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目的:本文运用不同前处理方法进行比较,解决国家标准方法[1]测定辣椒油中的酸价时,由于辣椒油中的色素存在而影响滴定终点的判断问题。方法:利用添加适量中性饱和食盐水及用活性碳吸附两种方法前处理后再按照国标法测定酸价,其结果与准确度和精密度都较高的自动电位滴定法相比较。结果:用添加中性饱和食盐水法和活性碳吸附法都可以清晰观察到滴定终点;辣椒油试样量在3~4 g,用添加中性饱和食盐水法与自动电位滴定法结果无统计学差异,结果准确;活性碳吸附法测定低浓度酸价的油脂相对偏差较大,高浓度的与自动电位滴定法无统计学差异。结论:对于深色油脂如辣椒油中的酸价首选自动电位滴定法,如没有自动电位滴定仪的基层单位,低浓度的可以用添加中性饱和食盐水方法,中、高浓度的可以用活性碳吸附法和添加中性饱和食盐水方法,两种方法都可以清晰地观察到滴定终点,结果精密度都较好,准确度较高。可以作为国标法中测定辣椒油中酸价的有效补充。
OBJECTIVE: In this paper, different pretreatment methods were used to compare the determination of the endpoint of titration due to the presence of pigment in chili oil when the national standard method [1] was used to determine the acid value in chili oil. Methods: The acid value was determined according to the national standard method after pretreatment by adding appropriate amount of neutral saturated brine and activated carbon adsorption. The results were compared with the automatic potentiometric titration with high accuracy and precision. Results: The endpoint of titration was clearly observed by the addition of neutral saturated brine and activated carbon adsorption. The sample volume of chili oil was 3 ~ 4 g. There was no statistical difference between the results of adding neutral saturated brine and automatic potentiometric titration The differences between the two methods were very good. The relative deviation of the fats with low acid value by activated carbon adsorption was relatively large. There was no significant difference between high concentration and automatic potentiometric titration. Conclusion: For the dark oil, such as chili oil, the preferred acid value of the automatic potentiometric titration, such as the absence of automatic potentiometric titration of the grass-roots units, low concentrations can be used to add neutral salt solution of saturated water, medium and high concentrations of available activity Carbon adsorption method and adding neutral saturated brine method, both methods can clearly observe the titration end point, the results are better precision, higher accuracy. Can be used as an effective complement to determine the acid value of chili oil in the national standard method.