The term 'stretching' milk is used to refer to the technique to heat and create a desired amount of foam for a milk based espresso drink. This post will explain a little about how to create the perfect latte, cappuccino or flat white through correctly steaming and stretching milk. To ensure you get the best results it is important to start with nicely chilled milk, followed by ensuring your milk pitcher is also cold. To achieve this it is best to keep your milk in the fridge up until the point that you need it, further to this I find that it is beneficial to put the milk pitcher into the fridge or even freezer for a minute or two before you start steaming.
To begin heating your milk, it is important to first purge the steam wand on your espresso machine. This simply allows any built up water to be released rather than being put into your milk. Choose the correct size pitcher for the amount of milk you are going to be heating, as milk will expand when heated and sometimes double in size (especially if you are creating a lot of foam) the rule of thumb here is not to fill the pitcher over about half full, this allows plenty of room for the milk to expand and for it to move in the jug.
When you are ready, raise the milk pitcher until the end of the steam wand is completely submerged in the milk and turn on the steam wand. This begins the heating off the milk, at this point you want to slowly lower your pitcher while the milk is still cold until the end of the steam wand meets the surface of the milk. You will know you are in the correct spot as it will make a 'kissing' sound. This kissing sound is and indication that air is being incorporated into your milk and creating micro foam bubbles. If you lower the pitcher too much the foam is going to consist of large bubbles which is not going to provide you with a smooth foam.
You should continue 'kissing' the milk (this is the stretching part) until you have the desired amount of foam for the drink that you would like, longer for a cappuccino and shorter for a latte. Once you have enough foam submerge the steam wand again until the milk reaches the desired heat.
At this stage you should shut off the steam wand, remove the pitcher and wipe down the steam wand to remove any milk. It is important then to purge the steam wand once more, doing so removes any milk from inside the wand and preventing it from making its way back into the steam boiler.
At this stage you have completed the stretching process, if there are any large bubbles in your milk you can gently tap the pitcher on the counter to remove these. You may need to work the milk slightly by swirling the milk in the jug, this will ensure that the foam is incorporated with the milk which is important when pouring your drink especially if you plan on practising your latte art! Your milk is ready to be poured over your perfect espresso shots and enjoyed!