This is part two of our series on porter. The series starts with an article on water treatment.
The color and roast flavor in a porter comes from darkly roasted grains, most commonly black malt and chocolate malt, but other dark grains can be used as well. Knowing a little bit about these grains and how they are produced can help you decide how to use them in porters and other dark beers.
Black malt, also called black patent malt by some maltsters, is arguably the most misunderstood malt in homebrewing. From many homebrew sources, you will hear that black patent results in a burnt flavor in your beer. If you understand how this malt is produced, you will see why this description is not correct.
Black malt is made from barley that has been germinated and dried to 5% moisture. In others words, it’s been malted except for the final kilning. Barley kernels destined to become black malt are full-sized kernels. Because the kernels of the final product are smaller than that of pale malts, it is sometimes erroneously stated that black malt is made from smaller kernels of barley. The malt is then roasted in drums at 420–450 °F (220–230 °C). The temperature of the malt is monitored carefully because it can combust or turn to charcoal if it reaches 480 °F (250 °C). As roasting proceeds, about 15% of the weight of the kernels is lost as they give off acidic fumes. (These fumes are actually retained, which is part of the reason why dark grains are acidic.) At the end of kilning, which takes 2 to 2.5 hours, the malt is quickly cooled by being sprayed with water. This water instantly turns to steam, cooling the malt. In addition, some of the liquid is absorbed by the grains, swelling them slightly and resulting in a moisture content of 1.5 to 3%.
The resulting black malt should be uniformly dark in color (500–650 °L) , but not contain charred or carbonized kernels. Although it is intensely roasted, and yields a sharp (sometimes described as acrid) flavor in large quantities, black malt should not be described as tasting burnt. That should be reserved for flavors resulting from actual combustion, and the products of intense roasting are not the same as the products of burning. An interesting thing about black malt is that it has very little aroma as the majority of its volatile compounds are lost during kilning. This is why many brewers use it for color adjustments to their beers — it can add small amounts of color without any dark roasted aroma or flavor.
[Note: These details of malting come from Briggs, et. al. “Malting and Brewing Science: Volume 1” (1981, Kluwer). In his text, “Technology Brewing and Malting“ (2004, VLB Berlin), Kunze gives slightly different details, including spraying the malt with water to reach 15% moisture — at 160–180 °F (70–80 °C) — then roasting for 1 to 1.5 hours at 360–430 °F (180–220 °C). He also specifies that the production of burnt characters is inhibited by periodic cooling of the malt by spraying with water.]
Black malt may also be made from dehusked barley. This is called debittered black malt because the roasted compounds that taste bitter in black malt are associated with the husks. Weyermann’s Carafa III Special (dehusked) is an example of this type of malt.
Chocolate malt is made in a manner very similar to black malt. The initial malt is plump barley malt and is simply kilned to a lesser degree (350–500 °L), either through lower temperatures, shorter roasting times or both (within the range given above for black malt).
Roasted barley is made in a similar manner to black malt and chocolate malt, with the exception that unmalted barley is kilned. The darkest versions (500–600 °L) of roasted barley are the heart of most stout styles. Roasted barley not only adds color and flavor to the beer, it will also darken the beer’s foam, something black malt or chocolate malt will not do.
Other Dark Malts
There are many other dark malts out there, including chocolate wheat malts, chocolate rye malts, coffee malts, pale chocolate malts. Weyermann has darkly roasted malts called Carafa I, II and III (in both regular and dehusked versions). For brewers interested in making a historical recreation type porter, brown malt can sometimes be found at homebrew shops. Be aware that malt types differ between maltsters. Chocolate malt from one maltster will differ from that of another. It’s best to write down the source of your dark grains when you brew dark beers, so you can recreate the beer later, if desired
Dark Grains in a Porter
In most modern porters, black malt is the most abundant dark grain. This is especially true if the porter is meant to be a robust porter (as categorized by the BJCP). A porter may, however, contain a significant amount of chocolate malt — up to 100% of the dark grain portion of the recipe — if it fits more into the brown porter mold. Many commercial porters are made with a blend of these two dark malts. A minority of commercial porters also contain a small amount of roasted barley along with the dark malts.
In a 5.0-gallon (19-L) porter recipe, 14 to 20 oz. (400–570 g) of combined black malt and chocolate malt will put you in the right ballpark of roasted flavor. Use the higher end of this range, with a higher percentage of black malt (with the caveat of not exceeding 16 oz. (450 g) of black malt in a 5.0-gallon (19-L) recipe), for robust style porters. Use the lower end, with a higher percentage of chocolate malt (up to 100%), for brown style porters. Don’t be afraid to aim for the middle ground, as I do in my porter. (I’ve done well with this porter in contests in which I’ve entered it as a robust porter.)
If you want to experiment, you can try substituting other dark malts for part or all of the dark grain component of your porter. Obviously, the more distinct the malt, and the more of it you use, the more your beer will drift away from the normal porter flavor profile. That doesn’t mean it couldn’t be great, though.
In the next installment of this series, we’ll look at the other ingredients — malts, hops an yeast — that round out a porter.