本研究之目的在探討不同剪速率(1.57-4.71*10/sup 4/s/sup -1/)在25.degree.C對黃豆分離蛋白黏度、分子量與乳化性之影響。剪作用時間在5分鐘內時,黏度隨剪速率與剪作用時間之增加而下降;但當剪作用時間增加且在高剪速率(4.71*10/sup 4/s/sup -1/)時,黏度反而隨剪作用時間之增加而增加。黃豆分離蛋白溶液之流變性質亦隨剪速率之改變而改變,由低剪速率之Thixotropy變為高剪速率之Time independency。疏水性隨剪速率之增加而增加;低剪速率時,疏水性不受剪作用時間之影響,但當在高剪速率時,疏水性會隨剪作用時間之增加而增加。黃豆分離蛋白之乳化容量與乳化安定性均隨剪速率之增加而增加,亦隨剪作用時間之增加而增加。電泳分析之結果發現其分子量會隨剪速率之增加而變大,有更多之大分子無法進入Stacking gel。上述結果說明了黃豆分離蛋白之構形會因受高剪速率之作用而暴露出疏水性基,疏水性基間之相互作用而導致其分子量與黏度之增加。另發現高剪力作用可增加備製黃豆分離蛋白時之萃取率。亦發現其可應用於素食火腿結著所需之結著劑之開發。此研究再次證明高剪速率作用是一良好改變蛋白質之功能性質之加工變數。 The objectives of this project are to investigate the effect of shear rate on the apparent viscosity, molecular weight and emulsion properties of soy protein isolate (SPI) and its applications. The viscosity decreases with increasing shear rates and shear time within 5 min shearing. But the viscosity increases with increasing shear time as shearing time above 5 min, especially under the high shearing rate (4.71*10/sup 4/s/sup -1/). The rheological properties of SPI solutions changes with shear rates. Thixotropy behavior at low shear rate changes to time independency at high shear rate. The hydrophobic interaction increases with increasing shear rate. The hydrophobic interactions do not affect by shear time at low shear rate; but it increases with increasing shear time as subject to high shear rate. The emulsion capacity and stability of SPI increases with increasing shear rates and shear time. The molecular weight of soy proteins increases with increasing shear rate. The high molecular weight above 72*10/sup 4/induced by shear can not penetrate into the stacking gel. The results indicate the increase in molecular weight and viscosity was due to the conformational changes and hydrophobic interactions of SPI induced by shearing. On the other hand, the application of high hear rate in purifying SPI from defatted soy flour finds it increases the purifying rate of SPI. It also can apply in the vegetable texture protein as binder. As a result, the high shearing action is a great process using in the changing the functional properties of soy protein.
