Biscuit Malt, a style of highly flavored specialty malt, is produced using a drum roaster. Biscuit malt is produced when germinated, kiln-dried barley is then roasted at high temperature but for a relatively short roasting time, resulting in a color of about 30° Lovibond/SRM. The high temperature applied to the malt at low moisture content, also known as dry roasting, develops the unique toasted, warm bread, biscuit, and especially nutty flavors and aromas characteristic of this malt type and the beers in which it is used. Biscuits malts have no diastatic power (enzymatic action) due to the high temperatures applied during roasting.
Biscuit malt is a relatively recent type of malt made possible by the invention of the first drum roaster in the early 1800s during Britain’s Industrial Revolution. The nutty flavors of biscuit malts make them popular when brewing brown ales, where they can make up as much as 10%–15% of the total grist bill.
The toasted, nutty flavors of biscuit malt also make it popular for usage at low percentages, adding subtle flavors and aromas to beer styles such as pale ales, amber and red ales and lagers, and bock and Oktoberfest/märzen beers.
In darker beer styles such as stouts and porters, low percentages of biscuit malt can help develop greater complexity and increase malt aroma.