How to Keep Your Coffee Machine's Milk System Clean

Why milk systems block

Milk contains proteins, fats and sugars. When milk is heated and left in tubes, frothers and wands, it dries into a sticky film, then a hard crust. Bacteria grow in it, causing sour smells and off tastes. In a few days, a thin film becomes a blockage. In a holiday home closed up for weeks in humid air, the whole milk system can be solidly blocked.

Types of milk systems

Automatic milk systems with a tube

The machine draws milk from a container or carton through a thin tube, froths it with steam and air in a small frothing head and dispenses it into the cup.

Milk carafes

A jug attaches to the machine, with a built-in frothing head and tube. You store the carafe in the fridge between uses.

Steam wands

A metal pipe that blows steam into a jug of milk that you hold. Common on manual espresso machines.

Daily care

Automatic systems and carafes

• After each use: most machines run a short steam rinse automatically or when you press a button. Let it run.
• At the end of the day: run the milk cleaning programme in the menu. It flushes the system with hot water or a cleaning solution.
• Store milk properly: do not leave milk standing in the container at room temperature.

Steam wands

• Before frothing: purge the wand briefly to clear condensed water.
• After frothing: wipe the wand immediately with a damp cloth, then purge again for a second or two to blow out milk sucked back inside.
• Never leave milk to dry on the wand.

Weekly deep clean

1. Dismantle the frothing head, carafe lid or milk spout according to your manual. They usually come apart into several small pieces. 2. Soak the parts in warm water with a little dish soap or a milk system cleaner. 3. Clean small channels with a soft brush or pipe cleaner. 4. Rinse thoroughly and let dry. 5. Replace the milk tube if it is discoloured or cracked; tubes are inexpensive. 6. Reassemble and run a hot water rinse.

Check your manual before putting any milk parts in a dishwasher. Some are dishwasher-safe, many are not.

Milk system cleaner

Specialised milk system cleaners dissolve milk proteins and fats far better than water alone. Use one regularly, following the product instructions, especially if your machine sees heavy use.

Before you leave a holiday home

This is where St Francis homeowners can save themselves a repair:

1. Run the milk cleaning programme. 2. Dismantle all milk parts and wash them thoroughly. 3. Dry every piece completely. 4. Store the parts separately, not assembled, in a dry place. 5. Leave the machine's milk outlet area open to dry.

When you return, reassemble, run a hot water rinse and you are ready.

Signs of a blocked milk system

• Milk spurts or sputters instead of flowing smoothly
• Little or no froth
• Milk comes out cold
• A hissing sound but no milk
• Sour smell or taste

Try a full deep clean first. If the system still does not work, the blockage may be inside the machine, in the steam valve or internal pipes, and a technician needs to clean or replace parts.

Steam wand not steaming

If the steam wand only hisses weakly or not at all, the tip may be blocked with dried milk. Soak the tip in hot water and clear the holes with a pin. If steam is still weak, scale in the steam circuit may be the cause, and a descale or service is needed.