The Emulsification Process

Can oil and water be mix together?

We can’t mix oil and water together because their chemical properties are so very different. If we shake them together, they will separate into two different layers after a while.

However, with the help of an emulsifier, and through a careful process, we can bind them together: the result is an emulsion. Basically, an emulsion is a mixture of two or more unmixable liquids like oil and water.

Emulsions are very common in this world. They can be found almost everywhere; in cosmetic and beauty products, paints, medicines, food, etc… But here today, we will only focus on emulsions in the kitchen.

The Emulsification Process – My Fascination

I can still remember my lesson on making mayonnaise in culinary school some years back. The chef-instructor was conducting a demo on making mayonnaise.

I was going like, ‘Wow!’

Under his magical whisk, translucent fluid oil was transforming into thick, creamy mayo right in front of my eyes. Fascinating stuffs.

‘So that’s how mayo is made.’ My curiosity was piped.

As a young cook, I had always been curious about the emulsification process. Emulsions are very common in the kitchen. In fact, so common that sometimes cooks don’t even realised that what they are doing is forming an emulsion.

Chefs love to use the word emulsion. You read on the menu…

“Rack of Spring Lamb, Mashed Potatoes, Emulsion of Carrot and Tomato”

Why use the word emulsion?

Because emulsion is a bigger word than sauce, and it seems to make the dish sounds nicer. Some people might not know what an emulsion is, and so they thought, ‘Hey, that’s sounds special. It must be good.’

The Emulsification Process – Demystify

Emulsions are fickle. Real fickle. They can be nice and thick one moment, and at the next second, before you know it, they spilt into two separate layers. In fact, emulsions are so erratic that some cooks believed in all sorts of kitchen myths, and have their own sets of rituals and prayers when making a hollandaise sauce.

Maybe that’s the reason for my fascination with it, to understand the emulsification process and to make it my friend.

I could still remember my days as an apprentice cook. There was this time… I could still recall, vividly…

‘You gotta whisk it only in a clock-wise direction; otherwise the hollandaise sauce would split.’

I ignored him and began whisking the mixture in an anti-clockwise direction, and then in a clock-wise direction, and in almost every direction I could think of, while drizzling in the melted butter.

He looked horrified, ‘You’d ruined the damned sauce!’

The sauce held, and came out thick and creamy; a perfect hollandaise sauce.

That was four years back. I was a trainee undertaking my industrial attachment in a five-star hotel’s kitchen. That guy was a chef who probably believed in one of the countless kitchen myths with no scientific basis.

What we are going to explore here is to understand the emulsification process; why it happens, how it happens, and what makes it happen.

The Emulsification Process– Types of Emulsions

Let’s take a microscopic look and see what happens during the emulsification process. An emulsion consists of a base liquid, with the other liquid contained and dispersed within the base liquid in tiny droplets. For simplification, we shall call the base liquid the ‘basic phase’ and the contained liquid the ‘dispersed phase.’

In an oil-in water emulsion, the basic or main phase is water, while oil is the dispersed phase. Common examples of oil-in-water emulsions in the kitchen are your mayonnaise and hollandaise.

For water-in-oil emulsion, the opposite holds true. Oil is the basic phase, and water will be the dispersed phase. The most common example will be butter.

The Emulsification Process – Intro to Emulsifiers

Simple vinaigrette is made up of basically one part vinegar to three parts oil. What happens when you shake and mix them hard? Tiny droplets of water will be dispersed throughout the oil. This is a temporary water-in-oil emulsion, and after a while, the liquid will separate back into two distinct layers.

So how can we emulsify them?

A common trick in the kitchen is to use a little bit of mustard to bind the two liquid together. It acts as an emulsifier. What an emulsifier does is that it is soluble both in water and oil, and it acts as the in-between between the water and oil molecules. Think of water and oil as conflicting ‘little guys with hands’, and emulsifier as the mutual friend in the center holding their hands together. Common emulsifiers and stabilizers are proteins, lecithin, gelatine, starch, gums, honey, and tomato paste.

The Emulsification Process – Secrets for Successful Oil-in-Water Emulsion

For successful emulsion, it is essential to always begin with the basic phase, and with a little emulsifier in it. For example, when emulsifying vinaigrette, start with vinegar and some mustard in it. When making a mayonnaise or hollandaise, egg yolks which contain both water and lecithin in it will be the basic phase. You can even use reduced stock with plenty of gelatine in it as the basic phase. It all depends on what sort of dressing/sauce you want to make.  

The next step is to add a few drops of the dispersed liquid (oil) into the base (water) and whisking it hard. The oil will be shattered in billions of tiny droplets surrounded by water molecules. This is to start the emulsion and have the water and oil molecules holding hands firmly together. It is important to start slowly and not to add too much oil in the beginning, otherwise, oil becomes the basic phase instead.

When the emulsified system is in place, you can now drizzle in more oil. You will notice the emulsification becoming thicker and more opaque. This is because as more oil droplets are dispersed and contained in the basic phase (water), they (the little oil and water guys) are blocking each other’s way.

Always blend and emulsify the previous batch of oil before adding more in. This is essential because this is one of the major reasons for split emulsions. At any one time, if too much oil is added before the previous batch is emulsified, there will be too much unemulsified oil in the mixture. The much-feared opposite will happen; oil will now be the basic phase, and water will be dispersed in it instead. The result will be an inverted emulsion that is oily and runny.

As more oil is emulsified, the sauce will become thicker and stiffer. Oil droplets are now squeezed very closely together, and there is simply not enough water to hold them. This is dangerous as the oil droplets are now so close together, the ‘oily guys’ may just pool together and hold each other’s hands, resulting in a split emulsion. Whenever you notice the mixture getting too stiff, add just a little more of the basic phase (water). There must be enough ‘water guys’ to hold the hands of the ‘oily guys.’

Hot and cold temperatures should be avoided in emulsified sauces. At temperatures above 60°C, molecules are very active and colliding very fast. The ‘water guys’ holding the hands of the ‘oily guys’ may just lose their grip of each other, causing the emulsion to split. On the other hand, at cold temperature, oil molecules will solidify and form sharp crystals that will pierce through emulsifiers when re-warmed.

For an even more stable emulsion, try using a machine blender instead of a hand whisk. The shearing power of a blender will shatter the oil droplets into more and smaller droplets surrounded by water molecules as compared to using a hand whisk. The emulsion is more secure and less likely to split into two separate layers.

Transforming a Water-in-Oil Emulsion into an Oil-in-Water Emulsion

Butter is made from cream. Is it possible to transform butter back to cream?

The answer is ‘Yes.’

What we are doing is to transform butter (which is a water-in-oil emulsion), into an oil-in-water emulsion. The classic French sauce ‘beurre blanc’ is made this way.

We need to kick-off the emulsion with a little water as the basic phase, so that there are ‘little water guys’ there to hold the hands of the ‘butter guys’ when they arrive. If you melt the butter just like that, you will simply end up with melted butter. Starting with cream instead of water is even better as it is already an emulsion.

First, heat just the basic phase. It can be anything that contains water, and just a tablespoonful is enough. You need the heat to re-arrange the molecules of the butter from solid state to liquid state. Add in cold cubes of butter one at a time into the basic phase, while whisking vigorously. Wait till the previous cube of butter had emulsified into the sauce before adding in the next. The application of heat here is vital. It must be hot enough to dissolve the butter when whisked in, but not so hot that the butterfat melts and separate. This process can go on and on until you have the amount of sauce you need.

There you have it; the answer to transforming a water-in-oil emulsion into an oil-in-water emulsion. This is just a simple butter sauce. However, you can flavour it by using vinegars, concentrated juices or vegetables purees as the base. Play around and experiment with it. The kitchen is just like a playground. Just make sure the base is very intense as the butter will dilute the flavour.

Hope this entry on the emulsification process will shed some lights regarding the mysteries of emulsions.