Effect Of Coating Treatment On Quality Maintenance In Postharvest Purple Radishes

The changes of main quality parameters and antioxidant activity in postharvest radishes("xinlimei") stored at different temperatures,the effect of sodium alginate treatment on main quality parameters and antioxidant activity,the changes in quality and antioxidant enzymes and the effect of sodium alginate coating on fresh-cut radishes were investigated.The results were as follows:1.The effects of different temperatures(20℃,10℃,1℃)on quality and antioxidant activity of the radishes were investigated.The results were that reducing sugar and protein contents rapidly decreased and hollowness was occurred.Low temperature significantly inhibited respiratory rate,hollowing incidence and maintained higher reducing sugar, protein,contents,thereby delayed quality loss and prolonged storage life of radishes,there was decline in the content of total flavonoids,Vc and superoxide radical scavenging activity during storage,low temperature inhabit the decline in the content of total flavonoids,Vc and superoxide radical scavenging activity.Total phenolics,anthocyanins content and DPPH radical scavenging activity declined during storage at 20℃and 10℃, while the reverse at 1℃.Low temperature maintained high levels of DPPH radical scavenging activity,superoxide radical scavenging activity and reducing power.Statistical analysis showed a significant positive linear relationship between total phenolics, anthocyanins content and DPPH radical scavenging activity.2.The effect of 0.5%,1%and 1.5%sodium alginate coating on quality and antioxidant activity in "xinlimei" radish during storage at 20℃for a month were investigated.The results showed that the respiration rate,hollowness and decrease of protein,reducing sugar and Vc contents in radish coated with sodium alginate were inhibited.Coating treatment increased DPPH radical scavenging activity,superoxide radical scavenging activity and reducing power and decrease MDA content.In three concentration of the experiment,fresh preserve effect of the radishes coated with 1%sodium alginate was best.3.The changes in quality parameters and antioxidant enzyme of fresh-cut radishes were investigated.The results suggested that the contents of reducing sugar,Vc,protein and amino acids of fresh-cut radishes markedly decreased.Cutting the radishes induced activities SOD,CAT and APX to an extent,stimulated the increase of MDA content and ion leakage,resulted in lipid peroxidation.4.Effect of 1%sodium alginate coating on quality and antioxidant enzyme of fresh-cut radishes was investigated.The results suggested decrease of protein,amino acids,reducing sugar and vitamin c contents coated with sodium alginate of radishes were inhibited. Coating treatment decreased activities SOD,CAT and APX,maintained lower level of membrane permeability and MDA content,thereby prolonging the storage of cutting radishes.