Level: Alchemist
Read Time: 20 minutes
I am a baker dessert maker and I also make chocolate. I noticed in your milk chocolate video you say only dry ingredients for chocolate you are going to temper. Which got me thinking, I make ganache and if you let it set and if you don't make it with a lot of cream it can set up nicely. So my question is this. Why no wet ingredients if you know how to incorporate them like in making ganache? Is it that it sets up better with dry ingredients? Do you have the science that can explain it better. Bakers generally are more scientifically minded So I am fairly sure I could understand the explanation.
We humans seem to like categories. We like to shove, and stuff, and coerce things into little cubby holes. I mostly get why we do it – at least I think I do. For me it is so that I can understand a complex system. Unfortunately, if you are not careful, you end up thinking that those arbitrary boxes you have divided something into are reality and not just a convenient way to think about them and the result is that nuance can be lost.
If I were to name something and ask you what it is very generally and I nudge you in the direction I want there is a good chance you might say it is a solid, a liquid or a gas. With only three choices you can wrap your head around the concept and put it in the appropriate box. And that is all fine and good.
Except.
You knew there had to be an exception in there.
It is all fine and good for a general conversation but just because you have put a pile somethings in a box doesn’t mean they are the same. It is like a box of Christmas ornaments. You can sort them by color giving you a box of red ornaments, green ornaments and purple ornaments.
But that doesn’t mean the box of red will look like this:
There is every possibility it will look like this
Yep, they are all red, but they are all different. The states of matter, solids, liquids and gases are the same way. I’m not even going to go into the fact that there are other states of matter (like plasmas, super critical fluids and neutron matter) that don’t want to be in those three boxes.
All this is by way of saying that our goal in making chocolate and them tempering it is not to make any old solid. Our goal is to make a suspension of cocoa solid, sugar and cocoa butter with the cocoa butter in a very particular crystal structure. And the addition of water makes those parameters nearly if not totally impossible.
To get into why that is it is probably helpful to talk about the pertinent kinds of solids we are talking about here. First off we are not talking about dwarf star alloy, super dense neutron star matter or exotic things like that. What we are talking about are things that melt and can harden into a solid and things that don’t melt but can be suspended in some manner in other fluids.
In the context of chocolate cocoa butter is the material that can melt and solidify. Technically sugar can melt and solidify but the temperatures are too hot to be compatible with chocolate so I’m going to ignore those (partly). We are then left with other solids like cocoa and milk solids that both don’t melt and don’t dissolve in the cocoa butter.
Prior to refining if you mix cocoa liquor and sugar you will find quite a bit of the sugar will migrate to the bottom. On the other hand if you examine what melted chocolate is you will find it is suspension. You have reduced the particle size of the cocoa and sugar to the point that it no longer wants to settle out of the melted cocoa butter due to the viscosity of the whole system. So that is one kind of solid. And specifically it is a solid that is reversible. You can melt and solidify it over and over. To my mind this is one of the hallmarks of chocolate.
It is worth at this point to talk about emulsions. Many people call chocolate an emulsion because it doesn’t separate and they want to know what emulsifier they have to add to keep it stable. This is where it gets a little bit complicated in that chocolate may have emulsion properties and can actively have structures call micelles that denote emulsions but the important part is they don’t have be have micelles.
What is a micelle? Before I can tell you I need to define its parts and how they form and I don’t have a good way to do that except by diving into the science a bit.
Molecules like water, sugar, cocoa butter and lecithin have a neutral charge. This is in contrast to something like dissolved salt such as Sodium Chloride. The Sodium ion has a positive charge and the Chloride has a negative charge. Just like positive and negative magnet ends, this opposite charge is why they come together in the first place to make a salt.
Water, while overall has no charge, does have slightly positive and negative portions, not unlike a magnet. The amount strength of this misbalance of charge is called its dipole moment. Think of it as a partial charge. Water, or H2O has two hydrogen atoms that have a slight positive charge and the Oxygen has a slight negative charge. That looks something like this:
Basically it has slight positive and negative sides and those sides can link up like magnets.
This linking up is called hydrogen bonding and without diving too deep into the subject that interaction is quite strong and is the reason water has surface tension that allows crazy things like this water strider literally standing on water.
The ends of the water, the hydrogen bonding, is so strong it can support this insect. The weight of the insect isn’t heavy enough to literally push those molecules of water apart. The point of this was really to tell you about Dipole moments and partial charges on the ends of molecules. Just keep that strength in mind for later.
This partial charge thing is also responsible for something you are probably familiar with to one degree or another. Emulsions. One of the most common ones that everyone knows about is mayonnaise. You take egg yolks and incorporate in oil in a very particular way. The egg yolks have compounds in them that have partial charges on their ends but unlike water that is very small, they look a lot like the oil you are incorporating. It is handy to think of them as sort of a hybrid oil. You are also quite familiar with the generic name of this class of compounds. It is also known lecithin.
What this allows is for the charged end to link up to other charged particles (like water) and present to the rest of the mixture this oil like structure. The result is that the system does not separate because the charged water is all isolated, no water/water hydrogen bonding happens and the mixture does not separate.
So if you stir water (or cream or any water based ingredient) in gently the water molecules are going to mostly stick together (recall that incredibly strong hydrogen bonding) and you end up with a separated mixture. They separate because the oils in there have a different density than the water and since they can’t bond to the water they will literally float to the top. On the other hand if you aggressively beat the egg/lecithin mixture and slowly add the oil you make a temporary suspension that is more or less homogeneous with the polar end of the lecithin molecules (one of the ground labeled R1) next to the polar ends of the water and the they will start to stick together. How? Of course with hydrogen bonding. What forms is called a micelle.
When you have a system that is full of micelles, secreting away water (or other polar molecules) that are tucked inside that cavity and oils are present, what you end up with is called an emulsion. The water (or other polar molecules) can no longer get to each other and bond together so the system now has no reason to separate. The oil in there basically only sees other oil like structures (the parts in blue/green) and the system is stable. Depending upon the particular characteristics of the emulsion, this can be viewed as a kind of solid.
Bringing this back to chocolate a bit, chocolate is primarily composed of three things on a macro level (I’m excluding all the trace amounts of flavor compounds): Cocoa butter, Cocoa solids and sugar. Cocoa butter is obviously the oil and is non-polar (it has no dipole moment or partial charge). Cocoa solids are a mixture of both slightly polar and non-polar compounds and sucrose (sugar) that is extremely polar (huge dipole moment).
You’ll note I did not mention lecithin. Lecithin is totally optional in chocolate making, although we will get into why it is important.
Chocolate is a pretty amazing. I know most of you agree with this, but I’m talking about it from a physical chemistry standpoint. It is kind of amazing to me that it naturally holds together without really any extra help. It is composed of polar and non-polar pieces and unlike mayonnaise that you have to work to make stay together, chocolate just does it naturally..
The polar parts of the cocoa solids bind a bit with the polar sucrose and each other and only does it just enough that the cocoa butter isn’t aggressively excluded and forced to float to the top. But that is only for refined chocolate where the sugar pieces are very small.
Take note of the very specific language I just used. I said the cocoa solids were only slightly polar. I also said sugar pieces and not sucrose molecules. The cocoa solids are not polar enough to break apart the very strong bonds holding the sugar crystals together. The best they can do is bind to them lightly and surround them in a pseudo micelle fashion if the particles are small enough.
Stated another way sugar has a very strong dipole moment. In the same exact way oil and water don’t mix (because water has a dipole moment and oil does not) cocoa butter and sugar don’t mix when on a macro scale and why sugar will settle to the bottom of melted cocoa butter. Again, I used very specific language here. Unrefined sugar usually does not settle to the bottom of chocolate to any meaningful degree. Why? Most people will say viscosity. Basically the chocolate is too thick. And that is not untrue. But WHY is it too thick? What is causing this viscosity? It is the thing I’ve just spent nearly 2000 words talking about. It is hydrogen bonding. That same force that gives water surface tension and allows that water strider to stand on water.
The sucrose is lightly binding (via hydrogen bonding) to the slightly polar cocoa particles and each other and the physical manifestation of that binding is the property called viscosity. Basically Hydrogen bonding causes viscosity. Just remember that.
So here is where I want to start putting it all together and try to get you to see why chocolate reacts as it does to various conditions, and I’m just going to list them off. Your job is to see why, on a molecular level, the reason.
· When you heat chocolate it becomes less viscous. Heat is energy and more energy makes things move in a liquid. That motion breaks those that lightly bond. With less bonding, you get less viscosity.
When you add lecithin to chocolate it becomes less viscous. The very polar ends hydrogen bond strongly with the very polar sugar particles and form micelles. That means there are less polar components to bond together and so viscosity decreases. If you happen to have a very small amount of water in your chocolate, the lecithin will also bind it into micelles further reducing viscosity.
If you heat up certain emulsions, you can cause them to ‘break’ causing the oil to separate. Why? You added too much energy to the micelle and it released the polar part inside. Those polar parts then hydrogen bond or stick together and the oil is literally squeezed out and floats to the top.
·Have you ever wondered why some chocolates are more viscous than others when the cocoa butter content is basically the same? I think you can see now there is a LOT more going on than how much oil is in there. More sugar with its high dipole moment adds more binding so more viscosity is the result. Different amounts of polar chocolate solids can cause the same thing. Sure, more cocoa butter helps isolate those polar parts but it does it by insulation, not really by being less viscous itself.
Now that you know how to make chocolate less viscous, how would be a great way to make it more viscous? How about adding something that would hydrogen bond more? What do we know that has LOTS of very strong hydrogen bonding?
Did someone say water?
Hell yeah!
What happens when you add water chocolate? It bloody seizes!! Why? Because hydrogen bonding just went through the roof so viscosity went WAY up to the point of solidification! And frankly more than that is happening. Basically, all hell is breaking loose. Since water has such a strong dipole moment and is comparatively small, it can work its way into those relatively delicate sugar/cocoa solid micelles and break them apart. Further, it can literally start dissolving the sugar molecules further increasing polar bonding. Basically polar water starts shredding our previously, and miraculously stable chocolate system from the inside out. All the polar parts (water, cocoa solids and sugar) stick together into one big thick viscous mess ala massive hydrogen bonding and you have seized chocolate.
So let’s bring this around to your question. Our goal isn’t to make the chocolate ‘set up’. We can do that by adding a bit of water to the point that it seizes and solidifies.
But that isn’t our goal. We don’t want just some random solid chocolate. Our goal is to form a different kind of solid. We want a crystalline solid of cocoa butter. Our goal is to stack up cocoa butter crystals in a very particular fashion (commonly known as type V) and we do this by tempering. Interspersed in there are stable micelles hiding away as many polar parts (sugar, water and some cocoa) as possible so we have a slightly, but not overly viscous chocolate.
So sure, you can set up your chocolate by making a ganache. But that isn’t a crystal structure nor solid you want for making chocolate. That is you beating in an emulsified product (cream) into the chocolate.
There you go. It isn’t so much you can’t add liquid ingredient but more specifically you don’t want to add polar ingredients that can interact with other polar ingredients and cause your meta-stable chocolate emulsion/suspension to become unstable. That is the really reason you can’t add water.
One last request, ruzz, who some of you know as my right hand and some know from the videos has been trying to get us a bit more organized. In that effort he’s asking that for any of you who have taken one of my seminars it would be super helpful for us if you could take a few seconds and fill out this questionnaire about it. We’re trying to bring more order to things and your experiences will help us.
Ok everyone. That is the last Ask the Alchemist for the year and goodness was it a big one. There is nothing like going out with a bang. We will be closed the entire week of Christmas and will talk to you again in 2019.
Be well, safe and awesome to each other.