Dry Irish Stout: Style Profile

 It is sometimes difficult, in a blind taste test, to distinguish certain dry stouts from such brews as Scotch ales,  Scottish ales or porters. In theory, of course, the distinctions are clear: A Scotch ale should be fairly dry, like a dry stout, but its roasted chocolate notes should be much more subdued. The leading mass-produced brands of Scotch ales and dry stouts, at least by my pallet, seem to converge on this point. A Scottish ale, on the other hand should be much more alcoholic than the average stout, although this is not always the case when you encounter modern mass-market Scottish ales. A dry porter should have just a little less body than a dry stout, but the difference is not always perceptible — depending on what brand, microbrew or homebrew you are comparing.

In practice, therefore, your palate may say porter when the label says stout, or it may say stout when the label says Scotch ale. In spite of these taste ambiguities, there are a few brew-technical characteristics without which a dry stout just wouldn’t be a dry stout. These traits relate mostly to malt choices and mash temperatures.

Simple Sugars Make Dry Beers    

The key to making a dry stout — or a dry beer in general, be it an ale or a lager — is the choice of malt you purchase and the temperature at which you mash it. The basic rule that applies is that a beer will ferment to a dry finish if the wort you produce (or purchase in a can) contains very few complex, unfermentable, residual sugars.

Because ale yeasts can ferment only simple sugars — that is, single-molecule and two-molecule sugars — you must purchase grains that have not been malted to contain a great deal of unfermentable sugars (Hint: avoid crystal malts). Likewise, you must create an environment in the mash tun that favors the enzymatic conversion of grain starches into simple sugars only. This means that you must also avoid a mash environment that favors the production of complex sugars.

First, some quick and heavy-duty terminology: The single-molecule sugars, or monosaccharides, in wort are mostly fructose and glucose. (Fructose, however, is not found in significant levels in all-malt beers or beers using rice or corn). The two-molecule sugar, or disaccharide, in wort is mostly maltose. The three-molecule sugars, or trisaccharides, in wort are mostly maltotriose and raffinose. All sugars of four or more molecules are called oligosaccharides . . . and there are hundreds of them. Certain oligosaccharides, called polysaccharides, can be split enzymatically in the mash to yield fermentable monosaccharides. Any leftover unfermentable polysaccharide fractions are called dextrins.    

Armed with this information, we know that we must compose our dry stout grain bill to obtain mostly mono and disaccharides. This means we should avoid all sweet caramel or crystal malts that are especially formulated by the maltster to create nutty-sweet richness and a full-bodied mouthfeel. For this reason, Munich or Vienna malts are out. Also forbidden are any brewer malts that are labeled Carapils or dextrin malt. All these otherwise wonderful specialty malts contain too many unfermentable sugars for our purposes. These often appear in the form of hardened glassy crystalline sugars that were formed during the malt’s pre-cooking and steaming in the maltster’s roasting drum.    

The base malt for a dry stout, therefore, should be a top-quality pale malt. Most purists would argue that the pale grist be an ale malt (such as Briess pale ale malt), but I have also made delicious dry stouts with pale lager malts (such as Weyermann Pils malt). For the opaque color of the dry stout, skip all malts in the middle of the color spectrum and go straight for the darker chocolate and black patent malts. I like Briess chocolate malt for a nice roasted, chocolate flavor as well as Briess roasted malt for a hint of coffee. There are also great malts from the U.K. like Crisp, Hugh Baird and Simpsons. If you like a touch of burnt flavors, Briess black malt works well.

If you are like me and enjoy the deep color of black patent malt but not some of the bitter notes that are normally associated with such heavily roasted malts, try Weyermann de-husked Carafa Special Type III malt. Any of these malts, individually or in combination, contribute plenty of darkness and complexity of flavor, even in small quantities, without adding excessive amounts of residual sweetness.    

The importance of a high proportion of fermentable sugars in dry stouts explains why the most common commercial Irish stouts also contain a significant portion — perhaps as much as 20 to 30 percent — of unmalted adjuncts. These may be based on barley, rice, corn or a combination of the three. Once subjected to a vigorous and prolonged boil in a cereal cooker, adjunct starches break down and change mostly to simple, fermentable sugars, which in turn promote a dryer finish. (The boiling does not actually hydrolyze the starch, it gelatinizes the starch so that malt enzymes can break the molecules down.)    

Fortunately for the all-grain homebrewer, who may not wish to mess with cooking cereals, there are un-malted, pregelatinized barley products (such as Briess Pregelatinized Barley Brewer’s Flakes) on the market. Such products are made by steam-cooking the raw grains until the starches are gelatinous and soft. The adjuncts are then rolled and dried into flakes. Because flakes of barley, rice or corn lack enzymes, they need to be mashed with enzyme-rich pale malt. However, they must not be milled! Cooked, dried adjunct flakes can become overly powdery when milled and cause lautering and extract efficiency complications. Briess insists that their adjuncts not be milled.
 
A Few Tips For Extract Brewers    

Dry stouts are more identified with Ireland than any other place in the world. This simple generalization is important for the extract brewer who usually does not know from which malt variety the liquid in the can is made. The safest guideline for selecting a liquid malt extract for a dry extract stout, therefore, is to pick one that is explicitly marketed for Irish stouts. Unfortunately, all the canned stout extracts that I know of come pre-hopped. This requires a compromise. For authenticity’s sake, I suggest using an entire can of Mountmellick hopped Irish stout malt extract, augmented by some Briess brewer’s corn syrup for dryness and some unhopped dark malt, such as Coopers, Glen Brew, Briess, John Bull, or Muntons (for quantities see our recipe).

This gives you a chance to keep control over at least some of the hopping in this brew. The hop quantities specified in the all-extract recipe, therefore, may strike you as low, but they take into account that you are already getting part of your bittering from the can.    

As for adjuncts, there are syrup preparations for extract brewers that are made from rice or corn and serve the same function as adjunct flakes in the mash tun. Use them in the kettle like liquid malt extract. These syrups are very pale though, and thus lighten the beer.  The color of a dry stout made from our combination of extracts and adjunct syrup will be much lighter than the target 70 SRM that we prefer to achieve — especially in the absence of the dark and black malts that are part of the all-grain brewer’s mash. Given the variability of the color values of dark LMEs, and given the fact that extract manufacturers rarely disclose the color values on their labels, any assessment of the true color is more of an educated guess.

I suspect that the beer made with our recipe has a color value of approximately 45± 10 SRM. You can either accept this “brightening” of your stout or you can use a completely natural preparation called SINAMAR made by Weyermann. SINAMAR is a liquid malt coloring agent made exclusively from de-husked roasted malt. It darkens beer without affecting its flavor. To figure the quantity of this liquid malt color, let’s assume we want to darken the beer by 20 SRM. To make five gallons of beer 1 SRM darker, you need approximately 0.2 fluid ounces or 0.25 ounces avoirdupois of this liquid malt color. For those who “think metric,” these values are 6 mL or 7 grams for 19 liters.

Lower Mash Temperatures Make Simpler Sugars    

The all-grain brewer has a certain control over the types of sugars that are produced in the mash tun, provided there are not too many dextrin, caramel and crystal malts in the grain bill. The key process variable in this context is the diastatic conversion temperature.    

For dryness in the finished beer, it is essential that you select a sugar rest temperature that favors beta-amylase activity. Beta-amylase produces only fermentable sugars but leaves behind non-fermentables that the alpha-amylase must break down (in concert with the beta-amylase) to produce the driest beers.    

Alpha-amylase, by contrast, produces complex sugars that are either not fermentable or need to be reduced to become fermentable. The activity levels of these diastatic enzymes are tied to temperature as well as mash viscosity (thickness of mash) and pH-levels.    

Here are the relevant temperature thresholds that we must keep in mind for activating the correct amylase during the mash:

At 104 °F (40 °C) beta-amylase show the first signs of activity.
At 140 °F (60 °C) alpha-amylase show the first signs of activity.
At 149 °F (65 °C) beta-amylase show peak activity.
At 158 °F (70 °C) beta-amylase are denatured.
At 162 °F (72 °C) alpha-amylase show peak activity.
At 176 °F (80 °C) alpha-amylase are denatured.   

This means that, if we keep our mash temperature roughly between 140 and 150 °F (60–65 °C), there will be mostly simple-sugar production and very little complex-sugar production. Many brewers, therefore, prefer to make a dry stout using a single-
infusion mash at a temperature of only 148 °F (64 °C). Alpha-amylase reach their peak level of activity at a higher temperature than beta-amylase, but there is an overlap in activity between beta and alpha-amylase in the temperature range between 140 °F and 158 °F (60–70°C). Any complex sugars produced by alpha-amylase in that range, therefore, still has a chance to be reduced to fermentable sugars by beta-amylase. Some 80% of amylase activity occurs during the first 15 minutes when the mash is at the correct temperature. During that time we want to give beta-amylase enough time to break down the sugars produced by alpha-amylase and must give the dry-stout mash a long saccharification rest of at least one hour.    

Once we leave our saccharification rest temperature of 148 °F (64 °C), however, and start pushing the mash past 158 °F (70 °C) on our way up to the mash-out temperature, we must ensure that the temperature rise is quick so as not to create unfermentables by alpha-amylase. You want to get through the main active temperature band for beta-amylase as quickly as possible to avoid the generation of dextrins. By reaching the temperature plateau for denaturing alpha amylase rapidly (at the temperatures indicated) you achieve this objective. Initiate a sparge with near-boiling water to send the mash as rapidly as possible to about 172 °F (78 °C) and then reduce the sparge water temperature to about 180 °F (82 °C) to maintain the mash-out temperature. (The reduction in sparge water temperature may vary with the thermal characteristics of your mash setup.)    

Maintaining the mash at about 172 °F (78 °C) during sparging retards (though it does not stop) alpha-amylase activity. However, you do NOT want to push the mash past 176 °F (80 °C), the temperature at which alpha-amylase are denatured.

Hops and Yeast    

You need a soft hop to provide a gentle note to the slightly astringent maltiness of a dry stout, but you should never over-hop a stout just to create a contrast to the brew’s roastiness. If you stick with tradition, you cannot go wrong. The combination of Fuggles for bittering and East Kent Goldings for flavor works very well. Using Galena for bittering and Willamette for flavor yields an interesting American variation on the dry stout theme.

Because we want a dry but complex brew, select a yeast that is known as a good work horse to the finish and leaves a slightly buttery note, such as Wyeast 1084 Irish or White Labs WLP004  Irish.

Quantity Calculations    

The amounts in our all-grain recipe for dry stout have been calculated for a system with an extract efficiency of approximately 65%. If your system’s efficiency is different, our recipe will give you proportionally more or less wort at the specified target gravity. In this case you must also adjust all hops amounts proportionally to your actual yield. Knowing your system’s efficiency, you can adjust the grain amounts proportionally up or down in advance to obtain a yield of exactly five gallons.
   
Horst Dornbusch writes the Style Profile column in every issue of Brew Your Own.