Effects of high CO2 shock treatment on physiological metabolism and quality of postharvest blueberry fruits

In order to explore the effects of high CO2 on physiological metabolism of postharvest blueberry fruits as well as the?mechanism, fresh blueberry fruits were put in 99.9% CO2 condition for 48 h, 96 h and 144 h, respectively. Then the fruits were moved into a polyethylene film bag with a slackened tie storage at 1℃. During the period of storage, fruit flavor index, respiration rate, rot rate, respiratory quotient, ethanol content in pulp and pH value were measured. Meanwhile, the activities of some free radical scavenging and formation-related enzyme such as polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT) and lipoxygenase (LOX) were analyzed. The results indicated that the pH value in pulp and fruit rot rate were significantly decreased, fruit firmness was well maintained, the storage period was effectively extended to 50 days, POD activity was increased and the LOX activity was decreased after the high CO2 shock treatments for 48 h and 96 h. The results indicated that the treatments slowed down the rate of metabolism and maintained the fruit quality of blueberry fruits. In contrast, 144 h high CO2 shock treatment caused irreversible damage, resulting in anaerobic respiration, off-flavor and fruit rot. It is suggested that as a shock-impact method, high CO2 shock treatment may be used before the storage of blueberry fruits to inhibit the physiological metabolism and maintain the fruits quality.