精炼工艺对菜籽油流变特性的影响

Effects of refining on rheological properties of rapeseed oils

以菜籽毛油为原料,分析了脱胶、脱酸、脱色和脱臭(四脱精炼)对菜籽油流变特性以及品质的影响。研究结果表明,四脱精炼对菜籽油的脂肪酸组成和折光指数无显著影响;在恒温下,随着剪切速率的增加,菜籽油的粘度先逐渐减小再趋于稳定,即菜籽油是由非牛顿流体逐渐向牛顿流体转化;同时在大范围的剪切速率下,剪切应力与剪切速率呈近线性关系,菜籽油为牛顿流体;精炼所导致的菜籽油粘度差别与微量成分相关,并且精炼可以降低菜籽油的屈服应力值;Herschel-Bulkley的简化方程τxy=τo+K(dVx/dY)或者Bingham方程相对适用于表征菜籽油在四脱精炼过程中的流变特性。

In order to understand the effects of refining on rheological properties of oil and fats,rheological property and quality of rapeseed oil were studied after degummed,deacided,bleached and deodorized.Fatty acid composition and refractive index showed no significant difference（P0.05） among tested rapeseed oils.When shear rate increased,oil viscosity decreased gradually and then stabilized at a constant temperature,indicating that rapeseed oil was gradually converted to Newtonian fluid from non-Newtonian fluid.According to the nearly linear relationship of shear stress and shear rate,rapeseed oil showed to be Newtonian fluid under a wide range of shear rate.Changes of viscosity due to refining was related to trace elements contents,and refining reduced yield stress values.The Bingham model and simplified equation of Herschel-Bulkley τxy=τo＋K（dVx/dY） were both suitable to describe rheological behavior of the rapeseed oils under refining.