Caramelization is the process of "cooking" sugar molecules. Sugar molecules start breaking down at 170oC (340oF). These molecules break down in several ways, which several hundred different molecules arising. Some of these are brown in colour and have a bitter taste, so producing the colours of "caramelization" and the bitter elements within the bittersweet taste of caramel. If you heat the sugars even further, they become carbon, i.e. black and burnt - the bottom of an overheated pan is caramel and carbon.
Different carbohydrates have different caramelization profiles. Fructose and sucrose caramelize fairly easily, whereas glucose (dextrose) does not caramelize really at all. Some complex carbohydrates caramelize really well, e.g. five carbon atoms' sugars are present in small amounts in rye and wheat bran, giving rye and wholemeal breads a characteristic caramel look and slightly burnt sugar aroma and flavour.
Caramelization is used in its purest form in the pudding crème caramel, where a sugar-water mixture is caramelized then poured over the top of a vanilla custard, then left to set. This gives a deep-brown, solid cover to the custard. Alternatively, this can be done by putting a layer of sugar over the custard and using a blow-torch to melt and caramelize the sugar.
- Davidson, A. (1999) The Oxford Companion to Food, Oxford University Press. ISBN 0192115790.