Sugar plays a crucial role in making the super fluffy foam. Even though the surfactants in coffee serve well to help stabilize bubbles while you're foaming the liquid, they aren't strong enough to maintain the foam. Instead, gravity will pull the liquid down, air bubbles float up and air bubbles merge together.

How do you fix whipped coffee?

If it takes too long to create any foam, try cooling the coffee solution down by refrigerating it for a few minutes. Be careful not to leave it in the fridge for too long though as you don't want your water to be ice cold.

Why does whipped coffee foam?

The denaturing of the proteins reveals their hydrophobic parts. These face the air in air bubbles, while the hydrophilic parts face the water surrounding the bubble. The denatured proteins bond to each other to form a structure that stabilizes the air pockets into foam.