Level: Apprentice
Reading Time: 15 minutes
Cocoa butter Silk is back, and so are the questions about it. I’m going to, of course, answer them, but also take the opportunity to pull out the analogies and get folks to REALLY understand the chemistry involved so they can apply it across the board and throughout their life. I guess I’m talking about deep understanding.
I made a bit too much silk, is there any reason I can't use it like cocoa butter when I go to the refining step?
I’m very much going to be tossing out the leading questions here. In many ways cocoa butter is like water. Yes, one is an oil and the other, well, is water. The key here is they both can be in a solid or liquid form. The technical way to say this is to say they have different phases, i.e. liquid and solid. You can freeze ice. It melts. You can freeze it again. You can melt it again. The water is just going from one phase to another with no inherent change in its composition or nature.
You now have new knowledge. Let’s ask that question again with water and ice being substituted.
I made a bit too much ice, is there any reason I can't use it like water when I need to boil my pasta?
The answer is obvious now, isn’t it? Of course you can use it however you would use cocoa butter. It is cocoa butter. The only difference in non-silk cocoa butter and silk is that the later is in a very specific structured crystal form. If you melt cocoa butter and silk, any crystals present in either one will go away and you are left with literally just unstructured cocoa butter.
If type 4 crystals melt away @ 81.1F and type 5 @ 92.8F why sous vide cocoa butter at 92.6F? Seems dangerously close to losing your type 5's... why not just 85F and give a nice buffer?
The short answer is 85 F doesn’t work. But that isn’t helpful.
Imagine you have a bunch of pencils that you want all lay in the same direction in a box. You put 100 of them in and start to shake the box. You start off really gentle and nothing happens. You shake a little harder and some start to move but they are just shifting around and don’t really do anything else. You keep increasing how hard you shake the box and at some point you find this sweet spot that the pencils start to move around a lot and begin lining up and settling to the bottom of the box in a nice flat stack. You keep doing that and eventually they all line up and your shaking isn’t doing anything. Out of curiosity you shake just a little harder and the pencils start lifting up and shifting and the whole thing becomes a jumbled mess again.
When you shake the box you are adding energy. Temperature is just a measure of how much energy a system has. When those pencils were not moving at all, you were below their “melting point”. They were acting as a solid. When you shook a touch harder, i.e. raised the temperature, the pencils melted and started moving. But they didn’t have enough energy to get into the stable form they needed to be. They were at your 85 F. The sweet spot was when you got to 92.6 F and almost like magic they started falling into place. But just a little more, say 92.8 F, and it would be too much energy and the pencils would get into place and then immediately jump out and eventually there would be a jumbled mess again.
The key to crystallization is giving the system just enough energy to nudge pieces into place but no so much that you knock them right back out again.
I’m following your guides and making my own silk. I feel like I’m doing something wrong as sometimes it works and sometimes it doesn’t. Sometimes I have to set my sous vide over 93 F and the butter stays hard and other times it is at 92 F and all liquid. This is breaking my head. Can you tell me why?
I really love this question as it probes at the complexity of crystallization and silk in particular. There is nuance here. Up above I said cocoa butter and silk could go back and forth without changing their nature. I lied. Well, I didn’t quite lie, but I didn’t tell you the whole truth. And also, I didn’t point out other lies that someone else laid out above.
Lie #1. There is no change in the nature of cocoa butter whether it is liquid or solid.
Here goes the nuance. Depending upon where you are in the cycle of melting the cocoa butter, it can indeed have a different nature. When I said it didn’t change I meant that the two end points remain (mostly - I tell another lie) the same. Fully melted cocoa butter will act one way and fully solidified cocoa butter will act another and you can go back and forth as many times as you want. Here is the rub though. How fast you melt or cool the butter can and will change the intermediate properties of the cocoa butter and it all comes down to cocoa butter being a polymorphic material. All poly (many) morphic (shape) means is that thing we all know, namely that cocoa butter can form many (6) different crystals (shapes). How much you have of one or another affects both how thick the cocoa butter is at any one temperature and even what temperature various crystals form.
When I make silk, I do 13 lb at a time. Early on I learned that if I melted the cocoa butter fully and then put it in the sous vide it very often would not thicken into that silky, opaque texture we want but instead stayed liquid just like you saw. It would sit and sit and sit at 93 F and never thicken. But if I put solid cocoa butter into the sous vide, it would get soft and be thick and opaque at 93 F (and often at 92 F).
How can that be? The answer that temperature is not a complete measure of energy.
Lie #2. Above I said temperature was the measure of how much energy was in a system. That is true if you don’t change phases and worked above because we were mostly talking about pencils moving, or the liquid phase. But it is more complex. Structures also hold energy and in this case, polymorphic crystals are structures.
Let’s do an example you can relate to. If you take a gram of water at 3 C and cool it to 2 C, you will have removed 1 calorie of energy. If you remove another calorie, the temperature will drop to 1 C. All well and good. Temperature is a great indicator of energy (calories are one unit of energy). If we remove another calorie the water will be 0 C. No surprise there. So what is the temperature if we remove another calorie? Interestingly it is still 0 C and it is still liquid. You have to remove a total of 80 calories before anything happens. At that point the water will turn to ice at 0 C.
Said another way, 1 gram of water at 0 C has a lot more energy (80 calories) than ice at 0 C and the same exact thing was true with my cocoa butter. When I melted it all and cooled it all to 93 F, it had a lot more energy than when I heated up the solid cocoa butter to 93 C and that extra energy was me shaking the box of pencils too hard and crystals would not form.
Those 80 calories for water are called the Enthalpy of Fusion of water. Yeah, fancy words. It is just the energy of freezing. Why we run into so many issues with cocoa butter silk (and all of tempering) is that each of those different crystals in cocoa butter have their own unique enthalpy of formation. You have to remove one amount of energy to get Type III crystals, and another amount to get Type IV and you guessed it, another amount to get Type V and they are all in there, mixed up in different amounts each time you try to make silk and tempered chocolate.
So pulling it together, how can cocoa butter be thick at 93 F one time and thin another time?
You have this. It is the amount of energy - crystal energy (OMG I never thought I would talk about the energy of crystals) is different in each case. The liquid one has a lot more energy and the only way to get that energy out of there so proper Type V can form is to cool it, sometimes well under 90 F. And yep, when you do that, you are no longer in the magic zone of 92.5 F to make silk.
Look, I know that might be confusing and partly it is my fault. I said ‘incubate your cocoa butter at 92-93 F for 24 hours’. I didn’t say it should be solid and should not be liquid and it is because I didn’t want to go into the why of the situation. But you folks are smart and clearly it has come time that you get better directions and the associated reasons behind it.
Here are your new Alchemist level directions for silk should you want to use them.
Melt you cocoa butter until it is liquid and clear. This will remove all crystals and maximize the amount of energy in the system. Then chill the cocoa butter until it becomes opaque but still liquid. That will take away enough energy so that Type V crystals can form when exposed to 92-93 F for 24 hours.
This is exactly what I do when I make silk and to date, I’ve not had a failure. That said, I want you to note the temperature range there and think about why that might be the case and why it can never be a more exact number. I think you know one of two of the contributing factors.
That’s right. The first is that more or less energy might have come out of the cocoa butter when you cooled it to make it go opaque and you the might need a slightly higher temperature to get more energy (shaking) back in there.
The 2nd contributing factor, which really is just an expansion of why the temperature needs to be higher, is that in our universe, energy can only move around when there is a difference in temperature, not a difference in energy.
Example.
Box of Pencil’s A, B and C are all at 92.5 F.
For Silk to form, you need 200 shakes of energy.
Box A has 180 shakes of energy and is solid.
Box B has 200 shakes of energy and is perfectly soft and opaque Silk
Box C has 250 shakes of energy and is slightly opaque but way too liquid.
The ONLY way for Box A to get more energy is to raise the temperature and the ONLY way for Box C to get rid of energy is to lower the temperature.
That is why there is and always will be a temperature range to make silk.
For our final question, it is an easy fly ball catch.
You've mentioned using 1%-2% silk against the total weight. I'm assuming that your "chocolate ninja skills" are so honed that you just have a feel for everything including tempering. As a noobie, I'm thinking I should go high to create more scaffolding, allowing for a more tolerant result. Does a higher % alter the end quality? Can I go too high and end up with something with a bad mouthfeel?
You are over thinking it. I’ve already given you a tolerance range. I rarely use more than 0.5% with my mad chocolate ninja skills. Try and follow what I say and not read between the lines of what I didn’t say.
Can you add too much? I mean, in practice sure, but in reality, no. If you add 20% it is going to alter your chocolate quite a bit but I’ve no idea why you would do that. You can easily add 5% with no issue and never is there a reason to add that much silk.
Alright. So what should take away from this? For me it is that everything happens for a reason...and that reason is usually physics. In this case, it is 100% physics (or if you want to get a touch more specific, physical chemistry and thermodynamics, but it is still under physics) and the ONLY issue people have with reproducibility of silk and tempering is that we don’t have all the data we need. We don’t all the variables. 1 gram of pure water at 98.00 C, at one atmosphere of pressure, will ALWAYS heat up to 99.00 C if you add 1.00 calorie to it, full stop. The entire key is adding exactly 1 calorie with zero heat loss, in isolation to the container that is holding it. The devil is in the details. Cocoa butter (and chocolate) is a natural product with thousands if not tens of thousands of variables (fat content, fatty acid composition of the fat content, exact crystal structure, impurities and so many more) that we have no way of knowing, worked with in a variety of conditions (temperature, humidity, pressure, air flow, etc). Because of that there are not one set of conditions that are universal to all those variables. There are ranges and that is good as it will get. Knowing that and more importantly, accepting that fact, should go a long way to easing your frustration when you think “why did it (whatever it is) fail???...I did everything EXACTLY the same!!!!” Respectfully, no you didn’t and ok, maybe you did, but you did NOT start with EXACTLY the same conditions and products because there are too many variables outside of your control and so what you did the same IS the problem since the different variable required you doing things slightly differently.
At the end of the day all you can do is do your best to control what is in your control, be as reproducible as you can, and grant yourself some grace when things don’t go quite as you expect. Hopefully not, you can look with new eyes that are things out of your control and you need to figure out how to work in that world.
As always, if you get totally stumped, feel free to reach out to me directly. That is why I’m here and in many cases I can help. Not because I have magic chocolate ninja skills (ok, maybe I do) but because I have failed a lot and learned something with the lion’s share of those failures and can hopefully pass them on to you.
Now go make some Silk.
