Historically, caramel malts were produced from green malt in a kiln covered with a tarpaulin. The tarpaulin reduced evaporation as the kiln was heated to perhaps 60°C to 75°C and kept at that temperature for up to 2 hours needed for saccharification of the starch in the endosperm. To dry and caramelize the grain, the tarpaulin would then be removed and the temperature raised up to more than 100°C while the grain was being ventilated.
Caramel malts – as the name implies – impart a strong caramel flavour to beer. This is the result of an extra stewing process that usually takes place in a roasting drum during malting, between germination and kilning. In the roaster, the green malt is kept at a temperature between 63°C and 75°C during saccharification stage.
This ensures that the starch from the endosperm is converted into a sugary liquid that is held under the husk. Subsequently, the stewed grain needs to be dried. Nowadays the drying is also done in the roaster.
The liquefied sugars are then caramelized into solid, semi-crystalline, unfermentable dextrins. During this process two different reactions take place: the degradation of sugars into brown colouring caramel products (pyrones, furanones) and Maillard reactions between sugars and peptides (melanoidins). At higher temperatures both reaction products form HMW (High Moluculair Weight) melanoidins that are typical for high temperature roasted caramels.
Colours
Because the caramelized sugars cannot be degraded during mashing in the brewhouses, they contribute directly to wort gravity. They are also responsible for malty-sweet flavours, deep colour, complex aroma, fuller body and mouthfeel, and improved foam retention of the finished beer.
Medium coloured caramel malts are used in amber and red Ales and Lagers, Märzen, and Bock beers. High coloured versions find their way to Porters and Stouts, while low coloured variants may be found in Pilseners and Lagers to improve the foam.