Why does chocolate overcrystalize

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Permalink Reply by Gap on December 8, 2010 at 4:48pm

I'm not a scientist so someone might jump in here and correct me, but my uderstanding is this: chocolate can form many types of crystals as it sets. Only one sort is correct for "tempered" chocolate. For chocolate to be tempered, I think you only need about 2-3% of the chocolate mass to have the correct crystal structure. The issue is, these crystals grow/multiply and cause "untempered" crystals to transform into tempered crystals so that the 2-3% of tempered crystals will grow to a larger number. This is what occurs when the chocolate becomes over-crystalised.

When you hit it with your heat gun, you melt some of the tempered crystals out, but they can still re-temper again over time if conditions are right.

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Permalink Reply by Mark Heim on December 8, 2010 at 9:40pm

The final temperature for tempering a chocolate is the point where the unstable crystals would be melted out. Best for the betas you want. But as mentioned by Gap, they continue to multiply. Taking you far above the 2-3% target of crystal fraction. Reheating is tricky and not a long term solution, just a quick fix for that last mold or two.

Easier to temper just what you need, then add chocolate that was just taken down from 110-120F full melt to a couple degrees above temper and add it to the tempered paste to thin it back out. You need to find the point where you match your usage rate to the amount of chocolate always tempered, to the rate you can add new paste. With some practice you get a rhythm down that works. But equipment the wrong size put limits on.

If you're just looking for a little more time each tempered batch, when you're tempered, hold a degree or two high with no mixing, just an occasional good stir to make sure temp is even throughout the mass. Mixing produces shear, promoting crystallization.

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Permalink Reply by Nat on December 8, 2010 at 9:53pm

it could also be something as simple as the humidity where you are. Do you know what it is? If you're in Iceland it should be fairly dry in the cold winter, but I'm not sure how a lot of snow might affect that.

If it's higher than 50% RH, try to install a dehumidifier or AC unit set on a comfortable temp which should also dehumidify.

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