酸碱滴定法在植物油质量检测中应用的改进

Application and improvement of acid-base titration in vegetable oil quality and safety control

酸价是检验植物油品质和质量以及食用安全性的一个非常重要的指标,实验室(尤其是中小企业)普遍用的测定酸价的方法是酸碱滴定法。本文从应用的角度出发,研究了在酸碱滴定实验中各个操作因素对实验结果的影响,并模拟企业现场,分别研究了在两种温度条件下测定油脂样品酸价的实验结果的差异,并分析了影响实验结果的因素;同时研究了氢氧化钾标准水溶液和氢氧化钾乙醇标准溶液这两种碱溶液的选择、乙醇乙醚和石油醚作为有机溶剂的选择、酚酞和百里酚酞作为终点指示剂的选择,对测定酸价实验结果的影响,通过多次的重复,得到实验结果:滴定过程中对不同工艺、原料的油脂(深、浅色),无论使用氢氧化钾乙醇溶液还是乙醇石油醚混合溶液都有利于提高滴定结果的准确性,并且百里酚酞适合用于作为深色油脂酸价测定实验中的终点指示剂。

Acid value is an important indicator of vegetable oil quality and safety. Acid-base titration method is the common used method in laboratory. In this paper,the influencing factors of acid value experiment were determined and analyzed. In the simulated factory situation at two different temperatures,the differences of oil quality were compared and analyzed. The choice between potassium standard aqueous solutionand potassium hydroxide ethanol standard solution,ethanol ether vs. petroleum ether organic solvent,phenolphthalein vs. thymolphylphthalideas the end point indicator on the determination of acid value were studied. The determination,regardless of dark or lightcolor oil,potassium hydroxide ethanol solution and ethanol petroleum ether mixed solution were moreaccurate. Thymolphane is more suitable as the end point indicator for dark oil acid determination.