利用光度計測biuret reaction定牛奶中蛋白質含量

Determination of Milk Protein by Means of the Biuret Reaction with Photometer

蔡惠燕(H. Y. Tsai) ； 古涵如(H. R. Ku) ； 賴雅韻(Y. Y. Lai)

《化學》 69卷3期 (2011/09) Pp. 271-276

https://doi.org/10.6623/chem.2011027

摘要

食品工業中測定食品中的蛋白質含量，主要用凱氏法 (Kjeldahl method) 分析氮的含量再乘以轉換因子，估算出食品中蛋白質的含量，此方法除了蛋白質外，其他含氮有機物亦會被偵測，導致不肖商人添加三聚氰胺製造食品含高量蛋白質的假象。Biuret reaction 是在研究實驗室中常用來測定蛋白質含量的方法，本研究改良biuret reagent，利用分光光度計偵測牛奶中蛋白質含量。結果顯示biuret reagent 可準確偵測牛奶中的蛋白質且不受三聚氰胺干擾。偵測線性範圍為0.15~1.2 mg/mL 的蛋白質銅離子錯合物，回收率在100 (± 5)% 之內，RSD ＜ 3%。是一個快速且便宜的方法，若利用此法定量蛋白質，應可減少不肖商人於牛奶中添加三聚氰胺的企圖。

關鍵字

蛋白質定量 ； 雙縮脲反應 ； 光度計

並列摘要

Kjeldahl method is the common assay used in the food industry for protein determination but it is not selective. Melamine is likely to be added to expand the apparent protein content of the foods. Biuret reaction was a common assay for quantitative analysis of proteins in research laboratory. We developed a method to measure protein content of milk without interference from melamine using biuret reagent and photometer. The biuret reaction can accurately measure the protein content of milk. The linear range was in 0.15~1.2 mg/mL of protein-Cu^(2+)complex with good accuracy (recovery ~100%) and reproducibility (RSD ＜ 3%), and importantly, the addition of melamine in milk did not affect the readings. We conclude that biuret reaction provide a rapid and inexpensive way to determine the protein content of milk. Melamine interference can be avoided, thus it can reduce the motives to adulterate milk with melamine.

並列關鍵字

Protein quantitation ； Biuret reaction ； Photometer