A Whey Protein Blend is any product or supplement that contains more than one protein source. This could be a combination of whey protein and whey protein isolate for example, or a blend of whey protein and casein, or egg protein.
In terms of rate of digestion / absorption of protein, different protein sources yield different digest rates. For instance, whey protein is considered the fastest digesting protein and casein is the slowest. Thus, combining different sources of protein will offer a longer digestion of the proteins as compared to whey protein alone. This particular type of protein blend (as commonly known as sustained-release protein), is the perfect “general purpose” protein.
Multi-source protein blends allow their bodies to better absorb the much higher protein intake per dose.