Melamine and Cyanuric Acid do not interfere with Bradford and Ninhydrin assays for protein determination.
Melamine and Cyanuric Acid do not interfere with Bradford and Ninhydrin assays for protein determination.
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DOI：
10.1016/j.foodchem.2010.01.018
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发表时间：
2010-08-01
期刊：
影响因子：
8.8
通讯作者：
Field, Jeffrey
中科院分区：
文献类型：
--
作者：
Field, Anjalie;Field, Jeffrey
2007年秋天，被三聚氰胺和三聚氰尿酸污染的宠物食品导致数千只动物患上肾结石。2008年夏天，中国爆发了更为严重的掺假乳制品事件，导致6名婴儿死亡，约29万名儿童患病。在所有案例中，三聚氰胺很可能是为了夸大食品的表面蛋白质含量而添加的。为了确定我们是否可以在不受三聚氰胺和三聚氰尿酸干扰的情况下测量蛋白质，我们在布拉德福德法和茚三酮法中测试了这些化合物，这是两种常见的基于染料的蛋白质分析方法，以及氨释放法，这是食品工业中最常用的分析方法。在浓度为bbb100 μg/ml时，Ninhydrin和Bradford试验均未检出这两种化合物。氨分析检测到三聚氰胺，但对三聚尿酸没有定论。为了开发出一种准确的食品检测方法，不把这两种化学物质作为蛋白质检测出来，研究人员对猫粮和重组奶粉进行了检测。布拉德福德法很容易测量出每种食物的蛋白质含量，重要的是，在重组牛奶中加入三聚氰胺或三聚氰尿酸不会影响读数。从重组奶粉中获得的蛋白质浓度与预期的一样，但由于猫粮的溶解度低，蛋白质浓度要低10到30倍。我们得出的结论是，染料结合法可以用于检测食品中的蛋白质，而不受三聚氰胺和三聚尿酸的干扰，从而减少了使用它们作为添加剂的动机。
In the fall of 2007 pet food contaminated with melamine and cyanuric acid caused kidney stones in thousands of animals. In the summer of 2008, a more serious outbreak of adulterated dairy food caused the deaths of six infants and sickened about 290,000 children in China. In all cases, melamine was likely added to inflate the apparent protein content of the foods. To determine if we could measure protein without interference from melamine and cyanuric acid we tested these compounds in the Bradford and Ninhydrin assays, two common dye-based assays for protein, as well as by ammonia release, the most common assay used in the food industry. Neither compound was detected in the Ninhydrin and Bradford assays at concentrations of >100 μg/ml. The ammonia assay detected melamine but was inconclusive with respect to cyanuric acid. To develop an accurate test for food that would not detect either chemical as a protein, assays were run on cat food and reconstituted milk powder. The Bradford assay readily measured the protein content of each food, and importantly, the addition of melamine or cyanuric acid to reconstituted milk did not affect the readings. The protein concentrations obtained for reconstituted milk powder were as expected, but those for the cat food were 10 to 30-fold lower, due to its low solubility. We conclude that dye-binding assays can be employed to detect protein in food without interference from melamine and cyanuric acid, thus reducing the incentive to use them as additives.
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