Saturday, September 24, 2011

Brewing with Adjuncts: A Cereal Mash HowTo

There are several reasons why you might want to do a cereal mash:
  1. You're brewing a style that calls for rice or corn adjuncts, such as a Classic American Pilsner.
  2. You're brewing an Oatmeal Stout or some other beer that calls for un-malted grains.
  3. You're using some un-malted barley or wheat.
In any of these scenarios, a portion of your mash will consists of grain that hasn't been malted. These grains lack the enzymes created during malting, and the starches they contain are not readily convertible to the sugars you need for brewing. Fortunately, the malted grains in your mash will have enough enzymes to convert all their own starch and more, but you'll need to go through an additional cooking process to gelatinize the un-malted starches to make them ready for the mash. If you think you might come up short on diastic power, you can replace some of the 2-row malt in your recipe with 6-row.

As with other brewing ingredients, there are shortcuts. If you're brewing a style that calls for rice or corn adjuncts, you can skip the extra process by buying pre-gelatinized “flaked” rice or corn at the homebrew store. No need to run any of this stuff through a grain mill, just toss it into your mash. As with malt extracts, buying special ingredients will be more expensive than using the 'regular' grains. You can also use instant rice, oatmeal or grits to reduce your cooking time.

Various sources use the term 'Cereal Mash', but it's really a 'Cereal Boil'. More on this later. The boil is used to break down the starches in un-malted grains to make them accessible to the enzymes in the main mash. If you're using grits or oatmeal, you won't need to mill these grains before starting the boil. If you're using rice, un-malted barley or wheat you'll want to mill them first. It will take significantly more effort to mill these grains than to mill their malted counterparts.

If you want to streamline the process you will need a pot large enough to hold your adjunct(s) and the boil water. Let's take a look a the process. Determine the amount of water you'll need, usually, about 3 to 4 quarts per pound of grain. Heat the water to boiling, add your grains and continue to boil for at least 30 minutes. Stir constantly so the mash doesn't scorch. Bits of grain will start to stick to your stirring spoon as the grain breaks down and the starches start to gelatinze.

Once the cereal boil is complete you can just add it directly to your mash. You can (and should) be strategic about this and use it as a way to do a stepped mash. You could (for example) mash in at 140, and use the cereal boil to raise your mash temps to 152. As long as your cereal mash is only a small part of the overall grain bill, you shouldn't notice any difference in the mash or sparge processes. If you're using a lot of adjuncts, you may want to add rice hulls to prevent a stuck mash.

I've never been able to figure out the reasoning behind what seems to be the 'official' way to do a cereal mash. The problem is that the 'mash' attempts to convert the starch that isn't convertible yet because it hasn't gone through the boil yet; using a quantity of malt that falls well short of  having enough enzymes to be useful. To make it work you'll need to manage two mashes at the same time, or you'll need to add a bunch of time to your brew day so you can com[plete your cereal mash before starting your real mash. But in case you're interested here's what to do:
  1. Add 1/4 cup of malt along with 2-3 quarts heated water per pound of grain to reach a mash temperature of about 158°F for corn or rice, 145°F for barley wheat or rye. Hold the temperature there for 15 minutes.
  2. Bring the cereal mash up to a boil and hold it for 30 minutes.
  3. Add the cereal mash to the main mash.


  1. I was also wondering why put malted barley in only to boil it, but you're the first I've seen ask the question.

  2. My thoughts as well. Surely the starches in the adjuncts wouldn't be available yet at the relatively low mash temperature. Then later when they do become available it's too late as you've killed the enzymes.