Milk and Plant-Based Drinks

Dairy milk is a stable emulsion of fat, water, and protein, and its protein is what lets it hold a foam. Plant drinks are suspensions built from ground nuts, grains, or seeds, and each one foams, splits, and sweetens differently depending on what it is made from and what has been added to it.

That is why one oat drink behaves beautifully in a flat white and another curdles on contact.

Protein is the tell.

Dairy and soy carry enough of it to build a stable foam, and the drinks that do not have to borrow structure from added gums and oils instead.

Splitting and foaming are separate failures with separate causes. A drink can foam beautifully and still curdle, because foam is a protein question and curdling is an acid and heat one.

Barista versions are a reformulation rather than a marketing tier. They add fat, protein or buffering salts specifically to survive a hot acidic shot, which is why the ordinary carton behaves differently.

Sweetness is often created rather than added. Oat drinks are made by treating the starch with enzymes that break it into sugars, so an unsweetened oat drink can carry more sugar than a sweetened nut one.

An opened carton fails abruptly rather than gradually. Plant drinks separate and sour with little warning, which is a different habit from dairy going off slowly.