When casein (a protein in milk) meets polyphenols (natural compounds in tea, wine, or fruit), they stick together in different ways—like magnets and glue—and this changes the protein’s shape and how it works.

Casein, a protein in milk, sticks to certain plant compounds and minerals differently depending on things like how acidic the environment is, how hot it is, or how salty the solution is — and also depends on the shape and size of the stuff it’s sticking to.

When you add milk to your coffee, the protein in the milk (casein) latches onto the healthy compounds in coffee, making it harder for your body to absorb them—so you get 30% to 60% less of their benefit.

When milk proteins (casein) mix with certain plant-based fibers (polysaccharides), they can either stick together or push apart based on conditions like acidity and salt levels, changing how the final dairy product feels and looks.