Cereal Chem 69:659-664   |  VIEW ARTICLE

A Room-Temperature, Rapid Method for the Determination of Protein in Wheat and Other Grains by the Biuret Reaction.

F. C. Strong III, and A. M. A. Duarte. Copyright 1992 by the American Association of Cereal Chemists, Inc. 

A rapid, room-temperature, biuret method for determining protein in grains was developed. Samples of wheat ground to pass a 0.105-mm screen were mixed for 5 min in a blender with 2 ml of isopropanol, 700 mg of basic cupric carbonate (bright green), and 100 ml of 0.500M NaOH in 30% isopropanol. After filtering with suction through a glass fiber filter, absorbance was measured at 550 nm. A calibration curve for wheat of absorbance vs. protein concentration gave a slope of 0.350 cm-1g-1L, compared to 0.310 for the official AACC method using heat. Satisfactory results were also obtained with rice and soybeans.