Influence of different pre-cooling methods on the postharvest storage of 'Kyoho' grapes (Vitis Labrusca × Vinifera 'Kyoho')

Abstract

Abstract Various pre-cooling methods for ‘Kyoho’ grapes were selected, such as forced-air pre-cooling (FAPC), vacuum pre-cooling (VPC), natural convection pre-cooling (NCPC), electrolyzed water pre-cooling (EWPC), cold water pre-cooling (CWPC), and fluid ice pre-cooling (FIPC). The aim is to determine the most suitable pre-cooling method for grapes. The storage temperature of grapes was (4±0.5) ℃, with a relative humidity of 85%, and physiological parameters were measured every 5 days. All precooling methods, except for NCPC, were able to complete the precooling process within 20 minutes. Interestingly, water and ice cooling methods were not suitable for pre-cooling grapes, probably due to microbial growth and damage to cellular tissue. In contrast, three groups of air pre-cooling methods were more effective in preserving freshness, the best of which was FAPC. It was found that FAPC inhibited grape weight loss, moisture loss, respiration rate, total viable count (TVC), malondialdehyde (MDA), and relative electrolyte leakage (REL), while stimulating the activities of superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL). It also suppressed the activity of polyphenol oxidase (PPO). Additionally, in the FAPC group, optimal hardness, titratable acidity (TA), and vitamin C (VC) content were observed. Among all the tested methods, FAPC demonstrated better efficacy in delaying the softening and senescence of 'Kyoho' grapes, thereby preserving the fruit's quality and nutritional content.