Optimisation Of Ultrasound Combined With Enzymatic Extraction Of Arabinoxylan From Wheat Bran

To improve the additional value of wheat by-products and the quality of wheat flour,this study used response surface method to optimize the ultrasound-assisted enzymatic extraction of arabinoxylan from wheat bran.Then the compositions and properties of wheat bran AX,as well as the influences of AX additive amount to two kinds of wheat flour and steamed bread had been researched.The optimum process conditions for the extraction of arabinoxylans from wheat bran were confirmed through single factor experiments and the results were shown as follows: ratio of solid to liquid 1:25g/mL,concentration of enzyme 5g/L,extraction time 90 min,extraction temperature 50 oC,ultrasound power 200 W.Under the condition of extraction temperature 50 oC,ratio of solid to liquid 1:25g/mL,concentration of enzyme 5g/L,extraction time 90 min,extraction temperature 50 oC,ultrasound power 200 W were chosen as the condition of the Box-Benhnken design(BBD)to optimize the ultrasound-assisted enzymatic extraction of arabinoxylan method.After regression analysis and experiment validation,the results showed that the yield of AX could be reached to 17.83% under the optimal conditions: ratio of solid to liquid 1:26g/mL,concentration of enzyme 5.6g/L,extraction time 97 min,extraction temperature 50 oC,and ultrasound power 200 W,which was approached to the prediction of theoretical model.The monosaccharide components of AX had been confirmed by the determination of monosaccharide components and the main components were xylose and arabinose besides a few of glucose and galactose.After ethanol fractionation,the values of A/X were different from each groups,which were lower than A/X values of the wheat bran(1.02~1.07);the highest proportions of AX's weight-average molecular weight in each groups were centralized distribution(1.53×104~2.51×104Da);the dispersion coefficient of A/X value was lower(1.54~1.81);the total phenolic amount in AX was 13.84mg/g;the total antioxidant capacity of AX was 2.84 unit/mg and there was a positive correlation between total antioxidant capacity and total phenolic amount.With the increasing of AX additive amount between 0.1~0.5%,the water absorbtion rate of No.1 wheat flour and high gluten flour were increased and the development time as well as stable time first rise and then decreased,which were reaching maximum at 0.2%.The degree of softening had been decreased.These two commercial wheat four's peak time and pasting temperature were decreased but the values of peak viscosity,trough viscosity,breakdown,final viscosity and setback were all decreased.The proportion of deep-bound water in No.1 wheat flour dough and high gluten flour were both first rise and the decreased..The water freedom degree in wheat flour dough could be decreased slightly with the increasing of AX additive amount.Using SEM could observe that with the increasing of AX additive amount(no more than 0.2%),the protein matrix in these two fermented wheat flour dough became more uniformly continuous but it could also be destroyed because of the excessive additive amount of AX.The proper amount AX could not only decrease the hardness and adhesiveness of these two wheat flour steamed bread and improved their springiness and texture characteristics,but also could decrease the brightness and increase the degree of yellow of steamed bread.The specific volume and sensory evaluation values of steamed bread both reached maximum when the AX additive amount was 0.2% then decreased with the increasing of AX additive amount.