Study On The Processing Technology Of Dried Fermented Noodles

Dried noodles are one of the unique noodle products in China,which occupy an important position in the food industry.At present,the dried noodles on the market lack pleasant flavor,and the noodles after fermentation can make up for this shortcoming.However,the lack of systematic research on the processing technology(raw materials,fermentation methods,fermentation parameters,etc.)of dried fermented noodles made from wheat flour is not conducive to the development of new fermented noodles and the standardization and large-scale production processes.Firstly,the relationship between flour quality and quality characteristics of dried fermented noodles was analyzed.Then the effects of different fermentation methods on the quality characteristics of dried noodles were investigated from four aspects:microstructure,noodle quality,flavor,and digestive characteristics.Based on this,the effects of the preparation technology of the pre-fermented batter(fermentation time and the amount of yeast added)and the production technology of the dried fermented noodles(the amount of the pre-fermented batter added)on the quality of the noodles were investigated,and the effects of the amount of the pre-fermented batter added on the rheological properties of the dough sheet and the properties of protein and starch of the samples during the noodle processing were investigated.The completion of this project provides new ideas and theoretical and technical support for the development of the dried fermented noodles.Firstly,the effects of flour characteristics on the quality of dried fermented noodles were studied.The results showed that the quality characteristics of flour were significantly related to the quality characteristics of dried fermented noodles.The moisture content(12-14%),ash content(<0.4%),starch content(85-86%),gluten index(82-95),swelling index of glutenin(418-424),a~*value(0-0.2),setback viscosity(1335-1335 c P),pasting temperature(68-70~°C),water absorption(63-65%),softening degree(71-75 BU),extensibility(116-158 mm)and stretching ratio(2-3)could be used as the indexes for selecting the high-quality flour for making dried fermented noodles.Secondly,the effects of different fermentation methods on the quality of dried fermented noodles were studied.The results showed that the total acidity and starch digestibility of fermented noodles were significantly higher than those of unfermented noodles.The dried noodles produced by liquid sourdough fermentation(SD)had the highest acidity and glycaemic index.Ketones and phenols were detected only in SD noodles.Although the volatile flavor components of SD noodles were rich,the mechanical properties of the SD noodles were poor,the cooking time was longer and the cooking loss was greater.The texture and tensile properties of the SD noodles were far inferior to those of noodles made by other methods.Low sensory acceptability scores were found in the SD noodles,so this method was not suitable for the production of fermented noodles.The dried noodles produced by direct fermentation(DF)had large holes in their interior,which were typical fermented kongxin noodles.With the increase of yeast addition,the central holes became larger and the noodles became thicker.The dried noodles produced by liquid prefermentation(PF)did not have large holes and there are many uneven small holes in their interior,which were a new type of fermented microporous noodles.The cooking and texture characteristics of the DF and PF noodles were easily affected by the amount of yeast added.The acidity of DF and PF noodles met the standard,and the flavor was better than that of unfermented noodles.Therefore,these two fermentation methods could be used to make dried fermented noodles.Thirdly,the dried noodles produced by liquid prefermentation and the effects of fermentation time and the amount of yeast added on the quality of dried fermented noodles were studied.The results showed that the total acidity of the noodles increased with the increase of fermentation time and yeast addition.When the fermentation time was less than 3 h,with the increase of the yeast addition,there would be more uneven holes in the noodles,and the thickness of the noodles also increased significantly.Therefore,the breaking strength,cooking time,and water absorption of the noodles increased,while the flexibility of the noodles became worse.When the fermentation time was increased to 6 h,the increase of yeast addition did not lead to a significant increase in the thickness of the noodles and pore size.Therefore,the force required to break the noodles was significantly lower than that of the noodles fermented for less than 3 h,while the flexibility of the noodles was not significantly different from the unfermented noodles and was significantly better than that of the noodles fermented for less than3 h.There was no significant difference in texture characteristics between different fermented noodles.Compared with unfermented noodles,the hardness and chewiness were lower and the tensile distance of the noodles fermented for 6 h decreased significantly.With the increase of the fermentation time,the types of volatile flavor compounds in the fermented noodles increased.When the fermentation time exceeded 3 h,2-pentylfuran was produced.When the fermentation time was 6 h,carboxylic acids were produced.Finally,the effects of the amount of pre-fermented batter added on the rheological properties of the dough sheet and the quality of the dried noodles were studied for the liquid prefermentation method.The results showed that there was no significant difference in the rupture stress among different batter addition,the rupture elongation increased and the apparent extensional viscosity decreased with the increase of batter addition.With the increase of the amount of pre-fermented batter,the total acidity and adhesiveness of the noodles increased,the hardness and chewiness decreased slightly,and the cooking time and breaking distance decreased.The content of glutenin macropolymer(GMP)in the crumbly dough was slightly lower than that in the control,and the content of SDS-extractable protein was increased with the increase of the pre-fermented batter addition.The addition of batter also prevented the covalent cross-linking of protein molecules in the dough sheet before and after resting,and the order of free sulfhydryl group content was 20%>10%>0%.The more the batter added,the greater the disruption of GMP and the more free sulfhydryl group and SDS-extractable protein in the dried noodles.Between the process of crumbly dough resting and noodles dried for 2 h,the reducing sugar content of the samples added 20%pre-fermented batter was always significantly higher than that of adding an amount of 10%,but the damaged starch content had no significant difference.This indicated that the damaged starch in the former noodle dough was hydrolyzed in large quantities and the intact starch granules were also involved in the hydrolysis process.The crystalline types of starch granules did not change but the relative crystallinity of starch decreased with the increase of batter addition.It could be seen that the texture properties of fermented noodles were inferior to that of unfermented noodles due to the destruction of the gluten network structure,the disruption of GMP,and the hydrolysis of starch in the process of making noodles.