… you must not allow water to touch it!
I am a proud member of the Chocoholics Club, so I thought it made sense to start with a post on chocolate. There will be of course many others, because chocolate has a lot of interesting physical properties to discuss. I chose this particular one to begin with just because of the catchy name 
.
The main ingredients of what we know today as chocolate are cocoa solids, fats and sweeteners. If you are lucky and the chocolate is good the fats will be cocoa butter and the sweetener used sugar. The problem is that fat and water do not mix easily, they need some kind of glue to keep them together (this is called an emulsifier).
To see this, just pour some oil into a glass of water and try to stir it until obtaining an homogeneous mix: the task is impossible. The most you can do is break the oil into small drops that will distribute throughout the glass for a while (like when you prepare vinaigrette), but if you wait long enough the drops of oil will recombine until you have one or two big drops of oil floating in your glass.
The instant chocolate powder that one can buy to make hot chocolate usually contains cocoa powder, sugar and dry milk but no cocoa butter or other fats, so one can solve it easily in hot water or milk.
A very good glue frequently used in the kitchen to keep water and fat together is egg. This is why you can mix chocolate with water or milk when you use it for a cake recipe that also contains eggs. But how this exactly works is material for another post.
The chocolate was mixed with sunflower oil to achieve fluidity.
What am I talking about then? I am talking of chocolate used for covertures, fondues or a delicious chocolate fountain. When we are melting chocolate for such uses and what we obtain seems to dense, it is very tempting to try and add just a bit of water to make it a little bit more liquid. But the result of doing that is exactly the opposite: you obtain a grainy mixture which is much less fluid than before (the chocolate has seized).
What is happening is that the water does not mix with the fats, only with the sugars forming big sugar lumps that don’t mix with the rest. I didn’t understand exactly how this works until I found this excellent post with a very clear explanation including pictures and graphics.
The key to understand this phenomenon is the lecthitin emulsifier. It turns out that sugar does not mix well with fats either (although it does in water, i.e. it is hydrophilic), although the cocoa solids do. To keep the sugar distributed evenly in the fat and cocoa mixture some kind of emulsifier is necessary. In this case it is lecthitin: a molecule that has an hydrophobic end and an hydrophilic end. The lecthitin groups around the sugar molecules making a bigger and fat-friendly molecule that can then be distributed inside the fats. When we add water, the sugar-lecthitin molecules group forming bigger lumps and giving chocolate a grainy consistency.
How to avoid it
If what you want is fluid chocolate at room temperature (as the one used for a chocolate fountain) you should add fats to your chocolate which are liquid at room temperature, that is oils. Make sure you don’t add oil which has a strong flavour on its own (such us extra virgin olive oil). If the chocolate is going to consume at a slightly higher temperature, as for example in a chocolate fondue, adding a little bit of butter works perfectly well.
Enjoy your melted chocolate!
Melted chocolate
Melted chocolate with water
Melted chocolate with oil
31/05/2009 at 19:33
Interesting post! Somehow, though, the idea of adding oil to chocolate (at least for dessert) is not something that is immediately appealing to me. The other post you mentioned suggests adding more water in order to create a phase inversion. Why is this then not preferable than adding oil?
31/05/2009 at 20:06
Yes, I was skeptic at the begining as well, but actually you don’t taste the oil at all (if you don’t use olive oil). After all, every kind of chocolate has a high content in some kind of fat, it is just a matter of buying it with it incorporated or adding it yourself later (and then adding one with a lower melting point). If you add a lot of water you can indeed inverse the situation, but you reallly need a lot of water and then the mixture will be too liquid for a fondue. I suspect that is the kind of situation you have when you make hot chocolate from grated solid chocolate and water or milk.
02/06/2009 at 01:10
Mmmmm… chocolaaaate.
I don’t know what I enjoy most: the title or the solution to my failed chocolates. Now I can try again, and succeed! Thank you, sweetie!
04/06/2009 at 17:40
I wonder if there is an almond-based oil available on the market. Now, that would be fantabulous.
04/06/2009 at 18:01
That is a great idea: rather that avoiding oils with strong flavors, use oils with flavors that match well with chocolate like almond-based oil, coconut oil, etc. I´ll be sure to try that in my next chocolate fountain
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