How to Make Froth in Coffee and Keep It Stable

Foam dissipates quickly when the milk foam lacks stability, which comes down to frothing technique, milk temperature, and coffee bean freshness. Injecting air into milk creates a foam that is lighter than the liquid, so once the drink sits still the foam floats up, the liquid settles, and the bubbles merge and burst. A stable foam can hold for around ten minutes before obvious breakdown.

How long to froth milk for latte matters, but so does when you stop. Over-aerating adds large bubbles that pop fast, while overheating milk weakens the protein film around each bubble. Use fresh milk, keep the pitcher and milk cold, and aim for fine, even bubbles rather than volume. Fresh coffee beans also help the crema support the foam.

A freshly made latte has a surface as smooth as silk, but after sitting for a moment it develops rough bumps and hollows—this is the process of milk foam dissipating. Milk foam is essentially foam formed when air is injected into milk; when left to stand, it separates into layers due to differences in density, and small bubbles gradually merge and burst. The speed of dissipation depends on milk foam stability, which is affected by multiple factors such as frothing technique, milk temperature, and coffee bean freshness. Drawing on Front Street store experience, this article systematically analyzes the major causes of rapid latte foam dissipation and offers practical improvement suggestions to help coffee enthusiasts enhance latte art quality and taste experience.

A just-finished latte usually presents a uniform, delicate surface that looks very smooth visually. However, if it is set aside without being drunk, you will observe that the originally level surface gradually becomes rough, with bumps and hollows of varying sizes appearing. This phenomenon is called "foam dissipation," and it is essentially the ongoing process of milk foam breaking down. Milk foam is a foam structure formed by injecting air into milk, so its density is lower than that of liquid milk. Under external forces such as frothing, shaking, and mixing, most of the foam will mix thoroughly with the liquid, and at this point the milk foam breaks down relatively slowly. But once it enters a resting state, the lower-density foam slowly floats upward while the higher-density liquid settles downward, and layering occurs as a result.

After layering, due to the pressure difference between the foam and the liquid, small bubbles gradually dissolve and merge with one another into larger bubbles. When the internal pressure of a large bubble exceeds the strength that the protein film surrounding it can withstand, the bubble bursts. Although the milk foam floating on the surface of a latte will eventually dissipate, the speed of breakdown varies. For example, a latte served at a Front Street store only shows obvious signs of foam dissipation after about ten minutes; while some lattes, not long after being made, already have many large bubbles on the surface, and the overall appearance is coarser.

The reason these two lattes differ so significantly in foam dissipation speed fundamentally lies in the level of milk foam stability. The higher the milk foam stability, the slower the dissipation; the lower the stability, the faster the dissipation. If you find that a latte dissipates quickly right after it is made, it often means the milk foam stability is insufficient. Among the many indicators for judging the quality of a latte, milk foam stability is one of them. There are many factors affecting milk foam stability. Below, Front Street will analyze them one by one for everyone, specifically what causes influence milk foam stability.

Front Street believes that a beautiful latte art piece cannot be separated from solid milk frothing technique, and it also requires a bag of fresh coffee beans with excellent flavor. Friends who want to practice latte art at home can choose Front Street Classic Blend. This coffee is composed of beans from three producing regions and is a medium-dark roasted espresso recipe. Its design inspiration comes from the early popular "Manba" combination, namely Mandheling and Brazil. In order to enhance aroma and crema, Front Street Classic Blend also adds a small amount of Robusta, further increasing flavor intensity, so beginners can easily extract espresso with golden crema at home.

If you prefer complex nutty aromas such as almond, apricot kernel, and walnut, Front Street Specialty Blend and Front Street Dark Cocoa Basic Blend are recommended. Both contain a high proportion of Brazilian coffee beans, bringing a pleasant bittersweet taste and an extremely smooth mouthfeel. Among them, Front Street Specialty Blend has the nut, chocolate, and caramel flavors characteristic of Colombian coffee, along with a pleasant acidity; Front Street Dark Cocoa Basic Blend incorporates the ripe plum acidity of Yunnan smallholder coffee and, after grinding, releases a creamy chocolate aroma. It has a balanced taste and high versatility; besides making lattes, it can also produce a variety of espresso drinks.

1. Improper milk frothing The most common reason is that the milk foam was not frothed properly. As mentioned earlier, milk foam is made by injecting steam into milk, but merely injecting air is far from enough; the large bubbles produced also need to be textured, cutting them into countless smaller, more stable microfoam bubbles. If the texturing stage is handled improperly, the quality of the milk foam produced will be lower, stability will be insufficient, and the latte made from it will dissipate much faster.

There are mainly three situations that lead to insufficient texturing. The first is that the texturing time is too short, usually because the milk temperature is not low enough, or the target frothing temperature is not high enough, causing the texturing time to be compressed. Without sufficient texturing time, the milk foam naturally will not be fine and dense enough, and the dissipation speed will be faster. The second situation is a problem many beginners often encounter: the milk is not driven by the steam to form a vortex during texturing.

When the milk does not form a vortex in the pitcher, the large bubbles generated earlier cannot be drawn into the milk and cut apart. This is similar to the previous reason: if the bubbles are not fully textured, the dissipation speed will naturally be faster. The third situation is one that even experienced baristas cannot always avoid: during texturing, the steam wand is accidentally exposed above the liquid surface, causing a brief second aeration, and because there is not enough time, these newly created large bubbles are not fully textured. Their presence will likewise accelerate milk foam dissipation.

The above three points are problems easily encountered during the texturing process. If after finishing latte art you can see many obvious bubbles in the pitcher, it is best to check whether any of the above situations occurred during texturing, and if so, improve them. In addition, after frothing the milk foam, we usually tap the pitcher to eliminate large untextured bubbles, which is indeed effective. But when the pitcher is tapped too many times, both the breakdown speed and the layering speed of the milk foam will accelerate. Therefore, when tapping the pitcher, try to control the number of times and the force.

2. Milk temperature too high Next is the milk temperature issue. As mentioned earlier, when the milk frothing temperature is not high enough, the milk foam will have insufficient stability because the texturing time is too short. Similarly, when the frothing temperature is too high, the stability of the milk foam will also decline.

When beginners learn to froth milk, the first thing they need to master is controlling the milk temperature. After frothing, the milk temperature is best kept between 55°C and 65°C. The reason for controlling it within this range is not only that this temperature can bring out the sweetness of the milk, but also that the milk foam can achieve quite high stability. When the milk temperature is below this range, as mentioned earlier, faster dissipation may result from insufficient texturing time; and when the temperature exceeds 70°C, some components in the milk will be damaged by the high heat, and milk foam stability will drop sharply. Not only will the dissipation speed become faster, but the taste and sweetness of the coffee and milk will also decline.

Therefore, when you need to make delicate latte art, the milk temperature is best controlled between 55°C and 65°C. If not for latte art, the milk temperature only needs to remain no higher than 70°C. 3. Material-related issues Besides operational factors, the use of materials can also determine the speed of milk foam dissipation. For example, when the coffee beans used are very fresh, foam dissipation will be accelerated. This is because fresh coffee beans contain a large amount of carbon dioxide. Although this helps extract richer crema, the crema itself is not stable enough and will break down quickly. When unstable crema combines with stable milk foam, the milk foam also becomes less stable, and the dissipation speed therefore accelerates.

This situation is the easiest to solve: simply let the coffee beans rest for about seven days, allowing the internal carbon dioxide to fully escape. The espresso crema extracted in this way will have higher stability and will not have much impact on the milk foam. These are the several reasons why milk foam dissipates quickly when a latte has just been made. In addition, the choice of milk, milk foam thickness, and mixing uniformity can also have an effect, but relatively speaking their influence is smaller, so Front Street will not elaborate on them in detail here.

The above content is compiled by CoffeeHunters, a coffee news website.