Determinations of the diamino acids in various wheat flours

Three samples of flour were quantitatively analyzed for histidine, arginine, and lysine. The three diamino acids were separated from each other and from the non-basic amino acids by precipitating histidine silver at pH 7 .4, arginine silver between pH 8.5 and 14, and lysine with phosphotungstic acid. The histidine was isolated as the nitranilate, arginine as the flavianate, and lysine as the picrate. Analyses were also carried out for moisture, ash, fat, protein nitrogen, and total protein; the probable ash in the whole wheat was also calculated. It was concluded that the method was not too accurate due to the many possibilities for error and the exactness of technique necessary, and also the procedure was too long for the accuracy obtainable. Improvements in the method and further work were suggested for the future.