| Wheat bran is the main by-product of wheat flour,which enriches most of the bioactive compounds of wheat kernels.It has great economic value and development prospects.In recent years,the production and consumption of whole-grain foods are developing rapidly.As an important branch of whole-grain foods,the whole wheat flour market has huge potential.Due to the shortcomings of reconstituted wheat bran in terms of safety quality,storage stability,and processing adaptability,this study comprehensively improved the quality of wheat bran and reconstituted whole wheat flour to provide theoretical guidance for the industrial production of whole wheat flour.The main results in this paper were shown as follows:(1)Based on flexible debranning method,the effect of 0-5% debranning rate on the safety quality,milling characteristics and nutrients of wheat kernels were studied,and the effects of traditional flour milling and flexible debranning flour milling on the quality of bran flour in industrial production was compared.The results showed that when the debranning rate was 1.08%,the reduction rate of aerobic plate count was80.11% and deoxynivalenol content was 15.82%.The breakage rate of wheat was0.15% and there was no significant difference in wheat hardness index,moisture and ash content.After the second debranning,there was no significant difference in the reduction rate of aerobic plate count and deoxynivalenol content.Wheat breakage rate gradually increased and the hardness index decreased.The ash content of wheat decreased significantly.The content of alkylresorcinol(ARs)in the pearled fractions increased significantly,and the content of ash and starch gradually increased.Observed from the microstructure of the pearled fractions and the cross-sectional structure of the kernels,1.08% of the debranning thickness was about 25-35 μm,most of the exocarp was debranned,and most of the endocarp and testa remain intact.When the debranned wheat was industrially milled,the bran paticle size was small but the upper limit was almost the same,and the ash content of the three types of flour was reduced.The aerobic plate count and deoxynivalenol content of the three types of flour and coarse and fine bran were significantly reduced,and the aerobic plate count was reduced by 23.02%、25.79%、32.63%、36.94%、41.32%;the removal rate of deoxynivalenol was 16.76%,17.76%,20.75%,16.46%,11.78%.Therefore,the debranning rate of 1.08% could remove the exocarp evenly without damaging testa,effectively reducing harmful pollutants on the surface of wheat and has little impact on grain processing and nutritional quality.In industrial production,this method could maintain the characteristics of wheat milling and obtained safer bran and low-bacterial wheat flour.(2)The bran stabilization system of "steam conditioning-heat preservation inactivation-controllable dehydration" was adopted to optimize the inactivation process parameters,and the first-level kinetic model was used to analyze the inactivation effect of wheat bran lipase.The stabilization process was evaluated according to the change of bran phenol content.The results showed that the inactivation effect of wheat bran lipase increased with the increase of moisture content,holding temperature and time.According to enzyme inactivation dynamic analysis,the value of inactivation rate constant k increased and the value of exponential decrease time D decreased with the increase of moisture content and temperature,indicating that conditioning treatment could effectively reduce the dependence of lipase on temperature.Based on the enzyme inactivation effect and caloric analysis,the optimized process conditions were: 30% moisture content,90℃for 4 hours,the lipase inactivation rate reaches 93.8%,and the residual lipase activity was 0.264 U/g.Under this condition,the free phenol content increased by 46.25%,the combined phenol content had no significant difference,and the total phenol content increased by 9.29%.Therefore,conditioning treatment could improve the efficiency of inactivating enzymes,and heat preservation treatment could reduce energy consumption.The inactivation of enzymes was effective and could fully retain the phenolic substances in wheat bran,indicating that the stabilization system could better meet the needs of industrial inactivation of wheat bran.(3)Study the relationship between the proportion of intact aleurone cell clusters in different sieved components of wheat bran after crushing and storage stability,and clarify the optimal degree of bran crushing,so as to optimize the parameters of the bran grinding by airflow vortex pulverizer.Furthermore,the effects of different processes of bran on the processing quality of whole wheat flour were compared.The results showed that the number of aleurone cell clusters decreased exponentially,the proportion of edge broken cells multiplied and the substance inside the cell leaked with the decreased of the bran size.The aleurone cell structure of the bran under the200-mesh sieve was basically destroyed,and the cell contents were fully leaked.The lipase activity of the bran without inactivated enzymes increased significantly with the decrease of the particle size,and the growth rate of bran fatty acid value increased exponentially.The target component yield obtained by multiplying the yield and the proportion of 80-200 mesh components was used to evaluate the fine pulverization effect.The optimization parameters of wheat bran were: feeder frequency 30 Hz,turntable frequency 50 Hz,and grading wheel frequency 30 Hz.The optimized process has the highest percentage of complete cell clusters in the bran aleurone layer while ensuring the crushing efficiency.In addition,the browning degree of the whole wheat dough sheets was relatively low,it has a certain tensile ability and the adhesion ability was relatively low,and the formation of the gluten network structure was better.Therefore,the higher the proportion of intact aleurone cell clusters after bran was crushed,the lower the fatty acid growth rate,and the higher the storage stability of whole wheat flour.The optimized process of bran was beneficial to improve the processing quality of whole wheat flour. |
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