Carbohydrates include the common sugar,
sucrose (table sugar), a disaccharide, and such simple
sugars as
glucose (from the digestion of table sugar) and
fructose (from fruit), and
starches from sources such as cereal flour,
rice,
arrowroot,
potato. The interaction of heat and carbohydrate is complex.
Long-chain sugars such as
starch tend to break down into
simpler sugars when cooked, while simple sugars can form
syrups. If sugars are heated so that all water of
crystallisation is driven off, then
caramelization starts, with the sugar undergoing thermal decomposition with the formation of
carbon, and other breakdown products producing
caramel. Similarly, the heating of sugars and proteins elicits the
Maillard reaction, a basic flavor-enhancing technique.
An
emulsion of starch with fat or water can, when gently heated, provide thickening to the dish being cooked. In
European cooking, a mixture of
butter and
flour called a
roux is used to thicken liquids to make stews or sauces. In
Asian cooking, a similar effect is obtained from a mixture of
rice or
corn starch and water. These techniques rely on the properties of starches to create simpler mucilaginous
saccharides during cooking, which causes the familiar thickening of
sauces. This thickening will break down, however, under additional heat.
