What ingredients will allow me to make a foam with a whipped cream charger?

Question

So I have an iSi whipped cream charger. There are a series of recipes that sound really interesting, but I don't quite understand what ingredients you need in order to make a stable foam / mousse. Some common ingredients seem to be cheese, cream, and gelatin. But I've also seen recipes with chocolate and water (melted and combined), lecithin, or even scrambled eggs with sous vide eggs, skim milk, and butter.

So what ingredients are a must for making a foam? How do they work?

I must admit, I'm more interested in the "how" than the "what". The what seems to be pretty well defined in the list or recipes, but I want to be able to create my own culinary treats and understanding the process is invaluable in making things up.

Answer 1

A foam is just a liquid with plenty of air incorporated into it. You can incorporate air into any liquid; in order to be able to create an actual foam, however, you need to be able to incorporate the air faster than it escapes.

What makes a liquid able to hold the air you're incorporating (and hence form a foam) is a foam stabilizer, also commonly called an emulsifier¹. I know of no specific taxonomy of stabilizers, but the vast majority are hydrocolloids AKA gelling agents and belong to some family of protein.

• Agar, carrageenan, alginate, xanthan, and pectin are all types of polysaccharide;
• Lecithin is mostly a random collection of phospholipids;
• Gelatin is denatured collagen, i.e. animal protein;
• Whey protein is the prevalent protein in dairy products;

And so on. Really almost any emulsifier will do. Basically everything in your list either is, or contains, one of the the additives mentioned above:

• Chocolate is almost always emulsified with soy lecithin;
• Eggs contain high amounts of lecithin;
• Milk and cream contain whey protein;
• Most "supermarket cream" also has emulsifiers like carrageenan already in it.

...you get the picture, I hope. The most basic answer I can give to this is that if you want to make a foam, you need to either use something that's already an emulsion (milk, butter, chocolate, etc.) or use an emulsifier/stabilizer additive (such as gelatin, lecithin, etc.)

If you want a relatively complete list of all of the food additives that qualify, you'll want to look at the E number, and specifically E400-499 (thickeners, stabilizers, emulsifiers).

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_{1. As commenter Erik very correctly points out, an emulsifier is not the same thing as a foam stabilizer. However, by convention, the terms seem to be used interchangeably all over the place, to the extent that I get blank looks when I refer to a "stabilizer" as opposed to "emulsifier". So, know the difference, but don't get too hung up on it.}

Answer 2

There are many, many methods to making a mousse. From simply folding melted chocolate into cream, to making a ganache and then folding that in, to making italian meringue and folding that in.......Normally, it is always something folded into a whipped cream.

My favourite way to make a supple, nice, flavourful mousse is to prepare a bombe, and fold that in.