Amino Acid Composition of Rye Flour and the Influence of Amino Acid Supplementation of Rye Flour and Bread on Growth, Nitrogen Efficiency Ratio and Liver Fat in the Growing Rat

Abstract

The amino acid compositions of 4 rye flours were similar except in the lysine content. Compared with the FAO reference pattern, rye protein appears to be low in methionine and cystine, tryptophan, lysine and isoleucine. For the growing rat the calculated deficiencies appear to be lysine, methionine and cystine, isoleucine or threonine, and tryptophan. In rat feeding experiments lysine was the first and threonine the second most limiting amino acid. No single amino acid or pair of acids increased the protein value of rye flour supplemented with lysine and threonine. This required a group of amino acids in which isoleucine appeared to be indispensable. A rye diet containing 8 times the optimal amount of L-lysine·HCl was still superior to a nonsupplemented rye diet and the addition of DL-threonine or L-isoleucine alone to a nonsupplemented rye diet had little effect on growth, nitrogen efficiency ratio and liver fat content. However, when essential amino acids other than threonine were added to rye diets fortified with lysine, a lowering of the protein value followed. This could be counteracted by threonine supplementation. Rye flour had a protein value superior to that of wheat flour but rye crisp bread was inferior to soft wheat bread.