Effects Of Hydrogen-rich Water And Vacuum Cooling On The Nutritional Quality Of Postharvest Pakchoi (Brassica Chinensis L.)

Pakchoi(Brassica chinensis L.)contains a variety of nutrients,which is deeply loved by consumers.However,due to the large surface area and vigorous respiration of pakchoi leaves,they are easy to lose water,wilt,yellow and age after harvest,thus shortening their shelf life.Therefore,it is particularly important to develop an effective preservation technology.Based on it.In this experiment,the pakchoi was used as the test material.Firstly,the effect of storage temperature on the shelf life span and nutritional quality of pakchoi after harvest was studied,The maximum storage period of pakchoi at different storage temperatures was defined.In addition,research and development of a hydrogen-rich water(HRW)treatment to delay the senescence of pakchoi after harvest and explore its influnce of HRW on the aging in pakchoi from the perspective of chlorophyll metabolism;The effect of HRW combined with vacuum cooling on oxidation resistance of postharvest pakchoi was explored.The main research results are as follows:(1)Under different temperature conditions,the aging process of pakchoi is different.Under the condition of relative humidity of 85% ~ 90%,the changes of storage life and nutritional quality of pakchoi after harvest under different storage temperatures(0,5,10,15,20,25 and 30 °C)were studied.The results showed that 15 °C was the inflection point temperature for the storage of pakchoi,When the temperature was less than 15 °C,the shelf life of pakchoi was significantly prolonged,while T > 15 °C,the shelf life was significantly shortened.When the storage temperature was 0 °C,pakchoi appeared chilling damage on the 22 nd day and slight yellowing on the 40 th day.(2)Through phenotypic changes,the suitable concentration and time for hydrogen-rich water(HRW)treatment of pakchoi were screened,and the optimal condition for HRW soaking pakchoi was determined to be 50% soaking for 10 min.The treatment condition can inhibit the activities of Chlase,MDCase,PPH and PAO during chlorophyll degradation,delay chlorophyll degradation,maintain the content of chlorophyll and its derivatives in pakchoi leaves,The key factors of HRW in the control of the aging of cymophilization in postharvest pakchoi were identified.(3)Vacuum cooling can quickly remove field heat.The parameters of vacuum cooling in this study are: final pressure 800 Pa,initial temperature 24 °C,final temperature 6 °C,time 30 min,and water replenishment rate 6%.These conditions have obvious effect on maintaining the nutritional quality of pakchoi.But vacuum cooling alone can easily lead to the loss of water indicated by the vegetables.On this basis,combining vacuum cooling with HRW treatment,the effect of 50% HRW immersion for 10 minutes combined with vacuum cooling on the antioxidant activity of pakchoi was studied.The results showed that HRW combined with vacuum cooling could reduce the accumulation of MDA content,maintain high antioxidant components(carotenoids,lutein,and total phenolic),inhibit the decrease of antioxidant enzyme activity(GR,CAT and SOD),and improve the scavenging rate of DPPH,and ?OH.HRW combined with vacuum cooling can not only avoid the water loss of pakchoi surface,but also have a significant regulatory effect on its aging,realizes the organic combination of preservation and cooling technology.In summary,HRW can delay the chlorophyll metabolism of postharvest pakchoi,and HRW combined with vacuum cooling can improve the antioxidant of postharvest pakchoi green,avoid the side effects of vacuum precooling,and provide potential technical support for postharvest pakchoi preservation.