油脂氧化安定性几种分析方法的比较

Comparative Study of Testing Methods for Oxidation Stability of Vegetable Oils

主要论述碘值法、过氧化值法、折光率法、电导率法等几种油脂氧化安定性的分析方法在85℃下不同的效果 ,以及电导率法在75℃至120℃的效果。结果表明85℃时的碘值变化不规则 ,过氧化值变化幅度非常小,折光率基本不变 ,而电导率则有一个规律性的明显突变 ,这代表了油脂氧化诱导期的结束 ;进一步对电导率法进行一系列的温度试验,证明当氧化温度不高于90℃时,电导率会产生突变点。若氧化温度高于90℃则电导率无突变 ,且油脂短时间内会有聚合物生成 ,所以,电导率法适用的温度范围是低于90℃。

The performances of various testing methods for oxidation stability of vegetable oils were evaluated at 85℃. The methods involved are: iodine value method, peroxide value method, refractive index method and electrical conductivity method. The evaluation results indicate that only the electrical conductivity method is satisfactory. It gives a sharp jump in conductivity at the end of the induction period. The iodine value testing gave irregular results at 85℃. The peroxide value method provided only small variation in peroxide values. Refractive index remained practically unchanged with time. Supplementary experiments show the suitable temperature range for the electrical conductivity is from 75℃ to 90℃. At temperatures higher than 90℃ polymerization occurred, and no abrupt change in electrical conductivity could be observed.