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Q & A: What causes caramelization?

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Most recent answer: 12/10/2013
hi, i am an electrician at a food processing plant and we have had an issue with sugar that carbonised within 2" stainless steel pipework. the pipework has trace heating wrapped around it to keep it at a constant temperature which was set at 20 degrees c. when the production lines called for the liquid sugar it would not pump across. we had to resort to cutting the pipework to find that sugar had turned black and solidified. this only happened in a one section of pipework and not the whole length between the pumps and the lines. what could have caused this? there was no fault with the trace heating (that we have found) and the temperature did not reach the extremes of cooking and burning the sugar as this would have been obvious (damage to the trace heating cable). any help would be much appreciated. kind regards, ben indge
- ben indge (age 26)
kings lynn, norfolk

We love questions of this sort, even though we usually can't quite answer them.

I have a first point to clarify. What sort of sugar is in there? If there's much free fructose, which caramelizes at ~110°C (see ) then it wouldn't take much overheating to do the damage. I suspect that if some part of the heating cable got to that temperature it wouldn't show any damage. Also, I don't think a saturated solution would boil at that temperature.

Also, what pH is the solution? According to that Wikipedia article, a low or high pH can accelerate caramelization.

If the solution is all water+sucrose, with a higher caramelization temperature (~160°C), the effect would be harder to understand.

Mike W.

(published on 12/10/2013)

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