turned red under cold stress, and programmed chilling treatment can control this phenomenon effectively.

Key words: blueberry, cold storage, red turning, programmed chilling