Ep 14: Emulsions Are Everywhere! Learn What They Are, and Why We Love Them!

This time of year, I think many of us find ourselves doing things we normally wouldn’t or seeing people we normally wouldn’t hang out with. But something, or someone is able to bring people together anyway, even if they don't like each other. Maybe we could consider that person to be an emulsifier? 

It's the holidays, which might mean family time. It might mean extra cooking or baking - for many its just a time of trying to hold everything together. So today we are going to discuss a different type of mixture - an emulsion. 

What is an emulsion? 

An emulsion is a mixture of two or more liquids that don't typically mix together. So in cosmetics this would be things like lotions, conditioners, creams, etc. But to start we are going to talk about food emulsions, because I’m sure almost everyone is familiar with those, even if they don't know it yet.

So when I say two liquids that don't typically mix, we are usually talking about water and oil. A very common example that I'm sure almost everything has observed is with a bottle of salad dressing. 

Did you ever just go into the fridge and find the salad dressing and shake it and watch it separate like a lava lamp? 

Well with an unmixed bottle of a vinaigrette, you can pretty distinctly see the two layers. On the bottom you have the vinegar and other water soluble ingredients, and on the top you have the oil.

Another way to describe these layers would be your aqueous phase and your oil phase. 

When you shake the bottle of dressing, the two phases mix together. What you will observe is oil droplets dispersed throughout the vinegar. So in this case the oil is the ‘dispersed phase’ and the vinegar is the ‘continuous phase.’ The energy that was put into mixing the two phases together created an emulsion. And in this case its an Oil IN Water emulsion. Because the oil droplets are inside of the water based phase.

After a couple minutes the two phases will separate back into two distinct layers again. This is because the emulsion is not stable. The water/vinegar and oil do not like each other. So they separate like this so they can have as little contact with each other as possible. 

But why don't they like each other?? 

In previous episodes we have talked about how atoms are made up of positive and negative particles. Molecules are formed when the electrons, or negative particles are shared or stolen. Just like on a number scale, a positive and negative cancel each other out and net zero - or a neutral charge. When molecules are formed, and the negative particles are moved around, the atom no longer has an equal number of positive and negative particles. The atom that took the electron will become negative and the one that lost one will become positive. 

With water, or h2o, oxygen is sharing electrons with 2 hydrogen molecules. But they are not sharing equally, and oxygen has a much stronger pull. And it is like an actual pull. If you had a rope and you had one knot in the middle, and one on each end. You could put it on the ground in a straight line, and then if you picked up the middle knot the other two would get closer together as gravity continues to push them down. 

The water molecule is in a v shape because oxygen is pulling on the electron its sharing with the hydrogens. The oxygen is slightly negative because the electrons are closer to it, and the hydrogens are slightly positive because they have less of their electron. We call this polar. 

Electrons moving around is important for.. Well everything. But the change in positive and negative charge creates electricity and magnets. The north and south poles of the earth are because the earth is essentially one giant magnet too. That's how a compass works, but now I've gotten too far off track. 

So water is kind of like a little magnet. And what do magnets do? Stick together! 

So going back to our salad dressing. You can shake it up, and what you are see are little bubbles. So you can shake up the bottle and if you put enough energy into it, it might even look uniform. But when you stop mixing it, the water doesn’t have the same attraction for the oil molecules as it does the other water molecules. Oil is non- polar. Which means that the charge is equally distributed throughout the whole molecule - so essentially its not magnetic. Magnets don't stick to things that are not magnetic.

So as soon as you stop putting in energy, those molecules are going to return to the state they are the most comfortable in. first you will start to see bubbles of oil. As the water molecules try to find each other. The oil gets pushed into little groups. Since they really don't like each other, they try to have as little contact as possible. It starts as round bubbles, because a sphere is the shape that has the least amount of surface area per volume.

Sorta like if you formed a ring around a group of people. You can fit more people inside than you need around the outside. As the water continues to try to connect with itself, the oil droplets get bigger and bigger as they get pushed together, until they just form a completely separate layer. This gives them as little contact with each other as possible. 

You might also notice this in some of the holiday parties or events you go to. You might have that friend who tries to have a party and combine friend groups. Or maybe you have family members who don’t get along, but they are all invited to the same dinner. I think you can often find people who like each other gravitating to one another and forming groups. Sometimes in a different room to minimize contact. And maybe there will be that person who suggests a game and people from both rooms come together to play it. 

 So we can stabilize mixtures by using something called emulsifiers. Sounds scary (jk). What this means is that you have a stable molecule, or emulsifier, and one end of the molecule likes water, and the other side of the molecule likes oil. 

Because this one molecule likes both phases, when we mix them together the emulsifier has the opportunity to bind with both water molecules and oil molecules. Which essentially disperses those oil molecules throughout the water phase, and keeps them there. 

This works by the formation of what's called Micelles. These are spherical formations that have oil on the inside and water on the outside. The emulsifier creates a spherical boundary between the two with the oil loving side on the inside with the oil, and the water loving part on the outside with the water. If a stable micelle is formed, then the oil bubble can exist comfortably inside of the water phase. 

So an emulsion is a bunch of microscopic oil bubbles surrounded by a transitional coating in water. The smaller and more uniform the oil bubbles are, the more stable the finished product will be.

If you have ever heard of micellar water - this is a cleanser that has emulsifiers in it that have the ability to form micelles with the oil on your skin. We will talk about these more in an upcoming episode. 

Stabilizing Emulsions

So going back to the salad dressing - we can, and do take mixtures like this, and stabilize them with emulsifiers. A common food emulsifier is egg. Especially the yolk. That's because it contains a mixture of different water loving and oil loving proteins, as well as a molecule called lecithin, which is both water and oil loving. So if we take our oil and vinegar mixture from before, but this time we add an egg - we can mix it together and create mayonnaise! 

Well sorta kinda. Its not quite as simple as just dropping an egg into your vinaigrette. That's because emulsifiers aren't just magical unifiers. 

WE MUST OVERCOME SURFACE TENSION

Surface Tension

Surface tension is actually really cool. And surface tension plays a big role in cosmetic formulation. So its essentially the measurement of how strongly the molecules of a liquid are held together. Liquid molecules tend to have some amount of attraction to one another - that's why they are liquids. If they had less attraction or repelled each other, they could be gases and if they had stronger attraction they could be solids. The surface tension of molecules can change based on temperature, pressure applied, or additional things being mixed in. 

Water is a great example of this. Water at room temperature is a liquid. If we heat it up, we decrease the surface tension between the water molecules, and they become less attracted to one another. If we apply enough heat, it will turn into steam. If we freeze it it becomes ice, which has a quite obvious increase in surface tension. 

`But the surface tension of water at room temperature is quite high. Meaning the water molecules are attracted to each other. There are many examples of the surface tension of water that we can see in day to day life. Its the reason rain drops are round, the reason it can hurt to slap water, and the reason water can be filled slightly above the rim of a glass. Water is very polar, also great Christmas tie in - north polar.

Overcoming Surface tension might be better described by going back to our family gathering scenario. So imagine you are going to a big thanksgiving dinner with your family and there is a well known political divide. We are talking like eyebrow piercings vs athletic polos.  

Chances are, if no measures are put into place, there is going to be some separation of groups and the like minded people will congregate. There are things that can be done to get these groups to mix together, but you need to be somewhat strategic about it. 

For example, you could create a seating chart for dinner. That way you can put people next to someone they have nothing in common with, and they can get to know each other. 

Nothing could go wrong! 

Maybe your seating chart is your primary emulsifier. But there are some additional things we can do to make sure the unification is more effective. Maybe you could have some talking points. 

I actually bring this up, because I know someone who attends family gatherings at one specific hosts house, and she not only has a seating chart - but they are separated into a bunch of small tables, and then one person at each table is the conversation leader. The host prepares a list of topics to discuss, and the leader is in charge of making sure the conversation stays on topic..

I have to imagine this host had a bad experience with unorganized conversation. 

But if you are trying to get a group of differing people to hang out for an extended period of time, you might want to be strategic about the topics you choose as talking points. You could add a question about the 2020 election, but that might do more harm than good. Instead you would want to look for things that are going to make each group like the other group more. Or look for things that are going to lessen the tensions in the group.

So why is this important for emulsions? Well, because in order to form a stable emulsion, we need to decrease the attraction between the water molecules

Water is an echo chamber 

We need to add things that will help decrease the surface tension - secondary emulsifiers. Glycols. Salts 

Increasing viscosity helps stabilize emulsions too. Less flow = less separation. 

This is just an Oil in Water emulsion - but you can also create water in oil emulsions. This means that water is the dispersed phase and oil is the continuous phase. I kind of think of it like a chocolate chip cookie vs a chocolate cookie with white chocolate chips. Not the same -  but both are cookies.

Different types of emulsifiers need to be used because for these you need to create reverse micelles. This means that you have water droplets surrounded by a oil. And the formations need to have the oil loving side on the outside and the water loving side on the inside. 

So how do we know which one to use? Well you can use the HLB or hydrophilic lipophilic balance to determine! Even though emulsifiers unify oil and water, they usually prefer one over the other. So if it likes water more, you want water to be the continuous phase. 

If an emulsifier has a low HLB, it likes oil more and is better used for water in oil emulsions.