Two causes, and they taste slightly different.
Overheating
The common one. Milk tastes sweeter as it warms up to about 65 °C, then turns. Past roughly 70 °C the lactose degrades and the proteins denature further, and the flavour goes flat, cooked and faintly sulphurous. People describe it as burnt, though nothing has actually burned.
The fix is to stop earlier than feels right. Hand on the side of the jug, stop when it becomes uncomfortable to hold. That is about 60 to 65 °C and it will feel cooler than you expect if you are used to overheated milk.
Plant milks turn earlier still — stop around 55 to 60 °C.
A dirty steam wand
The one people miss. When steam stops, the pressure drop draws milk back up into the wand as it cools. That milk sits there, warm, until the next use, when it is blown into your fresh jug.
The taste is sour and stale rather than cooked, though people often report it as burnt.
The fix takes five seconds: purge the wand for a second and wipe it immediately after every use, while the milk is still wet. Baked-on milk is far harder to remove than fresh.
Actual scorching
On machines with a heating element in direct contact with the milk — cheap jug frothers rather than steam wands — milk really can scorch onto the hot metal. That is a design problem, and it is why induction frothers and non-stick jugs exist.
If it tastes burnt from the first sip and you did everything right
Check the coffee. An over-extracted, bitter shot can read as burnt through the milk, and people blame the milk because it is the last thing they touched.
Questions people actually ask
How do I clean the inside of the wand?
Purging after each use handles most of it. Once a week, soak the tip in a milk-system cleaner and purge again — most machines let you remove the tip for a proper soak.
Does the machine matter?
Somewhat. Very powerful steam heats fast and leaves less margin for error, which is why cheaper machines with weak steam are paradoxically easier to avoid overheating on.
Last reviewed 8 August 2026