All about air

28-02-2019 in Techniques
All about air

Foam can add an interesting element to the structures in a dish. However, it can often be a source of frustration. Does this sound familiar? How can you make a foam that remains stable for long enough without ending up as a runny sauce on the plate? Is it possible to make a foam without using powders from molecular gastronomy?

Types of foam

There are several different types of foam. Cold foams such as the well-known espuma or an espresso and vanilla foam. Warm foams such as a foam made from roasted spinach or warm mayonnaise. You can also make extremely airy warm beurre blanc sauces by adding egg white.   

Warm foams

To create and maintain a warm and stable foam, you need to bear a few things in mind. When you add egg white to a sauce and froth it up using a hand-held blender, it will remain stable for longer. Make sure that you do not let the temperature exceed 75°C after adding the egg white. Above this temperature, the egg white will coagulate and flakes will become visible in your sauce.  
To make sure you create a stable foam, there are a number of emulsifiers that you can add, such as:

Can warm foams be made with a siphon?

These are the simplest foams to make. Just add egg white to a purée or soup base and mix together. Transfer to a siphon and aerate with one cartridge. Heat up in hot water to a maximum of 75°C. Is it really that simple? Yes, it is.

Cold foams

Cold foams behave slightly differently from warm foams. Foams based on yoghurt, quark, single cream, or whipping cream remain stable because of the fats they contain. If using liquids with less or no fats, the liquid needs to be gelled.  
Gelling agents for cold foams:

The amount you need to add differs per product. To make a stable espuma such as the firm watermelon espuma, add 16g of gelatin leaves to one litre of liquid. In other recipes, such as the cucumber and oyster foam, you need to add less than a third of this amount of gelatin to a litre of liquid. This is because of the milk in the recipe. The milk provides a small amount of fat in the liquid in which the air can be captured.

Keep it airy

Use one of the abovementioned products to make your foam stable. Make sure that the temperature is not too high or too low before the foam is brought to the table. Try to make the air bubbles in your foam as small as possible. These will be firmer and will last longer. To create an airy sauce, place a spoon with the hollow side next to the hand-held blender. The bubbles you create will remain small and will no longer be broken. This is something you cannot control if you make the foam using a siphon.

There are many different methods you can use to stabilise foam. Some of them you can find in your store cupboard, others can be bought from a supplier. Consider the temperature of the foam. Foam that is too cold is less frothy and foam that is too warm will collapse. If you feel inspired after reading this explanation on foam, then take a look at the technique page working with a siphon where you will find various types of foam or have a look at the various warm sauces to see which ones can be frothed up for serving.

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