戴飞 吴贝贝 关敬媛 张浩杰

摘要 [目的] 对凯氏定氮法测定固体饮料中蛋白质含量的不确定度进行评定。[方法] 根据JJF 1059.1—2012标准中要求，建立了凯氏定氮法测定固体饮料中蛋白质含量的测量不确定度的数学模型，分析了凯氏定氮法中不确定度的主要来源，对已识别来源的不确定度分量进行分析评价。[结果] 固体饮料中蛋白质含量为11.60%，扩展不确定度为0.46%（95%，k=2）。测量结果的不确定度主要来源于测定样品实际消耗硫酸标准溶液的体积与测量重复性，标准溶液的影响次之，样品质量、取样体积与定容的体积带来的影响可忽略不计。[结论] 系统介绍了蛋白质测量不确定度的评定过程，提高了检测数据的可靠性和一致性。

关键词 凯氏定氮法；蛋白质；固体饮料；不确定度

中图分类号 TS278 文献标识码 A 文章编号 0517-6611（2017）07-0076-03

Evaluation of Uncertainty in Determination of Protein Content by Kjeldahl Method in Solid Beverage

DAI Fei， WU Bei-bei， GUAN Jing-yuan et al

（Ningbo Yufangtang Biological Technology Co.， Ltd.， Ningbo， Zhejiang 315012）

Abstract [Objective] The uncertainty in determination of protein content by Kjeldahl method in solid beverage was evaluated. [Method] According to the requirements of JJF 1059.1—2012 standard， a mathematical model for uncertainty in determination of protein content by Kjeldahl method in solid beverage was established， various sources of uncertainty were analyzed， the uncertainty components of identified sources are analyzed and evaluated. [Result] The concentration of protein was 11.60% and the expanded uncertainty was 0.46 %（95%， k=2）. The uncertainties of measurement result were mainly from volume determination of the actual consumption of sulfuric acid solution and measurement repeatability， the influence of standard solution on the second， the sample quality， the influence brought by sample volume and volume of constant volume was negligible. [Conclusion] The evaluation process of protein measurement uncertainty is introduced systematically， and the reliability and consistency of the data are improved.

Key words Kjeldahl determination；Protein；Solid beverage；Uncertainty

測量结果都不可避免地会有不确定度，不确定度可以给出测量结果的可信程度，是对测量结果质量的定量评定[1]。不确定度评估可以作为产品质量评价的一个重要指标，也可以反映数据可信的程度。检测结果一般是用数值来表示，而检测数值的可信程度则一般用它的不确定度来表示，数值只有包含了可置信的范围，检测的最终结果才有意义。不确定度的大小，表述了测量结果与被测量真值的接近程度，不确定度越小，离真值更近，则测量结果质量越高；不确定度越大，离真值越远，则测量结果的使用价值就越低。因此，在给出测量结果时，应相应给出它的测量不确定度，使人们可以更直观地评定其可靠性，使检测结果更有意义。……