涂石蜡大米石蜡含量定量方法研究

近几年,市场上出现了用石蜡抛光大米的非法现象。本研究旨在研究涂石蜡大米石蜡含量测定方法。本文针对一种大米,自配制含0.02%～1.5%液体石蜡不同涂量的大米样品,用无水乙醚提取大米中粗脂肪(抽提时间3h),通过测定大米粗脂肪的皂化值(方法1)和不皂化物含量(方法2),确定石蜡的涂量(空白大米的皂化值用气相色谱法分析脂肪酸的组成来确定)。结果表明,采用方法1,大于0.05%的石蜡涂量的样品的回收率在80%以上,方法2的回收率均在98%以上。综合实际操作难易程度,用皂化值大小确定大米涂石蜡的方法更简便、快捷。

Determination of Liquid Paraffin in Races Coated with Liquid Paraffin

This research aims at studying a method to determine the content of liquid paraffin in rice coated with liquid paraffin. The varieties rices were coated with liquid paraffin of 0.02%～0.05%. Using diethyl ether extracted the crude fat from samples (extracting time is 3h) , the saponification value(methodⅠ)and unsaponification’s containing(methodⅡ) are determined to confirm the content of the liquid paraffin on the surface of the rice. The recovery with method Ⅰ is more than 80% to samples coated liquid paraffin beyond 0.5%. That of the methodⅡ is more than 98%. The developed method has feasibility.