Heat shock pretreatment and low temperature fluctuation cold storage maintains flesh quality and retards watercore dissipation of watercored 'Fuji' apples

Watercored apples have a unique flavor and particular flesh morphology. However, watercored apples are subject to loss of water core, browning, and softening during postharvest storage. In this study, heat shock pretreatment, hot air (HA) or hot water (HW), was combined with low temperature fluctuation (LTF) cold storage to delay the disappearance of the water cores and the flesh browning and softening during a 120 d storage. The apples were evaluated for appearance characteristics, texture parameters, enzyme activities, reactive oxygen content, membrane lipid oxidation degree, tissue microstructure, and cell morphology during the storage period. The results showed that HW combined with LTF was most effective in maintaining the visual quality and texture quality of watercored apples compared with other treatments and the control. Moreover, HW-LTF could effectively inhibit the accumulation of malondialdehyde (MDA), retard the increase of electrolyte leakage (EL), reduce the membrane lipid peroxidation, and maintain the tissue microstructure and cell morphology. Meanwhile, HW-LTF inhibited the activities of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) and reduced the degree of flesh browning. Therefore, the HW-LTF is of guiding significance for the cold storage of watercored apples.