Milk proteins and caffeine in espresso The swirl of milk and espresso—a small storm in your cup—does not affect the dynamics of milk proteins, according to research published in ACS Food Science & Technology. Researchers took a molecular look at how milk proteins and caffeine molecules interact with each other in water and in coffee. The results suggest that the structures of milk proteins remain intact, which means they retain their original mouthfeel and taste in your morning drink.

Adding milk to coffee causes the proteins (e.g., combining or repelling) to interact with compounds extracted from roasted, ground coffee beans, which could change the mouthfeel of the milk proteins and the way they are digested. Milk proteins could also potentially affect the absorption, or bioavailability, of caffeine in the human body. To shed light on these mysteries, Tobias Weidner and Fani Madzharova used 2D infrared spectroscopy to investigate the molecular structures and dynamics of milk proteins when in coffee. They evaluated increasingly complex mixtures of store-bought full-fat milk (3.5%), water solutions with milk and caffeine, and handcrafted cappuccino.

Unaltered protein structure
They found that the folding of milk proteins was not altered by the presence of caffeine in these beverages, even in cappuccino, which contained components extracted from coffee beans such as chlorogenic acid. Additionally, while previous studies reported that caffeine slows the molecular movement of water, this study showed no significant effects of caffeine on the mobility or dynamics of milk proteins. These experimental results provide a useful molecular picture of some components affecting the texture, taste, and nutritional properties of coffee drinks with milk ingredients, which researchers say could be applied in future beverage engineering.

Significance of funding
The authors acknowledge funding from the Novo Nordisk Foundation, the Danish National Research Foundation through the Center of Excellence for Chemistry of Clouds, and the European Union through the Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant.

Source: ACS