Effects Of Gelatinization Treatments On Properties Of Tartary Buckwheat Dough

To improve the viscoelasticity and inactivate the activity of rutin degrading enzymes of tartary buckwheat dough, tartary buckwheat grains were treated by roasting, steaming, boiling and microwave, while the whole tartary buckwheat flour was treated by extrude, then the different gelatinization treated flour were obtained and they were mad into dough. The effects of gelatinization treatments on physicochemical properties of tartary buckwheat dough and rutin degradation were explored. At last, the corresponding product(noodles) properties were determined. The results are shown as follows;After adjusting buckwheat grains moisture, the flour with higher gelatinization degree,flavonoids and rutin and lower quercetin was obtained. The conditions of four treatments were confirmed which were roasting at 130℃ in 2h, steaming in 10 min, boiling in 10 min,microwave on moderate heat in 4min. The buckwheat flour was extruded to obtain extrusive flour whose gelatinization degree can reach to 94.33% whose flavonoids lost most and reached to 22.34%. Roasting treatment led to the mixmum loss of rutin and reach to 6.62%.Analyzed the effects of gelatinization treatments on the physicochemical properties of tartary buckwheat flour, the results showed that, value of L of gelatinization treatment decreased, while the value of a and b increased. The water retention increased and extrusive flour rose 1.69 of whole buckwheat flour to 5.52. The pasting property changed significantly.The value of breakdown and setback of whole buckwheat flour were 223 BU, 3410 BU, while the value of breakdown of roasting was 108 BU and the value of setback of boiling was1014 BU. There was no large change between whole flour and gelatinized flour of gelatinization temperature and time, the value were about 63.60℃, 6.7330 min. SDS-PAGE electrophoretic showed that the protein bands had no obvious missing by gelatinization.However, that of extrusive protein increased several bands among 26.0~33.0 ku. Rutin will be degraded 73.88% in one minute when blending tartary buckwheat flour with water and its content was no longer change after fifteen minutes. Quercetin content increased from0.031mg/g to 6.46mg/g in 30 seconds. The rutin retention rate of roasting dough was 4.94%,the other gelatinization treatments were abve 90%.Accrding to the results of TPA, hardness increased in all treatments, microwave treatment dough had the lagest hardness. Microwave, boiling, steaming treatments dough had higher adhesion than the whole flour dough. The adhesion decreased slightly while dramatically of extrusive dough. Extrusion treatment dough had the higheat cohesion,microwave dough took the second place, boiling and steaming had less influence. But it decreased after roasting. By the results of stress relaxation characteriatics showed that the five treatments improved elasticity and viscosity of dough and internal bond strength, since the modules of elasticity, damping coefficient and relaxation time went up. SEM observation showed that extrusion treatment promoted the formation of continuous and homogeneous gel network. Rutin and quercetin content of roasting dough was 1.71mg· g-1and 11.26mg·g-1,while ruin conten was high and quercetin was low in the other treatments dough.Gelatinization degree had an influence on the properties of buckwheat dough. Cohesion,modules of elasticity, damping coefficient and relaxation time of the dough whose gelatinization was 90% were the highest, while the adhesion was the least. When it was added to wheat flour with different proportion and the addition reach to 70%, hardness and cohesion achieved the maxium.After cooked, there is a great difference of texture including extension, shear and adhesion tests among of three kinds of noodle. In terms of the parameters, cooked noodle was greater than that of raw one, wheat noodle was superior to gelatinized buckwheat noodle,mixed flour-wheat noodle was better than whole buckwheat noodle. From the results of sensory evaluation,whole buckwheat noodles and roasting noodles got lower score. 90%gelatinization degree buckwheat flour-wheat flour noodles got higher sorce than normal flour-wheat flour noodles.The results in this research showed that extrusion treatment can improve the cohesion of dough significantly, while it is not remarkable of the other gelatinization treatments. Except roasting treatment, the activity of rutin degrading enzyme was inhibited by the gelatinization,resulting to less bitter of tartary buckwheat product.