Milk is more than a good source of protein, calcium, and vitamin D. It can be a good source of valuable medical foods, says a University of Wisconsin-Madison food scientist.
Many researchers and health experts agree that milk proteins appear to posses extraordinary health benefits beyond basic nutrition.
“These proteins have special medical benefits in humans that aren’t found in plant proteins or other sources of protein like fish or eggs,” says Mark Etzel, a food scientist and chemical engineer at the College of Agricultural and Life Sciences. “And we can take advantage of that to try to improve the health of people, and create value for the dairy farmer by exploiting those special benefits.”
Many of these medical proteins, including lactoferrin, alpha-lactalbumin, and glycomacropeptide, end up in whey, the watery byproduct of cheesemaking.
Lactoferrin, an iron-binding protein, helps babies absorb more iron from their food, when added to infant formula. It also may help prevent ear infections and keep harmful bacteria from sticking to intestinal walls. Alpha-lactalbumin, a calcium-binding protein, enhances calcium absorption and is one of the few proteins that stay clear when heated during the bottling process. It could boost the nutritional value of fruit juice.
Glycomacropeptide, or GMP, is the only known protein naturally free of phenylalanine, an essential amino acid. Amino acids are the building blocks of protein. Essential amino acids are not made in the body and, therefore, must come from the food we eat.
Etzel recognized that the phenylalanine-free characteristic of GMP could be particularly important for the one in 10,000 babies born in the United States each year with an inherited disorder called phenylketonuria, or PKU. People with PKU cannot digest phenylalanine because they lack the enzyme needed to break it down. Consequently, the phenylalanine reaches high levels in the bloodstream.
Just as glucose or sugar continues to circulate in the bloodstream in diabetics, so does phenylalanine circulate in the bloodstream of people with PKU. The excess phenylalanine eventually begins to damage the central nervous system, including the brain.
Too much phenylalanine in the diet can lead to irreversible mental retardation, delayed growth and possibly seizures in infants and children with PKU. In adults, too much phenylalanine can lead to mental illness, cognitive impairment, and nervous system damage.
As a result, people with PKU must follow a lifelong strict low-protein diet to avoid phenylalanine, which is abundant in most protein-rich foods such as meat, dairy foods, eggs, nuts, and beans. GMP could be a rich source of protein for these people. But only in a purified form.
Etzel has been extracting these economically and medically valuable proteins from whey for several years using a process he patented through the Wisconsin Alumni Research Foundation. His “whey refinery,” as he calls it, converts whey into usable value-added products, much as an oil refinery produces kerosene and gasoline from crude oil.
“We”re using ion-exchange chromatography to purify the proteins from whey,” Etzel says. “With the whey refinery we”re trying to make up to five different proteins in one fell swoop with the same equipment, in order to maximize the amount of revenue we get from the equipment.”
Ion-exchange chromatography separates whey proteins by the electrical charge they carry, either positive or negative, as they travel through the separation materials, called exchangers, in the “refinery.” GMP carries a negative charge in whey at acidic pH, unlike other whey proteins. So, the GMP flows through the ion exchanger while the other positively charged proteins bind to it. Etzel can then recover the GMP from this final liquid.
This purified GMP sells for around $30 per pound instead of $0.60 per pound for WPC 34, the commodity whey powder.
“That”s 50 times more valuable,” Etzel says. “That”s a huge difference in value for the dairy industry.”
Etzel wants to produce GMP as an ingredient that can be added to already existing medical foods for people with PKU.
Etzel wants to push the dairy industry toward making high value-added products, such as GMP powder, by taking advantage of technology developed in the biotech and biopharmaceutical industries. And, Wisconsin”s dairy industry provides a convenient source of GMP and other proteins in whey.
“The state”s strong in biotech, in agribusiness, and in dairy processing,” Etzel says. “This project ties these strengths together.”
Etzel is working with a local whey processor to make the GMP product. Then, he expects to sell the GMP to companies that already make low-protein foods such as bread mixes. These companies sell their products nationally and internationally.
“This is really a needed product,” says Sally Gleason, a registered dietitian and PKU specialist at the UW-Madison”s Waisman Center, a leader in PKU research and treatment. Gleason says the biggest challenge of all is getting people with PKU to take the low-protein formula, which provides them with calories and nutrients they might not get otherwise.
“This is a diet for life,” says Gleason who provides dietary counseling for about 125 PKU families through the Waisman Center”s Biochemical Genetics Program.
“The biggest difficulty for home cooks is breadmaking because the low-protein wheat starch they”re using doesn”t have much structure,” Gleason says. “GMP restores the spongy structure and allows the bread to brown,” adds Etzel.
“Here we are in the dairy state,” says Etzel, “and there”s this dairy protein that the University of Wisconsin has developed a technology to isolate, that treats this disease that Wisconsin is pioneering treatments for … I can”t think of a better place than Wisconsin to do this because of our strengths.”