How to Froth Milk for Latte? What's the Ideal Thickness for Espresso Foam? Beginner's Guide to Milk Frothing

Frothing milk is an unavoidable hurdle for many milk coffee enthusiasts. That's why FrontStreet Coffee has even brought out a blackboard to provide step-by-step guidance on how to create smooth, delicate milk foam.

Why Froth Milk?

Originally, latte coffee was simply made by heating milk and then mixing it with coffee, without any milk foam. Milk foam began to appear around the mid-20th century, when coffee machines were already equipped with steam heating wands, allowing one machine to handle both espresso making and milk heating simultaneously.

However, the heating principle of steam wands works by injecting high-temperature water vapor into milk to heat it. This heating method creates milk foam whenever air is introduced into the milk. People discovered that lattes with dense milk foam have better texture and superior heat retention. Later developments in latte art further advanced the study of milk frothing techniques.

How Can Beginners Master Milk Frothing Techniques?

First, let's understand the principle. Coffee machines use steam wands to inject water vapor into milk for heating. When the steam nozzle is in a semi-submerged state (half in milk, half exposed to air), it introduces air into the milk, and milk proteins wrap around this air to form milk foam. When the steam nozzle is fully submerged, it won't create new foam.

Here we can learn a key point: "The amount (thickness) of milk foam depends on how much air is introduced, a process called 'frothing'." During the air introduction process, there's a sharp "squeak~ squeak~~ squeak~~" sound, so some people use the "squeaking" sound as a reference for how much air to introduce.

The foam created during frothing is very coarse, meaning it has many large bubbles. These large bubbles are unstable, break quickly, and significantly affect texture. Therefore, a process called "texturizing" is needed. This is quite simple - just submerge the steam wand deeper to avoid the "squeaking" sound.

At this point, use the impact force of the water vapor to break down large milk bubbles into many tiny ones. Tiny milk bubbles have stable structures, last longer, and provide better texture. Both steps should be performed systematically, meaning we need to "direct" them to move in one direction, concentrating force to defeat the enemy rather than moving randomly without discipline. This is why we use a milk pitcher (latte art pitcher) positioned at an angle to the steam wand to create a vortex.

Practical Demonstration

1. Optimal milk volume for frothing: Frothing milk requires an appropriate volume. FrontStreet Coffee suggests using 40-60% of the pitcher's total capacity. Too little or too much milk both challenge your frothing technique. Of course, besides this factor, consider the actual amount of milk needed for one coffee to avoid excessive waste. The pitcher used by FrontStreet Coffee has a capacity of 550ml, with 250ml of milk (just reaching the bottom of the pitcher spout).

2. Frothing position: Before starting, turn on the steam wand to release condensed water vapor (then turn it off). Position the steam wand at a 45-degree angle, using the spout to stabilize its position. In this demonstration, the steam vortex rotates counterclockwise, with the steam wand positioned to the right of the liquid surface center cross, in a semi-submerged state.

3. Frothing stage: Turn on the steam switch, and you'll hear a "squeak—squeak" sound. This is the frothing stage. The frothing time varies depending on the desired foam thickness (longer frothing time means thicker foam). For 5 parts milk expanded to 6 parts (latte foam thickness), frothing takes about 3 seconds. The milk rotates uniformly to form a vortex.

4. Texturizing stage: Now fully submerge the steam holes, only heating without frothing. Don't bury the steam holes at the very bottom - it's recommended to keep them in the foam layer, which helps with texturizing (breaking down coarse foam into fine foam). When should you stop? This depends on your milk temperature, generally controlled between 55-65°C. Higher temperatures cause protein denaturation (typically, heat-induced protein denaturation in food occurs around 60°C).

5. Swirling and tapping: After frothing, the foam will gradually separate from the milk. At this point, you can swirl gently to let the foam and milk fully mix. If there are still 2-3 large bubbles after frothing, you can tap the pitcher on the table to break them. Of course, this action accelerates foam settling, so 1-2 taps are sufficient.

Practice Tips from FrontStreet Coffee

In the process above, FrontStreet Coffee has summarized some practice methods for beginners:

When starting to practice, use ice water first. This isn't just to save milk - well, actually, it's mainly to save milk... In general, when practicing with water, focus on two points. First, find a suitable position to create a vortex. The air inlet point mentioned by FrontStreet Coffee is just one of countless methods. In fact, each FrontStreet Coffee barista has a different air inlet point, but this doesn't prevent them from creating dense, delicate milk foam. So, what works best for you is what matters most.

Second, familiarize yourself with the relationship between heating temperature and time. Milk frothing is divided into two stages: the frothing stage and the texturizing stage. The total duration is the time it takes to heat milk from 7-11°C to 55-65°C, which is basically fixed. Therefore, it's about time allocation between the frothing and texturizing stages. Many beginners spend too much time in the frothing stage, leaving insufficient time for texturizing, resulting in coarse foam that breaks easily.

Of course, many beginners master the timing well but still can't achieve dense foam. One main reason is that the steam wand is buried too deep, causing the vortex to appear at the bottom while the surface foam isn't being texturized, though heating continues. Therefore, the optimal position for the steam wand during the texturizing stage is just deep enough to avoid making the "squeaking" sound.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473