Study On Processing Characteristics Of Pentosan From Corn Stalk

Pentosan has unique physicochemical properties and functional properties and has been attracted much attention.But most of the research focused on the grain by-products such as wheat bran,and the research and application of pentosan derived from hemicellulose in agricultural and forestry wastes were few.In this study,pentosan was extracted from corn stalk by alkali method,and the structure and properties of pure pentosan were analyzed.The effect of corn stalk pentosan on the properties of wheat dough was studied,and its effect on dough system was clarified.Meanwhile,the effect of corn stalk pentosan on the baking quality and aging degree of bread were evaluated,and the interaction mechanism between corn stalk pentosan and macromolecules in dough was preliminarily investigated.The main contents and results are as below.The optimal of extraction condition of pentosan from corn stalk was studied by single factor and orthogonal experiments.The results were as follows:the concentration of Na OH was 10%,the solid-liquid ratio was 1:30（g/m L）,the reaction temperature was 70°C,and the reaction time was 6 h,and the extraction yield was 26.53±0.54%.The homogeneous component was purified by DEAE-Cellulose-52 and Sepharose CL-4B,and its M_wand polydispersity were 3.24×10⁶Da and 1.03,respectively.On this basis,the structure and physicochemical properties of Corn Stalk Pentosan I（CSPI）were studied by HPLC,GC-MS,FTIR,NMR,rheometer and chemical analysis.The results showed that CSPI was mainly composed of Ara,Xyl,Gla and Glc,and the molar percentage was17.97:62.44:10.61:8.98.The main chain was formed by 1→4-Xylp and 1→3,4-Xylp,and1→5-Araf was the main side,1→4-Galp and non-reducing terminal glucose residues were also attached to the side chain,showing a typical pentosan structure.CSPI does not have a triple helix conformation,and its solution was a typical pseudoplastic fluid.It has certain scavenging ability of DPPH free radical and ABTS⁺free radical with IC₅₀of 0.41 mg/m L and 0.39 mg/m L,respectively.The effects of corn stalk pentosan on flour gelatinization properties,dough rheology,tensile and texture properties were studied by Braband viscosimeter,rheometer and texture analyzer.The results showed that with the increase of pentosan,the peak viscosity,disintegration value and recovery value of flour decreased,indicating that pentosan can improve the stability and shear resistance of flour,and inhibit the recovery.The G’and G’’increased,and the elastic characteristics were more obvious.The hardness,tensile resistance and tensile area of dough increased,while the ductility decreased,suggesting that the interaction between pentosan and gluten could promote the formation of gluten network and improve the crosslinking stability.However,excessive pentosan can interfere with the hydration and development of gluten,inhibit its extension,form large aggregates,and destroy the structure of gluten network.The effect of corn stalk pentosan on bread quality was studied by means of texture analyzer,color difference analyzer,X-ray diffraction analyzer and chemical analysis.The results showed that pentosan could reduce the baking loss rate of some bread,and significant increase the water content of all the bread.2.0%and 3.0%pentosan could signigicantly reduce the hardness of bread core.3.0%pentosan could slightly deepen the color of the bread core and increase the internal large pores.During the storage period,the water loss rate,hardness growth rate and relative crystallinity of bread added with pentosan decreased,indicating that adding appropriate amount of pentosan can effectively inhibit aging phenomenon and prolong shelf life.In addition,pentosan reduced starch hydrolysis rate by 7.22%and glycemic index by 6.84%.FTIR,SEM,CLSM,LF-NMR and DSC were used to investigate the interaction mechanism between pentosan and gluten.It could be seen from the results that the content of theβ-sheet increased and the contenr of theβ-turn decreased with the increase of corn stalk pentosan.And the content of free water in the dough was reduced and the water mobility was reduced overall.The observation results of dough microstructure showed that the dough was firmer with 0.5%and 1.0%pentosan and 3.0%addition can make starch particles fall off obviously.The addition of corn stalk pentosan adversely affected the thermal stability of wheat dough.On the one hand,the strong oxidative crosslinking and water holding capacity enhance the interaction between pentosan itself and gluten,and the degree of protein aggregation increases,the network structure is more continuous and firm,and the whole system is more stable and orderly.On the other hand,the corn stalk pentosan in this paper has high molecular weight and low degree of substitution,so it has higher molecular flexibility,stronger self-cross-linking ability and is more likely to form large aggregates.Excessive addition will affect its interaction with gluten,resulting in internal structure instability and unable to fully form continuous gluten network.