Effects Of Low Power Microwave Treatment On Postharvest And Senescence Of Early Maturing Cuiguan Pear

The Cuiguan Pear belongs to precocious sand pear system,which is the main cultivar in southern China.The fruits is well-known by Causal flesh crisp,excellent flavor and comprehensive quality.Cuiguan pear is highly welcomed by consumers.However,Cuiguan pear matures in mid to late July,harvested at hot raining season and is susceptible to deterioration after harvest.The pear's physiological activity is easy to lose water,brittle,flavor fades and aging rot,conventional storage and transportation cycle is only 5-7d.Seriously hinder the fruit market circulation sales.To explore the appropriate storage conditions and preservation methods,it is of great importance for the development of Cuiguan Pear.Low power microwave was used to treat Cuiguan pears,microwave output power were 32.5,65,97.5,130 and 162.5w,the treatment time was 5min,set 1-MCP treatment and no treatment as a control group.The fruit is treated with PE bag and lined with plastic bag.The Cuiguan Pear is stored in a cold storage at 2-4?and RH85-90%.The experiment regularly tests the respiration rate,pulp release rate,pulp hardness,pectinase activity,polyphenol oxidase activity,total phenol content,MDA,relative conductivity,soluble sugar,titratable acid content,peel color,water loss rate,rot rate and other indicators.The experiment studied the impact of the low power microwave treatment on the postharvest mature,aging characteristics and storage quality for Cuiguan Pear,explored the low-power microwave preservation mechanism.The main results of the study are as follow:The study investigated the effects of microwave treatment at different power on the heart temperature of Cuiguan pear.and the output power of microwave treatment at 32.5,65,97.5,130 and 162.5w were determined,all the treatment time was 5minite.The effects of different power microwave on the physiological indexes of Cuiguan pear were studied.The results showed that the respiration rate and ethylene release rate of Cuiguan pear showed a tendency to rise first and then decrease in the storage process.The control group reached the ethylene peak and respiration peak at30 days.Microwave treatment of 65w effectively delayed the increase of respiration rate and ethylene release,reached the peak of ethylene release at 40 days,the peak value was 1.49?L/kg·min.The group reached the peak of respiration at 50 days,the peak value was 10.89 CO₂ mg/kg·h.Compared with the control group,the microwave treated group reduced the peak,indicating that low-power microwave treatment slows down the physiological processes of the fruit.The effects of different power microwave on the softening degree of Cuiguan pear were studied.In the control group,the activity of PG increased rapidly,so the hardness decreased the fastest.The hardness decreased from 7 kg/cm²to 3.37 kg/cm².Microwave power of 65 and 97.5w treatment group PG activity is lower,So the trend of hardness decline is more gentle,always at a high level.In the late storage period,the hardness was maintained at about 4.8 kg/cm².Indicating that low power microwave can inhibit the activity of PG and peak,delay the softening of the fruit.The effects of different power microwave on the browning degree of Cuiguan pear were studied.It was found that the activity of polyphenol and the activity of PPO began to decrease after 30 days storage in Cuiguan pear.Microwave power of 65 and97.5w treatment group in the storage process of polyphenol oxidase activity is low,the total phenol content at a high level,so the degree of browning was significantly reduced,The total phenol content at the end of storage was about 57 ug/g?FW?.The total phenolic content of the control group was only 35.72ug/g?FW?.Indicating that low-power microwave treatment can delay the occurrence of browning.The effects of different power microwave on the senescence of Cuiguan pear were studied.The results showed that the malondialdehyde?MDA?and the relative conductivity were increasing in the storage process of Cuiguan pear,which indicated that the membrane permeability of the membrane increased and the degree of membrane lipid peroxidation was deepened.The control group had a higher level of malondialdehyde?MDA?and conductivity than other treatment groups,the content of malondialdehyde and relative electrical conductivity were 0.87?mol/L and 78%.While the microwave power of 65w and 97.5w treatment group malondialdehyde content and conductivity was significantly lower than other groups.The content of malondialdehyde and relative electrical conductivity were 0.48?mol/L and 63%.To a certain extent,the experiment indicated that low-power microwave protect the integrity of the cell membrane and delay cell membrane damage.The effects of different power microwave on the storage quality and storage efficiency of Cuiguan pear were studied.It was found that the soluble sugar decreased first and then decreased during the storage process,the TA content gradually decreases.The contents of soluble sugar and TA in the control group were significantly faster than those in the other treatment groups,while the microwave power of 65 and 97.5w treatment group decreased slowly,fruits nutrient loss is less.The peel color of L*,a*,and b*of the control group changed greatly,while the microwave treatment of the peel color changes more gentle,maintain the appearance of the fruit quality.The water loss rate of the control group was 10.29%,The decay rate was 26.32%.Microwave power of 65 and 97.5w treatment group of water loss were 8.0%and 8.22%,rot rate control in 6.5%.Indicating that low-power microwave treatment can effectively maintain the good flavor and quality of Cuiguan pear during storage,extended storage period.The microwave treatment with suitable power has a positive effect on the storage and preservation of Cuiguan pear,it can effectively inhibit the fruit respiratory strength,slow down the physiological and biochemical process,maintain high hardness and quality.Maintain high hardness and quality.The best treatment group is65w/5min or 97.5w/5min,after 60 days of storage,it still maintains good commercial and edible value.