High Efficiency Lignin Degradation And Effect Of Wheat Bran Fermented By White Rot Fungus On The Quality Of Noodle

Wheat bran is rich in dietary fiber,so adding wheat bran to noodle is a good way to supplement dietary fiber.However,due to the poor edibility of wheat bran noodle,the acceptability of consumers is low.Therefore,in order to improve the quality of noodle,it is necessary to modify wheat bran.In this paper,white rot fungus which can degrade lignocellulose of wheat bran efficiently,were used to ferment and modify wheat bran,effect of fermented wheat bran on gluten protein characteristics and noodle quality were investigated,so as to provide theoretical basis for improving the quality of wheat bran noodle.Firstly,strain AP3 was screened from white rot fungus that can degrade lignocellulose of wheat bran efficiently.The lignin peroxidase enzyme activity in AP3 fermentation broth was up to 119.42 U/m L,the manganese peroxidase enzyme activity was up to 124.35 U/m L,and the laccase enzyme activity was up to 173.45 U/m L.After 15 days of liquid fermentation by AP3,the degradation rate of lignin reached 36.24%.Secondly.Effects of wheat bran mass concentration,Cu²⁺mass concentration,p H value and shaking speed on the enzyme activity of white rot fungus in liquid fermentation were studied.The optimal conditions for liquid fermentation of AP3 were determined by single factor and response surface tests:the bran mass concentration was 41.5 g/L,the Cu²⁺mass concentration was 1.30 g/L,the initial p H value of the medium was 5.18,the shaking speed was 182 r/min,the laccase activity reached 188.54 U/m L.The degradation rate of wheat bran lignin after optimization was 1.9 times of that before optimization.Then the wheat bran was fermented by AP3 under the optimum liquid culture condition.Mixed wheat flour was obtained by adding fermented and unfermented wheat bran to wheat flour in different proportions.The gluten protein in the mixed wheat flour was extracted and the test samples were obtained.Effect of fermented wheat bran on the characteristics of gluten protein were investigated by analyzing the changes of the free sulfhydryl group and disulfide bond content,secondary structure,molecular weight distribution,microstructure and thermal properties in the gluten.The results showed that compared with the unfermented wheat bran group,the content of free sulfhydryl group in the gluten of the fermented wheat bran group decreased and the content of disulfide bond increased.In the secondary structure,the ratio of?-turn and?-helix increased,the cotent of?-sheet and random coill decreased.Low content of fermented wheat bran?less than 6%?promoted the crosslinked polymerization of gluten proteins.Compared with the unfermented wheat bran group,the pyrolysis temperature of the samples in the fermentation group decreased and the weight loss rate increased.Finally.Effect of fermented wheat bran on the pasting properties and farinograph characteristics of wheat flour,the dynamic rheological characteristics and color of dough sheets,as well as the moisture distribution,tensile characteristics,cooking characteristics and texture characteristics of the noodles were studied.The results showed that compared with the unfermented wheat bran group,the peak viscosity,trough viscosity,final viscosity and setback of the samples in the fermentation group increased,as well as the breakdown and pasting temperature decreased.Fermentation modification had no significant effect on the moisture content and ash content of the samples.Compared with the unfermented wheat bran group,the crude protein content and crude starch content of the samples in the fermentation group decreased.The stability time,farinograph quality index,water absorption and weakening degree of the samples in the fermentation group increased.The fermentation deepened the color of the wheat bran,so the noodle are darker.The values of G',G''and loss factor of the samples increased after fermentation,and the viscoelasticity of the dough sheets were stronger.The creep variables of the sample with 4%fermented wheat bran was higher than that of the unfermented sample,but on the whole,the fermentation modification had no significant effect on the creep variables.Compared with the unfermented group,the A21value of fermented group decreased and the A22 value increased,the cooking loss rate of fermentation group decreased and the water absorption rate of the noodle increased.The pulling force and the pulling distance of the samples in the fermentation group increased.The hardness,chewability,elasticity,resilience,cohesion and adhesiveness of the samples in the fermentation group increased.