Milk systems on bean-to-cup machines are the part most likely to become a hygiene problem.
After every use
Run the rinse cycle. Almost every machine has one, usually prompted automatically. Let it run.
Refrigerate the carafe immediately if the milk is staying in it. Milk at room temperature in a tube is a bacterial culture.
Never leave milk in the system overnight.
Daily
Rinse the carafe, lid and tubes under warm running water, dismantled.
Most carafes come apart further than people realise — the lid usually separates into three or four pieces, and milk collects in every join.
Weekly
A milk-system cleaning solution through the full cycle. These are alkaline detergents that dissolve milk proteins and fats, and water alone does not.
Soak the removable parts in the same solution for 20 minutes and brush the tubes with a small brush.
What builds up
Milk stone — a hard deposit of calcium and denatured protein — forms on surfaces and cannot be rinsed off. It harbours bacteria and it needs a proper detergent.
For manual steam wands
Simpler and just as important: purge immediately after use and wipe with a damp cloth while still hot.
Soak the tip weekly in milk cleaner and clear the holes with a pin.
The signs it is overdue
A sour smell, reduced steam or milk flow, and visible residue in the tubes.
Last reviewed 8 August 2026