Peel Pectin Extract,Pulp Polysaccharides Separation,Purification,Structure Analysis And Biological Activity Studies From Seed-used Watermelon

In order to improve the comprehensive utilization value of the seed-used watermelon,the pectin extraction method of the seed-used watermelon peel was optimized,and the polysaccharide extraction,purification,antioxidant activity and structure of its pulp were studied.The results are as follows:1.The best extraction methods of pectin by traditional acid hydrolysis method were as follows:water bath temperature 90?,pH value 1.5,the heating time of 150min,Solid-liquid ratio than 1:40,the yield of pectin is15.25%;The best extraction methods of pectin by microwave assisted method were as follows:Solid-liquid ratiol:50,microwave power 500w,microwave time 7min,pH value 1.5,the yield of pectin is 19.37%;The best extraction methods of pectin by ultrasonic assisted method were as follows:ultrasonic time 50min and solid-liquid ratio 1:40,pH value 2,ultrasonic temperature 50?,ultrasonic power 120w.Ultrasound-assisted extraction was the best method for pectin extraction,the yield of pectin is 19.94%.This method was used to extract pectin from seed-used watermelon rind of different varieties of seed-used watermelon.Results the variety with the highest pectin yield was daeba red seed melon(radiolabular net),with a yield of 19.26%.2.The best extraction technology of crude polysaccharide is:3.5h extraction temperature 95?,extraction time,Solid-liquid ratio than 1:100,At this time,the polysaccharide yield was 2.30%,The variety with the highest crude polysaccharide yield was daoxian red seed-used watermelon(6.30%).3.The results of in vitro antioxidant tests of refined polysaccharides showed that the refined polysaccharides of every variety of seed-used watermelon flesh had scavenging effects on hydroxyl radical,superoxide radical and DPPH radical.Comprehensive comparison showed that the antioxidant activity of Zhengzhou seed-used watermelon and Daoxian red seed-used watermelon was stronger.4.The refined polysaccharides of Zhengzhou seed-used watermelon and Daoxian seed-used watermelon were obtained by DEAE Sepharose Fast Flow cellulose column chromatography.Z-SI,Z-SII,Z-SIII and D-SI,D-SII,D-SIII,and Z-SI and D-SI had the highest polysaccharide content.5.The antibacterial effect of Z-SI and D-SI was determined.The results showed that the two polysaccharides had no inhibitory effect on Rhizopus oryzae and Aspergillus niger,and the inhibitory effect on Staphylococcus aureus,Bacillus subtilis and Escherichia coli was not obvious.It had an inhibitory effect on yeast,and the inhibitory effect was enhanced as the concentration of polysaccharide increased.6.Z-SI and D-SI have molecular weights of 1747 Da and 1798 Da,respectively,as determined by high performance liquid chromatography.Z-SI monosaccharide constitute and their percentage content were:mannose 2.4%,rhamnose 2.2%,galacturonic acid 6.6%,glucose 36.8%,galactose 32.1%,xylose 7.2%,arabinose 12.7%The D-SI monosaccharide constitute and its percentage content were:mannose 4.7%,rhamnose 8.9%,galacturonic acid 5.9%,glucose 15.4%,galactose 41.7%,xylose 7.5%,arabinose 15.7%.7.The results of IR and NMR showed that the structure of Z-SI and D-SI were similar,and they were complex heteroglycan compounds composed of various monosaccharides,in which glucose and galactose were a-D,mannose was ?-D,and rhamnose was ?-L.