Study On Extraction And Isolation,antioxidant Activity And Bifidobacteria Proliferation Of Polysaccharides From Purple Sweet Potato

Purple potato,an herbaceous plant of the spinosaur family,contains vitamins,amino acids,minerals,anthocyanins,polysaccharides and other active substances.At present,the research on purple potato is mainly concentrated on anthocyanins,and the research reports on purple potato polysaccharides are still relatively small,therefore,this project selects purple potatoes of violet varieties as raw materials,enzymes extract purple potato polysaccharides and optimizes the response surface process,and characterizes and analyzes the structure of purple potato polysaccharides by infrared,electron microscopy,XRD and thermogravimetric methods,Then the graded alcohol deposition is carried out by 3 different gradients of ethanol,The chemical composition of each alcohol sedimentation component,the ability to scavenging free radicals,the antioxidant capacity and stability of rapeseed oil were analyzed.Correlation analysis and principal component analysis of each index were carried out,Finally,the proliferative effect of purple potato polysaccharide on three bifidobacteria species was explored.The main conclusions are as follows:(1)The optimal extraction conditions were as follows:enzyme dosage 2.5%,extraction temperature 50 ℃,extraction time 180 min,pH 3.5,the yield of purple sweet potato polysaccharide was 9.53%.Much higher than water extraction and alcohol precipitation.By scanning electron microscopy and XRD diffraction,it was found that the purple potato polysaccharides were loose powder structure.It was found that purple sweet potato polysaccharide had characteristic absorption peak of polysaccharide by infrared spectrum,and the thermal stability of purple sweet potato polysaccharide was studied by thermogravimetric analysis.The results showed that purple sweet potato polysaccharide had three weight loss stages,and the weight loss was mainly caused by water loss at 40～170 ℃.When the temperature was between 180 ℃ and 300 ℃,the hydrogen bond within the polysaccharide molecule might be broken,while the weight loss around 300 ℃ and 500 ℃ might be caused by the decomposition of a large number of polysaccharide molecules.(2)Three components,PPSP-40%,PPSP-60%and PPSP-80%,were obtained by fractional alcohol precipitation.PPSP-80%had the strongest scavenging ability on DPPH,ABTS and superoxide anion radical,PPSP-60%had the strongest scavenging ability on hydroxyl radical,and PPSP-40%had the worst scavenging ability.The three alcohol-precipitate fractions can also reduce the contents of hydroperoxide and malondialdehyde in rapeseed oil,and also have a certain antioxidant effect,the best effect is PPSP-80%,the second is PPSP-60%,the worst effect is PPSP-40%.The stability test results showed that PPSP-40%had the worst stability,PPSP-60%had the best stability under extreme alkaline conditions,and PPSP-80%had the best stability at 121 ℃.According to the formula of principal component analysis model,the comprehensive score of each alcohol sediment component was calculated as PPSP-80%>PPSP-60%>PPSP-40%,indicating that PPSP-80%has good research and application value.(3)The PPSP-80%has a certain proliferation effect on the three kinds of bifidobacteria,and the optimal addition level is 2%.Through the analysis of the changes of OD value and reducing sugar content in the fermentation process of the three kinds of bifidobacteria,it is found that the OD value of bifidobacteria increases gradually from 0 to 36 h,and the reducing sugar content decreases gradually,indicating that the growth and reproduction of bifidobacteria are faster from 0 to 36 h,and that from 36 to 48 h,The OD value tends to be stable,and the reducing sugar content no longer decreases,indicating that the growth and reproduction of bifidobacteria youth is inhibited from 36 to 48 h,and the OD value of bifidobacteria youth is the largest.By measuring the conductivity of fermentation liquid,it was found that the three bifidobacteria used glucose and PPSP-80%conductivity were almost the same,indicating that PPSP-80%did not damage the integrity of bifidobacteria cells,proving that PPSP-80%could be used as the carbon source for the growth of the three bifidobacteria.Through to the fermented liquid and the organic acid content and pH,live index PI analysis,found that three kinds of bifidobacteria fermented liquid are acidic,and youth bifidobacterium produce acid,most lowest pH,the largest also,live index shows PPSP-80%for three kinds of the proliferation of bifidobacterium has certain effect,and the youth bifidobacterium proliferation effect best.