Federico Harte, Food Science and Technology

Archeological records show that humans began milking goats 7,000 years ago during the Neolithic era. Yet even with our long-term relationship with fluid milk, dairy products and dairy-based ingredients, key questions still remain on the structure and function of several crucial milk components.

In the institute’s Department of Food Science and Technology, researcher Federico Harte is working to determine the structure and function of casein micelles in milk. A casein micelle is a spherical structure (think soccer ball) of four protein molecules that forms when suspended in a fluid, in this case milk. Casein micelles are responsible for giving skim milk its distinctive whitish/bluish color. Their main accepted function is to transport calcium from mothers to young in all mammals. But there the agreement ends, with some scientists arguing there are other, so far nonunderstood, biological purposes. Research in Harte’s lab and in his department’s Biopolymers Group aims to find answers and identify functional uses of casein micelles for novel food and nonfood applications.

Despite over 100 years of research on milk proteins, Harte is the first scientist to produce a molecular model of a casein molecule — you can see it in 3-D at his lab’s website. With collaborator T. Dokland of the University of Alabama-Birmingham, Harte used cryo-electron tomography to demonstrate that the casein micelle is an open structure whose void spaces explain why skim milk is such an excellent vehicle for transmitting vitamins such as vitamin A, which is commonly added to milk. With UT chemistry professor S. Campagna, Harte has demonstrated that casein micelles also deliver nutrients, such as sphingomyelins, that aid infant development.

Harte says research in his lab is not only focused on biological and health aspects of the casein micelles. “We’re also conducting research on how processing affects the technological properties of the casein micelles. We’re using homogenization at very high pressure — five times the pressure in the bottom of the ocean’s Mariana trench — to modify the size and structure of casein micelles to promote better binding to other molecules.” This, Harte says, can lead to improvements in the quality and yield of traditional dairy products, such as yogurt and cheese. It also shows promise for creating new applications for dairy ingredients and that, Harte says, could benefit us all.

“Who knows?” Harte says. “Maybe in the next five years we will able to consume zero-fat yogurt, zero-fat ice cream and zero-fat cheese that fully resemble their full-fat counterparts but without sacrificing flavor and texture and with no added stabilizers!”

After all, casein micelles are part of the structural backbone of all dairy products, and improvements will happen when scientists fully understand the architecture of this fascinating component in milk. Harte’s work through UT AgResearch is paving the way for this breakthrough.

Federico Harte supplied the information for this article. Two dairy companies, the Dairy Research Institute, the U.S. Department of Agriculture and the National Institutes of Health provide funding for his research.

Figure. This is why skim milk is white: the casein micelle (there are 1,000 trillion casein micelles per milliliter of milk). This model shows a protein rich fraction (light blue), calcium phosphate-rich clusters (pink), and void areas that aid in the transmission of milk additives, such as vitamin enrichment.

The knowledge that AgResearch scientist Federico Harte is generating on casein micelles has enormous implications for the dairy industry, and Harte recently won the American Dairy Science Association’s Scholar Award in dairy foods — a tremendous honor for him and UT. Earlier this year he was recognized with the institute’s 2013 T.J. Whatley Young Scientist Award for his achievements and professional promise. His work has resulted in five disclosures and a pending patent with Bush Brothers on a technology that enables tracking the change in weight, volume and density of seeds during hydration.