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Grain Husks Explained

Here at Brew Your Own magazine, we field a lot of questions that revolve around the husks of brewing grains. Grain husks serve a very specific purpose for many all-grain brewers and can be both a benefit and a drawback at times. Learning what grains have husks and those that do not, as well as when huskless grains may benefit your beer or when adding husks to a mash can be advantageous to your brewing goals.

What Is The Husk?

There are several synonyms for a grain’s husk, such as the hull or chaff. A grain’s husk is its protective sheath and it is inedible to humans, so farmers have always worked to remove a grain’s husk after harvest. The grain’s husk is distinct from the bran layer, though some processing techniques, such as pearling, will remove both the husk and the bran of a grain. One of the easiest to understand examples is found with rice. Rice hulls are the almost plastic-like outer shell of a rice grain and are never included when you buy rice. The bran layer on the other hand is what makes brown rice, brown. Remove both the husk and the bran and you are left with white rice. The bran contains of lot of the fiber, proteins, and minerals of the grain.

Traditionally grains had their husks removed via a two-step process: Threshing (loosening the husk) followed by a winnowing (husk removal process). Once the husk is removed, the grain is now said to be “naked.” Some grain’s husks are rather easy to remove and simply tossing the grains around in a basket is enough to winnow the husks off. But with some grains the husk is thick and firmly attached to the outer bran layer of the grain. That is the case when dealing with barley husk, so unless specially marked, barley that we brew with will all have husks on them. Wheat on the other hand is easier to thresh and winnow, so malted and unmalted wheat we purchase for brewing will be naked. Rye malt you will find is huskless, while oats are husked unless specifically marked, like in Simpons’s Golden Naked Oats®. Meanwhile, flaked and rolled grains no longer contain husks.

The Downsides Of A Husk

The composition of husk is really more closely aligned to wood than it is to the rest of the grain. Composed of cellulose, lignin, hemicellulose, and a protein matrix, the structure of the husk allows it to be a great shield for a maturing grain seed. But from a brewing perspective, this aspect means that it provides very little in use for us chemically speaking. And during the malting process, the husk can actually turn against us. Those same compounds that provide the structure to the husk can also contribute astringency, and burnt-acrid flavors when highly roasted. For some beers and beer styles, a brewer may actually want a little bit of this characteristic, so grains such as black patent malt and black/roasted barley still have their husks included. But for smoother flavor in darker beers, brewers may want to select dehusked roasted malts. It is easy to find dehusked black malts if you know what you’re looking for. Any dark roasted wheat malt or rye malt will be dehusked. For barley you can seek out Debittered Black Malt, or Weyermann’s Carafa® Special line, or Briess’ Blackprinz® malt. To take it a step even further, some roasted malts will even be pearled, removing both the husk and the bran layer that contains a lot of the grain’s polyphenols, such as Viking’s Pearled Black Malt (not to be confused with the Pearl variety of barley).

Benefits of the husk

All-grain brewers of all sizes and levels gain a huge advantage thanks to a benefit that husks provide. Acting as mini-spacer in a mash, husks allow liquids to flow through a grain bed. Without any husks, the grains and their associated beta- glucans, which can be extremely gummy, will create a thick porridge-like mass in the mash tun. Without the “structure” provided by the husks, the grain bed is more like a ball of dough then a grain bed. It’s just not efficient and in lauter tuns the compaction can be enough to prevent any water from draining through the grains. At that point, we brewers have what is known as a stuck mash. There is simply no avenues for the liquid to move through the thick, starchy mash. The husks create those micro-sized pores that allow the liquids to sieve their way through.
If you plan on using a high percentage of huskless grains such as wheat malt, luckily for us we can easily toss in some rice hulls. These husks are by-products of rice processing and all-grains brewers should always keep some on hand. I know many Brew-In-A-Bag (BIAB) brewers are saying “we don’t need rice hulls!” But even BIAB brewers benefit from a more porous mash where liquids are able to diffuse and they allow for a quicker drain of their grains.