Cereal Mashing

Mention the word “cereal,” and most folks think of ready-to-eat breakfast food. To a brewer, cereal is the grain produced by any number of grass crops from Avena sativa (oat) to Zea mays (corn) that has not been sprouted to make malt. Cereal grains make up the greatest quantity and provide the most energy to the human diet, more than any other type of crop in the world. As brewers are well aware, barley in its malted form serves as the staple cereal grain of brewers worldwide because of its high enzymatic power when malted, and a husk that serves as a convenient filter following the mash.

But in a broader sense, what we are really engaged in when it comes to mashing is converting starch to sugar so it can be fermented by yeast. While the starch contained in cereal grain is in a fairly handy package, almost any starchy plant material from seeds to roots or tubers can be included in a mash — as long as it is handled appropriately.

So why should you as a homebrewer bother concocting a cereal (or other type of starchy adjunct) mash to include in your brew? Historically, starchy adjuncts have been used in beer to add flavor, save money or because of the sheer necessity of making beer with whatever starch source was available. Homebrewers today use cereals or other starchy adjuncts (hereafter referred to simply as adjuncts) for the same reasons, and also to exercise the creativity allowed by performing your own mash.

To explore the world of adjunct mashing you should first consider several questions: What style of beer do you plan to brew and how would various adjuncts complement that style? Are you going to perform a step mash or double (split) mash? What adjuncts do you plan to use and how should they be handled?

Cream ale or American lager are two beer styles that typically employ a mash with corn and/or rice. However, there are many interesting possibilities to explore by using either traditional or unusual adjuncts to modify existing beer styles or create something truly unique. Traditional adjuncts include corn, rice, wheat, barley and oats. Some unusual adjuncts include sweet potato, pumpkin, sorghum, millet, and rye among many others.

The question of whether to perform a double mash with the main malt bill mashed as a single infusion (and the adjunct mash then added to it, hence the name double mash), or a step mash is largely a matter of equipment. A step mash works best if you have a mash vessel to which you can apply heat (i.e. kettle), and a double mash works best if you have a mash vessel to which you cannot apply heat but is well insulated (i.e. converted cooler). In either case the adjunct mash itself will be prepared in a separate pot that can be heated on a burner.

With either approach, an adjunct mash is prepared and then added to the main mash. With the step mash procedure, the main mash is held at a low enough temperature so that the temperature can be increased to starch conversion range even after the hot adjunct mash is added. With the double mash procedure you will not have the luxury of applying heat to the main single infusion mash other than by means of adding hot water. Because there are obvious limits on the size of the mash vessel and the desired consistency of the mash, a brewer cannot simply add excessive quantities of water to accomplish the task of adjusting the mash temperature. Therefore, some special attention needs to be paid to monitoring and adjusting the temperature with a limited amount of water after the adjunct mash has been added when using the double mash procedure.

There are various approaches that can be used in the double mash method to control the temperature of the single infusion mash to which the adjunct mash is added. One approach is to prepare a slightly thick single infusion mash near the low end of the starch conversion range (149 °F or 65 °C) and allow the boiling hot adjunct mash to raise the temperature of the whole combined mash nearer to the higher end of starch conversion (158 °F or 70 °C) temperature. When using this approach, keep some cold water or ice cubes on hand to cool things down if you overshoot the temperature somewhat.

Another approach is to allow the adjunct mash to cool down very near to the main single infusion mash temperature before combining the two. This should have minimal impact on either the temperature or consistency of the combined mash. If you are going to use a double mash system, take careful notes of quantities and temperatures when the adjunct mash is added and any temperature adjustments that were made to help predict or modify your process as needed in the future.

Now let’s run through an example adjunct mash procedure using corn grits and a step mash system.

First, prepare your main barley malt mash as usual in a kettle on a burner except to start at 133 °F (56 °C) and reserve enough malt to include in the corn grit mash. Then hold the mash at that temperature while you prepare the corn grit mash in a separate pot.

Corn grits are commercially produced by soaking dried corn kernels in an alkaline solution, rinsing, and then drying and grinding them into meal. Polenta is coarsely ground corn. Cornmeal is degermed corn ground somewhat finer than polenta. Any of these products can be used, but the polenta or cornmeal may require a longer cooking time than corn grits. Usually, grits are a bit easier to work with. Combine the grits with between 15% and 30% crushed barley malt (by weight) and enough water to get the mash to the consistency of soupy oatmeal in a pot on the stove and begin heating.

Stir the mixture frequently and add water if necessary to keep the consistency thin and prevent scorching. Bring the temperature of the mixture to the upper limit of starch conversion (158 °F or 70 °C) and hold it there for at least five minutes. This gives the modest amount of barley malt enzymes a chance to reduce the size of the starch granules and reduce their sticking together or causing the mash to stick to the pot.

The starch granules will then become coated with water, loosening hydrogen bonds and dissolving some of the amylose off of their surfaces. This will allow the starch to absorb water and become gelatinous or “gelate.” This gelation is essential in order for the amylase enzymes of the malt to penetrate the starch in the grits and convert it to sugar after it is added to the main mash.

After the five minute rest, continue to heat the corn grit mash to boiling, stirring constantly to prevent sticking or scorching. Boil the mash for 30 minutes to assure that the starch has absorbed enough water to gelatinize. Starch gelation occurs when starch is cooked in water between 140 °F (60 °C) and 200 °F (93 °C), depending on the type of starch.

Then, stir the corn grit mash into the main mash and heat the entire mash up to the desired conversion temperature, which is between 149 °F (65 °C) and 158 °F (70 °C). Hold the mash at the desired conversion temperature for at least 45 minutes before adding the sparge water and lautering as usual.

If you are going to use a starchy adjunct other than a cereal, be sure it is either coarsely ground or in small pieces that will gelate without an excessive amount of cooking (more than 30 minutes) to avoid a sticky or scorched mash.

Several starchy adjuncts often used in brewing are also available in flaked or torrified form. Flaked grain is steamed then rolled, and torrified grain is moistened and heated until it pops. Barley, rice, oat, wheat, rye, and corn (maize) are commonly available in flaked form, and wheat is readily available in torrified form. Both flaked and torrified grains have already undergone gelation and so can be added directly to a standard mash containing barley malt for conversion without prior mashing or cooking.

There is some debate in brewing circles regarding the differences in finished beer flavor between the use of cooked adjuncts or flaked/torrified adjuncts. While the flaked and torrified products may be more convenient and sometimes yield more extractable sugar than cooked adjuncts, many argue that the cooked adjunct mash produces better flavor.

So join the debate and add to your brewing skills by learning to do an adjunct mash. That way, you can decide for yourself if it results in better beer for you!

Issue: December 2007