Studies On Extraction,Characterization And Antioxidan Tactivities Of Polysaccharides From Onion Skin

Onion peel is popular all over the world due to its abundant nutrients and various functional properties,polysaccharides are main active ingredients.In this study,The selected key parameters were optimized using ultrasonic-assisted extraction with Box-Behnken experimental design.To obtain fine polysaccharide of onion skin by decolorization,deprotein,dialysis.The chemical composition,physicochemical and antioxidant of these polysaccharides were systematically studied.The fine polysaccharide was Studied by the infrared spectrum analysis,nuclear magnetic resonance(NMR)analysis,XRD analysis and GCMS analysis method.At the same time,using an onion skin extract liquid to research and development of a kind of wolfberry-onion peel compound beverage,and processing technology.its study results are as follows:1.The optimum conditions of extracting polysaccharides from onion was investigated and identified extraction temperature 87?,solid-liquid ratio 1:41(w/v),ultrasonic time 35 minute,ultrasonic power 160 W,extraction time 80 minute.Under these conditions the polysaccharides extraction rate was 3.385%.2.The contents of total sugar and uronic acid are 58.72% and 10.25% respectively.The solubility of polysaccharide is affected by temperature intensively.When NaCl concentration ranged from 0 to 0.2%,NaCl concentration had a significant influence on the dissolution time of polysaccharides.NaCl concentration ranged from 0.2 to 0.8%,and the dissolution time of polysaccharides was about 12.5 minute.The solubility of polysaccharides in onion skins was obviously weak under strong acid conditions,but with the decrease of acidity,the solubility of polysaccharides was obviously enhanced.3.The constituents of the monosaccharide were determined by gas chromatograpy-mass spectrometry(GC-MS)as: xylose,fructose,mannose,arabinose,rhamnose,glucose and galactose.The content of 1.23%?0.66%?11.35%?3.09%?42.99%?19.97% and 20.72% respectively.The polysaccharide of onion skin contains functional groups such as O-H,CH,CH2,CH3,C=O,C-O,and a pyranose ring,and there are two kinds form which is ? and ?-configuration.The polysaccharides of onion skin are polycrystalline,amorphous structures.4.The polysaccharides of onion peel have strong clearing effect on DPPH radica and antilipid peroxidation,the effect of scavenging DPPH· is more remarkable than that of anti-lipid peroxidation.However,the scavenging effect on superoxide radical and reductive capability was not abvious.In addition,the polysaccharides of onion peel have certain clearing effect on ABTS capability.5.The optimum conditions of wolfberry-onion peel compound beverage:the feeding speed is 260 m L/h,the air inlet temperature is 120?.And the optimal conditions were composed of 2.51% wolfberry juice,11% maltodextrin,0.09% acacia senegal,10.00% white sugar,2.1% citric acid,0.03% CMC-Na,and the powder rate reaches 25.15%.The moisture content,Density,solubility,dissolution time of onion peel beverage powder prepared under this technological condition is 3.95%,0.81g/cm-1,84.5% and 45 s respectively.The polysaccharide content was 5.29% as determined by the phenol-sulfuric acid method.The wolfberry-onion peel compound beverage have a good quality of sensory and dissolve.It is sweet and sour,with a hint of onion-specific aroma and astringent odor.After microbial inspection and pesticide residue detection,the solid beverage accord with national standard.