Study On Intensification Effects Of Steam Explosion On High-solid Enzymatic Hydrolysis Process Of Wheat Bran And Development Of High-fiber Food

In this paper,the steam explosion technology was innovatively used to modify wheat bran,strengthen its high solid enzymatic hydrolysis process,and applied in the production of high-fiber gluten food,which provided effective technical means and laid a theoretical research foundation for promoting the intensive processing of wheat bran and other grain processing by-products,and has positive significance for the research and development and application of high-fiber gluten food.The main research results are as follows:Firstly,the effects of steam explosion treatment on the basic composition and microstructure of wheat bran were studied.The results showed that steam explosion treatment damaged the porous structure of wheat bran and deepened its apparent color.After steam explosion treatment,IDF content of wheat bran decreased from 43.37%to 36.15%,SDF content increased from 5.45% to 9.75%,with an increase of 78.9%.These results indicate that the hydrothermal cooking and physical blasting in the process of steam explosion can effectively destroy the dense structure of wheat bran and promote the transformation from IDF to SDF in wheat bran.The change of physical structure of wheat bran matrix caused by steam explosion was beneficial to subsequent cellulolytic transformation.Secondly,by studying the product formation,substrate transformation and system rheological changes in the enzymatic hydrolysis process of air-burst wheat bran,the mechanism of air-burst enhanced high-solid enzymatic hydrolysis process of wheat bran was revealed.The results showed that SDF enzymatic hydrolysis rate of air-burst wheat bran was significantly higher than that of raw wheat bran,and increased first and then decreased with the increase of solid load,and decreased gradually with the increase of enzyme content.A fractal kinetic model was established to investigate the conversion efficiency of wheat bran cellulase with solid loading.With the increase of solid loading,the rate constant k and the fractal index h of the enzymatic hydrolysis of air-burst wheat bran decreased.Under the condition of high solid load,the k and h values of wheat bran enzymatic hydrolysis system after steam explosion were 2.58 ～3.30 times and 1.35 ～1.77 times higher than those of raw material system,respectively.In the enzymatic hydrolysis process,with the increase of solid load,the viscosity of enzymatic hydrolysis system increased,and the content and fluidity of adsorbed bound water and capillary water decreased.With the increase of enzymatic hydrolysis time,the viscosity of enzymatic hydrolysis system decreased,and the adsorbed bound water gradually changed to capillary water.The viscosity of high solid enzymatic hydrolysis system was negatively correlated with enzymatic hydrolysis conversion.However,the viscosity of the enzymatic hydrolysis system was always lower than that of the raw material system,and the content of adsorbed bound water and capillary water was higher than that of the raw material system.These results indicate that steam explosion can reduce the viscosity of wheat bran enzymatic hydrolysis system,increase the fluidity and water absorption of the system,promote the enzymatic mass transfer process and improve the enzymatic hydrolysis effect and process efficiency.Thirdly,several strengthening strategies were constructed for the enzymatic hydrolysis process of high solid content of air-burst wheat bran,such as batch feeding of feed enzyme and subsection gradient regulation of oscillation rate.The results showed that under the condition of high solid load,the strengthening effect of batch-feeding and batch-feeding on enzymatic hydrolysis was in the order of batch-feeding > batch-feeding > conventional enzymatic hydrolysis.It was found that the stirring power increased with the increase of solid load.Under the condition of high solid load,the stirring power of enzymatic hydrolysis of raw wheat bran was15.38 times and 47.18 times of that of steam explosion wheat bran.Based on the relationship between the oscillation rate and the conversion rate of cellulase,a stepwise gradient strengthening strategy was proposed.Based on the above research,a numerical model was further established to calculate the mass transfer coefficient during the enzymatic hydrolysis process of wheat bran.It was found that solid load and oscillation rate had good exponential negative correlation and linear positive correlation with the mass transfer coefficient,respectively.Based on the above relationship,the strategy of simultaneous supplementing and gradient oscillation strengthening for feeding enzymes in high solid system was established.Under this strategy,the enzyme hydrolysis conversion rate of high solid system was 1.21 times that of the simultaneous supplementing strategy and 1.72 times that of the oscillation rate gradient strengthening strategy,respectively.Finally,steam explosion,enzymatic hydrolysis and steam explosion combined enzymatic hydrolysis of wheat bran were applied to make high-fiber bread containing gluten,and the effects of different modification methods of wheat bran on bread basic composition,color and texture,texture structure and specific volume,sensory score,in vitro digestibility and hardness during storage were studied.The results showed that the content of SDF increased,the dough color deepened to yellow brown,the pores in the texture structure increased,the specific volume of bread increased slightly,the total score of bread sensory evaluation decreased,the hydrolysis rate of starch in vitro decreased,and the hardness of bread during storage decreased.