Caramelization is a complex and poorly understood series of pyrolysis reactions (decomposition caused by high temperatures) that occur in carbohydrates when they are subjected to intense heating under relatively dry conditions. There is a dehydration of the sugars, followed by their condensation. Isomerization, fragmentation, and polymerization reactions occur, variously leading to the development of an assortment of flavors and color.

In a matrix such as malt, there are of course diverse carbohydrates, but in pure sugar systems the caramelization temperatures are 110°C (230°F) for fructose, 160°C (320°F) for glucose, and 180°C (356°F) for maltose.

Caramels are complex mixtures of diverse components, including high-molecular-weight colored substances. In commercial operations, caramels are produced by heating sugar (most frequently glucose), sometimes with agents such as ammonia or sulfite. Processes may involve at least 1 week at ambient temperature, with an ensuing 90°C (194°F) overnight stand and then approximately 3 hours at 120°C (248°F). In the early stages of caramelization, diacetyl is produced—hence the butterscotch flavor of caramels. See diacetyl. Other flavor substances produced include hydroxymethylfurfural, hydroxyacetylfuran, hydroxydimethylfuranone, dihydroxydimethylfuranone, maltol, and hydroxymaltol.

The high-molecular-weight color components of caramel are positively charged and therefore relatively stable in beer. Where used in brewing, caramel can either be added during the wort boiling stage or to adjust color downstream. In Belgian brewing, caramelized dark candi sugar syrup is used to bring color and flavor to dark styles such as dubbel. See candi sugar.

Rather than using caramels as colorants and/or flavorings in beer, many brewers choose to use caramelized malts. These are produced by the intense heating of stewed malts. These range from the comparatively light carapils (color specification perhaps 15–30 EBC) through to Crystal (color specification perhaps 75–300 EBC). See carapils and crystal malt.

In Carapils production, the surface moisture of green malt is dried off at 50°C (122°F) before stewing over 40 minutes. In this stage there is a promotion of carbohydrate and protein breakdown to provide substantial levels of sugars and amino acids. Sometimes high-protein-content malt is used. Thereafter the temperature is increased to around 100°C (212°F), followed by curing at 100°C–120°C (212°F–248°F) for less than 1 hour. Crystal malt is prepared as for Carapils, but the first curing is at 135°C (275°F) for less than 2 hours. It will be appreciated that apart from caramelization reactions between sugars, there will also be Maillard reaction events in these processes. See maillard reaction. These malts have pronounced toffee, caramel, sweet characters but lack the burnt harshness of the more heavily kilned malts in which roasting is applied to dry pale malt starters.

Caramelized flavors are very important flavor components in many styles of beer and can form the backbone of a beer’s ability to pair successfully with many foods. Harmonization of a beer’s caramelized flavors with similar flavors in sautéed, roasted, fried, or grilled foods can provide beer pairings that are substantially different than those achieved by wine. See food pairing.