Introduction: The Science Behind Foams
Foams are a great culinary invention. They can be traditional as well as modern, they can be decorative and at the same time taste well. You can be really creative with the color, density, texture and airiness of the foam. There are quite a few foaming agents and tools that you can use to make foams but I would like to show you the basic foams (and how to make them) using the ingredients and equipment that you already have at home or that is easy and inexpensive to get.
Step 1: Bubbles
The bubbles are the lightest type of foam. They are really great choice if you want your meal to look modern. The only downside is that they don't hold for very long, therefore, you should add them to the dish right before the consumption. To make the bubbles a bit more resistant, use a foaming agent.
Bubbles without foaming agent
In the first two pictures you can see some raspberry smoothie made with full-fat milk. No foaming agent was used. How to make it: Use a potent table blender which will create much more foam. Combine 2 cups of raspberries with 0,5 liter of milk. Add some sugar or honey if you want the smoothie to be sweet and blend it for several minutes changing from the highest speed to lower speed and back.
Bubbles with foaming agent
What you see in the second picture is parsley foam made with a foaming agent - xanthan gum. The ratio to make light foams (and that I use to make bubbles) is 0,1 %. That means that if I use 100 grams of mixture, I add 0,1 % of xanthan gum. How to make it: Combine handful of parsley leaves and some water to give in total 100 grams. Blend it well, this time even with a stick blender. Then add 0,1g of xanthan gum and blend it again.
Step 2: Fluid Gel Foams
As you probably guessed, these foams have the consistency of somewhere between gel and shaving cream. To make them you need a foaming agent and a whisk (electrical or just simple hand whisk, I explain below why this type of foam cannot be made just with a blender). I find the easiest ingredient to make a fluid gel foam is the banana. To give you an example, I made some banana foam using two different ratios of xanthan gum - 0,2 % and 1 %. You can see the difference in the second picture. The foam made with the smaller ratio is somewhat more airy, the second one is more dense.
How to make it: Blend a large ripe banana until it's completely smooth and liquid. Add the desired ratio of xanthan gum and whisk it fast (I use the fastest speed on my whisking machine). It is import to really whisk and not just blend these ingredients, as a blender will make the foam too liquid.
Step 3: Whipped Foams
Whipped foams are very dense and wet, such as the whipped cream. They hold their shape pretty well (although that also depends on the ingredients) and you can make them with or without foaming agents. Whisking is absolutely crucial here, maybe you have tried putting egg whites into your blender. In this case you already know what happens - the egg whites become very liquid.
Without foaming agent
A typical example are whipped egg whites (first picture). To stabilize them you can add some foaming agent and here I want to give you a tip on how to use the whipped egg whites for decoration: Place 2 egg whites in a bowl and whip them until they are completely dense - turn the bowl upside down and the egg whites shouldn't move. Then add a tablespoon of powder sugar and slowly mix it in by hand. Use cake decorating set, fill the tube and use this mixture to decorate cakes and cookies. The mixture will harden quite fast. In the second picture you can see a decorated gingerbread heart.
With foaming agent
In the last picture you can see again some parsley foam, this time made with gelatin. I used 2 teaspoons of gelatin powder for 100g of mixture because I wanted my foam to be very dense but you can use lower ratio or just follow the instructions on the package. How to make it: Boil about 100ml of water with 2tsp of gelatin powder. Switch off the stove and add a handful of parsley. Blend all well and let the mixture cool down. When it's completely cool, it shouldn't be liquid anymore. Now take an electrical whisk and whip it very fast.
Step 4: Meringue
Maybe the Pavlova cake comes to your mind. A meringue is made from whipped egg whites combined with sugar and sometimes other ingredients, and baked. How to make a simple meringue: Whisk 2 egg whites like in the previous step and then slowly mix in a tablespoon of powder sugar. Place a baking sheet on a tray and with a cake decorating set or just with a teaspoon put small portions of the mixture on the baking sheet. Preheat the oven on 150 °C, place the tray in the oven and bake the meringues for 10 minutes, they should become golden brown. Then lower the temperature to 50 °C and keep baking the meringue until it's completely dry. It should melt in your mouth. To make this recipe a bit more interesting, you can mix in also a tablespoon of grated coconut.
I hope you enjoyed this instructable and that you have lots of fun foaming it up!