水杨酸钠-次氯酸钠比色法测定食品中总凯氏氮的研究

研究应用Willis等最新提出的水杨酸钠-次氯酸钠显色反应测定食品（蛋黄粉、奶粉和大豆）中总氮的含量。在本试验条件下，选择的测定波长为680nm，建立了相关性较好的标准曲线（线性范围0.02～0.2mgN）。还应用Willis比色法与凯氏定氮法同时测定了蛋黄粉、奶粉和大豆中的氮含量，试验表明两方法测定结果差异不显著。而Willis比色法比凯氏定氮法省去了蒸馏和滴定步骤，可成为食品蛋白质测定的准确可靠、简便易行的方法。

Study on Salicylate-hypochlorite Colorimetric Determination of Total Kjeldahl Nitrogen

A new salicylate-hypochlorite colorimetric method described by Willis et al (1996) is applied to analyzing total Kjeldahl nitrogen in foods (egg yolk powder, milk powder and soybean). Under experimental conditions, the ammonia is measured at 680 urn. A calibration curve is obtained in 0. 02-0. 2 mg N. The Willis method and conventional Kjeldahl method are compared by analyzing total Kjeldahl nitrogen in egg yolk pow der, milk powder and soybean. There are no difference between the two results. Willis colorimetric assay can be used as an accurate and simplified method in determining food protein content.