Dextrose is another name for naturally occurring glucose. Chemical compounds can have two forms or mirror images called stereoisomers. In nature the dominant form of glucose produced is the right-handed isomer called D-glucose, with the left-handed form referred to as L-glucose. D-glucose is commonly referred to as dextrose, the shortened version of “dextrorotatory glucose.” Dextrose is a monosaccharide, a simple sugar, and is used as a building block for biological structures or can be broken down to power life-sustaining biochemical reactions. During the production of beer, mashing of grain breaks down many compounds with starch comprising a bulk of the targeted compounds. The starches are broken down by enzymes into the constituent parts, and some of these are dextrose molecules. During the kettle boil some dextrose binds with nitrogen-containing substances in a color- and flavor-forming Maillard reaction.
In the United States, dextrose is almost exclusively derived from corn starch hydrolyzed with exogenous enzymes. It can, however, be produced from many different starches, including rice, cassava, and wheat. As dextrose is highly fermentable, it facilitates the brewing of very dry high gravity beers. Dextrose is also commonly used as priming sugar for bottle-conditioning.