Study On The Mechanism Of Effect Of Arabinoxylan And Its Hydrolysates On Heat-induced Aggregation Of Gluten

In recent years,whole-grain foods have attracted increasing attention due to their good health benefit on the human body.However,the interaction between water-unextractable arabinoxylan(WUAX)in wheat bran and gluten protein resulted in the poor quality of whole wheat foods.However,xylanase could improve the negative effect of WUAX on the functional characteristics of dough.At present,the study on the interaction between WUAX and gluten protein was not complete.Therefore,WUAX was extracted from wheat bran and treated with enzymatic hydrolysis.The molecular weight and physicochemical properties of WUAX and its hydrolysate were determined.Then,the effects of WUAX and enzymatic hydrolyzed arabinoxylan(EAX)on the physicochemical properties of wheat gluten were investigated at different heating treatment temperatures,and the interaction mechanism between WUAX and EAX was analyzed.It was provided a scientific theoretical basis for the quality improvement of whole wheat food and the development of new products.This article main research contents are as follows:First,the water unextractable arabinoxylan of wheat bran was extracted by alkali extraction,the results showed that WUAX with purity of 87.65% and branching degree of0.53 was obtained.The gluten-WUAX system was used to investigate the effect of WUAX on the heat-induced aggregation behavior of gluten proteins.The results showed that WUAX significantly reduced the storage modulus and loss modulus of the gluten.At 95℃,WUAX increased the weight loss rate of the gluten(2.46%),reduced the particle size(66.4%),and increased the free sulfydryl group(47.4%)of the gluten.WUAX enhanced the hydrophobic interaction in the heat-induced aggregation of gluten.Meanwhile,at 95℃,WUAX affected the aggregation of the glutenin subunits,which reduced the content of high molecular weight glutenin subunits(HMW-GS)(21.2%)but promoted the formation of low molecular weight glutenin subunits(LMW-GS)(3.84%)at 95℃.Subsequently,the WUAX was treated by the endo-xylanase.Size exclusion chromatography,dynamic light scattering analysis and rheology were used to analyze the differences in physical and chemical properties of the WUAX before and after enzymolysis.The EAX with the best rheological property improvement effect on gluten protein was selected to study the effects of EAX on gluten protein heat-induced aggregation behavior.The results show that EAX enhanced the storage modulus and loss modulus of the gluten.At 95℃,EAX decreased the weight loss rate of the gluten(2.87%),increased the particle size(34.2%).Meanwhile,at 95℃,the EAX increased the free sulfydryl group(75.6%)of the gluten.EAX could promote the cross-linking and aggregation of gluten molecules by enhancing the hydrogen bond and hydrophobic interaction between gluten molecules,thus induced the formation of HMW-GS(25.0%)and LMW-GS(15.3%).Next,the secondary structure,tertiary structure,and microstructure of gluten proteins and the interactions WUAX and EAX with gluten were evaluated to explore the mechanism of different influences of WUAX and EAX on gluten during the heating process.The results showed WUAX increased the maximum fluorescence intensity and surface hydrophobicity of the gluten,while EAX decreased the maximum fluorescence intensity and surface hydrophobicity of gluten.The van der Waals force and hydrogen bond interaction were the main interactions between WUAX and gluten molecules during heat treatment.At 25℃ and60℃,the interaction between EAX and gluten protein was mainly hydrophobic interaction,while at 95℃,it was mainly van der Waals force and hydrogen bond interaction.Finally,the specific volume of whole wheat bread treated by xylanase(15.1%)was increased significantly,the texture was improved and the porosity was reduced by 19.9%.These results indicated that the EAX,produced after xylanase hydrolysis,could induce the enhancement of hydrogen bond and hydrophobic interaction between gluten protein during the heat-induced aggregation,and reduce the steric hindrance of WUAX,thus xylanase could significantly improve the product quality.