Tuesday 15 October 2013

Hello And Chocolate

Hallo

I'm Chris, and I've decided to start another blog. I already have myrobotblog.blogspot.com, but it is specifically robot oriented, and I wanted a place to put random thoughts/facts/things I think are of interest to the world. So here it is.

This first blog post is about chocolate tempering.

What Is Chocolate Tempering And Why Should I Care?

Chocolate is a pretty fancy combination of molecules that work together to give awesomely tasty food. In amongst those chemicals are a set of fats that when stuck together correctly result in that nice shiny, brittle tasty material you find in any fine box of chocolates. However, if they stick together incorrectly you get a much less fancy looking matte and crumbly material that (while still tasty) is not worthy of your desert.

Tempered vs untemptered chocolate
http://www.thesavagefeast.com/2011/06/dark-chocolate-covered-strawberries/

A more scientific way of looking at the problem is in terms of crystallization. This is the molecular process that occurs when a liquid compound solidifies and it attains a rigid structure. In simple solutions not much can go wrong, but there are 5 different molecular structures that chocolate can attain as it solidifies - 4 different ways all the bits can be glued together, and only 1 of them (type 2) is the fancy shiny crackly type!

Tempering chocolate is the process of encouraging the chocolate to turn back into the shiny type 2 crystal when it solidifies, resulting in things you can't resist eating.

Some sciencey stuff

The basic issue is that the type 2 is not the most natural type of crystal for chocolate to form. When we melt that shiny version, the crystals break apart and we get tasty liquid chocolate. When it solidifies without us stepping in, it doesn't form type 2 crystals and we end up with crumbly stuff.

Chocolate going wrong (please note: not accurate scientific representation. there is no such thing as choctonium)

There are a few ways to force the right crystals to form, but the easiest way for us mere mortals is simply to put aside a little bit of chocolate before melting. This chocolate is already tempered (it's shiny when you buy it), and we can use a process called 'seeding' to get all of the melted chocolate back to crystal type 2. The idea is that if you add a small amount of a certain form of crystal to a liquid while it cools, the molecules around it will naturally attach to the crystal and repeat it the pattern:



If the existing tempered chocolate as added into the cooling melted chocolate at the right time in the right amounts, it'll cause the rest of the chocolate to reform as nice shiny type 2 crystals. Below about 91F the chocolate will still be fairly liquid, but the crystals will have reformed and you will have regained chocolate that will go shiny and crackly once it cools!

Actually doing it

There's a lot of temperatures here, but dark chocolate requires slightly different heats to white and milk chocolate. The guide is:

  • Peak heat (how hot to get the melted chocolate initially):
    • Dark chocolate: 115F
    • Milk/white chocolate: 110F
  • Tempering heat (the crucial point at which crystals break apart)
    • Dark chocolate: 91F
    • Milk/white chocolate: 89F
  • Low heat (the low but still liquid point to cool your chocolate to)
    • Dark chocolate: 84F
    • Milk/white chocolate: 83F

This process works with any amount of chocolate, but below a certain quantity it gets a bit tricky to handle. I would recommend trying it with at least 600g of chocolate, plus a little extra spare to handle mistakes.

Before I start, this sounds complicated, but only cos there's lots of numbers in there. If you're used to recipes with more than a couple of ingredients/steps then you can handle this no problem!

For this you'll need:

  • A pan
  • A bowl
  • An accurate cooking thermometer
  • A cheese grater

There's a fancy setup with a fancy name for heating chocolate, but I call it a bowl on top of a pan. Set things up like this:


Note that the bowl is not touching the water.

This setup (with the hob on a very low heat) gives you very precise control over the chocolate temperature. If it gets too hot you just remove the bowl, to heat it up again place it back on the pan. And once you've got things just about going you can use the still hot water without the hob turned on to heat the chocolate very slowly.

Take 3/4 of your chocolate, chop it up into small chunks and throw it into the bowl. Let it melt and get up to the peak temperature (115F for dark). Don't worry if you go a little over - chocolate can take a lot of melting.

Grate the remaining 1/4 of the chocolate. This is the seed chocolate, and we're grating it to give it maximum surface area so it is very effective at causing crystallization.

Once your chocolate is hot enough, remove the bowl and watch the temperature. Keep it stirring so the temperature stays even and wait for it to cool to around 102F. This doesn't have to be too precise, but the next step cools it a lot and we want to end up with chocolate falling slightly down past the tempering heat.

Now throw in the seed chocolate, stirring as you go to encourage it to melt in. This'll cause the temperature to drop significantly, probably down to around 90F. All you need do now is let it cool to the low heat (84F for dark).

You can now heat your chocolate up a little, but avoid letting it get above 88F. You'll probably need to keep cooling and heating the chocolate to keep it in the mid 80s while you work with it. If it goes above the tempering heat then the crystals will break down and you will need to retemper it with more seed chocolate (hence why I said keep some aside).

Extra thing to remember - don't let a single drop of water get in the chocolate! It causes the liquid to seaze and kills the crystallization process. If some water does get in, just heat back up and retemper it.

Top tip - if you want to know if the chocolate has tempered, take a tiny bit out and let it cool. If it goes crackly then success. If not, just reheat, reseed and go again!

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