Abstract:

In order to compare and analyze the precision, accuracy, correlation and testing cost of Kjeldahl and Dumas combustion methods for determination of protein content in rice, this study was conducted to examine the determination of protein or N content in rice （ 40 polished rice and 10 unpolished rice) and 5 reference compounds using Kjeldahl and Dumas combustion methods, respectively. The results showed that RSD of Dumas combustion method for determination of protein content in whole wheat flour reference compound was 0.10％, lower than Kjeldahl method （RSD=0.30％）. RE of Dumas combustion method for determination of protein content in unpolished rice reference compound was 0.8％, lower than Kjeldahl method （RE=1.0％）. With Dumas combustion method， the range of coefficient of variation（CV） of polished and unpolished rice respectively were 0.01％～0.80％ and 0.01％～1.10％, lower than Kjeldahl method （0.02％～1.70％ and 0.20％～1.50％）. Good linear correlations（R2=0.9858 in polished rice and R2=0.9788 in unpolished rice） were obtained between the two different methods. The time and manpower required by Dumas combustion method is about 1/2 of that of Kjeldahl method for the same number of samples. Therefore, Dumas combustion method is an environmentally friendly and efficient method for rice protein determination, and it could be used as a regular method for determination of protein content in rice.

Key words: rice, protein, Dumas combustion method, Kjeldahl method

摘要：

选用40个精米、10个糙米样品和5种标准品为试验材料，分别采用杜马斯燃烧法和凯氏定氮法测定其蛋白质或全氮含量，并对两种方法测定结果的精密度、准确度和相关性及检测成本进行了比较分析。在对全麦粉标准品进行蛋白质检测时，杜马斯燃烧法的RSD为0.1％，精密度高于凯氏定氮法（RSD=0.3％）；对糙米标准品进行蛋白质检测时，杜马斯燃烧法的RE为0.8％，准确度优于凯氏定氮法（RE=1.0％）；杜马斯燃烧法测定精米和糙米样品的变异系数分别为0.01％～0.80％和0.01％～1.10％，低于凯氏定氮法（0.02％～1.70％和0.20％～1.50％）；两种方法测定精米蛋白质结果间存在显著的线性相关（R2= 0.9858），糙米测定值也存在显著的线性相关（R2= 0.9788）；在检测成本方面，完成相同数量样品检测，杜马斯燃烧法所需时间和人力都约是凯氏定氮法的1/2。因而，杜马斯燃烧法是一种环保和高效的稻米蛋白质检测方法，可作为稻米蛋白质检测的常规方法。

关键词: 稻米, 蛋白质, 杜马斯燃烧法, 凯氏定氮法