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has been criticized for over-estimating the value of some animal
proteins for growth while under-estimating the value of some
vegetable proteins. While the PER method has been used for
nearly 100 years, and was once used by many countries (
including the United States) as the recognized procedure for measuring
protein quality, it is no longer widely used globally for regulatory purposes.
With time, more studies on human amino acid requirements and protein bioavailability have become available. Consequently, newer methods for protein quality assessment have
been proposed and used. The Protein Digestibility-Corrected
Amino Acid Score (PDCAAS), which compares the amino
acid composition of a dietary protein to a reference amino acid
profile and adjusts for protein digestibility, was introduced in
1991, and has been adopted by regulatory agencies globally.
PDCAAS is expressed as a decimal score or percent, with 1.00 or
100% indicating that the protein can supply all amino acid needs
when fed at nutritionally appropriate amounts. Scores above
100% are truncated for reporting based on the rationale that
there is no benefit for an amount in excess of needs. Strengths
of the PDCAAS method are that it is relatively easy and economical to conduct, it is based on human amino acid needs,
and PDCAAS values can be calculated for a blend of proteins.
While the method has been criticized for a variety of reasons
(fecal digestibility is not the best indicator of the availability of
individual amino acids, truncation of values to 1.00 or 100%
FIG. 1. Protein Digestibility-Corrected Amino Acid Score (PDCAAS) values of selected foods