Lactic Acid Bacteria-Aspergillus Oryzae Complex Fermentation Of Wheat Bran And Its Application In Noodles

Wheat bran is rich in dietary fiber,protein,Vitamins B and phenolic active substances,etc.In recent years,with the diversification of residents’dietary structure and the increase of people suffering from hypertension,hyperlipemia,hyperglycemia,cardiovascular and cerebrovascular diseases,the demand for products containing wheat bran is increasing.However,the content of insoluble dietary fiber in wheat bran is too high,and it contains some bitter flavor substances such as n-hexal and acetone.Direct addition of wheat bran will deteriorate the sensory quality of the product.In this study,wheat bran was treated by microbial fermentation to degrade cellulose and improve the quality of flour products.The main research results are as follows:（1）Solid fermentation of wheat bran was performed using L.plantarum,L.rhamnosus,P.pentosaceus,and L.buchneri,respectively.Wheat bran was sampled at an interval of 8 h.The dynamic changes of SDF,crude protein,starch,TP,phytic acid and DPPH free radical scavenging capacity during wheat bran fermentation were studied.The results showed that four lactic acid bacteria grew rapidly in wheat bran substrate within 24 hours.The content of soluble dietary fiber in wheat bran was increased significantly by lactic acid bacteria fermentation,the content of soluble dietary fiber increased from 4.72%to 6.58%after 48 h fermentation by L.buchneri.With the increase of fermentation time,the content of starch in wheat bran gradually decreased.While,the content of crude protein firstly increased,then decreased slightly,and finally tended to be constant.L.plantarum was more efficient in increasing polyphenol content than other strains;the polyphenol content could be increased from 1.34 mg/g to 3.86 mg/g,and the antioxidant activity of wheat bran was increased significantly.Furthermore,the phytic acid content in wheat bran could be significantly reduced.In conclusion,L.plantarum and L.buchneri used in this study are quite effective in improving the nutritional attributes of wheat bran.In conclusion,L.plantarum and L.buchneri used in this study are quite effective in improving the nutritional attributes of wheat bran.（2）According to the results of co-culture experiment,the wheat bran was fermented by L.buchneri and Aspergillus oryzae.The effects of fermentation temperature,compound ratio and fermentation time on the SDF and TP contents of wheat bran were determined by single factor experiment,and the conditions of compound fermentation were determined by orthogonal experiment:fermentation time 3 d,compounding ratio 2:3,and fermentation temperature 31℃.Under these conditions,the contents of SDF and TP in wheat bran are 8.44%and 3.30 mg GAE/g DW respectively.By observing the microstructure of wheat bran,it was found that the external structure of unfermented wheat bran was smooth,dense and uniform.After fermentation,the original dense wheat bran structure cracked and the smooth and dense surface structure of wheat bran was destroyed.After fermentation,the grinding efficiency of wheat bran was increased and it was easier to be crushed into smaller particle size.In addition,the determination of FTIR showed that after fermentation,significant changes occurred in wheat bran mainly at 1407 cm^-1,1655 cm^-1,1736 cm^-1,2926 cm^-1 and 3385 cm^-1,corresponding to the stretching vibration of-CH₃ or-CH₂ in lignin side chain structure and the contraction and vibration of-OH bond in cellulose and hemicellulose,indicating that fermentation had a significant effect on the structure of wheat bran cellulose.（3）Wheat bran before and after fermentation was added to flour in different proportions to investigate the effects of wheat bran addition on farinograph property,gelatinization properties and gluten content,sulfhydryl/disulfide bond content,protein secondary structure and SDS-PAGE gel electrophoresis.The results show that under the same additive quantity condition,the formation time,weakening degree and stability time of dough in fermentation group were lower.The content of gluten and disulfide bond was higher in the fermentation group,and the negative effect of wheat bran addition was weakened by fermentation.Wheat bran before and after fermentation was added to wheat flour in different proportions to investigate the effects of wheat bran addition on the properties of flour,gelatinization,gluten content,sulfhydryl/disulfide bond content,protein secondary structure and SDS-PAGE gel electrophoresis.The results showed that the formation time and weakening degree of dough in fermentation group were lower and the stability time was higher under the same dosage.The content of gluten and disulfide bond was higher in the fermentation group.The fermentation of wheat bran improved the quality of the mixed flour.（4）Wheat bran before and after fermentation was added to wheat flour in different proportions to explore the effects of wheat bran before and after fermentation on texture characteristics and cooking characteristics of noodles.The results showed that the cooking loss of noodles in the fermented group was significantly lower than that in the unfermented group,and the stretching length was significantly higher than that in the unfermented group,and the types and relative contents of flavor substances in the fermented group were higher than those in the unfermented group.In addition,the simulated digestion in vitro showed that the maximum release of polyphenols in noodles was at the stomach stage,and the bioavailability of polyphenols in noodles in the fermented group was higher than that in the non-fermented group.The fermentation of wheat bran improved the texture characteristics of noodles containing wheat bran and increased the bioavailability of polyphenols.In conclusion,the complex fermentation of wheat bran by lactic acid bacteria and A.oryzae can break the intermolecular linkage and increase the contents of soluble dietary fiber and polyphenols.Compared with the unfermented group,the cross-linking effect of gluten was increased by fermentation treatment,and the cooking properties and texture properties of noodles containing wheat gluten were improved.