A guide to food emulsions, culinary foams, and gels

We’ve come a long way since the days of the random, often non-edible, garnish placed on the plate in the name of presentation. Wrestling a length of tomato skin into something vaguely resembling a rose is no longer considered sane or sensible. Fast forward to this century and your garnish can make or break your plate.

An integral part of any dish, a well-considered garnish will add layers of flavour and texture that bring both variety and balance. And yes, colours and shapes for visual appeal are important too. Take away the garnish and what you have is an unfinished plate of food.

Getting it right involves three things. An understanding of what you are trying to achieve. The knowledge of how to get there. And the right tools for the job.

One way to garnish glory is a thorough understanding of emulsions, gels, and foams. Emulsions in food are nothing new and many classic sauces are emulsions. Foams and gels have been part of the chef’s repertoire for a good while too. Yet a more precise understanding of underlying principles coupled with advances in ingredient technology has led to a greater freedom of expression than ever before.

Let’s begin by going back to basics.

What is an emulsion?

An emulsion is a mixture of two liquids that are unmixable. Oil and vinegar, for example. A vinaigrette dressing is one of the simplest forms of emulsion in the kitchen. Most of the emulsions in cooking are of oil in water, where the oil droplets are suspended throughout the water. Like our vinaigrette.

Another, less common form of emulsion in food is water in oil, where the water droplets are suspended in the oil. Butter is a water in oil emulsion, with milk suspended through butterfat.

Emulsions can be temporary, semi-permanent, or permanent.

In the case of our vinaigrette, we have a temporary emulsion. A vigorous shake is all it takes to disperse the oil in the vinegar, but it will separate back out almost immediately. Shake it again, however, and it will emulsify once more. You could do this indefinitely.

Hollandaise is a semi-permanent emulsion. Eventually it will split out, and it takes more than a simple whisk to bring it back together.

Mayonnaise is a permanent emulsion. It may split out if you try to add more oil than it can manage, but once made it will stay that way.

What is the difference between a gel and an emulsion?

A gel follows the same principles as an emulsion yet rather than have two unmixable liquids coming together, this time we have a liquid suspended in a solid. That’s a pretty strange concept but take a second to think about how jelly moves, and it makes perfect sense.

Emulsions, foams, and gels all belong to the same family of compounds. A group known as colloids. What’s a colloid? A colloid is a mixture where an insoluble substance is suspended within another substance. Like oil in vinegar. Or water in jelly.

So, what’s a foam then?

A foam is a gas suspended in liquid. In cooking, the gas is most often air incorporated through the action of whisking. Whipped cream for example. Strictly speaking, whipped cream is an emulsion and a foam. Cream, like butter, is an emulsion of fat, water and milk protein, which creates a structure in which to trap the air.

And that brings us nicely to espuma.

Espuma is just foam, right?

Espuma is to blame for all of it. Espuma called time on all the haphazard garnishes and pointless things on the plate. Espuma was the re-invention and re-interpretation of flavour.

Espuma is simply the Spanish word for froth or foam. Remember how Ferran Adria was one of the pioneers of molecular gastronomy? In Spain? Well, the term espuma is used for foams created specifically using a siphon. Overnight, the thing that used to be called a cream gun became the espuma gun. Its purpose was to create culinary foam without an emulsifier. Adria felt that bypassing the emulsifier was the way to purer, cleaner, unadulterated flavours. A way of introducing a natural flavour but in a different form. Capturing the very essence of flavour.

Which begs the obvious question…

What is an emulsifier?

Let’s return to our definition of an emulsion. Two unmixable liquids mixed together, right? Oil and vinegar whisked together do indeed form an emulsion. You do not need an emulsifier to create an emulsion. But, as we all know, vinaigrette is more than just oil and vinegar. Something else is in there, and it is not just for depth of flavour. That thing is mustard. The addition of mustard creates a new thing altogether. A lovely viscous substance that now clings and caresses instead of sliding sadly apart.

Mustard is an emulsifier. It contains complex sugars that aid emulsification. It brings two unmixable liquids together and keeps them there. Not indefinitely, because vinaigrette is still a temporary emulsion, and mustard is fairly unstable as emulsifiers go. But it will hold together far longer than just vinegar and oil.

How do emulsifiers work?

Most molecules attract either oil or water. This is why substances are usually only soluble in either oil or water. Emulsifiers have the chemical structure to attract both. Soluble in both oil and water, they work by pulling both substances together and locking them there. The oil particles are surrounded and prevented from grouping back together.

Emulsifiers in food

Egg yolks

Lecithin, a protein in egg yolks, is a common emulsifier in the kitchen. In fact, two egg yolks can hold almost half a litre of oil. Soy also contains lecithin; a product that has been commercially isolated and is now widely used as an ingredient. Long used by the food industry, if a product contains soy lecithin, then chances are it is there as an emulsifier. Soy lecithin is massively useful as a vegan alternative.

Butter

As an emulsion itself, butter can also work as an emulsifier. Cream can also aid emulsification. This is because both contain the milk protein casein. Clarified butter contains no milk solids and is not an emulsifier.

Mustard

As we saw earlier, mustard contains complex sugars that act as emulsifiers.

Honey

Honey, added to a salad dressing for instance, will help it hold it together just like mustard.

Garlic

Contrary to popular misconception, aioli is not a strong garlic mayonnaise but an eggless dressing that relies on pureed garlic to emulsify the oil.

It was largely eggs, cream, and butter that Ferran Adria was trying to avoid in his use of the espuma gun. Not only do they bring their own textures and flavours to the mix, but the fats can dull sensation on the palate. Not a bad thing at all, just not what he wanted to achieve.  

The other part of the emulsification equation is force. The smaller the droplets, the more stable your emulsion will be. So, it makes sense to use a machine even for smaller quantities.

Emulsion sauces

Three of the most versatile sauces in cooking are emulsions; mayonnaise, hollandaise and beurre blanc. From these, endless variation is possible. Bearnaise, for example, is a classic variation on hollandaise. Check out our tutorial on how to make bearnaise sauce with our Robot Cook thermo-blender.

Types of emulsion sauces

There are several ways to group emulsion sauces. They can be cold, and they can be warm. They can be made with egg yolk, butter, or both. Or neither.

Egg yolk emulsion

Hollandaise and mayonnaise are both made with egg yolk as the main emulsifier. 2 egg yolks will hold about 300ml cold oil in suspension, but half that of warm butter. Mayonnaise is a cold emulsion as it is made with oil. On the other hand, hollandaise is a warm emulsion as it is made with butter; a solid fat that only becomes liquid when warm.

The best machine to make hollandaise sauce

Choosing kitchen equipment is a commitment and there are generally more ways than one to achieve results. It depends on your kitchen, your menu, and your output. The best machine to make hollandaise sauce, for example, is the one that you get the most use out of.

The classic method of making hollandaise sauce involves a bain-marie and a whisk. Not to mention a strong arm and nerves of steel. Factoring in the heat makes it a more complex process than making mayonnaise.

We recommend using our Robot Cook thermal blender to make hollandaise sauce. Being able to precisely control heat and blend at the same time has revolutionised the way we cook, and there are reasons you should be using PROFESSIONAL kitchen equipment in your PROFESSIONAL kitchen.

Stick blender hollandaise

Alternatively, you can make hollandaise with a commercial stick blender. It does the job of a wire-whisk, but the force of the blades makes for efficient emulsification, breaking up the oil particles for a more stable emulsion.

The best machine to make mayonnaise

Without the heat requirements of hollandaise you have more scope when it comes to choosing the best machine to make mayonnaise. Again, consider what equipment you have and what you do with it. A professional immersion blender gives you more freedom, but a commercial food processor may already be the equipment of choice in your kitchen.

The best immersion blender for making mayonnaise

Choosing the best immersion blender for making mayonnaise depends on the volume of mayonnaise you want to make. We make commercial stick blenders for kitchens of all sizes, and they are built to last.

Can you make mayonnaise with an electric whisk?

An electric whisk is ideal for making mayonnaise. Our combi range of power mixers feature a whisk attachment that is ideal for making emulsions, foams, and gels. A stick blender is an exceptionally versatile tool, but a whisk attachment opens up a world of possibility.

Making mayonnaise in a food processor

You can of course make mayonnaise in a food processor, and many chefs prefer the hands-free option. It is far easier to control the oil when you don’t have a whisk in the other hand and a moving container in front of you. The Robot Cook is also an option. Just because you have precise heat control doesn’t mean you have to use it on every occasion.

Butter emulsion

We have already mentioned that butter is an emulsion. Water is held in suspension, in butter fat, with the help of the milk solids that act as an emulsifier. It works as a weak emulsifier by expanding its range of emulsification. Basically, it can take on more water.

What is beurre blanc?

Beurre blanc is a warm butter emulsion, made without egg yolks, that relies on butter (and maybe a splash of cream) for its emulsification.

Warm butter remains in emulsion until it starts to come apart at about 70C. Cold butter is added to a beurre blanc, over a slow heat, in order to keep it emulsification. Too high a temperature and it will split. Clarified butter is pure fat, and not an emulsion. So, you cannot make beurre blanc with clarified butter. A splash of cream will also help it keep stable because of the milk solids present in the cream.

The Robot-Cook is ideal for making beurre blanc, as you can see in this video tutorial.

Culinary foams

Culinary foams are the chemical cousins of emulsions. Still a colloid, still a suspension of one thing in another, foam is the food the critics love to hate. Yet the creation of foam, essentially incorporating air into food, has always been a classic technique the chef must master. Whipped cream, meringues, and mousses. All foams. Bread and cake. Both foams, albeit arrived at via an alternative route. Airs, froths, and the ubiquitous espuma, are all just variations on a theme. The natural evolution of culinary technique.

The idea of a foam as a garnish is to harness a natural flavour within the texture of a foam. Absence of texture, even. The original espumas were not without issue. Air and volume dilute flavour. Ingredients can be held together in an espuma gun but once on the plate they are not so stable. To carry off these nuances of flavour requires a solid understanding of how they work. Done well, they can be a triumph. Not so well,  and the critics may have a point. Why bother with asparagus air when the real stuff in season is such a treasure.

Like everything on the plate, a foam should be there for a reason. It needs to enhance the dish with textural nuance and create another layer of flavour.

Types of foam

Culinary foams vary widely in their consistency, sitting anywhere on a spectrum that spans the range of fine to coarse, wet to dry, and light to dense. These variables will affect the concentration of flavour, how they feel on the palate, and how they behave on the plate.

A finely textured foam will have smaller, more evenly dispersed, bubbles than the open and irregular texture of a coarse foam. Finer foams are usually wetter, with more liquid in the structure. They are dense and mousse-like. Coarse foams have less moisture in the structure. With larger bubbles, they are light and airy.

You can serve a foam warm or cold. A souffle is a classic warm foam, but you are certainly not limited to that interpretation. Playing with consistency, and pushing boundaries, is the key to creating memorable foams. Foam can be frozen, like ice cream. Or dehydrated, like meringue. Quite often it is that shift of expectation from sweet to savoury that creates the drama. Like hearing your dog moo. Temperature is another way to defy expectation.

Modern foams began as an exploration of flavour and aroma, inspired by the sensual world. Conjuring up essences of seawater or smoke. Recreating the scent of a citrus grove or the fleeting sensation of a snowflake on the tongue. In most situations this seems utterly far-fetched, yet it is at the fringes of creative possibility that new classics are born. After all, we once thought that the world was flat.

How to make culinary foam

Espuma gun aside, to make culinary foams you will need an immersion blender. Light airy foams are easy to achieve but with a whisk attachment you can achieve denser foams without the siphon. A foam gun may seem like the most efficient route, and there will be occasions when it still is, but strange things can happen inside a siphon and the last thing you want is a whimper instead of a bang. Just know that you have options.

Emulsions and foams each require mechanical force. But unlike emulsions, the goal with foams is to incorporate air. So, you can make mayo in a food processor but not whip cream. Air is not magically introduced; it must be pulled in from outside the mixture.

To create a flow of air with an immersion blender the blade must be only partially submerged. Our Aeromix blade is specifically designed for aeration; a unique blade that helps to introduce the air when using a stick blender. It comes as standard with our MicroMix immersion blender, designed for making emulsions and foams directly at the pass.

Light and airy foams are the easiest to make and the MicroMix is the ideal tool for the job. Stable for up to one hour, an air requires a mixture of liquid and lecithin. You could also use xanthan gum.

Whipped foams, with the dense and wet texture of mousse or meringue, can be made with the whisk attachment on an immersion blender. Created using liquid and a stabiliser these foams are more stable and can be made further in advance. They are also suitable for freezing and dehydrating.

The mechanical force of the whisk or blender is used to introduce air and trap it within the liquid structure. As the surface area increases, expanding with air, it needs strength and resilience. Without this surface tension, the bubbles just pop. Your fluffy foam becomes slurry on the plate.   

Stabilisers are used to add this strength. There are many products out there to use as stabilisers. They range from traditional ingredients to substances once only found in the food science lab. Most new products have a neutral flavour, but they will all behave in totally different ways. What suits one recipe may be entirely unsuitable for another. Mouthfeel is a major consideration when deciding which product to use.

What’s the difference between a stabiliser and a thickener?

Emulsifiers, stabilisers, and thickeners are all closely related.

A true emulsifier has that double nature thing going on that we talked about earlier. Those water-loving, oil-loving properties. They help to form and stabilise emulsions.

Thickeners add body. They are mostly starches or gums.

Emulsifiers and thickeners can both act as stabilisers.

Lecithin is an emulsifier, whilst xanthan gum is a thickener. Both can be used in the creation of a light foam.

To create a heavier foam, more thickener is needed. The more thickener that you use, the greater the likelihood of ending up with an unpleasant mouthfeel. But there is an alternative.

And where does that lead us? Yeap, gels.

Gelling and gelling agents

Right now, we are interested in gelling for two reasons. One, because it completes our set of colloids. And two, because of their use in making foams. There are many other ways to make use of gelling in your dishes and garnishes, in a myriad of colours, textures, and shapes.

A fluid gel is the best way to make a denser foam without using heavy thickeners. Think about shaving foam. The texture is foam, yet also oddly elastic. That’s because it is a gel foam.

Gelling, if you remember, is liquid suspended in a solid. The solid is usually some form of protein.

There are two parts to the gelling process. Dispersion is the distribution of the gelling agent throughout the liquid. Hydration is the absorption of liquid and the subsequent swelling that creates a solid mesh in which the liquid is trapped. Dispersion comes first, followed by hydration. Except with gelatine, which must be dehydrated before being dispersed.

Gelling agents all act differently. Some are more complicated in their requirements than others, involving pH value or mineral content. Temperature is a key factor in the gelling process.

Gels can be hot or cold. Agar gels are brittle, whilst gelatine gels are elastic. Iota carrageenan gels are elastic, yet kappa carrageenan gels are brittle; both are ideal for making gels from dairy ingredients. Sodium alginate is used for spherification and methylcellulose forms a hot gel that melts as it cools. Gellan has come from the chemistry set of modernist cuisine to the mainstream kitchen and is often the chef’s choice of gelling agent. The point here is that for successful gelling you need to pay close attention to the scientific detail and follow the instructions.

Gel foams begin with fluid gels. These are created using small proportions of gelling agent. Once set, they are blended into a liquid gel.

To make a gel foam, simply whisk the fluid gel as you would with any other liquid. Other than the espuma gun, an immersion blender with a whisk attachment is the most efficient way to make a gel foam.

Gelatine as a gelling agent

Gelatine is the original gelling agent. A protein derived from collagen, it is an animal by product and therefore unsuitable for vegans or vegetarians. For that reason, chefs often seek alternative products to get the most from their menus.

Gelatine is flavourless and transparent. It also melts at around body temperature, so it literally melts in the mouth. Hydrated in cold water, and then dispersed in warm, it is for use as a cold gel only.

Use a ratio of between 0.5% - 1.0% gelatine to liquid for a soft gel.

Agar-agar as a gelling agent

Agar-agar can be used for hot and cold gels. It makes a brittle gel with a totally different texture from gelatine.

Agar-agar can be affected by pH values and is hydrated at boiling point.

Use about 0.2% agar-agar to liquid for a soft gel.

Food emulsions, culinary foams, and gels form the basis of inspiration for a huge range of dishes, whether your aim is confident classic or ground breaking avant-garde. When it comes to choosing your kitchen equipment, there are many options to suit. Why not arrange a live video demonstration and see what Robot-Coupe can do for you?