Objective: Brew a German-style helles lager using step mashing

Through each course at Homebrew U, we have learned how to take more control over the wort-production stage of brewing. In Homebrew 501, we will harness the potential of the enzymes beta and alpha amylase and use these biological tools to produce a highly fermentable wort from a grist bill primarily comprised of lightly kilned malt. The result will be a crisp and refreshing German-style helles lager with high drinkability. 

Single-infusion mashes, such as the mash we performed in Homebrew 401, work well with beer styles that are not known to be “dry.” The Scottish ale that we brewed in Homebrew 401 is a great example of a beer best brewed using the infusion mash technique. In some beer styles, however, more than one mash temperature is required to coax the naturally present enzymes in malt to behave in such a way to maximize both fermentability and extraction efficiency.

In beer-geek lingo, we would say that helles wort has a high fermentability, perhaps around 80 percent. This means the beer would start at 12° Plato (this equates to an OG of 1.048) and finish at 2.4° Plato (a bit less than 1.010 FG). A Scottish ale wort has a lower degree of fermentability, perhaps as low as 70 percent. It might start at 15° Plato (1.060 OG) and finish at 4.5° (1.018 FG). °Plato is another way of expressing specific gravity; it’s based on the percentage of dissolved solids, such as sugar, in the wort.

To use lightly kilned malts to their full potential, a step mash is required. A step mash is one in which the temperature is gradually “stepped up” over time at progressively higher rest temperatures. To perform the step mash in Homebrew 501, you will need a mash tun that can be heated with a propane burner or electric heating element. It should not have a false bottom or slotted pipe like the combined mash-lauter tun we used in Homebrew 401. We’ll explain why a bit later.

We’ll use a step mash to brew a crisp and refreshing beer style with great drinkability, a German helles lager. This style of beer is typically light in color, has an assertive, yet balanced hop bitterness and a subtle hop aroma from the use of traditional German hop varieties like Tettnang and Hallertau.

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New Skills

step mashing

Equipment List

lauter tun

Vocabulary

helles lager: “helles” or pale lagers are the most popular beer in Bavaria. They are noted for their pale, straw color, delicate malt flavor, balanced bitterness and piney hop aroma

drinkability: buzz-word coined by big domestic brewers. Beers with drinkability are characterized by low diacetyl, high wort fermentability and moderate bitterness. These beers show their flaws and are considered more difficult to brew than big styles like stout and barleywine

lightly kilned malt: malt that has been dried at cool temperatures and received a final "cure" temperature around 180° F to minimize malt color and flavors produced by browning reactions, especially the Maillard reaction

step mash: mash conducted at several temperatures to optimize the activity of the active enzymes in a brewer's mash. Step mashing is accomplished by directly heating the mash vessel or by adding small amounts of hot water to the mash

starch-conversion rest: confusing name describing the rest around 158° F. The name implies that this rest is the only time that starch is converted to smaller carbohydrates. This is not true, as beta amylase catalyzes the degradation of starch at much lower temperatures. The name comes from the fact that the mash is "converted" from testing iodine- positive to iodine-negative around the temperature optimum of alpha amylase

lauter tun: specialized vessel used to separate wort from spent grains. Step mashing and decoction mashing typically use a separate vessel for wort separation because these mashes are stirred while being heated in the mashing vessel. A lauter tun is essentially a vessel equipped with a screen and a valve located below the screen. Most lauter tuns also have some sort of sparging device

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The mash rests

In our step mash, we are going to mash over a temperature range spanning from 131° F to 158° F for a total of 90 minutes, not including the time required for heating. In a step mash, the time spent at each different temperature is called a “rest.”

There are two types of rests commonly used in step mashing. The most common is the rest named for the enzyme substrate acted upon at a certain temperature. For example, the starch-conversion rest occurs around the optimum temperature for alpha amylase of 158°F and the protein rest occurs around the temperature optima of several proteolytic enzymes.

Sometimes brewers want to slowly heat the mash. You will find that this technique is very difficult to control. This is also hard for commercial brewers to control since most mash vessels are designed to heat at about 1.8°F per minute. An easy way to decrease the heating rate is by adding intermediate rests. For example, if you want to slowly heat your mash from 140°F to 149°F, you can simply add a short rest around 145°F. In fact, you may want to modify the mash profile described above to include such a rest. I’ll discuss why this sort of rest is important later.

In Homebrew 401, we had a single rest at 158° F. At this temperature there is little beta-amylase activity because this high temperature causes rapid denaturation of beta amylase (for a detailed discussion of mashing enzymes, see “Homebrew Science” on page 51). Wort produced by infusion mashing at this high temperature has decreased fermentability. For our helles, we want to produce a very fermentable wort and need as much help from beta amylase as possible.

Barley starch and the action of beta and alpha amylase

There are two types of starch found in barley: amylose and amylopectin. Amylose comprises roughly 25 percent of the starch content but the bulk is amylopectin. Amylose is a straight-chain molecule made exclusively of glucose molecules that are chemically linked with a bond called an “alpha 1-4 bond.” Amylose has two features that are important to brewers. The first is that it is soluble in hot water without requiring “gelatinization.” This means that it is soluble at temperatures less than 140° F, the gelatinization temperature of barley amylopectin.

The second key feature of amylose is the absence of branches caused by the alpha 1-6 bond. Beta amylase attacks starch from the reducing end of the starch and continues to munch its way down the molecule, producing a maltose molecule with each bite, until it runs into an alpha 1-6 bond. Beta amylase is called an “exo-enzyme” because it attacks from the end of the molecule. Since amylose contains no alpha 1-6 bonds, beta-amylase can convert almost all of the amylose found in malt into maltose.

Maltose is the principle fermentable sugar found in wort and over 95 percent is produced by beta amylase. For this reason, beta amyalse is known as “the fermentability enzyme.”

Amylopectin does contain alpha 1-6 bonds and it is these bonds that make amylopectin a branched molecule. Amylopectin can be drawn as a tree, and the trunk of the tree is the one and only reducing end of the molecule. The tips of all of the branches are referred to as non-reducing ends. The significance of this is that amylopectin has only one spot where beta-amylase can bind to starch and produce maltose. This reaction does not last long because of the large number of branch points in amylopectin.

Amylopectin has another feature that makes it more difficult to degrade than amylose, and that is its crystalline structure. As amylopectin is heated this crystalline structure begins to “melt” or gelatinize and the starch becomes soluble. Gelatinization of barley amylopectin begins to occur around 140°F. When starch is gelatinized it absorbs water and becomes very thick. This is why starch from wheat flour or corn starch thickens gravy and stir-fry.

This is where we really need the help of alpha amylase. Unlike beta amylase, alpha amylase is an endo-enzyme and randomly breaks alpha 1-4 bonds from the inside of the molecule. Using the tree analogy, alpha-amylase is like a tree removal guy using a chain saw to cut a big tree into several medium-sized pieces. With every cut, a new trunk is created and beta-amylase can latch onto the trunk (a reducing end) and do its thing until it runs into another alpha 1-6 branch.

The take-home message from this is that we get a more fermentable wort when beta and alpha amylase work together. And the best way to accomplish this is with step mashing.

Alpha amylase rapidly decreases the size of amylopectin. In doing so, it reduces mash thickness, creates more spots for beta-amylase to act upon and is responsible for changing the result of the iodine test from positive to negative. Alpha amylase is known as “the liquefaction enzyme” because of its dramatic effect on mash thickness. An iodine test is an easy way to see if all of the starch has been converted to sugar in the mash. You can buy an iodine kit at almost any homebrew store.

Raising the mash temperature

The most common method used to heat step mashes in a commercial brewery is with an external application of heat, usually though a steam jacket. In the old days flame heat was common, but steam is much cooler than direct flame and it is easier to control the rate of temperature change.

When applying heat directly to the outside of a mash vessel, the mash must be stirred to ensure even heating. Uneven heating results in temperature fluctuations throughout the mash and defeats the purpose of attempting to accurately control mash temperature. At home, we can heat our mash either with an electrical element or flame from a propane burner or gas range. Whatever you choose to use, try to keep the heat low and the gentle stirring constant to prevent rapid, uncontrolled heating and scorching.

The intermediate temperature rest mentioned earlier may come in handy during the heating steps. For starters, it gives you a minute to allow the mash temperature to equalize so you can get a good temperature reading. The intermediate rest also slows the rate of heating. When trying to produce a very fermentable wort this helps a bunch, especially in the 140° to 149° F range, because it gives more time for beta and alpha amylase to work together.

An alternative method for mash heating is to add boiling water to the mash. If you choose to use this method, add small volumes at a time and use plenty of stirring to minimize hot spots in the mash. To heat this mash from 131° F to 140° F will require about 54 fluid ounces of water at 208° F. The mash becomes thinner after each heating step and the volume of water required to change the mash temperature by 9° F increases. The last heating step to mash-off will require 142 fluid ounces of 208° F water and the total amount of water in the mash will have increased from 3 gallons at mash-in to 5.6 gallons. While a thinner mash increases extraction efficiency (yield), it also makes enzymes more sensitive to temperature. Many brewers steer clear of this method for this reason.

The mash out

Once the starch-conversion rest is completed and the iodine test is negative, we will mash out as we did in Homebrew 401. If you are heating by adding water, it will take slightly more water to raise the temperature to 169° F than it did for the infusion mash. After raising the temperature to 169° F, the mash is ready for transfer to the lauter tun. We must use a separate lauter tun for this beer, because you will be stirring the mash quite a bit. It’s problematic to do a lot of stirring in a combined mash-lauter tun, because the false bottom gets clogged. Also, the screen interferes with even heating.

Prior to transfer, cover the false bottom of your lauter tun with hot water to prevent creating an airlock beneath the mash. Try to minimize splashing during transfer, as splashing can darken wort and cause oxygen pick-up. It’s important to let the mash settle in the lauter tun before beginning wort recirculation. Ten to fifteen minutes is a typical lauter rest time.

Collect the wort as you did in Homebrew 401. Recirculate for 20 minutes to achieve good clarity. Then run off the wort off at about 2 quarts every 5 minutes. This is an important time to be patient, as an overly aggressive collection rate can result in a stuck mash bed. A stuck mash does nothing but cause stress and prolong a relaxing brew day. Begin sparging just before the grain bed is exposed and collect 6 gallons of wort.

The boil and beyond

We will use a 60-minute boil for our helles. Three hop additions impart a balanced hop character. Hop bitterness is accentuated in dry beers, so the hopping rate is kept at 20 IBUs. After the boil, cool the wort using the method described in Homebrew 401.

After cooling, it’s time for wort aeration, yeast pitching and fermentation. We want to produce a clean lager and will ferment between 50° and 55° F. After fermentation is complete, rack to a secondary fermenter and age in the secondary for two weeks at 40° F to produce a clear beer. Clarification will continue in the bottle and our helles will be ready for consumption three weeks after bottling. —Ashton Lewis

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What’s happening in the mash?

131° F: mash solids are wetted, amylose begins to dissolve and beta amylase begins producing maltose.

140° F: amylopectin begins to gelatinize, alpha amylase begins to reduce the size of starch molecules and beta amylase continues its activity. 140° to 149° F: The “ramp” when beta and alpha amylase work together to make a highly fermentable wort 149° F: beta amylase begins to fade out because of denaturation, alpha amylase becomes more active and starch continues to dissolve into the wort. 158° F: more starch dissolves and alpha amylase is at its fastest rate. Any starch extracted during this temperature is reduced in size by alpha amylase and “conversion” is completed. 169° F: mash-off stops enzyme activity and reduces wort viscosity prior to wort collection.

The protein rest no more

The protein rest is a temperature rest in the mash around 121° F where protein degradation was long thought to occur. But research conducted over the past two decades casts doubt on the significance on the protein rest. Dr. Michael Lewis' group at the University of California at Davis originally stirred up controversy and debate among brewers in the early 1980s when they published data showing an initial peak in protein content in the mash, followed by a decrease in high molecular weight protein fraction. No increase in lower molecular weight fractions was recorded.

If protein-degrading enzymes attack proteins during the protein rest, one would certainly expect to see a decrease in large molecules and a related increase in smaller molecules. Lewis’ group concluded that the initial peak in protein content was due to proteins going into solution, like amylose, and the decrease in the high molecular weight fraction over the course of the mash was caused by denaturation, not enzymatic activity.

The same studies produced data showing an increase in amino acids, agreeing with the notion that some proteolytic activity is present. The enzyme carboxy-exo-peptidase was attributed to the increase in amino acid content. This enzyme is an exo-enzyme and can produce a lot of amino acids without significantly altering the size of a protein.

As the initial shock of this research faded, other research groups repeated the experiments and obtained data that agreed with that of Dr. Lewis. Many breweries changed their mash profiles based upon these studies. It is widely held that most of the proteolytic activity occurs during malting and that this enzyme group is denatured during kilning. Protease activity during malting is extremely important and many measures of malt modification, such as the Kolbach index, are based on proteins. Today, many brewers refer to the rest at 121° F (50° C) as the beta-glucanase rest” because there is active beta-glucanase present in malt. Some beers, especially those made using raw barley, benefit from a beta-glucanase rest because beta-glucans can cause real problems during wort separation and beer filtration. — Ashton Lewis

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Grain to Extract and Back!

Here is a radical thought: The only real difference between extract and all-grain brewing is convenience, since the liquid or dry extract brewer merely buys what the all-grain brewer makes himself. To switch your recipes from all-grain to extract and back again, all you really need to know are a few simple and approximate conversion rules. Homebrewing does not need to be serious!

Rule One

The average liquid malt extract contains about 20 percent water and 80 percent solids, while dry extract (as the name implies) contains virtually no moisture. This is the basic rule of thumb from which all other conversions follow.

Rule Two

Therefore, 1 pound of liquid extract contains the rough solids equivalent of 1.2 pounds of milled, two-row, malted grain. Or, conversely, 1 pound of two-row grist can be substituted with 0.83 pounds of liquid extract, while 1 pound of dry extract contains the rough solids equivalent of 1.46 pounds of milled, two-row, malted grain. Or, again conversely, 1 pound of two-row grist can be substituted with 0.68 pounds of dry extract.

Rule Three

1 pound of liquid malt extract contributes about 8.75 °Plato (1.035 specific gravity degrees) to 1 gallon of water, or 1.75 °P (1.007 SG) to 5 gallons of water. One pound of dry malt extract contributes about 11.25 °P (1.045 SG) to 1 gallon of water, or 2.25 °P (1.009 SG) to 5 gallons of water.

Rule Four

Now do your own math!— H.D.

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German-style helles lager

OG = 1.048 FG = 1.009 IBUs = 20

7.5 pounds lightly kilned malt (pilsner malt or lager malt)
0.25 pounds Briess Cara-Pils malt
2.75 AAU Tettnang bittering hops (1/2 ounce at 5.5% alpha acid)
2.75 AAU Tettnang flavor hops (1/2 ounce at 5.5% alpha acid)
2.25 AAU Hallertau, Mount Hood or Liberty aroma hops (1/2 ounce at 4.5% alpha acid)
Wyeast 2124 (Bohemian Lager) or White Labs WLP830 (German Lager)

4 days before brew day
Make 2-liter (68 ounce) starter wort with an OG of 1.048 using dry malt extract
Cool starter, aerate and add yeast

On brewing day
Note: This beer style benefits from soft water.
Purchase 10 gallons of distilled water (not spring water) and add 1 gram of calcium sulfate to each gallon jug of water.
This will give us about 50 ppm of calcium in the water and no carbonates.
Mix 3 gallons of 143° F water with the crushed grains.
The mash temperature should be 131° F.
Allow mash to rest at 131° F for 20 minutes.
Raise mash temperature to 140° F.
Allow mash to rest at 140° F for 30 minutes.
Raise mash temperature to 149° F over a time period not less than 5 minutes.
This gives us a ramp of no more than 1.8° F per minute.
Allow mash to rest at 149° F for 20 minutes.
Raise mash temperature to 158° F.
Allow mash to rest at 158° F for 20 minutes.
Check for starch conversion using the iodine test.
If the test comes up negative (no blue or black color in the wort sample) go to next step.
If the test is starch positive, extend rest until you get a negative test.
Raise mash temperature to 169° F.
Gently transfer mash to lauter tun.
Recirculate wort for 20 minutes.
Begin collecting wort at the rate of about 12 ounces per minute (roughly 2 quarts every 5 minutes).
When top of grain bed becomes visible (but not dry), begin sparging with 169° F treated brewing water.
Maintain about 1 to 2 inches of sparge water on top of the grain at all times during wort collection.
Collect 6 gallons of wort.
Bring wort to boil.
Add bittering hops at boil.
Add second hop addition 30 minutes after start of boil.
Add last hop addition 55 minutes after start of boil.
Stop boiling 60 minutes after start of boil.
Cool wort with wort chiller.
Siphon cooled wort to fermenter.
Aerate wort.
Pitch yeast starter.
Ferment for 7 to 10 days at 50° to 55° F or until specific gravity is below 1.012.
Rack beer to secondary fermenter and decrease temperature to 40° F and hold at 40° F for 2 weeks.

About 3 weeks after brew day
Prime and bottle beer when specific gravity is constant for three days.
Condition for 1 week at room temperature
Refrigerate for 2 weeks

6 weeks after brew day
Beer is ready!

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