| The brassica pekinensis is crisp and contains rich nutritional value,which is loved by consumers.Postharvest brassica pekinensis has a strong respiratory metabolism,which is prone to water shrinkage,detachment and decay during storage.This brings great challenges to storage.Therefore,in order to promote the industrial development of brassica pekinensis and maximize the economic benefits of their cultivation,it is necessary to explore and improve the storage,transportation and preservation methods of brassica pekinensis and delay the post-harvest quality deterioration process.Modified atmosphere preservation and 1-MCP are currently well-developed postharvest preservation techniques that have been widely used to improve the storage quality of fruits and vegetables and other agricultural products and extend the shelf life of commodities.Therefore,in order to provide a reference for the practical application of post-harvest storage and preservation technology of brassica pekinensis,this article uses modified atmosphere packaging technology and 1-MCP for post-harvest treatment of brassica pekinensis,and analyzes the preservation effects of these two technologies on brassica pekinensis from the changes in quality,nutritional composition and antioxidant resistance during storage.The main research contents and results are as follows:(1)Under normal temperature(23 ± 2)℃ and 80～90%relative humidity,4 different thickness polyethylene films(10,20,30,40 μm)were used for packaging brassica pekinensis,took the commercially available PVC packaging as a control,the best packaging materials were selected through phenotypic observation,sensory evaluation,quality indicators and enzyme activity measurement.Afterwards,the most suitable film material was taken as the research object to further explore the effects of this material on the storage quality of brassica pekinensis under the shelf temperature(15 ± 2)℃.The results show that the 30 μm thick polyethylene film packaging material has the best preservation effect on brassica pekinensis under normal temperature storage.When stored to 28 days,the soluble sugar,protein and MDA contents are 13.49 mg/g and 3.79 mg/g,1.51 μmol/g,respectively.The activity of CAT,POD are as high as 51.87,775.2 U/g.During storage at shelf temperature,this material also has a good fresh-keeping effect on brassica pekinensis,which is mainly reflected in the effective inhibition of the growth of the total number of bacterial colonies on the surface of brassica pekinensis,and the maintenance of higher ascorbic acid,total phenol,soluble sugar,total glucosides,sulforaphane and MYR activity in tissues.As a result,the decay is slowed.On the 40th day of storage,the brassica pekinensis in the film packaging group still had commercial value.Compared with the control group,the shelf life was extended by 20 days.The contents of ascorbic acid,total phenol,soluble sugar,total glucosinolate,sulforaphane and the activity of MYR were 179.6,117.4,237.3,222.2,167.5,and 113.8%of the control respectively.In addition,the results of the comprehensive evaluation of the principal component method also showed that the 30 μm thick film packaging is ideal for slowing the deterioration of the quality of brassica pekinensis,and it is the suitable material for packaging,storage and transportation of postharvest.(2)In order to screen out the appropriate silicon window area,the brassica pekinensis was stored at(20±1)℃ and 80～90%relative humidity.The phenotype different of brassica pekinensis were selected as the evaluation standard.It was found that the embedding of 0.25 cm2 silicone rubber film can effectively inhibit the browning of the root of brassica pekinensis.Afterwards,the impact of the 0.25 cm2 silicon window areas on the freshness of brassica pekinensis was explored.The control was the polyvinyl chloride packaging in the market and also compared with the 30 μm PE film packaging.The results showed that:compared with the control group,silicon window air conditioning and film packaging all have obvious fresh-keeping effects,and the good appearance quality of brassica pekinensis was still maintained when stored for 20 days.At the same time,the modified atmosphere packaging of the silicon window delayed the decrease of the total phenol,ascorbic acid,isothiocyanate and anthocyanin contents,but the packaging treatment of the two groups had no obvious inhibitory effects on the accumulation of CO2 content,and the respiratory rate of brassica pekinensis only showed a significant difference from the control group on the 20 th day of storage.However,the use of silicon window atmosphere control can effectively suppress the browning of the root of the brassica pekinensis,keep the O2 concentration in the box at a high level of 15%,and maintain the higher antioxidant capacity of the brassica pekinensis tissue.The L*value and b*value of the roots were 103,105 and 122,120%of the film packaging group and the control group respectively.The removal rates of DPPH,hydroxyl radicals and superoxide anion radicals were 109,115,and 128%of the film packaging group respectively.Therefore,modified atmosphere packaging with silicon windows can maintain the higher nutritional quality of brassica pekinensis than film packaging.(3)Under the condition of(20 ± 1)℃,60～70%relative humidity,with the same volume of distilled water fumigation as the control(CK),the post-harvest storage quality and anti-oxidation of brassica pekinensis under the treatment of 1 μL/L 1-MCP fumigation were studied.The results showed that 1-MCP treatment can delay the decline in the appearance quality of brassica pekinensis during storage,maintain the loss of cell membranes,reduce the loss of nutrients,and improve the antioxidant capacity.Thereby,the good storage quality was matained.After 24 days of storage,the brassica pekinensis still has commercial value.Compared with the control group,1-MCP effectively inhibited the increase of the respiratory intensity the production of O2·-and the accumulation of MDA and H2O2 contents of baby cabbage;delayed the decrease of soluble sugar,protein and total glucosinolate content;Kept high contents of total phenol,ascorbic acid,carotenoids and sulforaphane.On the 24 th day of storage,the respiration rate,MDA,and H2O2 contents of the chickweed of the 1-MCP group were 73.50,81.87,and 88.7%of the control;soluble sugar,protein,and total glucosinolate contents were 160.2,114.3,and 134.3%of the control;The contents of total phenol,ascorbic acid,carotenoids,sulforaphane were 114.2,123.2,161.4,134.1%of the control.Correlation analysis showed that during storage of brassica pekinensis,DPPH,hydroxyl radical scavenging rate and the four major antioxidant enzymes(POD,CAT,SOD,APX)reached a very significant positive correlation level(P<0.01),while the content of antioxidant substances was significantly positively correlated with DPPH,hydroxyl radical and reducing ability.In summary,1-MCP treatment can maintain the storage quality of brassica pekinensis after harvest and is closely related to maintaining a high antioxidant capacity in the tissue.The antioxidant capacity during storage and the level of active oxygen metabolism are jointly affected by antioxidant enzymes and non-enzymatic antioxidants. |
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