Malting Barley Grain at Home

by Brad Smith on December 5, 2009 · 56 comments


For the adventurous home brewer who wants to take all grain beer brewing to yet another level, you can malt your own grains at home. While most micro and home brewers start with malted grain, it is possible to purchase unmalted grains and go through the malting process at home. The equipment required is modest, and bulk unmalted grains can be purchased at a fraction of the cost of malted ones.

Unmalted barley is widely used for animal feed, so a good place to purchase unmalted grains in bulk is likely a local feed store. Usually it is sold in large quantities – typically 50lb to 100lb bags. Smaller quantities can be purchased from some brew stores, pet stores or equestrian specialty shops.

There is a lot of variation in unmalted barley quality. If possible, you want to choose a barley that is low in protein as high protein will result in cloudy beer. Inspect the grains if possible before buying to look for minimum broken grains, absence of mold or bugs, consistent color and general overall quality.

Steeping the Raw Barley

The first step in home malting is to steep the barley in water to begin the germination process. Start with a large bucket that can handle the grains plus enough water to float all of the grains. Add water until all of the grains are floating, and let the grains sit in the water for 2 hours.

Remove the grains from the water (a strainer is good for this) and let the grains air out and dry for about 8 hours. This step is important as if you leave the grains in the water they will drown and eventually die.

After the grains have dried for about 8 hours, steep them again in a clean batch of water for another two hours, and dry them again for 8 hours. You will likely have to continue this for a third cycle. Within 24 hours of starting, you should see small roots start to grow from the base of the kernel (called chits). Stop your cycles of steeping and drying once you have 95% of the grains germinated.

You should have added approximately 40-45% moisture (water) at this point. Assuming you started the dry grains with ~9-10% moisture content, adding 35% moisture will result in a weight gain as follows: 1 kg of grain has ~100 g of water before steeping. Adding 350g of water (45% water content) results in a total of 1.35kg. So if you started with a given weight of grains, you can stop steeping when the grains weigh 30-35% more than when you started.

Germinating the Grains

The grains must now be germinated in a cool, slightly moist, but well ventilated area to grow the small leaflet inside the grain called an acrospire. This generally takes 2-5 days. The ideal temperature for germination is 64F, or about 18C.

You want to keep the seeds cool, spread them out well and moisten them periodically with a little spray mist. The germination process generates heat, which can lead to bacteria or mold growth so its important to aerate the grains and turn them every few hours in a cool location to avoid infction. Many early malters actually spread the grains on a concrete “malting floor” to keep them cool and make it easy to turn them periodically.

You continue malting until the small leaf (acrospires) within the grain is approximately 80-100% of the length of the grain. Note that the acrospires is inside the grain, so you need to actually split the grain open with a knife or razor blade and look for the white leaf that is part of the endosperm and attached to the rootlets. Typically the external portion of the rootlet will be about 2x the length of the grain when it is finished, but checking the actual acrospire length is the best method to determine when to stop.

Drying the Malt

Drying the malt can be difficult as it requires a steady temperature of between 90-125F (31-50C). Drying at a higher temperature will destroy the enzymes needed for mashing. If you are fortunate enough to have an oven with temperature control that can go this low, then leaving it in the oven for ~24 hours is an excellent way to go. In some cases, even the oven light is sufficient to reach the 90F temperature needed, though it may take some time to finish.

If you live in a sunny dry climate, sun drying is also an option. Some care is needed to keep birds and other small scavengers away, but you can leave it out in the sun for 2 days which should be sufficient to dry the malt.

A third option is to use an actual food dehydrator. Inexpensive home food dehydrators are available for as little as $30-40 and work quite well.

You are targeting a finished moisture content of approximately 10%. Assuming you have not lost much material in the first two steps, this would mean the finished weight of the grains with their rootlets attached should be close to the total weight of the unmalted grains before you started the steeping process. Recall that we started with about 10% moisture content in the original unmalted grains. Therefore you can stop drying when the grains plus rootlets weight are back to approximately their original unmalted weight.

Finishing the Malt

The last step is to separate the dried, malted grains from the rootlets growing out of them. After the grains are sufficiently dry, the rootlets will simply fall off them with a little agitation. You can use a colander or some screen to shake the grains around and separate the dried rootlets. Note this is a bit of a messy process, as the rootlets tend to get on everything, so you might want to do this outside.

At this point you have pale, malted barley equivalent to that which you would normally purchase from your brew supply store. You can crush it and use it just as you would any pale barley base malt.

If you wish to make specialty malts from your pale barley, you can toast the malts in the oven to make varying shades of crystal, toasted, brown malts. For the lightest of crystal type malts, try toasting at 275F for one hour. For a medium crystal, try toasting at 350F for 15-30 minutes. If you toast at 350F for an hour you will come close to a commercial brown malt. You can also get different variants by toasting wet vs dry malts. A wet toasted malt will impart a slightly sweeter toasted flavor.

For more on home malting, her is an article on Bodensatz by Dan Carol which I used when malting on my own for the first time. Geoff Cooper also has a short article on roasting malts.

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