Milk that has been steamed once cannot be steamed again to any useful effect.
Why
The proteins have already been denatured. Casein and whey unfold during heating and wrap around air bubbles. Once they have done that, they cannot do it again.
Re-steaming produces large, unstable bubbles that collapse immediately.
The taste
Milk heated twice tastes distinctly cooked — flat, slightly sulphurous, with none of the sweetness that fresh steamed milk has.
Every additional heating makes it worse.
The food safety angle
Milk held between 5 °C and 60 °C is in the temperature range where bacteria multiply. Steamed milk left in a jug on the counter and re-steamed later has spent time there.
Cafés discard leftover milk for this reason and it is a real one.
What to do instead
Steam what you need. Fill the jug to just under the spout for the drink you are making.
A small jug for one drink is the practical answer — trying to steam 100 ml in a large jug does not work, so people over-fill and waste.
Using leftover steamed milk
Drink it, cook with it, or discard it. It is perfectly fine to add to a filter coffee or use in porridge.
Do not put it back in the bottle.
The exception
Milk that was heated but not steamed — warmed in a pan and never aerated — foams no better, and it is at least not degraded further. Still not ideal.
Last reviewed 8 August 2026