双缩脲反应是肽和蛋白质所特有的，而为氨基酸所没有的一种颜色反应。一般分子中含有两个氨基甲酪基（即肽键：-CO-NH-）的化合物与碱性溶液作用，生成紫色或者蓝紫色的络合物。
茚三酮反应呈阴性，用酸水解后茚三酮反应和双缩脲反应呈阳性。
Its ninhydrin reaction was negative, but after acid hydrolysis, its ninhydrin reaction and biuret reaction were positive.
用双缩脲反应法可以测出发酵鱼粉中水溶性总肽的含量，用凯氏定氮法可以测出被沉淀的多肽的含量，从而可以计算出发酵鱼粉中寡肽的含量。
Total solvable peptide content in the fermented fishmeal was determined by using the biuret method, and polypeptide in the precipitate by using Kjeldahl method.
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