Dextrinisation is a kind of browning that occurs when foods containing starch are cooked, or exposed to an alkali, acid or enzyme. Dextrinisation is a chemical change in the starch molecule caused by the break down of sugar chains within the molecule.
The sugars, transformed into shorter chains and separated from the parent molecule, are called dextrins. Those produced specifically from heat are called pyrodextrins. These dextrins are brown in color and have a distinct taste and consistency. They reduce the viscosity of the food they are in, and they are sometimes added to food as thickeners. Although yeast can cause dextrinisation, it is more often produced by acids or heating. A combination of dextrinisation with other browning processes results in the color and flavor of thoroughly toasted bread.