PDCAAS stands for “Protein Digestibility Corrected Amino Acid Score” and is a method for assessing protein quality that has been used since the 1990s. The amino acid pattern of a protein is compared with a reference pattern and then adjusted for the digestibility of the protein as a whole. The scale is capped at a value of 1.0, even if a protein would theoretically score higher.
In practice, PDCAAS is still used in some regulations and on some packaging outside Europe, even though the newer method DIAAS is considered more accurate. By PDCAAS, whey protein, casein, egg and soy protein, among others, reach high values close to the upper limit, while some other plant proteins are lower.
How different plant proteins can be complemented sensibly is explained in the guide Combining plant protein sources, and the entry Biological value offers more on the older method commonly used in Germany.
