Study On Preparation And Functional Properties Of Arabinoxylan Of Millet Bran

Millet Bran is the main by-product in the process of millet production and processing,which rich in protein,fat,dietary fiber and other nutrients.Arabinoxylan(AX)is a major component of millet bran hemicellulose.It has been reported that cereal arabinoxylans possessed various biological activities such as controlling blood sugar level,decreasing blood lipid,anti-oxidation and so on.Currently in the country,the extraction method of AX mainly are the use.Qf alkaline solution and the combination use of alkaline solutions and other substances such as hydrogen peroxide,dimethyl sulfoxide,while enzymatic extraction is rarely reported.But this alkali distillation may damage the structure of AX,or even cause the loss of its physiological activity.It has been confirmed that the method of enzymatic hydrolysis has various advantages such as moderate reaction conditions,strong selection specificity and so on.It should be mentioned that enzymatic procedures are more acceptable from an environmental point of view than the chemical procedures.In addition,ultrasonication has been applied in the course of procedures for extraeting of AX,and was confirmed to improve the extraction efficiency of AX.In this study,we treated millet bran with protease,cellulase and other enzymes to extract water extractable arabinoxylan(WEAX)and water un-extractable arabinoxylan(WUAX),and to compare the study,aimed at providing a solid theoretical basis for the further exploitation and utilization of millet bran.The main research contents are as follows:1.The extraction of arabinoxylan from millet bran.The effects of the fineness and the defatted millet bran to water ratio(g:mL)on the extraction yield of AX were studied.The results showed that the optimum grain size for WEAX was 100 mesh and the material ratio was 1:12,the extraction yield was 0.952±0.003%.The enzymatic extraction method of WUAX1 was determined as follow:treating directly with cellulase followed by xylanase treatment extraction,the extraction yield was 0.208±0.002%;the extraction method of ultrasonication assisted enzymatic hydrolysis of WUAX2 was as following:treating directly with cellulose and xylanse followed by ultrasonication extraction,the extraction yield was 0.224±0.004%.Finally,several deproteinization methods were compared according to the loss rate of AX and the removal efficiency of protein.Then trichloroacetic acid(TCA)-n-butyl alcohol was chosed as the separation reagent of protein,in which the AX loss rate was 3.58 ± 0.12%,the total sugar loss rate was 3.75 ± 0.15%,and the protein clearance rate was 56.77 ± 0.12%.2.The determination of physicochemical properties of the arabinoxylans.The results of monosaccharide composition,molecular weight,infrared spectrum and ultraviolet spectrum of WEAX,WUAX1 and WUAX2 showed that main chains of AXs were composed of xylopyranose,but the compositions of side chain were different.The molecular weight of WUAX was more concentrated,which may also contained a large amount of pectin.Except for high yield,high purity,containing a part of pectin,WEAX may also contain a small part of the polysaccharide.The results of UV spectroscopy were consistent with the results of Bradford method and monosaccharide composition.3.The study of functional properties of arabinoxylans.The usual measurement methods for the determination of polysaccharnde antioxidant capacity were applied,it was found that the scavenging ability of DPPH radical,ABTS+.free radical scavenging ability,iron ion reduction ability of WEAX were stronger than WUAX1 and WUAX2,whereas the metal ion chelating ability of WEAX was weaker.WUAX1 had stronger ABTS+.scavenging ability and metal ion chelating ability as compared with WUAX2,but the iron ion reduction force of WUAX1 was weaker.