| Peaches are soft and vulnerable to mechanical damages during the post-harvest logistics,and are then easily infected by pathogenic bacteria.Proper temperature management can reduce the physiological response of fruit tissue to mechanical injury and reduce the appearance of bruising symptoms.Precooling treatment and transfer-toshelf treatment are important preservation methods based on temperature control.However,there are few studies on the effects of change rates of temperature on the improvement of fruit quality deterioration and reducing mechanical damage during precooling and shelf transferring.In this study,’Hujingmilu’ peach was used.The effects of different precooling rates(the fruit was cooled from 27 °C to less than 9 °C within 3 h or 16 h,respectively)on reducing postharvest mechanical damage and maintaining quality of peaches were investigated.The effects of different temperature rising rate of transfer-to-shelf treatment(6 h treatment: the fruit temperature was increased to 12 °C in the first 2 h,and then risen to 25 °C in the next 4 h;.12 h treatment: the fruit temperature was increased to 25℃ uniformly)on slowing down the quality deterioration of peaches with mechanical damaged during shelf life was investigated.The main findings are as follows:1.Effects of precooling rate on reducing mechanical damage and improving storability of peaches.The results showed that the bruise index of peaches in the control group(CK),the 3 h fast precooled group and the 16 h slowly precooled group at the end of the storage period was 32.2%,20.6% and 26.7%,respectively.There was a significant difference in the fruit bruise index of the three groups.The bruise index of the two precooling groups was significantly lower than that of CK;The weight loss rates were 9.5%,6.4%,and 9.2%,respectively.The weight loss rate of peaches treated with 3 h fast precooling was significantly lower than the other two groups.At the end of the 3 d shelf life,the decay rate of peaches in CK,the 3 h fast precooled group and the 16 h slowly precooled group was 26.4%,18.1%,and 23.6%,respectively.Peaches treated with 3 h fast precooling had significantly lower decay rate than the other two groups.2.Effects of precooling rate on physiology and quality changes of peaches with slight mechanical damage during storage.The results showed that both 3 h fast precooling and the 16 h slow precooling significantly inhibited the increase of respiration rate and ethylene caused by mechanical injuries and delayed the decrease of firmness.3 h fast precooling and the 16 h slow precooling also inhibited the increase of malondialdehyde(MDA)content and polyphenol oxidase(PPO)activity,and maintained higher phenylalanine lyase(PAL)activity.Peaches treated with 3 h fast precooling had better effect on maintaining fruit firmness.Both 3 h fast precooling and the 16 h slow precooling had no significant effect on the content of titratable acid(TA)compared to CK.3.Effects of rising rates of temperature during transfer-to-shelf treatments on the physiology and quality changes of peaches with slight mechanical damages.The results showed that the firmness of peaches in 6 h and 12 h group was 10.2 N and 13.0 N in 1 d after transferring to the shelf,and that of CK was 6.2 N.The firmness of peaches in three treatment groups all decreased to less than 10 N at the end of the shelf life.It indicated that 6 h and 12 h transfer-to-shelf treatments were beneficial to slow down the decline of firmness but did not affect the normal ripening of the fruit.The 12 h transfer-to-shelf treatment had better effects on delaying the decrease of firmness and inhibiting the increase of MDA content than CK and 6h transfer-to-shelf treatment.In addition,peaches treated with 12 h transfer-to-shelf treatment had higher content of soluble solids(TSS)and TA content than that of the other two groups.6 h and 12 h transfer-to-shelf treatments had no significant effect on soluble sugar and total phenol content.4.A laboratory equipment suitable for studying the effect of precise temperature control on fruit quality after harvest was developed.The equipment can compile a multi-stage change control procedures to achieve accurate control of fruit temperature based on the temperature control requirements,and provide equipment support for the study of better post-harvest precooling and transfer-to-shelf strategies.In this study,the equipment was used to achieve precise control of precooling rate and temperature rising rate during transfer-to-shelf treatment. |
