A dairy scientist in the US has developed a milk protein powder that aims to dramatically expand the food choices for people with phenylketonuria - more commonly known as PKU - a genetic disorder. People with PKU lack the enzyme needed to digest phenylalanine, an amino acid that is found in protein. If phenylalanine builds up in a child's bloodstream, the child will suffer brain damage and become mentally retarded. Adults with PKU are at risk of mental illness and cognitive impairment. People with PKU avoid foods with protein. That means no meat, no cheese, no eggs. Their diet is based on a special formula they drink at mealtimes, supplemented by fruits and vegetables. Professor Mark Etzel has patented a method to separate glycomacropeptide - known as GMP -- from whey, a cheap and abundant byproduct of cheesemaking. GMP is the only known protein naturally free of phenylalanine. The white GMP powder he produces can be used to make bread and other baked goods that will look and taste more like conventional foods. Because protein is what makes bread brown in the toaster and cake hold together, the baked products people with PKU can eat now can be unappetizing, Etzel said. "Now we're transferring the technology into the private sector and working on developing recipes," he said. Etzel has already launched a new research project focusing on lactoferrin, a milk protein that helps babies absorb more iron from their food and helps prevent ear infections. "In order for the dairy industry to move into more profitable areas, we need to exploit these proteins you won't find in other sources," he told the Wisconsin State Journal.