凯氏定氮法检测乳制品中蛋白质含量的优化方法

目的]优化全自动凯氏定氮法检测乳制品中蛋白质含量的检测条件。方法]采用凯氏定氮法检测乳制品中蛋白质含量,通过对比不同称样量、消化时间及消化后冷却时间对检测结果的影响,选择最佳参数条件,实现对全自动凯氏定氮法检测方法的优化,并提高检测效率。结果]混合均匀的乳制品,一定范围内称样量对结果的影响不大,精密度符合国标要求,但是灭菌乳、调制乳、饮料称样量增多,精密度对应越好,发酵乳则称样过多后精密度有所下降;在230 ℃消化30 min,420 ℃时消化80 min,可消化完全,精密度可以控制在1%以内;消化后样品及时冷却,48 h内,对检测结果没有显著差异。结论]通过本试验证明,使用凯氏定氮法检测乳制品中蛋白质含量时,调整称样量、消化时间、冷却时间,对检测结果没有显著影响。

Optimization of Kjeldahl Method for Determination of Protein Content in Dairy Products

Objective]To optimize the detection conditions of automatic Kjeldahl method for detecting protein content in dairy products. Method]The protein content in dairy products was detected by Kjeldahl method. By comparing the effects of different sample weights,digestion time and cooling time after digestion on the detection results,the best parameters and conditions were selected to optimize the automatic Kjeldahl method and improve the detection efficiency. Result]For dairy products with uniform mixing,the influence of sample weight within a certain range on the results was small,and the precision met the requirements of the national standard. However,the more the sample weight of sterilized milk,prepared milk and beverage was,the better the precision was. For fermented milk,the more the sample weight was,the lower the precision was. Digest at 230 ℃ for 30 min and 420 ℃ for 80 min, which can be completely digested,and the precision can be controlled within 1%.The samples were cooled in time after digestion,and there was no significant difference in the test results within 48 hours. Conclusion] Through this test, it is proved that when using Kjeldahl method to detect protein content in dairy products, adjusting sample weight, digestion time and cooling time has no significant impact on the test results.