AbstractThe functional and physical properties, rather than the nutritional value, of protein in protein‐containing products will largely determine their acceptability as ingredients in prepared foods. The nature of the protein per se, the presence of other constituents naturally present in protein‐containing products, the degree to which the protein product is refined, the presence of other ingredients in a food system to which protein products are added, manufacturing conditions and a number of other factors, working singly or together, will influence the way proteins (as well as other ingredients) exert their functional characteristics. Differences in these characteristics are presented with examples of the manner in which various factors can influence functionality. Nonfunctional properties may be of interest for certain applications.