Study On The Effects Of Bran Fermentation On Quality Characteristics Of Semi-dried Whole Wheat Noodles

Whole grain foods have high nutritional value and can satisfy the consumers’need for healthy diets.Semi-dried noodles taste better and the development prospects of semi-dried whole wheat noodles（SWWN）should be extremely broad.However,the addition of wheat bran had negative effects on the edible quality of SWWN,and the relatively high moisture content resulted in the relatively short shelf-life.Therefore,in this study,bran fermentation was applied in the production of SWWN.Based on the existing processing method of semi-dried noodles,liquor koji and yeast were used to ferment the bran,and then the bran was immediately mixed with flour,following the sheeting,noodle fermentation and drying processings to obtain SWWN.This study aims to improve the edible quality,nutrition,flavour and storage characteristics of SWWN.Firstly,the effects of different making parameters（addition of yeast and liquor koji,bran fermentation time,noodle fermentation time）on the appearance,cooking quality,and texture property of SWWN were studied.With 1.0%yeast addition,1.5%liquor koji addition,210 min bran fermentation time and 180 min noodle fermentation time,the eating quality of SWWN was improved obviously.Compared to the no addition group,the cross-section of the SWWN fermented with the above parameters showed obvious pores.The noodles slightly swelled and the colour of surface was also improved.The optimal cooking time decreased from 533 s to 377s and cooking loss reduced significantly by 22%（p<0.05）.Secondly,the effects of different bran fermentation methods on the characteristic of whole wheat dough and wheat bran,main components（starch and protein）and microstructure of SWWN were studied.Low-field nuclear magnetic resonance analysis showed that the fermentation of liquor koji and yeast increased the T₂₁ value and decreased the T₂₂ value of whole wheat dough（p<0.05）.The elastic modulus G′and viscosity modulus G"of whole wheat dough decreased after liquor koji and yeast bran fermentation.After noodle fermentation,the elastic modulus G′and viscosity modulus G"of whole wheat dough increased,which indicated that noodle fermentation improved the quality of whole wheat dough.The combined fermentation of liquor koji and yeast significantly increased the content of water-extractable arabinoxylan（WEAX）in the bran from 1.01%to 6.15%（p<0.05）,and the water holding capacity of the bran was also reduced（p<0.05）,which was consistent with the change of dough characteristics.At the same time,the peak viscosity,valley viscosity,final viscosity and swelling power of starch in the SWWN fermented by liquor koji and yeast increased significantly（p<0.05）.The results of SDS-polyacrylamide gel electrophoresis and size exclusion high-performance liquid chromatography showed that some proteins in the liquor koji and yeast fermented（LKYF）SWWN were slightly degraded.Furthermore,observed by SEM and CLSM,the pores in the cross-section of noodles were extremely obvious in the LKYF group,and the internal structure wass relatively loose.The protein evenly combined with the starch and distributed continuously,which improved the internal structure of SWWN.Then the changes in the nutrition and flavour characteristics of fermented SWWN were studied.Fermented by liquor koji and yeast,the phytic acid content in the SWWN was significantly reduced,and the free phenol content was significantly increased（p<0.05）.The content of the insoluble dietary fiber was also lower than that in the unfermented group.At the same time,compared with the unfermented group,the total amount of free amino acids in the SWWN of liquor koji and yeast fermented group increased from 149.94 mg/100 g to 399.39mg/100 g and the amount of essential amino acids increased form 32.14 mg/100 g to 121.28mg/100 g.The amino acid composition was improved.The analysis of in vitro starch digestion showed that the glucose release rate increased during the digestion of fermented SWWN.GC-MS analysis results showed that the total content and type of flavour substances in SWWN increased after fermentation by liquor koji and yeast.The relative contents of flavor substances such as ethanol,isoamyl alcohol,ethyl acetate,ethyl caproate,and ethyl palmitate increased,and the flavour of SWWN was improved due to the LKYF treatment.Finally,the storage characteristics of fermented SWWN were studied.At 25°C,the shelf life of the SWWN fermented by liquor koji and yeast was extended by 4 days compared to that of the unfermented SWWN.The p H value was significantly lower than that of the unfermented group（p<0.05）.Gas chromatography analysis showed that the ethanol content of the LKYF group was significantly higher than that of the other groups during the whole storage.Appropriate packaging materials were also selected and combined with the deoxidizer to preserve the SWWN,which effectively extended the shelf-life to more than two months.