A combination of hot air and methyl jasmonate vapor treatment alleviates chilling injury of peach fruit

Peaches (Prunus persica Batsch cv Baifeng) were harvested at the firm-mature stage and treated with various combinations of methyl jasmonate (MJ) and hot air (HA). Severity of internal browning and flesh mealiness, firmness, extractable juice, total soluble solids (TSS), total acid, vitamin C and total phenolic contents were measured after 3 and 5 weeks of storage at 0 °C plus 3 d at 20 °C for shelf-life. The activities of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), superoxide dismutase (SOD, EC 1.15.1.1), polyphenol oxidase (PPO, EC 1.10.3.1), peroxidase (POD, EC 1.11.1.7), pectin-methylesterase (PME, EC 3.1.1.11) and polygalacturonase (PG, EC 3.2.1.15) were analyzed during the cold storage period. The results showed that fruit treated with 1 μmol L−1 MJ vapor at 38 °C for 12 h (HMJ), and heat treatment at 38 °C for 12 h and then treated with 1 μmol L−1 MJ vapor at 20 °C for 24 h (HA + MJ) had the highest quality and lowest percent of chilling injury symptoms. HA treatment alone significantly inhibited internal browning, but caused more severe flesh mealiness than other treatments. This side effect was counteracted by MJ. The percent of extractable juice in combined treatments was higher than that in the control, however, no significant effect was found on firmness. TSS was 23% and 25.3% higher and total acid was 59.4% and 62.5% higher in treatments of HMJ and HA + MJ, respectively, than those in control fruit after storage for 5 weeks. Vitamin C and total phenolic contents were also maintained at higher levels in combined treatments. In addition, the combined treatments resulted in higher activities of PAL, SOD and PG, and lower activities of PPO, and POD than the control. The combination of HA and MJ vapor treatment might be a useful technique to alleviate chilling injury and maintain peach fruit quality during cold storage.