Unfortunately, sorghum poses some problems for the home maltster. The first of which is that the warm germination temperatures required to sprout sorghum are perfect for the development of molds and fungus which can produce aflatoxin and other mycotoxins. There are 13 strains of aflatoxin with the B1 strain being the most dangerous. Ingested in small doses over long periods these toxins can cause liver cancer, severe respiratory and digestive problems. Ingested in large doses they can actually kill you. This paper, Control of microbial proliferation on sorghum during malting by Mathoto Lydia Lefyedi is well worth reading. There are test kits that you can buy to determine the levels of mycotoxins in your grain but I believe they are quite expensive.
- Warning Without the proper means to test for the toxins associated with sorghum I believe malting sorghum at home is too risky an endeavor. The benefits to drinking a gluten free beer are seriously outweighed by the potential health risks posed by these toxins. You have now been officially warned!
The best solution to this problem is to disinfect the grain with an initial 4- 6 hour steep in a 0.2% lye solution (sodium hydroxide). Yes, the same chemical that’s found in drain cleaner that can cause burns if handled improperly. Sounds bad I know, I wanted to avoid it myself but after doing more research I would consider this a mandatory step when malting sorghum. Without it, you’re guaranteed a certain percentage of mycotoxins. The solution used is quite dilute, 2 grams of pure lye per litre of water will give you a pH of between 11-13. As well, the malt is rinsed and steeped in plain water a few more times afterward. There is also food grade lye, which I believe means that it is produced in a facility that would have zero risk of contamination from any other chemical product.
Diluted lye solutions are used in a variety of food preparations like pretzels and certain types of noodles. Because it comes in its dry concentrated form, which you have to dilute yourself it’s very dangerous. Lye can cause severe burns so wearing gloves and eye protection is an absolute must.
- Never add water to lye as it will boil and splash. This is what usually causes burns. Always add your lye to your water so it’s diluted immediately
- Never use Aluminum with sodium hydroxide solution as they will react
Depending on the sources, recommendations are for either a 0.2% solution or a 0.3% solution of Lye steeped from 4 to 6 hours. Personally, I went with the 0.2% for 4 hours. To make a 0.2% solution the ratio is 2 grams of lye per 1 liter of water. I used 8 liters of the solution to steep 12 lbs. of Sorghum. After soaking for four hours some of the solution will have been absorbed by the grain which is good for killing any fungus within the surface layers of the grain. Subsequent steeps in clean water should dilute the absorbed solution. Although I did not do this, a second short 20 min soak in a lye solution right before germination sounds like a good idea, just make sure it’s rinsed several times after.
A lot depends on the quality of the sorghum you use. For my first batch of sorghum malt, I started with 12 lbs of grain. Huge mistake, the due date said I was buying it before the due date but I found out later that the due dates are two years from the harvesting dates. The malt turned out to be too moldy with black kernels and a lot of ungerminated grains. These are visible, I just hadn’t bothered to look. Old grain appears dull in colour with many gray or black kernels. Reddish kernels can also indicate fusarium mold. I decided to throw it out as there were too many moldy grains to pick out. For my second test batch started with 3 lbs of grain (starting small this time) and it was much cleaner.
Steeping schedules for sorghum seem to vary quite a bit. One schedule from the Journal of the Institute of Brewing vol. 117 issue 3 calls for 6- hour steeps at 40 C followed by 3-hour air rests until the moisture content is 40% (Ogbonna). 40 C for steep water is very warm. I’ve also read that 30 C is ideal with a moisture content of 33% (Briggs, Malts and Malting) Or 40-43% (Ezeogu Sorghum Malting pg 61). For germinating, one article recommends, for maximum diastatic power germinate at 30 C for 4-5 days. Although 25-28 C is recommended in another article. You can sift through all of these articles in the Information on Malting section of this blog under Sorghum.
I steeped at room temperature (22C) but used warm 30C water. I didn’t bother to maintain the steep water temperature during the 6-hour steeps. I steeped with 3- hour air rests in between the 6-8 hour steeps (although one air rest went on for 7 hours accidentally, not a big deal) until I had a moisture content of 39%. I also germinated at room temperature and the grain would heat up on its own depending on the depth of the pile. I managed to keep it between 25 and 30C in piles that varied in height from 4″ to 10″. If it was getting too warm I would spread it out into a shallower pile, if the temperature dropped below 25 C I would pile it up deeper. Because of the heat produced the grain can dry out so most articles recommend spraying water once daily to keep it hydrated.
Growth takes 4-5 days, keep it in a darkened room. Sorghum is hulless so the acrospire (growth shoot) is visible along with the roots. On day two it seemed pretty dry and the roots looked a little wilted so I added about 6 oz of water and it was quickly absorbed by the roots overnight. After 4 days I noticed a couple of acrospires turning green, once this happens the grain becomes bitter so I figured it was time to kiln the batch. Most information on malting sorghum recommend kilning at 50C until it’s dry to maintain as much diastatic power as possible. However, I found that it was next to impossible to remove the roots and acrospires without curing it. With barley once the moisture level is below 10% it is cured at higher temperatures to drive off moisture within the grain and to make it more friable. So this is what I did with the sorghum and cured it at 170F for three hours. This worked well and the roots and shoots came off easier.
It’s important to remove the roots and acrospires because they contain a chemical called Dhurrin which when mixed with the enzymes in the mash creates hydrogen cyanide or prussic acid, a very poisonous substance. Nice, like the risk of aflatoxin isn’t enough! The roots are removed by rubbing the grain over a strainer or wire screen. Consider this your second warning!
Brewing: The gelatinization temperature of sorghum starch is higher than that of barley, 68-75C or 156-166F which is above our mashing temperatures or the temperatures at which our enzymes are most effective. Even though the malting process has broken down the starches somewhat it is suggested that mashing would be more effective if the starches were gelatinized. This is done by “Decantation” mashing. This involves soaking the crushed grain at 45C or 113F for 30 minutes to dissolve the enzymes into the wort. The majority of the wort is then drawn off or decanted from the grains which are then boiled to gelatinize the starches. The grains are then added back to the wort carefully so that the temperature does not exceed 149F or whatever saccharification temperature you’re using. Mashing is continued at this point as you would with barley malt. I am not sure how much water is used during the initial mash. When I used a normal liquor /grist ratio it did not seem like enough. (This could have been due to the large amount of rice hulls I used) I was worried there wouldn’t be enough enzymes preserved in the small amount of wort, so I ended up drawing off all of the wort and adding just enough extra water to the grains to boil them. Once the grains were added back this gave me a slightly thinner mash than I would normally use.
After two hours of mashing at 154F, yes I overshot the temperature, an iodine test revealed that I hadn’t converted any starch – it was black. I thought this was yet another big fat fail of an experiment but I then took a reading with my refractometer and it read over 10 degrees. Good enough? Moving on to boiling for an hour with Huell Melon hops and my original gravity was 1.049 not too shabby.
The beer – Visually very cloudy, most likely due to the starch that didn’t convert. Perhaps I didn’t boil the grains enough to fully gelatinize them or the grains were undermodified. Or, curing at 170 reduced my diastatic power. Yet another reason could be time, perhaps this beer just needs a lot of time to settle.
Flavour- Clean, slightly tart like wheat. The melon flavour of the hops is present but overall this beer is kinda boring. This isn’t surprising given the fact that it’s just a low kilned base malt fermented very dry and without any caramelized or roasted grains (other than my scorched pot accident) I used safale us-05 yeast. There are no off flavours that I can detect, it tastes like beer. However boring this brew may be, I can see why gluten free brewers use sorghum to replace barley. Add some roasted or caramelized sorghum malt or even roasted millet (also gluten free) more hops, a different yeast and some great beer can be made. That is if you’re ok with a little aflatoxin and cyanide.