Protein Quality and Its Measurement

Dietary protein adequacy (aside from the energy/protein relationship) is a function of several protein-dependent factors the protein content of the food, the digestibility/bioavailability of the protein/amino acids within the food, the quantity of indispensable amino acids within the protein, and the relative ratio of the amino acid content to the requirements of the person(s) or amino acid standard in question. The final protein quality score is dependent on the lowest level of bioavailable indispensable amino acid, the limiting amino acid. 

PDCAAS is calculated as true protein digestibility (TD) x Amino Acid Score (AAS) (WHO/FAO/UNU Expert Consultation, 2007). 

TD is determined by rat bioassay (AOAC International, 2000), although as will be seen the rat may not be an appropriate model to estimate the protein digestibility of sorghum in humans. 

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