氢化棉籽油等温结晶动力学的研究

Kinetic study on isothermal crystallization of hydrogenated cottonseed oil

用脉冲核磁共振(PNMR)法测定了两种氢化条件下氢化棉籽油的固体脂肪含量(SFC)。根据不同温度下固体脂肪含量随时间的变化绘制等温结晶曲线。等温结晶曲线有两种:双曲线和反曲线。当过冷却度高时,结晶曲线为双曲线;当过冷却度低时,结晶曲线为反曲线。用Avrami方程进行氢化棉籽油的等温结晶动力学分析,结果表明:过冷却度与晶体的成核和生长方式有显著相关性。当过冷却度高时,结晶常数较小,晶体成核和生长速率快;当过冷却度低时,结晶常数较大,晶体成核和生长速率慢。研究氢化棉籽油的结晶行为对人造奶油、起酥油和可可脂替代品基料油的选择有一定的指导意义。

Solid fat contents （SFC） of hydrogenated cottonseed oil under two hydrogenation conditions were determined by pulse nuclear magnetic resonance （PNMR）. Isothermal crystallization curves were described according to the change of solid fat content with time under different temperatures. The curves showed two different shapes： hyperbolic curves and sigmoidal curves. When supercooling was high, isothermal crystallization curves presented as hyperbolic curves, whereas the sigmoidal curves were obtained with low supercooling. The Avrami model was used to study the isothermal crystallization kinetics of hydrogenated cottonseed oil, and the results demonstrated that supercooling had a significant effect on nucleation and growth mechanisms. When supercooling was high, crystallization constant was lower, and nucleation and growth of crystal were quicker. With low degree of supercooling, crystallization constant was higher, and nucleation and growth of crystal were slower. Study on isothermal crystallization of hydrogenated cottonseed oil is conductive to select suitable base oil for margarine, shortening and cocoa butter substitutes.