Several improvements and extensions of the Udy dye method for estimating protein content in natural products are discussed. The many outstanding physical and chemical properties of the monosulfonic azo dye, acid orange 12, are presented. This dye is used in a stablizing pH 2 buffer system to react with the protein's basic groups that originate from the basic amino acids (BAA) histidine, arginine and lysine. A complete analysis requires less than 5 min. The ionic reaction rate is limited to the exposure rate of each binding site. Regression equations relating nitrogen content and bound dye are presented for several oilseeds, grains, legumes and animal products. Random mixtures of products, having wide differences in dye-binding capacity, are not amenable to this method of protein estimation. Because nonprotein nitrogen is not measured, and the critically essential amino acid, lysine, is measured only when it is nutritionally available, it is suggested that the amount of dye bound by the protein's BAA offers a better nutritional index than conventional nitrogen procedures.
Results are reported of a collaborative study on the determination of sprout damage in wheat. Methods of analysis included falling number, amylograph, and a colorimetric α-amylase assay. Data for the 3 methods were linearly interrelated. Primary source of error for each method was lack of agreement among collaborators. The 3 tests adequately differentiated among sprout damage levels within a single laboratory. The colorimetric test was the most sensitive to change in α-amylase content and appeared to have greater potential for standardization than the other 2 methods
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