Protein quality assessment of commercial whey protein supplements commonly consumed in Turkey by in vitro protein digestibility-corrected amino acid score (PDCAAS)
Athletes, bodybuilders, and physically active individuals extensively consume protein-rich products such as whey, soy, casein, and egg (Williams, 2005). Among these, whey and casein are the preferred proteins in terms of quality (Tipton et al., 2004). Whey and casein are mostly derived from cow milk. Cow milk protein consists of 80% casein and 20% whey protein. Whey protein is consisted of β-lactoglobulin (β-LG) and α-lactoglobulin (α-LG) and a small amount of immunoglobulin (Bobe et al., 1998). β-LG has 162 amino acids and the most distinctive feature of whey protein compared to casein is that it has 5 cysteines in its structure (Sava et al., 2005). This significant difference is used to determine the quality difference between casein and whey protein (European Union, 1990; Ballin, 2006).