Making the Most of Your Mash

As mentioned in the first article of this issue on page 5, mashing is just soaking crushed grains in hot water, then draining off the unfermented beer. The ancient Sumerians supposedly discovered the process by accident, and brewers throughout the centuries honed the process to what it is today. Most homebrewers roughly retrace this historical sequence when learning to mash — they don’t exercise a lot of control over their first few mashes, but gradually they fine tune their process.

In this article, we’ll discuss the refinements you can make once you’ve got your first few mashes under your belt. We’ll describe the variables that have the biggest impact on your finished beer and also touch on some of the practical aspects of being an all-grain brewer.

Buying and Storing Grain

One benefit of all-grain brewing is that your per-batch cost is lower than in extract brewing. (Of course, this is partially offset by the one-time cost of new equipment.) You can save even more money if you buy some of your grains by the sack. A sack of grain usually weighs either 50 or 55 lbs. (23 or 25 kg) and your cost per pound is less than a buck. Many all-grain homebrewers buy a sack of base grains, then buy the specialty grains for each batch as they go. Keep in mind, though, that malt is a food product and does go stale over time so buy what you will use.

Also remember that rodents and insect pests would love to get into your grain, and they will if you don’t store it properly. Many homebrewers buy a 55-gallon (208 L) plastic garbage can with a sealable lid to store their grains in. This will keep pests out and — if located in a cool, dry place — your (uncrushed) grains should keep for about a year.

The Crush

As discussed in the section of this issue about milling on page 16, one thing you can do that greatly affects your brewing is to get a good crush. The degree your malt is crushed affects many aspects of your mash, and the wort you yield from it.

The fineness of a crush varies from the grain kernels barely being disturbed to the grain kernels being ground into a uniformly fine powder. The optimal crush lies between these two extremes. The finer you crush, the higher your extract yield. However, with finer crushes, it is harder to collect your wort as the grain husks are too small to act as an efficient filter. In addition, the more pieces the grain husks are broken up into, the more tannins and other unwanted husk components will end up in your wort. Ideally, you want to crush finely enough that you get a good extraction efficiency, but coarsely enough that you can lauter with ease and minimize off flavors and astringency. So how do you do that?

The biggest variable affecting your crush is your mill gap — the space between the rollers in your grain mill. It would be nice if there was an optimal mill gap, but the best gap size depends on the grains you are milling and — to a lesser extent — the speed at which the rollers on your mill rotate. In general, however, a mill gap between 0.035 and 0.050 inches (0.89 and 1.3 mm) is thought to be a good, all-purpose setting for barley malt.

A second variable affecting your crush is the speed that the rollers rotate. The rollers on hand cranked mills rotate much slower than the rollers of commercial mills. (Their average speed is 400 RPM, for the optimal 9.8-inch (250-mm) diameter rollers). As such, hand cranked mills crush more coarsely when set to the same gap size. In contrast, home malt mills powered by a portable drill greatly exceed the proper speed and may crush too finely. To get the proper grain mill speed, you need to get a motor and control the speed with “pulleys,” more properly called sheaves.

Most homebrew malt mills are suboptimal in one or more respects when compared to full-size commercial mills. Most are either hand cranked or drill powered (i.e. rolling too slowly or too quickly). The diameter of the rollers on homebrew mills is frequently smaller than on commercial mills. And, many mills have a fixed gap, so the mill cannot be adjusted for different grains. Still, most all-grain homebrewers manage to get crushes that yield extract efficiencies in the same ballpark as most brewpubs or microbreweries. How is this?

You can judge the quality of your crush by examining the grain discharged from the mill or by brewing with it. What you want to see is few or no uncrushed kernels, plenty of kernels broken into two to four pieces and a minimal amount of flour. If you think your grain looks like it is crushed too finely — or you get high efficiencies, but stuck mashes and astringent beers — you have a couple options. You can switch to a larger gap setting, if your mill is adjustable, or start hand cranking, if you were using a drill to power your mill.

Conversely, if your grain looks undercrushed — or you get low efficiencies, but have no problems lautering (even when you run the wort off quickly) — you can set a smaller gap or motorize your mill.

In the case of undercrushed malt, you can also mill the grain twice. Even if you have a non-adjustable, hand-cranked mill, a second run through the mill will break up the kernels a bit further. Of course, the second crush can be a bit of a pain, as the grain won’t flow as easily in the hopper as it did when it was whole. So, the second crush may take considerably longer than the first. But, it can be worth it if you are brewing a big beer (and need all the extract efficiency you can get) or if your efficiency is very low.

The point is, although we homebrewers typically use mills that commercial brewers would deem sub-standard, there are workarounds we can use to get a decent crush. These operations would be impractical for commercial brewers who crush much larger amounts of grains and, for economic reasons, need to do so quickly (thus ruling out hand cranking or milling the grain twice). But, when milling less than 20 lbs. (9.1 kg) of grains on Saturday morning, it’s usually not that much of a hassle.

Temperature Differences

Everyone knows that temperature is important in mashing. However, one temperature-related aspect of mashing is usually left for the homebrewer to figure out on his own — temperature consistency and stability.

It’s fairly easy to end up with temperature differences in your mash. Variables that increase the potential for temperature differences include: Direct heating of the mash, thicker mashes, less stirring of the mash, large initial temperature differences between your grains and strike water and large temperature differences between your target mash temperature and your mash tun.

If you have a mash tun that you can heat, be sure to stir well when doing so. You may even want to stir for a minute or so after you turn off your burner as heat can continue to flow into the mash through the metal near the burner.

Most homebrewers mash fairly thickly, with mash thicknesses around 1.25 quarts of water per pound of grain (2.6 L/kg or a 2.6:1 ratio) being popular. However, if you are going to be heating the mash, you may want to go with a bit thinner mash. For example, if you were doing a heated step mash, a mash with a thickness around 1.9 qts./lb. (4 L/kg, or 4:1) would be easier to even out than a thicker mash. (This is because water conducts heat better than grain solids.)

When mashing in, your crushed grains are going to be much cooler than your strike water. Ideally, mixing the two should yield a mash right at your target temperature. For grains stored at around room temperature, heating your brewing liquor 10–11 °F (5.5–6 °C) over your target temperature will get you in the right range (assuming a roughly average mash thickness). Some software packages will calculate your ideal strike water temperature based on temperature and weight of your grain and target mash thickness. You can also determine the correct temperature by trial and error. Note your strike water temperature and initial mash temperature for two or three brewing sessions and you’ll quickly get a good feel for what your strike water temperature needs to be. The closer your strike water is to the correct temperature, the quicker your mash in will be. Also, a little stirring should quickly even out any temperature differences in the mash.

The temperature of your newly mixed mash can potentially be affected by the temperature of your mash tun. Ideally, you want to heat the mash tun to right around your target mash temperature prior to mashing in. Filling your mash tun with brewing liquor heated to a few degrees above your target mash temperature should do the trick. Let the water sit for a couple minutes, then return it to your hot liquor tank to be used later as sparge water. If you mash in a non-heated mash tun, the sides of your mash will quickly become cooler than the middle of your mash.

Temperature Stability

Once you are mashed in, your grain bed will start losing heat. The better insulated your mash tun is, the less heat loss you’ll suffer. Temperature losses will be greatest near the edges of your vessel. You can insulate your mash tun simply, for example with towels, with a fitted “jacket” that goes over the vessel or by wrapping it in fiberglass insulation. Even if your mash vessel is fairly well insulated to begin with — for example, if you mash in a converted picnic cooler — adding a little extra insulation will help you retain more heat.

So essentially, differences in mash temperature may exist initially within the mash and can form during mashing due to heating or cooling. In all cases, stirring thoroughly will even out the mash temperatures.

However, as you need to open your mash tun to stir, you’ll also lose heat each time you do. As such, you’ll want to add some heat each time you stir. If you are mashing in your kettle (or have a heatable mash tun), just heat the mash as you stir. If you can’t apply direct heat, you’ll have to add near-boiling water. In the latter case, you should only open the mash vessel and stir if you suspect significant temperature differences exist. The only way you’ll have any idea if this is the case is to take good notes the first few times you mash. Take the temperature at several places once you are mashed in. Stir until the temperature differences even out and seal the mash tun. After 15 minutes, open up your mash vessel and take the temperature near the middle and near the edges, then add some boiling water and stir to bring the temperature back to your original target. If the temperature changed little and showed little differences from the middle to the edge over 15 minutes, next time let the mash rest longer before opening it up. If you’re losing significant heat in under 15 minutes, you’ll definitely want to insulate your mash vessel to a greater degree.

On a 5-gallon (19 L) scale, try to keep your mash within 3 °F (1.5 °C) of the target temperature and keep temperature differences under 2 °F (~1 °C). Many homebrewers will mash in the kettle and have a fitted “sleeve” to put over it for insulation. To keep within 3 °F (1.5 °C) target, you may need to open up, heat and stir every 20 minutes. You’ll have to decide for yourself what amount of temperature deviance you are willing to put up with. The tighter the control you seek, the more you are going to have to monitor, stir and heat your mash. Also, if you are adding hot water to keep your temperature up, you may end up thinning the mash too much or running out of room in your mash vessel.

Wort Collection

Once the mash is over, the mash out has taken place and the wort is recirculated, wort collection begins. One factor that greatly affects the quality of your beer is how much wort you collect. The first bit of wort you run into your kettle is high in gravity (up to SG 1.100, depending on your mash thickness) and contains no undesirable elements extracted from the husks. As you continue to run off wort and rinse the grain bed with hot water (sparge), the gravity of the runnings drops and, at some point, the extraction of unwanted husk materials begins. Thus, for every unit of grain you mash, there is a volume of wort you can collect that yields the maximum amount of extract before wort quality suffers.

To find your proper volume of wort to collect per weight of grains mashed, you need either a calibrated hydrometer or a pH meter. Measure the specific gravity or pH of the runnings as you collect the wort. When the specific gravity drops to 1.010 or the pH rises to 5.8, stop collecting wort and make note of the volume of wort in your kettle in your notes. Divide this volume by the amount of grains you mashed. For example, let’s say you mashed 12 lbs. (5.4 kg) of grains and collected 6.5 gallons (25 L) of wort before stopping. This means that you collected 0.54 gallons of wort per pound of grain (4.5 L/kg). Finding this ratio on your system will allow you to plan ahead of time how much wort to collect from any future grain bill by multiplying the weight of your grains by this number. From this, you can figure if you’ll need to add water to your wort, based on your expected boil time. This may be necessary when brewing low-gravity beers from small grain bills. On the other hand, with strong beers — brewed from correspondingly large grain bills — you can use this calculation to predict how long you will need to boil to reduce your wort volume.

Control Mash Thickness (By Ashton Lewis)

Control mash thickness by varying the ratio of water to malt. Perfect this technique to tame the enzymes that cause important reactions in the mash, influence fermentability, and affect beer flavor.

On the surface the brewery mash appears to be a simple mixture of malt and water. When held hot for a period the mash begins to thin, producing a cloudy, semi-sweet liquid, then transforming into a mixture of clear, intensely sweet wort and spent grains.

Beyond these macroscopic changes lie important biochemical reactions that convert the starch found in the grain into sugar. Malt enzymes act as catalysts, in a sense causing these reactions.

Mashing begins when malt solids dissolve. These solids are primarily made up of starch but also include a significant portion of proteins. Included among the proteins are the catalysts, malt enzymes. The enzymes latch onto mainly starch and smaller carbohydrate molecule chains in a mash, bringing about a chemical reaction. These starch and carbohydrates are called substrates, because they are broken down by the protein-based enzymes during the reaction.

Smaller proteins, smaller beta-glucans (viscous gums that contribute to wort viscosity), sugars, and dextrins (unfermentable carbohydrates that add body to beer) are the products of enymatic attack and their parent compounds — proteins, beta-glucans, and starch — are called enzyme substrates.

Taking Charge

A brewer’s challenge is to let nature travel its free-wheeling road but in a controlled environment. Mash temperature, mash pH, water chemistry, enzyme concentration, substrate concentration, and product concentration are the mash variables that can be easily controlled.

Mash temperature has a great influence on which enzymes are active, because enzyme activity depends on temperature. Temperature also can cause enzymes to denature and permanently lose their catalytic activity. The principle enzymes involved in mashing all have different optimal temperatures.

Like temperature, mash pH affects enzyme activity. Enzymes must be in specific pH ranges to be active catalysts. In general the mash pH should fall between 5.2 and 5.4, because the enzymes of interest to brewers are active in this range. With most brewing waters and malts mash pH naturally falls in this range, so pH is not one of the mash variables that demands vigilant monitoring.

Other attributes that affect enzyme action are the concentrations of enzymes, substrates, and their products. These features are very important, because they influence the rate at which starch is broken down in the mash. As this reaction proceeds, the concentration of products (such as smaller carbohydrates) begins to build up and can slow down the reactions occurring in the mash. In addition to the speed or rate of the reaction, concentration can affect enzyme stability.

What Does It All Mean?

The concentration of enzyme, substrate, and product fall under the umbrella of “mash thickness.” Mash thickness is the weight ratio of water in the mash to malt in the mash.

Since one liter of water weighs one kilogram, mash thickness is easily determined when malt is measured in kilograms and water is measured in liters. For example, if 12 liters of

water go into a mash with four kilograms of malt, the mash thickness — or if you are British, the liquor to grist ratio — is 3:1. Although this is the most common way of expressing mash thickness, some brewers use the ratio of malt to water and express the ratio as a percentage. In the previous example the mash thickness could also be called 33 percent malt. In both cases it is simply the weight ratio of water to malt.

Although there are infinite mash thicknesses to use in brewing, three generic ranges of thickness are used in practice. These are the “thick mash,” the “medium-thick mash,” and the “thin mash.” These terms do not define thickness in absolute terms, but they do convey some important messages to the brewer.

Thick Mashes

In a thick mash the concentrations of enzymes, substrates, and products are all high, since there is a bunch of malt in a little bit of water. In numerical terms a thick mash is anything less than about 2.5 parts water to one part malt. The rule of thumb for mash thickness quoted in many homebrewing books is one quart of water per pound of malt; as a weight ratio that is 2.1:1. That is a pretty darn thick mash!

The thick mash has certain ramifications. The most striking feature is that it provides substantial protection to the enzymes present in the mash. In other words the enzymes are less likely to be denatured (stripped of qualities that allow it to catalyze the desired reaction) by high temperatures. This feature allows beta-amylase and alpha-amylase to work in concert, which is handy for a single-temperature mash. Without the protection of the thick mash, beta-amylase could be quickly denatured and the resulting wort would be predominated by the products of alpha-amylase action. Such a wort would have a high concentration of unfermentable carbohydrates. The resulting beer would have a higher terminal gravity and lower alcohol content than a beer made from a more fermentable wort.

Thick mashes do have obvious advantages, but there are some problems. Water is required to break down starch. Water is chemically inserted between the glucose molecules of the starch polymer during hydrolysis (the enzyme-directed breakdown of starch) and a shortage of water can cause incomplete breakdown of starch during mashing. Although mashes are rarely thick enough to cause incomplete starch conversion, very thick mashes can slightly decrease wort fermentability.

A less subtle result of thick mashes is noticeably lower extract yield. Thick mashes simply cannot bring all of the malt starch into solution. Although decreased extract yield is not going to send any homebrewer to the poor house, commercial brewers are not very fond of this side of the thick mash.

The last major problem with thick mashes is the high concentration of starch breakdown products. This feature is easy to spot when the specific gravity of the first runnings from the mash is taken. In thick mashes the first running gravity is usually greater than 20 °Plato (1.078). These products can interfere with enzyme action, resulting in what is called product inhibition.

Product inhibition may serve to control the millions of enzymatic reactions occurring every second in the human body, but it is not the brewer’s best friend. In the mash, product inhibition can lead to incomplete starch breakdown and decreased extract yield and fermentability.

Some enzymes, especially proteases (enzymes that attack protein), are very sensitive to product inhibition and are not very active in such environments. Periodically stirring a thick mash can help to alleviate product inhibition, since stirring distributes the enzymatic products that naturally accumulate near enzymes.

Medium-Thick Mashes

If a mash thickness less than 2.5:1 is thick, then a mash thickness between 2.5:1 and 4:1 should be medium. In practice a thickness of about 3.25:1 best captures the feel of the medium-thick mash. These mashes retain many advantages of the thick mash but few of the downsides. Additionally, mashes in this range of stiffness are easy to move around. This feature is important when conducting stirred, multi-temperature mashes as it allows for easier mixing and better heat transfer than a thick mash. These mashes are easy to pump, if required. Commercial breweries, for example, pump the mash from the mash vessel to the lauter tun.

Although thinning out the mash makes the enzymes less concentrated and hence more susceptible to temperature denaturation, this only occurs if the mash is conducted at an unacceptably high temperature. In general an infusion mash temperature of 150 to 155 °F in a medium-thick mash allows sufficient beta-amylase activity before rendering it inactive (beta-amylase usually begins losing activity above 149 °F).

After beta-amylase is denatured, alpha-amylase remains active because it is less sensitive to these temperatures, it can survive up to 170 °F. If multi-temperature mashing is used, then these problems are alleviated, regardless of thickness. But the thinner mash makes stirring easier.

The thinner mash also decreases the concentration of substrates and products. This minimizes the effects of product inhibition, the slowing of chemcial reactions caused by build-up, and also eliminates the loss of extract associated with very thick mashes.

In general the medium-thick mash provides for good enzyme activity, allows for easy stirring and pumping, will produce a wort with a high degree of fermentability, and produces a good extract yield from the malt. However, if a mistake is made by mashing in too hot, then the chance of causing irreversible enzyme loss is higher than if the same mistake is made in a thick mash.

Thin Mashes

Thin mashes are any mashes where the water-to-malt ratio exceeds 4:1. Like the medium-thick mashes, thin mashes are easy to move around and provide excellent heat transfer. They also give high extract yields, since the malt solids are easily dissolved.

The problem with thin mashes is enzyme stability. Enzymes are less stable in a thin mash and denaturation can become a real problem. The enzyme of concern is beta-amylase, since there is a limiting supply of beta-amylase in comparison to alpha-amylase. If beta-amylase denatures too quickly, then the resulting wort will have a decreased fermentability.

Some multi-temperature mash schedules suggest adding very hot water to increase temperature. This technique thins the mash and can render enzymes, especially beta-amylase, inactive when they are most needed. You may not like the results of using this method unless you want to limit fermentability.

Issue: Special Issue: Guide to All-Grain Brewing