How to froth soy milk

Every day more and more people discover that they are lactose intolerant, and in my house, this happened seven years ago when my daughter was born. To simplify things, we all decided to switch to other types of milk, and of course, today we make our cappuccinos with soy milk. Nowadays we can’t live without this vegetable milk which is so good for us.

The problem is that soy milk does not create froth like cow’s milk. Frothing cow’s milk is easy once you have practised a little, but frothing soy milk is a different story. As this milk is different, the technique will be different too, but you can achieve better results with a little care than with traditional milk.

How is it made, and what is soy milk?

To understand how to froth soymilk correctly, we must first understand what it is and how it is made. Soy is a legume rich in essential fatty acids, proteins, vitamins and minerals, from which soy milk is obtained.

To get the milk from this legume, you have to clean it, boil it, and grind it with water. The result is a supernatural (100% vegetable) and rich drink, with a texture and consistency very similar to cow’s milk.

Soy milk has a characteristic flavour that creates unique drinks when mixed with coffee. You won’t want to go back to cow’s milk once you get used to drinking a good cappuccino with soy milk. Moreover, the digestion of this product is light and fast.

What exactly is milk froth?

I’m sure you know the difference between good and bad milk froth. Low-quality milk foam has large bubbles and little consistency that disappears after a few minutes. On the contrary, a good quality milk froth remains in the cup for a long time, where the microbubbles are so small that you can hardly see them.

When a good quality milk froth is made, it resembles a “cream” rather than a foam. Even when stirred with a spoon to mix it with the coffee, the froth changes colour but remains on the surface of the cup. To achieve a consistent and long-lasting milk froth, we need to create the froth “physically and chemically”:

  • A physically created froth is created by blowing bubbles into the milk with a frother or frother.
  • A physically and chemically created froth is one that not only creates the micro-bubbles but also combines them with the milk proteins to give them elasticity and consistency.

How to froth soy milk?

As we have just seen, to achieve a quality froth, we need to create it physically and chemically. From a physical point of view, we will treat the soymilk more or less as we treat cow’s milk by introducing air into it to create micro-bubbles. However, the chemical composition will be more difficult because of the differences in the proteins and fats in the two kinds of milk.

The proteins and fats help us give elasticity and consistency to the microbubbles we form in the milk. One of the strong points of cow’s milk is the presence of large quantities of proteins and fats, which are also very resistant to temperature. In contrast, soy milk contains fats and proteins that are more sensitive to temperature and break down easily.

1. Use of soymilk with additives

To froth soymilk like a pro, the ideal is to use milk containing specific additives like Gellan gum. This is a food additive of natural origin, very resistant to high temperatures, which is added to certain soy milk specifically for foaming.

Gellan gum and other additives such as carrageenan have natural origins, so they are suitable for vegans. Gellan gum is obtained from the fermentation of sugar with certain bacteria. This component gives soymilk a particular texture and stability, especially when it is heated and frothed.

In the image below, you can see a picture of Alpro Soy Professional milk with Gellan gum:

Gellan gum
Gellan gum

2. Start frothing with cold soy milk

Soy milk has a lower protein content than cow’s milk and is very sensitive to temperature increases. In addition, these proteins decrease as we heat up, so a very rapid temperature rise could lead to curdling of the milk.

So that our soymilk does not heat up too quickly while forming the microbubbles, it is advisable to start frothing the milk quite cold. Always keep the soymilk in the refrigerator so that the temperature rise during frothing is as slow as possible.

Never mix cold soymilk with hot soymilk in the jug to ensure you start from the coldest possible temperature. Also, cool your jug as much as possible before adding the soymilk to ensure you start from a low temperature.

3. Don’t overheat soy milk

Cow’s milk is usually heated to 60 – 63ºC when frothing, which is the limit when the steam wand of a coffee machine starts to make a high-pitched sound. Novice baristas use thermometers to maintain this temperature; however, with practice and the appearance of the frothed milk, we will know when we have reached this range.

As the weak soy milk proteins are very sensitive to temperature, we will not heat the milk too much. If we were to bring it to too high a temperature, we would find ourselves with too much froth, which would ruin our final drink, not to mention the possibility of the milk curdling.

A step-by-step guide to frothing soy milk

Now that you know the strengths and weaknesses of soymilk, it’s time to get down to work. Remember that we can’t bring the milk to high temperatures, nor can we do it too quickly. Below, we will explain how to froth soymilk step by step, using different means:

Frothing soymilk with Aeroccino

  1. Always use cold milk. Avoid mixing it with room temperature or heated milk.
  2. Stir the milk well before pouring it into the Aeroccino. As it is vegetable milk, it may not be well mixed.
  3. Fill slightly lower than you would with cow’s milk.
  4. If you use an Aeroccino 3, remove the spring to make less foam. If you use the Aroccino 4, press the lower froth button.
  5. Stop the process as soon as the froth is generated. Too much froth could ruin your cappuccino or latte if you froth too much.
  6. Do not overheat the milk, or it may curdle when it comes into contact with the coffee.
  7. When adding the foam to the coffee, add it slowly to avoid curdling.
Select the lowest frothing level on the Aeroccino
Select the lowest frothing level on the Aeroccino

Frothing soymilk with a steam wand

  1. Always use cold milk. Avoid mixing with leftover milk from other preparations or milk at room temperature.
  2. Stir the milk carton well before use.
  3. Use a clean, cold metal jug.
  4. Fill the jug less than half full, as soymilk froths more than cow’s milk.
  5. Do not open the steam wand to the maximum, as you will need less steam to generate the froth.
  6. Insert the steam wand shallower than you would with cow’s milk.
  7. Once the froth has been created, stop the preparation so as not to overheat it and curdle.

Frothing soy milk with an electric hand frother

  1. Slightly heat the soymilk in the cooker. Do not heat it as much as you would heat cow’s milk.
  2. Pour the hot milk into a jug suitable for frothing.
  3. Insert the whisk lightly into the milk.
  4. Start frothing in 5 to 10-second intervals, stopping the process for another 5 to 10 seconds.
  5. Froth until the desired foam is achieved, but do not overdo it, or your final drink will not have a good finish.
Written by Pablo Barrantes Nevado
I am Pablo Barrantes, a coffee lover. I decided to start this website to solve all the doubts that arise every day when preparing our favorite drink: coffee. I am an industrial engineer by profession, but I have worked in coffee shops for many years, where I have learned all the secrets about coffee machines and coffee. My passion for coffee has led me to investigate and study beyond the obvious, and thanks to this, I can offer solutions and give news about coffee and coffee makers. I hope you enjoy reading as much as I research, document and write here.

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