全自动光度滴定法测定粮食中的脂肪酸值方法适用性研究

以磁力搅拌器作为提取装置，用无水乙醇提取试样中的脂肪酸，百里香酚蓝作为指示剂，用全自动光度滴定仪以氢氧化钾标准滴定溶液中和样液中的游离脂肪酸，以消耗的氢氧化钾标准滴定溶液的体积计算脂肪酸值。仪器自动完成从样液提取、过滤、定量转移、滴定、计算全过程。研究表明，方法滴定精密度高，测定的重复性、准确性、稳定性符合国标方法的要求；仪器台间一致性可以达到国标方法的重复性要求；测定用时稻谷是电位滴定法、手工滴定法的三分之一，玉米是电位滴定法的五分之二、手工滴定法的二分之一，小麦粉是电位滴定法、手工滴定法的二分之一。方法操作简便，适用范围广，测定过程受人为因素干扰小，适用于批量和快速测定；为基层粮食收储企业收购粮食时的储存品质把关检验和粮食检测机构大批量脂肪酸值检测工作提供适用方法。

The Applicability Study for Determination of Fatty Acids in the Grain by Using Automatic Photometric Titration Method

A fatty acid value determination method in grain was developed by using automatic photometric titrator with KOH as standard titration solution in this paper, in which magnetic stirring apparatus was selected as extraction device, anhydrous ethanol was used as extraction solvent, and thymol blue was used to control directing terminal. Finally, the fatty acid value was calculated by combining the consumed volume of KOH''s standard titration solution. The instrument can automatically complete the whole process of extraction, filtration, quantitative transfer, titration and calculation. The results showed that the determination method has high precision, and the repeatability, accuracy and stability can meet the requirements of the national standard method, the consistency between instruments can meet the repeatability requirement of national standard method, the measuring time of paddy and wheat flour were one-third and one-half respectively of those by potentiometric or manual titration, and the measuring time of maize was two-fifths of the potentiometric titration and one-half of the manual titration. With a wide application range, the method was easy to operateand less to be disturbed by human factors, it is very suitable for batch and rapid determination of fatty acid value in grain. In a word, this method provided a suitable method for strict quality control in the grass-roots grain storage companies when purchasing grain and detection of large quantities fatty acid value in grain inspection agency.