Protein Quality in Consumer Products and Diets

Although dietary recommendations focus primarily on quantitative protein intake, protein quality is critical to consider as well. Large differences in dietary protein intake are observed globally, with diets dominated by plant protein sources typically being poorer in quality. This can be attributed to the less favorable amino acid composition and lower digestibility of plant proteins. The latter is related both to protein structure and to the presence of anti-nutritional compounds, such as trypsin inhibitors, tannins, and phytates in some products. Food processing can also notably affect protein quality. Glycation of lysine residues in proteins, resulting from the Maillard reaction with reducing carbohydrates, can significantly reduce protein quality, whereas processing-induced denaturation and aggregation of proteins can both improve and reduce protein quality. Processing-induced inactivation of trypsin inhibitors and removal of tannins and phytates can improve protein quality, but care should be taken that such processing does not cause negative impacts via, for example, protein glycation. Overall, dietary protein quality is an intricate balance that should be considered at a consumer product level, rather than the raw material or protein ingredient level. Consideration of dietary protein quality at a meal level is essential to account for the complementarity of protein sources.