Coffee

# Barista Guides | Milk Basics

THE SCIENCE

Milk contains a number of different vitamins, minerals and proteins but we will be looking at the three main things that will impact how we use it on an espresso bar:

  • Lactose
  • Fats
  • Proteins

Lactose Lactose is responsible for the sweet and pleasant taste we find in milk, it is a solution made of sugars that is mixed into the liquid. The more we increase the temperature of the milk the more we dissolve the lactose, therefore increasing the perceived sweetness. If heated higher than around 60ºc, however, milk begins to lose it’s sweetness.

Fats The percentage of fats that milk contains can range from 0% - 4%. Higher fats increase the body or fullness of the flavour of the milk, making for a more pleasant texture.

Proteins Proteins are responsible for making milk foam the way it does and are very complex structures. These give stability to the air bubbles that we incorporate when steaming a jug of milk, allowing them to maintain their shape and become ‘micro-foam.’ At temperatures higher than around 60ºc the proteins begin to denature and lose stability, no longer maintaining the silky and creamy result we want.

STEAMING MILK

Step One: Start with cold milk and a cold jug. Starting at a low temperature gives you more time to texture the milk. When pouring milk into the jug, it should come to the bottom of the spout - too much milk will risk overflowing and spilling, and not enough will be too hard to steam properly.

Step Two: Wrap a clean cloth around the steam tip and purge for two seconds, removing any condensation left in the steam wand.

Step Three: Submerge the steam wand with the tip just under the surface. Activate the steam pressure then slowly and precisely lower the jug to introduce air into to milk - this will sound like a slight crackling noise. Make sure it’s controlled and you aren’t letting any big gulps of air in. The depth of the steam wand will determine how much foam is created on the top of the milk, (i.e. Cappuccino vs Flat White). Deeper will be thinner milk, shallower will be thicker.

Step Four: Make sure the milk is spinning like a whirlpool - this is called ‘texturing’ the milk and is how we make it silky. The easiest way to do this is to adjust the point at which the steam wand enters the jug (see diagrams). If it’s closer to the centre line, it will spin slower. If it’s further away, it will spin faster. The angle of the steam wand will also affect this.

Step Five: When the jug becomes an uncomfortable temperature and is too hot to hold, turn off the steam pressure and lower the jug.

Step Six: Wipe the steam tip thoroughly with a clean cloth and purge the steam wand again for two seconds, removing any milk residue.

Step Seven: Swirl to remove any larger bubbles. If you tap the jug gently on the bench you'll compromise 'microfoam' integrity. The more you turn the jug the more elastic & shinny the milk.

If all these steps were followed correctly, your milk should:

  • Be between 55ºc - 65ºc in temperature
  • Appear smooth, glossy and without any bubbles on the top
  • Have increased volume by 20% - 40% depending on type of drink (latte, cappuccino etc.)

TROUBLE SHOOTING

POURING THE MILK When pouring the milk it’s important to preserve the crema on the top as it’s responsible for that initial flavour that we taste when drinking a milk coffee and can influence the perceived ‘milkiness’ of the drink. We use two variables to control this: flow rate and the velocity of the fall of the milk, which is controlled by height of the jug from the cup. By limiting the flow rate we can limit the dissipation of the textured milk on top of the crema. By controlling the velocity we can push any textured milk that’s settled under the crema, enabling us to create that nice brown colour.