The effects of alkali-cooking of corn and supplementation with amaranth seed on its deficiencies in lysine and tryptophan.

Corn, made into tortillas (flat cakes baked from lime-treated corn) is the staple food of Mexico. The amino acid deficiencies of tortillas (TT) and boiled corn (BC), and the supplementary value of amaranth seed (PA), another traditional Mexican food, roasted to the point of "popping", were studied. The feeding tests were 14-day PER trials using weanling rats; each diet contained 8.95% crude protein, all from corn, or with PA providing 3.6% protein and corn the remainder, with vitamin and mineral supplements. In addition each diet was supplemented with lysine (lys) so that tryptophan (trp) would be the first limiting amino acid or vice versa. In no comparison did TT give a significantly different value from BC. With trp limiting, the mean PER for the two corn preparations alone was 1.55, and with PA, 2.22. The amaranth had shown a high trp value (1.55 g/16g N). g N). With lys limiting, the mean PER for corn was 1.15; adding PA failed to improve this. Popping amaranth also reduced its reactive lysine value (by dye-binding) from 5.9 to 4.0 g/16g N. It appears that making tortillas has no adverse effect on protein value, but that 'popping' can reduce the value of amaranth seeds. The higher PER for corn with trp as the limiting amino acid (rather than lys) was due to lower ad libitum food intake with the same weight gain.