Dragon Fruit Stem Gel Juice, Polysaccharides, A Preliminary Study

The stem of pitaya contains a variety of plant polysaccharides and minerals,vitamin E and sterols,which can adjust the various functions of the human body,improve human immunity.It has gerat prospects and potential high value.In recent years,it received wide attention from the country and abroad.But the research about the gel preparation and extraction of polysaccharide from the stem of pitaya,the biological efficacy of the gel and the polysaccharide have not been reported.Fresh stem of pitaya was the material for experiment in this paper.First,through a series of orthogonal experiment to determine the optimal extraction method to get the gel from pitaya stem and optimize the process of decolourization and clarification of extracting the gelatin.The optimal technological conditions were as follows:the ratio of solid to liquid was 1:3,extraction time 60min,extraction temperature 45℃,0.05%pectinase.And the best decoloration conditions were:2%of activated carbon,decoloration temperature 60℃,decoloration time 30min.And then,we did some analysis and detection of biological efficacy of the gel from the stem of pitaya.The results showed that in the gel the content of total dietary fiber(TDF-Total Dietary Fiber) was 728.4g/kg;the content of insoluble dietary fiber(IDF-Insoluble Dietary Fiber) was 462.9g/kg;the content of soluble dietary fiber(SDF-Soluble Dietary Fiber) was 193.3g/kg;the activity of super oxide dismutase(SOD-Super Oxide Dismutase) dynamic was 4.416U/mL;the activity of lipase was 2.16U/g;the activity of proteinase was 6.46U/mL;the content of polysaccharide in the gel was 130.48ug/mL;the content ofprotain in the gel was 1619.17ug/mL. DPPH method,pyrogallol and salicylic acid method were used to detect the efficacy of free radical scavenging of the gel from the stem of pitaya.The results showed that a total of DPPH free radical scavenging rate was 48.55%,the superoxide anion radical scavenging rate was 13.96%and the hydroxyl radical scavenging rate was 59.30%.The tyrosinase activity inhibition method was done to determine the effectiveness of the whitening.The result showed the activity of tyrosinase inhibition rate was 21.41%.Through the human body moisture,it was found that its moisture content was higher than the control group,the water loss rate was lower than the control group;imaging system through the skin of young women testing the efficacy of stem pitaya smearing was found that after the gel decreased,skin was roughness.Anti-allergy experiment was done.We found that it could effectively alleviate the situation of skin allergy by comparing the responses to allergens of the skin which used the gel before and after.At last,polysaccharide was extracted from the stem of pitaya by hotwater,enzyme- assisted and microwave-assisted method.Finally the microwave-assisted extraction was proved to be the best one by general evaluation.The results showed that the main factors affecting the yield of polysaccharides in the process of microwave-assisted extraction were sequenced as follows:time＞microwave power＞temperature,the optimal technological conditions were as follows: extraction time 10min,extraction temperature 80℃and the microwave power 200W.The rough Stem of Pitaya Polysaccharide(SPP) was extracted from the fresh stem of pitaya.The content of total polysaccharide in SPP was 27.85%determined by phenol-vitriol method using D-glucose as standard.The content of protein in SPP was 4.61%using BSA as standard.Sevage-protocols were applied to deprotein of the SPP and the optimum condition was obtained by the experiments of orthogonal design.Then the first step purified stem of pitaya polysaccharides (SPPS) was obtained after dialyzation and freezing dryness.Using the optimal technological conditions,the yield of SPP was 1.42%.After purifying,the yield of SPPS was 0.74%.SPPS was analysised by IR,MALDI-TOF-MS and dement analysis technique.It was approved to be a kind of polysaccharide mixture,and the molecuLar weight was between 3900 and 4300.Compared with other biological efficacy,it had great efficacy in moisture retention.This paper will provide a technical reference for the future applications of the stems of pitaya.