Study On The Fermentation Characteristics Of Semolina Flour Dough And The Influence On Steamed Bread Making Quality

As a typical fermented dough product,steamed bread is one of the traditional staple foods in China.The pursuit of the "white and bright" appearance of steamed bread has made the wheat flour used in steamed bread more and more fine-grained,which not only causes an increase in energy consumption during wheat processing,but also brings problems such as instability during dough fermentation.In China,semolina flour(also known as sand flour and coarse grain flour)is commonly used to make steamed foods such as steamed bread and noodles.At present,there is a lack of systematic research on the basic quality characteristics of semolina flour,dough fermentation characteristics,steamed bread quality and the correlation between them at home and abroad.This topic selects seven typical semolina flour,systematically analyzes its powder characteristics,dough fermentation characteristics and the impact on the quality of steamed bread,and clarifies the difference in quality between semolina flour and conventional particle size wheat flour;crushes semolina flour,controls its particle size within the range of ordinary wheat flour,and investigates the difference in dough fermentation characteristics and steamed bread making quality before and after crushing semolina flour;analyzes the physicochemical properties of macromolecules(protein and starch)to analyze the reason for the difference in steamed bread making between semolina flour before and after crushing,and provides a theoretical basis for the application of semolina flour in steamed bread production,the main findings of this thesis are as follows:(1)The powder properties and typical quality characteristics of semolina flour were investigated and found that: ash and damaged starch content of semolina flour ranged from0.17%-0.26% and 0.85-16.05 UCD(Chopin Dubios Units),respectively;D50(medium grain size)ranged from 82.38-100.50 μm,and powder water absorption ranged from 57.20%-59.35%.d50 was negatively correlated with damaged starch(r = 0.886)and water absorption(r = 0.786)showed different degrees of negative correlation(P < 0.05).Compared with common wheat flour,the microscopic morphology of semolina flour existed mainly in tissue block structure,and semolina flour was characterized by low ash content,low damaged starch content,large particle size,good fluidity,high crude starch content and gluten index,and high dextrinization viscosity.(2)The study on the dough fermentation characteristics and steamed bread making quality of semolina flour found that: the gas retention rate of semolina flour dough ranged from79.75%-90.00%,which was significantly and positively correlated with D50(P < 0.05),and the dough start air leakage time ranged from 48.00-80.25 min,compared with common wheat flour,the gas retention rate of semolina flour dough was higher and the start air leakage time was longer;in the fermentation During the fermentation process,the maximum tensile resistance,storage modulus(G’)and loss modulus(G")required for the semolina flour dough were smaller than that of common wheat flour,and the loss factor(tanδ)was higher than that of common wheat flour,indicating that the dough prepared from semolina flour had better ductility and was easier to shape;compared with common wheat flour,the chewiness(1006.39-1717.00)and gluability(1117.25-1893.00)of the steamed bread made from semolina flour(1117.25-1893.44)were smaller,significantly negatively correlated with dough gas retention(P < 0.05),and larger specific volume,aspect ratio and porosity.The granulated flour had better dough fermentation characteristics and produced better overall quality of steamed bread,and granulated flour F1(D50: 100.50 μm,damaged starch: 0.85 UCD,ash:0.25%)had the best dough fermentation characteristics and steamed bread quality.(3)The semolina flour F1 was crushed to control its particle size within the range of common wheat flour,and the changes of semolina flour quality characteristics and steamed bread making quality were investigated before and after crushing.It was found that: after crushing F1,particle size decreased,specific surface area increased,wet gluten content and gluten index decreased,and damaged starch content increased;solubility and swelling potential increased at 55,65,75,85 and 95°C,water SRC(solvent retention capacity),lactic acid SRC and sodium carbonate SRC were increased,sucrose SRC was decreased and pasting viscosity was decreased;the degree of starch short-range ordering,double helix structure,α-helix and β-folding were decreased and irregular curl structure was increased;the maximum expansion height,gas retention rate and starting gas leakage time of dough were decreased and G’ and G" were increased;the produced steamed bread had small specific volume,low porosity,high hardness,gluing and chewiness.(4)The doughs made of semolina flour F1 before and after crushing were fermented for 0h and 1 h,and starch and gluten protein were extracted.By analyzing the changes of physicochemical properties of starch and gluten protein,the mechanism of semolina flour particle size changes on dough fermentation characteristics was investigated,and the results showed that: for starch physicochemical properties,F1 starch had large particle size,low damaged starch content,low solubility and swelling potential;small crystallinity;low paste viscosity.For gluten protein physicochemical properties,F1 gluten protein has higher extractable rate and free sulfhydryl content,gluten protein,alcoholic protein and gluten protein are easy to hydrolyze and extract;less α-helix content and more total β-fold;larger G’ and G"of gluten protein.