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January 22, 2019

A sweet idea: Converting dairy leftovers into profitable products

Written By: Sam Million-Weaver

A strategy for transforming waste from the Greek yogurt-making process into a high-value sweetener product might pave the way for millions of extra dollars per year for dairy producers.

“We think this technology could definitely reduce the environmental impact of the dairy industry while generating extra revenue,” says Mark Lindsay, a chemical engineering student and the project’s lead researcher at the University of Wisconsin-Madison. The team has been awarded a grant from Dairy Management Inc., the marketing branch of the dairy industry, to support their efforts.

Mark Lindsay
Mark Lindsay

Greek yogurt has taken American supermarkets by storm in recent years. Spurred on, in part, by the popularity of low-carb diets, millions of people enjoy Greek yogurt as a creamy, slightly tangy high-protein breakfast go-with or a daily snack.

But Greek yogurt has a whey problem. Unlike the remnants of cheesemaking, which can be readily dried into high-value whey powders, the liquid left over from Greek yogurt production is too low in protein and too highly acidic for cost-effective processing.

That means a massive amount of liquid, called Greek yogurt acid whey, goes down the drain: U.S. Greek yogurt producers must dispose of roughly 2 million tons of the fluid annually.

“There aren’t good solutions for using or disposing of Greek yogurt acid whey,” says Lindsay. “Most of it goes to wastewater treatment plants, but that’s expensive and not great environmentally.”

Greek yogurt acid whey is mostly water, but it contains some sugars, salts and minerals. At 4 percent by volume, the most abundant component in whey besides water is lactose, which is the sugar responsible for some people’s intolerance to dairy.

In addition to causing allergies, lactose is far less sweet than table sugar, and it’s considered a low-value product for the chemical industry.

In fact, says Lindsay, lactose itself can be further broken down into two smaller sugars, glucose and galactose.

“There are a lot of ways to make high-value products from lactose if you split it in half,” he says.

Once split in half chemically, the two components can form the basis for a sweetener that could stand in for high-fructose corn syrup. That means Greek yogurt producers could flavor their products with a natural syrup, made in-house, while also diverting whey waste away from the drain.

It’s a sweet deal—especially as increasing numbers of health-conscious consumers seek products with no added high fructose corn syrup.

“The people we’ve contacted in the dairy industry say this could be very good,” says Lindsay. “And, the economics suggest that it could be very beneficial.”

The researchers’ economic analysis, done in collaboration with chemical engineering postdoctoral researcher Kefeng Huang, indicate that a large Greek yogurt facility could milk the process for almost $3 million per year, after taxes.

And the initial costs for constructing a Greek yogurt acid whey processing facility should run around $7 million, according to their estimates. That means a producer would be able to recoup its investment within a few years.

Currently, Lindsay and colleagues are working to optimize the process with solid catalysts; up until this point they’ve used liquid sulfuric acid to promote lactose-splitting, and and solid catalysts can be more practical at an industrial scale.

In the future, the scientists hope to investigate strategies for splitting the lactose in whole, unprocessed milk, which is a much more difficult problem due to the large amounts of fats and proteins in fresh-from-the-cow dairy. If successful, their efforts could dramatically reduce the cost of lactose-free milk.

A native Wisconsinite, Lindsay was quick to appreciate the project’s potential to benefit farmers in his home state. His research is somewhat unique compared to that of his lab colleagues, however—his advisor, Richard L. Antoine Professor of chemical and biological engineering George Huber, is world-renowned for studies of biofuels and breaking down plant materials into useful products.

“I’m the only grad student from Wisconsin in my lab, and I ended up with the dairy project,” he says.

Christos Maravelias, the Vilas Distinguished Achievement Professor and Paul A. Elfers Professor in chemical and biological engineering, advises Huang. Professor Scott Rankin of the Department of Food Science also collaborates on the project. The researchers have filed patent applications with assistance from the Wisconsin Alumni Research Foundation. The research is supported by Dairy Management Inc. grant # 133-AAA7735 A071300 4.