Investigation On After-ripening Mechanism Of Wheat

The quality of wheat changed instability in the early storage time, the storage stabilityhas been improved and achieved the desired state undergone the after-ripening. It is veryimportant to prove the mechanism of the wheat after-ripening and then take measures toreduce the period of wheat after-ripening. The study uses five different hardness wheat Jimai17,Jimai22,Jimai620709,Zhengmai366and the Taikong6as raw material, which stored atroom temperature. Determine the change of wheat grain quality, processing characteristics,content of carbohydrate, protein components and structures, pasting properties andrheological properties, and analyze the variation and correlation of indicators. The mainresults are as follows:(1) During the storage time, the hardness of the wheat, bulk density remain basicallyunchanged; the gradually reduced trend in diameter of grain and weight begin with changemakedly; the junction of endosperm and aleurone structure are broadly unchanged, Starchdistributed in the endosperm internal structure gradually uniform, Starch grains and proteinmatrix combine gradually close, the number of exposed starch gradually reduce; the flouryield showed gradually increased; the change of flour whiteness and fineness showsinconsistent in varieties.(2) Reducing sugar content, amylase content,the enzymatic activity of a-amylase andcatalase, and the pasting properties of flour change more markedly in the initial stage ofstorage, it has achieved steady until about75to90days; The trend of reducing sugar contentshows sharply reduce and fell to stable; The trend of amylose content is rising; The activity ofthe two enzymes both are decreased with time; Peak viscosity,final viscosity and setbackdecreased with rised markedly in30days, at about75to90days achieved the steady trends.(3) Wet gluten content and total protein content are essentially the same with storagetime; During storage time, gluten index, albumin content, globulin content, gliadin content,glutenin content, the proportion of gliadin ratio, content of sulfhydryl, content of disulfide,content of high and low glutenin subunits changes more markedly early in the storage; Andthe proportion of gluten and gliadin, content of sulfhydryl show a downward trend, others arethe opposite; α、β、γ gliadin content of wheat were increased with storage time except Taikong6, ω gliadin content difference with their varieties; The trends of tensile,tensile resistence anddegree of extense are increased, the rheological properties of the flour has improved duringstorage. (4) Hardness,moisture content,flour yield,falling number, rheological properties all havecertain relationship with storage time, the hardness is negative correlation, moisture content,flouryield,falling number, rheological properties are positive correlation; Hardness and density hasrelationship with the flour yield; Whiteness has relationship with particle size distribution;Falling number and the peak viscosity of flour pasting properties, final viscosity andretrogradation values are all positive relationship; Content of sulfhydryl, content of disulfide,content of high and low glutenin subunits and content of gliadin all have certain relationshipwith rheological properties of the flour; While content of high and low glutenin subunitsincreased, area of tensile curve of dough, stretch resistance, elongation are increased; Thetrend of ω gliadin and dough forming time change consistently, contrary to stable time.