Millet belongs to the same grass family as barley, maize, and sorghum. It’s said to be a versatile crop because of its ability to thrive in harsh conditions. One source mentioned that millet is one of the oldest crops known to humans, possibly dating back to 2800 B.C! There are numerous varieties of millet, with proso millet (Panicum miliaceum L.) “common millet” is likely what you will find at a place like Whole Foods or a local organic market in bulk (this is what I was able to find). There doesn’t appear to be a vast amount of research done on brewing with millet, but from what I could locate, it does appear to produce acceptable beers. Across the literature, millet was often compared very closely to sorghum, which has been used in many parts of the world mainly in European-type lagers.

One reason some might want to experiment brewing beers with millet is because it’s gluten-free. Other carb-rich grains that could be used in brewing that don’t contain gluten are buckwheat, amaranth, and quinoa (I’ve experimented with quinoa with good results, although as a part of a barley grist). Oats can be tolerated by most, but not all people intolerant to gluten. The gluten content of beers is fairly low considering the high amounts present early in the brewing process (6,864 ppm present in wort going all the way down to around 200ppm in finished beer or around 1.9%).

High Gelantinzation Temperature

Although the gelatinization temperature will likely slightly change with different varieties, overall, millet has a very high gelatinization temperature compared to most grains. In a study of over 20 varieties, the range was from 168ºF-173ºF. Because this range is warmer than typical mashing temperatures, a cereal mash would have to be performed. In my case, I simply boiled the millet for 10 minutes, drained, and added directly to the mash. Make sure to properly adjust the mash-in temperature to account for the recently boiled warm grains.

Color & Head Retention

A study looking at lager beers brewed with millet (pennisetum maiwa), sorghum and barley malts found that the millet beers were darker in color than barley and sorghum beers (5.3 SRM to 3.5 SRM for the barley beer). Maybe most important, the millet beers were scored lower than both the sorghum and barley beers with tasters. I too saw a darker than usual color in the experimental beer I brewed with millet outlined below. The authors weren’t quite sure why they saw a higher color with millet but mentioned it’s possible the reason was a higher tannin in millet. The millet beer had better head retention than sorghum, but not the barley beer. This could be because millet varieties tend to have decent protein counts, which are around 11.3%-12.7% compared to 9.5%-11.5% for most pale barley malts. This Agu study also found 66.8% attenuation limit with millet compared to 88% from the barley.

Extract Potential & Soluble Nitrogen

Zarnkow found the average extract content from millet to be lower of barley (76-85% for barley to 43%-63% for millet). This could be because millet has a much higher husk content than barley. So if you are going to make up a large percentage of your grist with millet, you should probably take into consideration a loss in your typical expected mashing efficiency. Poor filtration rates were also reported with millet beer, due to the low beta glucanase developed when malted.

Zarnkow also reported the soluble nitrogen was lower in millet than in barley. Barley malts are typically measured around 600-900 mg/100 g, millet was found to have 368-561 mg/100 g (averaged 457 mg/100 g across all the varieties tested). Soluble nitrogen is important for head retention and for increased mouthfeel. As I mention in my tasting notes for my experimental beer with millet, I noticed a thinner mouthfeel than I typically get with similar style beers, although the head retention was similar.

Mash Run-Off

In my experimental beer brewed with 25% unmalted millet, I had a hell of a time with stuck sparge. This, of course, isn’t a big deal if you mash with a fine mesh bag or utilize rice hulls. For comparison purposes, when I brewed a beer with 40% unmalted oats, I had a much smoother runoff. Although detailed for sorghum in a study, which millet closely resembles, this was likely due to varying percentage of branching in starch amylopectin and to varying bonding forces in the granules. Interestingly, tested viscosity values for millet were actually lower than of barley.

Fermentation

Wort made from lots of millet will be high in glucose, which could lead to fast fermentations because of yeast ability to ferment this quickly. One study fermented a beer with 100% malted proso millet and found fermentation was effectively over after just two days. This particular study found that millet beers fermented basically as expected with a champagne, altbier, kölsch, and Brettanomyces bruxellensis strains.

Malted millet (Sossat) was found to produce an appropriate amount of amino acids required for fermentation as well as the optimal development of diastatic power and soluble nitrogen.

Home Malting Millet

Because malted millet is likely hard to come by, you could try malting it yourself at home (or just use it raw like I did!). You can order malted millet online (even crystal millet!), Gluten Free Homebrewing has a great selection. If you do try home malting it, a good germination temperature would be around 71°F and hold for a few days. You might see higher diastatic power if you increase the germination time (from 2-6 days). A good kilning temperature and duration appear to be around 122°F for 18 hours. Muoria also noted that malted millet had a saccharification time of 20 minutes, which is slower than typical well-modified barley malts (10-15 minutes), but not a dealbreaker.