Effect Of Low Power Microwave Treatment And Hypobaric Treatment On The Resistance To Antioxidation And Softening Of 'Kyoho Grape'

Kyoho grape is an excellent fresh food species owing to its large fruit,sweet taste,easy cultivation and adaptability;it is widely loved for its rich nutrition,sweet juice,and delicious taste.As early as in 2007,the grape planting area in China reached 438,400 hectares,with a yield of 6,697,000 tons.Now it has become one of China's five largest fruits,and more than 65% of the grapes will be eaten fresh.At present,the world's viticulture area is nearly 80 million hectares,and the output has reached 60 million tons,accounting for about 20% of the world's total fruits,ranking second in the world.However,because of its large fruit size and short fruit brushing,problems such as easy falling,dry stemming,water loss,rot,etc.,have a serious impact on the storage period and storage quality.Therefore,the search for suitable storage conditions and preservation methods is of great significance to meet the needs of the market for Kyoho grapes.This paper studied the effect of low power microwave pretreatment,decompression pretreatment,ultra-low pressure pretreatment and different pressure continuous decompression storage methods on the preservation of Kyoho grape,through the regular detection of malondialdehyde(MDA),Peroxidase(POD),polyphenol oxidase(PPO),pectinase(PG),cellulase(Cx),anthocyanins,total phenols,DPPH radical scavenging rate,superoxide anion radical scavenging rate,The primary pectin and soluble pectin and other indicators were used to preliminarily investigate the effect of low power microwave pretreatment,decompression pretreatment on the storage quality of Kyoho grape,and ultra-low pressure pretreatment,and the effects of different pressure continuous decompression storage on the softening and antioxidation of grape.1)Kyoho grapes were treated with low-energy microwaves with powers of 0 W,32.5 W,65 W,97.5 W,and 130 W,respectively,and stored at 0-2 °C.The results showed that the low-power microwave treatment of 97.5 W and below had a positive effect on grape freshness,and could significantly delay the maturity and senescence of Kyoho grapes.Among them,the microwave treatment effect of 32.5 W was the best.Compared with the control group at the end of storage,low-energy microwave treatment inhibited the rapid increase of malondialdehyde content,making the DPPH radical scavenging rate of the treatment group about 33 % higher than that of the control group.The particle rate was reduced by 10 %,and the polyphenol oxidase(PPO)and peroxidase(POD)enzyme activities were reduced by about 1/3.2)Using the crisper as a convenient and movable decompression device,Kyoho grapes were subjected to hapobaric pretreatment(70 kPa)for 0 d,1 d,2 d,3 d and 4 d,respectively,followed by refrigeration.The results showed that decompression pretreatment inhibited the rapid increase of weight loss rate and DPPH free radical clearance in different degrees.Among them,the decompression 3 d treatment group had the best effect,and its polyphenol oxidase(PPO)and peroxidation at the end of storage.The POD enzyme activity was only about 2/3 of the control group,the malondialdehyde content was 1/4 less than the control group,and the shattering rate was only 1/2 of the control group.3)Using a vacuum dryer(equipped with a pressure gauge)to pretreat Kyoho grapes at 0,2,4,6,and 8 days at ultra-low pressure(15 kPa),and then refrigerate at 0-2 °C for 32 days.The results showed that ultra-low pressure pretreatment could inhibit the increase of polyphenol oxidase(PPO)and peroxidase(POD)activity without causing degradation of anthocyanins.In the different treatment groups,only the 3 d group was stored under reduced pressure.The clearance rate of superoxide anion radicals at the end of the study was significantly higher than that of the control group(P<0.05);the total phenolic content was higher than that of the other groups,which was about 27 % higher than the control group(P<0.05).The ultra-pressure decompression pretreatment can inhibit and delay the decrease of total phenolic content of grape.4)Set four pressures of 15 kPa,45 kPa,70 kPa,and 101 kPa,respectively,and periodically(every 2 days)conduct vacuum ventilation on the vacuum dryer(with pressure gauge).Analyze continuous low-pressure storage of Kyoho grape softening during cold storage.The results showed that the continuous low pressure treatment could delay the softening of grapes during the cold storage,and the 45 kPa effect was the best.At the end of storage,the activities of PG enzyme and Cx enzyme were significantly lower than those of the control group,and the fruit firmness and protopectin content were also significantly higher than those of the control group(P<0.05).It has been demonstrated that continuous low-pressure storage can slow the softening of Kyoho grapes during storage.