The Effects Of Storage Conditions And Ripening Treatment On The Quality Of The Two Stalks And The Antioxidant Activity Of The Stalk Extract

This study was focused on two kinds of edible dasheen petiole(green petiole,purple petiole)to investigate the change of different month on the nutritional components and active components,as well as the changes in quality of two kinds of edible dasheen petiole during postharvest storage and different cooking treatments on the nutritional components and active components of two kinds of dasheen petiole.Additionally,the experiment is designed to apple response surface analysis method to study the best extracting method of the total phenolic in two kinds of dasheen petiole,and the antioxidant activity of different solvent extracts of dasheen petiole was measured.The aim of this study was to provide a theoretical basis for the promotion of the specialty vegetable dasheen petiole,and to provide a good reference for the further study of the nutritional f-unction of the dasheen petiole and the development of new products.The main research results were as follows:(1)The nutrients of two kinds of dasheen petiole were various,but great difference in content.The moisture,chlorophyll and the content of mineral elements Ca of green dasheen petiole were higher than that of purple dasheen petiole in 6-10 months,while the the content of crude fiber,total flavonoids,total phenolic,and mineral elements Mn of purple dasheen petiole were higher than that of the green dasheen petiole.The vitamin C,chlorophyll,total phenol and the content of mineral elements Ca,Fe,Cu and Mn of green dasheen petiole reached the maximum in August,and the total flavonoids,protein and the content of mineral element S,P,Mg and Zn reached the maximum in July.The total pheno and the content of mineral elements P and K of purple dasheen petiole reached the maximum in August;The total flavonoids,soluble sugar and the content of mineral elements S and Cu reached the maximum in July.In view of the change of the nutrient,the best harvest time of two kinds of dasheen petiole was in 7?8 month.(2)The dynamic changes of the contents of weight loss,vitamin C,soluble sugar,soluble protein,total phenol,total flavonoids and nitrate of two kinds of edible dasheen petiole which were storaged under different conditions were determined.The results showed that sealing storage at low temperature(4?)compared with normal temperature(25?)scaling,normal temperature exposure,low temperature exposure could significantly slow the content of the vitamin C,soluble protein,soluble sugar,total flavonoids of two kinds of dasheen petiole,maintain the weightlessness rate at a lower level,reduce the nitrite content of two kinds of dasheen petiole.under cold(4?)and scaled environment can maintain the sensory quality of dasheen petiole,reduce the loss of nutritional components,slowdown the quality decrease of dasheen petiole effectively,and extend the shelf life.(3)Results showed that the two kinds of dasheen petiole's hardness,protein,Vitamin C,Chlorophyll and soluble dietary fibre reduced after being boiled,stir-fried and stewed.The content of available carbohydrates and the mineral of S?P?K?Mg?Ca?Fe?Cu?Mn?Zn all went down after being boiled and stewed.The total phenol and flavonoids content of two kinds of dasheen petiole treated by frying rised.The free radical scavenging capacity of DPPH of green dasheen petiole treated by boiling and,frying changed from the fresh sample of 62.30%up to 68.00%and 72.29%respectively.However,the DPPH's free radical clearance of purple dasheen petiole treated by boiling and stewing decreased to 40.67%and 31.96%.(4)Ethanol-ultrasonic assisted extraction of total phenol from two dasheen petiole.During the extracting process,four main factors including the concentration of ethanol,ratio of solid to liquid,ultrasonic extraction time and ultrasonic extraction temperature were studied by using single factor analysis method.Employing response surface methodology,the optimum technological conditions for extracting total polyphenols in green dasheen petiole were obtained that ethanol volume fraction was 56.6%,solid-liquid ratio was 1:20.05(g/mL),ultrasonic extraction temperature was 63.87?,ultrasonic extraction time was 30.01 min,and the extraction yield of total polyphenols in this condition was 7.84%;While the optimum extraction conditions in purple dasheen petioles were that ethanol volume fraction was 36.67%,solid-liquid ratio was 1:17.37(g/mL),ultrasonic extraction temperature was 70.49 ?,ultrasonic extraction time was 28.76 min,and the extraction yield of total phenol in this condition was 9.95%.(5)To determine whether the petroleum ether,chloroform ether,ethyl acetate,n-butanol and water fractions of two kinds of dasheen petiole have antioxidant activity,evaluated DPPH free radical scavenging activity,ABTS radical scavenging,total antioxidant activity and potassium ferricyanide reduction of them.The results showed five fractions from dasheen petioles exhibited the antioxidant activity.ethyl acetate fraction exhibited strongest antioxidant activities among all the fractions.The total phenol content extracted by ethyl acetate extract from two kinds of dasheen petiole in different solvent extraction were highest,which respectively were 34.35 mg/g and 49.10 mg/g in green and purple dasheen petioles.