A reaction involving sugars that occurs during coffee roasting. A caramelized sugar is less sweet, but has greater complexity of flavor and aroma. Caramelization is slower than Maillard reactions, and requires higher temperatures. These reactions involve only sugars. They really begin up around 150C to 180C, with water being lost from the sugar molecule beginning the chain of events. In all cases the sugar is converted to a furfuryl. These are a type of furans that have a caramelly, slightly burnt and also slightly meaty notes. The same compound is produced via a different route in the Maillard reactions. However it is with prolonged high temperature that many other types of aromas are generated. Caramelisation is more predictable than Maillard reaction due to less variation in the starting compounds. Without the sulphur or nitrogen found in the amino acids caramelization is unable to produce flavors as meaty as Maillard reactions. It is interesting to note how the sugar solutions taste changes in caramelization. A sugar solution initially will be sweet with no aroma. Through caramelization it becomes both sour and a little bitter, as a rich aroma develops. Generally the longer sugar is caramelized the less sweet it tastes, so the key is to balance the benefits of uncaramelized sugar sweetness while avoiding light roast astringency and sourness.

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