Candi Syrup is most widely used in Belgium for the production of special and Trappist ales.
There are several types of candi syrup, ranging from light to dark, and virtually all brewers use it in liquid form. The flavor of candi syrup can be very clean and sweet at the light end and very caramel-like and toffee-like at the dark end.
Candi syrup production is proprietary, but generally involves heating beet sugar with water in the presence of various salts to create Maillard reaction products, thus caramelizing the sugar to different degrees.
When added to wort, candi syrup is fully fermented and results in a beer with lighter body and more alcohol because it is more fermentable than malt sugars. This is one of the reasons that many Belgian beer styles are notably drier than most types from other countries. Typical usage rates are from 10%–30% of the original gravity.
Brewers often use the lighter-colored candi syrup for lighter-colored beers such as tripels and special golden ales. The darker-colored sugars are used in dark beers such as dubbels. Here the dark candi sugar gives flavors of high-temperature caramel, raisins, and even burnt sugar. Even though the color of dark candi sugar is similar to that derived from many roasted malts, the flavors are entirely different; for example candi sugar generally does not give coffee-like notes. Often, beers that include candi sugar are high-alcohol beers with a deceivingly smooth drinkability.
Many homebrewers use candi sugar in crystallized, hard candy form. These crystals are either dark or light and are added to the brew kettle. They are used to recreate many of the famous Belgian styles of beer.