| The quality characteristics of wheat flour will change after it is heated,and the heating of wheat flour during processing is unavoidable.The middle gluten protein wheat flour was used as raw material to study the effects of different heating conditions on the physical and chemical properties,dough and steamed bread characteristics of wheat flour during processing,and discuss the quality changes mechanism from the perspective of protein component structure and the distribution of moisture in dough.The physicochemical properties of wheat flour changed significantly after being heated.The study results showed that the moisture content of wheat flour decreased significantly after heating.With the increase of heating temperature,the extraction rates of albumin and globulin decreased,and the extraction rates of gliadin and glutenin first increased and then decreased.When the heating temperature was 70,80 and 90℃,the gluten index of wheat flour was lower than that of the original flour.As the temperature increased and the time prolonged,the falling number increased first and then decreased.The flour color got worse.As the temperature increased,the peak viscosity,the minimum viscosity,the breakdown,the final viscosity and the setback value of the wheat flour after heating generally increased first and then decreased.With the heating temperature increased and the time prolonged,the wheat flour had lower stabilization time and degree of weakening.And the stability,kneading resistance and damage resistance of the dough were reduced.When the dough was proofed for 45 and 90 minutes,the dough strength of the original flour was the strongest.When the dough was proofed for 135 minutes,the dough strength did not change much.At45 and 135 min after proofing,the gas-holding capacity of the heated wheat flour dough increased.After it is heated,the dough characteristics and food preparation characteristics of wheat flour were change significantly.The results of the study indicated that the wheat flour had higher firmness（45 min）and viscoelasticity（45 min）when the wheat flour was heated at a higher temperature for a longer period of time.After heated,the bread width-height ratio of wheat flour increased,and the specific volume increased.As the temperature increased and the time prolonged,the steamed bread score generally increased first and then decreased,and the color of the steamed bread got worse.After heating,the hardness and viscosity of steamed bread decreased.Steamed bread under higher temperature and longer time had less adhesiveness and chewability,higher recovery and cohesion.The changes of protein component structure and dough moisture distribution in wheat flour can show the mechanism of wheat flour quality change to a certain extent after heating.The relationship between wheat flour protein and quality was analyzed.The results of the study showed that with the temperature of heating increased and the time prolonged,the content of free sulfhydryl groups showed a trend of first increased and then decreased.When the time was prolonged,the disulfide bond content decreased first and then increased.When the temperature increased,the disulfide bond content trend was opposite.When the temperature increased,theβ-fold content decreased first and then increased.The random coil content,α-helix content,andβ-turn content showed opposite trends.Heating conditions only had a significant effect on T22.And had a significant impact on the moisture distribution ratio.After heating,the binding ability of wheat flour dough to the binding water was enhanced,while the binding ability to the intermediate water and free water was weakened.Disulfide bond,β-sheet,random curl andα-helix had important effects on the flour quality of wheat flour;free sulfhydryl group andα-helix have important effects on the gelatinization properties of wheat flour.The change of thiol,β-sheet andβ-turn when heated leads to the change of steamed bread quality. |
