Gradient Extraction,Structural Characterization And Functionality Of Polysaccharides From Seamum Indicum L.

Sesamum(Sesamum indicum L.),is an important oil plant and a homologous food.Sesame products are of various kinds and rich in nutrition,which are deeply loved by consumers.In the production and processing of sesame products,in order to ensure good edible quality,sesame seeds are mostly separated into two parts: sesame hull and dehull seeds.On the one hand,sesame hull as a by-product is mostly discarded.On the other hand,dehull sesame seeds is mostly used to make oil and produce by-product,or after simple processing directly edible.The abundant polysaccharide components in sesame or its by-products,such as cellulose and watersoluble heteropolysaccharides,which are bound to the cell wall in a very complex form by chemical bonds,have not been thoroughly studied and utilized in high value.Therefore,this dissertation studied the classification,extraction,characterization,and function of polysaccharide from sesame seeds.The main research contents and conclusions are as follows:1.Firstly,the sesame hull was extracted by ultrasound-assisted lye extraction method,and then purified by deproteinization,decolorization and column chromatography.Three groups of polysaccharide fragments(SHP-1,SHP-2 and SHP-3)were obtained,among which the main fragment was SHP-2(58.14%).All the three fragments were heteropolyaccharides with molecular weights of 25213 Da(SHP-1),16925 Da(SHP-2),and 11781 Da(SHP-3).The main monosaccharides were galacturonic acid,arabinose,and xylose.SHP-2 component contained the largest number of monosaccharides and a large amount of uronic acid(65.1%).Through the analysis of nuclear magnetic map and methylation results of SHP-2,the residues of SHP-2 were mainly 4-?-L-Rhap,1,3,4-?-D-Galp A,1,6-?-D-Glcp,1,2-?-D-Glcp A,etc.In addition,SHP-2 and SHP-3 have good free radical scavenging ability.2.Study on the extraction and application of cellulose from sesame hull.In this chapter,the subcritical water method(SW)and the traditional alkali method(AT)were used as pretreatment methods to extract the crude cellulose from the sesame hull,and then the microcrystalline cellulose(MCC)was successfully prepared by acidolysis.The results showed that the infrared spectra of MCC obtained by the two pretreatment methods were basically the same,and the yield of MCCSW-200/60 was similar to that of MCCAT.The crystallinity of all MCCSW samples was higher than that of MCCAT,with smaller diameter and better thermal stability.Therefore,sesame hull is a good material for extraction and utilization of MCC,and subcritical water method also has the potential to replace the alkali method with high pollution.3.Then,for dehull sesame seeds,polysaccharides were obtained by extracting and removing impurities.Five fragments of SMP-1,SMP-2,SMP-3,SMP-4 and SMP-5 were successfully purified,with molecular weights between 8505-268649 Da,which were more widely distributed than SHP.The main monosaccharides were arabinose and galactose.The monosaccharide composition is mainly arabinose and galactose,and the three components of SHP differ greatly.SMP-2 mainly include T-L-Araf(1?,?5)-L-Araf(1?,?3)-D-Galp(1?,etc.and the structure of SMP-2 was preliminarily predicted.In terms of antioxidant activity,SMP-3,SMP-4 and SMP-5 showed better antioxidant activity than the components of sesame hull polysaccharide.The above aspects are different from the purified components of SHP.4.There were also water-soluble oligosaccharides in sesame meal.In this study four oligosaccharide samples were studyed,namely ORPM(oligosaccharide of roasting-pressing meal),OPM(oligosaccharide of pressing meal),OLM(oligosaccharide of leaching meal),OSM(oligosaccharide of subcritical propane meal).Molecular weight was 413 Da,1159 Da,803 Da,754 Da,respectively.The monosaccharide composition was mainly glucose(44.97-60.77%)and some galactose,galacturonic acid and so on.All the four oligosaccharide samples had very good free radical scavenging ability,of which ORPM was most obvious.5.For the cellulose polysaccharides of dehull sesame seeds,different concentrations of lye(0.5,1.0,2.0,3.0 mol/L)were used to extract the product components are mainly cellulose and semi-fiber heterosaccharide components of coarse fiber,and then simulated digestion was performed.The results showed that the surface features,thermal stability,and infrared spectrum of the reduced sugar had some changes before and after digestion,but they were not very significant.In addition,the release of reducing sugar was relatively low(4.8%-5.1%),so it had anti-digestion ability and different lye to get the crude cellulose resistance to digestion capacity is different.In addition,the digestive juice also has a certain free radical scavenging ability.