A plant food is rarely short on every indispensable amino acid — usually just one runs low, and that single limiting amino acid caps how well the whole protein can be used. Pair two plant foods whose shortfalls differ, blend the protein between them, and watch the low bar rise to the reference line.
Combined amino-acid profile
Amino-acid score
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Each bar is one indispensable amino acid as a % of the adult reference scoring pattern (FAO/WHO/UNU, mg per g protein). The shortest bar is the limiting amino acid, and it sets the amino-acid score. SAA = methionine + cysteine; AAA = phenylalanine + tyrosine.