The Mixing Ratio: Cereal and Legume Proportions That Meet an Amino-Acid Target for Weaning Foods

Cereal and legume proteins are said to complement each other, but the claim is usually made without the ratio at which the complementation is best, the score that best ratio actually reaches, or the pairs for which no ratio is good enough. This paper computes all three. Against the FAO reference pattern for children from six months to three years (lysine 57, sulphur amino acids 27, tryptophan 8.5 mg per g protein), every stated staple alone scores below 1.00: maize 0.474, sorghum 0.368, rice 0.632, millet 0.526, and even the legumes alone fall short on sulphur amino acids — soy 0.963, cowpea 0.815, bean 0.778, groundnut 0.614. Optimising the legume share of protein for six cereal–legume pairs, only the two soy pairs reach the target: maize with soy reaches a limiting score of 1.025 at 86% of protein from soy (60.6 g soy flour per 100 g of mixed flour), and millet with soy reaches 1.015 at 82%. Maize with cowpea peaks at 0.984 and rice with bean at 0.984 — close, repairable with 4% of protein as milk powder — while sorghum with cowpea peaks at 0.913, needing 24% of protein as milk powder, and maize with groundnut peaks at 0.614 at pure groundnut itself, needing 51% of protein as milk powder, which is a replacement rather than a repair. At the best ratios, the daily flour quantity meeting a stated complementary-food protein target (6 g at 6–8 months, 7 g at 9–11 months) needs 156.6–362.0 g of porridge per day, 32.0–82.8% of the stated daily gastric capacity, so quantity is not the binding constraint — amino-acid balance is. Household rules in cups are given for each pair, with the score of the rounded cup ratio recomputed and printed.