Protein quality assessment of commercial whey protein supplements commonly consumed in Turkey by in vitro protein digestibility-corrected amino acid score (PDCAAS)

Abstract

Whey protein is preferred in sports nutrition because of its rich essential amino acids and protein digestibility rate compared to other protein sources. The purpose of this study was to determine the amino acid content and in vitro protein digestibility of whey protein supplements and evaluate their protein quality using the in vitro protein digestibility-corrected amino acid score (PDCAAS) method. The amount of amino acids were determined using high performance liquid chromatography (HPLC) and the protein digestibility was determined by in vitro simulated gastrointestinal tract. A high levels of glycine and very low levels of cysteine were detected in some samples. The ratio of glycine in 4 out of 14 samples ranged between 7.4 and 40.3%. The ratio of essential amino acids and branched chain amino acids in all samples were less than the reference protein. The in vitro protein digestibility of whey proteins ranged from 50.4 to 79.6%, which was very low compared with the values indicated in the literature. The PDCAAS values of whey proteins were very low and ranged from 0.08 to 0.71 in the samples. Based on these results, manufacturers should revise their processing techniques in order to provide high quality whey protein.