Do Adjuncts “Dry Out” Beer? Fining Beer, Smoky Off-Flavor, and pH 7

Q I hear a lot about corn and rice “drying” out a lager. What is it about these adjuncts in particular that makes them ferment out more?

Robert Deal
Palo Alto, California

A Dryness is a perception when used as a sensory term and as an analytical/numerical thing when used to describe fermentation. When wort is “fermented to dryness,” all fermentable sugars have been fermented by the yeast strain being used. Because of differences among yeast strains some yeasts can ferment sugars that others cannot, and some strains secrete enzymes that convert dextrins, which are unfermentable by all brewing yeasts, into glucose, which is fermentable by all brewing yeast strains. In other words, “fermented to dryness” is influenced by wort carbohydrate profile and by the brewer’s yeast strain selection.

Rich and malty beers, like doppelbocks and Scotch ale, can be both dry from an analytical perspective, i.e., no fermentable sugars are left in the beer, and have residual sweetness when described in sensory terms. That’s because these beers contain unfermentable, sweet-tasting compounds from malt and because salivary amylases in the mouth can convert unfermentable carbohydrates, which are not particularly sweet, into glucose, which is sweet.

Flaked rice, as seen up close, is often used by brewers to thin out the body of a beer. Photo courtesy of Adventures in Homebrewing

OK, so let’s focus on beers brewed with rice and corn adjuncts. In the early 1900s, these adjuncts represented about 10–15% of the total extract in North American lagers. Over the past century, the adjunct ratio in these beers has increased to where some mainstream lagers derive up to about 55% of the carbohydrate extract from adjuncts. Adjuncts are used for a variety of reasons, including how they influence beer flavor. Here is a fun question: Do beers like Budweiser have a lower apparent extract (finish gravity) than all-malt Pilsner beers with similar original gravity (OG) and ABV? Before answering the question, let’s add in that almost all trained beer tasters will agree that beers like Budweiser have a lighter mouthfeel than their all-malt cousins. In the vernacular of the consumer, these types of beers are described as thin, light, crisp, and watery. But the interesting thing is that these beers have apparent extracts that are aligned with their all-malt cousins, with the caloric values to prove their heft.

What’s going on here? It seems that thin mouthfeel would go hand-in-hand with a lower finish gravity, right? The main differences between malted barley and adjuncts, like rice and corn, are that malt contains hydrolyzed carbohydrates and proteins going into the kiln for the final step in the malting process. As malt is dried in the kiln, so-called reducing sugars react with free amino groups of amino acids and proteins to form Maillard reaction products (MRPs).

MRPs contribute a wide range of aromas, tastes, and colors to beer and foods. In addition to MRPs, malt contains proteins that don’t participate in the Maillard reaction, beta-glucans, and arabinoxylans. These large molecules contribute mouthfeel, body, and foam stability to beer. And this is really why beers brewed using adjuncts are generally perceived as being dryer than all-malt beers. The same explanation is true for how brewing sugars, like sucrose and dextrose/glucose, lighten the body of weighty styles like double IPAs and Belgian golden ales.

When wort is “fermented to dryness,” all fermentable sugars have been fermented by the yeast strain being used.

I am certainly not arguing that beers brewed with rice and corn always have the same final gravity as all-malt beers with similar OGs, but I am stating that many do. When brewers want to boost wort fermentability, changes to mash profile and mash time can be made, exogenous enzymes can be added, or different yeast strains may be chosen. And with what we now know about hop creep, dry hopping with hops known to cause creepin’ is another tool we can use.

In practical terms, worts made from starchy adjuncts are often produced using more intensive mashing methods that result in more fermentable wort compared to single-temperature mashing. The typical adjunct brew employs the double-mash method where one part of the mash goes through a cooking process to gelatinize adjunct starches while the second part of the mash, known as the rest mash, is started in a mash mixer. The rest mash cools the hot mash from the cooker, resulting in a blended mash temperature in the 154–158 °F (68–70 °C) range. As the two parts of the mash are blended, there is interplay between beta and alpha amylase; depending on how quickly the two parts are mixed, wort fermentability can be pushed up or down. The same basic process is used in decoction mashing and explains why some brews made from decoction and double mashes have a lower final gravity than beers made from a less intensive mashing like a single-infusion.

Q What is your preferred method of clarifying beer, including removing chill haze? I’ve tried finings (isinglass, silica-based, and gelatin), and filtering down to 1 micron but never had results as good as just leaving the beer chilled for a month or two.

Don Harwood
Oxfordshire, England

A My preference of clarification method is based more on process constraints than any true affinity for a particular method. Gravity plus time, finings plus time, filtration, centrifugation, and combinations of these can all be used to produce clear beer. From a commercial perspective, I prefer methods that are fast and effective while consuming as little energy and producing as little effluent as possible. This column is geared towards homebrewers and I am going to steer my answer in the direction of ease and reliability.

As you point out, gravity never takes a day off and works well to clarify beer. Nothing really beats the simplicity of cold-aging, a.k.a. lagering, for beer clarification. The primary downsides to this method include failure to remove chill haze, beer damage during lagering, space and equipment requirements, and the relatively long waiting time for something that can be conducted in a much shorter timeframe. Let’s dig into a couple of these points in more detail.

Chill haze is formed when proteins and polyphenols/tannins react at cool temperatures to produce beer haze. Beer clarification at cool temperatures works well, but if the clarified beer is packaged and chilled to lower temperatures, chill haze forms. The best temperature range for cold, gravity clarification is between 30–34 °F (-1 to 1 °C). Chill haze can also be prevented by adding silica gels or PVPP to adsorb chill haze reactants. One practical challenge with using these stabilizers is that they are not completely removed by gravity sedimentation and require filtration for complete removal . . . this comment is really intended for commercial brewers who are reading this. The bottom line is that cold-aging works great for both ales and lagers as long as the aging temperature is less than the serving temperature.

Beer damage can occur during lagering if oxygen pick-up occurs during racking or if microbes start to slowly grow and produce off-flavors. Both of these problems are easy to avoid by using good brewing techniques when handling beer and keeping a clean environment that helps minimize microbiological headaches.

Personally, I do like fining for homebrewing because fining agents speed up the rate of clarification. It also minimizes storage time and the equipment that is tied up with aging beer. I am not a vegan and have no issue using isinglass. Of all of the beer finings used, isinglass is the winner when it comes to overall effectiveness. And when so-called auxiliary finings, for example acidic polysaccharides and alginates, are added to beer before isinglass, the combined fining action produces very clear beer with a compact sediment in a short timeframe. This method of fining is best exemplified by brewers of cask-conditioned ales. Gelatin is another source of collagen, but instead of coming from the swim bladders of fish (isinglass), gelatin is usually rendered from pig and cattle skin. Not all collagen proteins are the same and the collagen from gelatin is not as effective a fining as isinglass (also called piscine collagen).

For those brewers who don’t want to use porcine, bovine, or piscine collagen for beer fining, silicic acid sols are a great alternate. These products are added to beer after fermentation and rather quickly settle yeast, although the sediment is usually not as compact as the sediment from isinglass fining.

Filtration is definitely an effective method of beer clarification and is a method that I personally favor for many beverage clarification applications. However, I don’t think most homebrewed beer should be filtered because beer haze generally has zero effect on beer flavor, provided that beer is not overly yeasty. And when filters as tight as 1 micron are used, flavor stripping can occur.

Your question asked for my opinion, so here it is. Homebrewers should focus on brewing the best tasting beers as possible. Once that goal is accomplished and the brewing of great beer becomes normal, then cosmetic methods can be pursued. But even then, I question the objectives. Is it to produce Pilsner that looks like something from a bottle? Or is the goal to brew great beer with minimal special tools? For me homebrewing is not trying to emulate commonly available commercial beer at home. Why? Because it’s much easier to buy a six-pack of great beer if your goal is simply to drink laudable beer. Homebrewing to me is about brewing what I cannot buy at my local grocery store/beer store. My jam is playing with raw materials and technique so that I am tasting what I did to brew my beer. I wear wrinkled clothes and don’t polish my shoes, and I don’t need a filter at home to produce aesthetically pleasing beer.

Q Where do you think a smoked off-flavor (aroma and flavor) may be coming from in a 100% Maris Otter American Pale Ale, with Columbus, Mosaic®, and Citra® hops? The beer was fermented with Voss kveik yeast at 86 °F (30 °C), under 10 psi of pressure, and started clarification yesterday. It clearly did not taste close to what I expected.

Arthur Davila
Sao Paulo, Brazil

A I like to troubleshoot off-flavors by thinking through the brewing process as a way of brainstorming. Plugging these thoughts into a visual aid like a fishbone diagram really helps to identify possible causes of the problem in question. Figure 1 illustrates the possible causes of smoky beer aroma that I can think of. I will dig into each of these and hopefully shed some light that may help better understand this problem.

Figure 1

Let’s start with yeast because certain yeast strains are able to convert ferulic acid from malt into 4-vinyl guaiacol (4VG). Although this compound is typically described as clove-like, it can also be perceived as smoky. Low temperature mash rests around 113 °F (45 °C) can increase ferulic acid levels in wort. So-called POF+ yeast strains convert ferulic acid into 4VG. Examples of POF+ (phenolic off-flavor positive) strains include Belgian wit, German weizen, some English ales, all Saccharomyces cerevisae var. diastaticus, and wild yeast. And wort spoilage bacteria, such as Hafnia and, Klebsiella, can also produce 4VG. Yeast is probably the most common cause of phenolic aromas in beer.

Another common source of smoky/phenolic aromas in beer is from chlorine or chloramine in water reacting to phenols produced by yeast during fermentation. Chlorophenols are potently aromatic and are often described as medicinal because some medicinal products, like Chloraseptic®, contain chlorophenols. Campden tablets, aka potassium metabisulfite, can be added to water to remove chlorine and chlorophenols. Activated carbon filtration is another useful method used to dechlorinate brewing water. The idea here is to remove compounds that may react with beer to form smoky aromas.

The last major source of smoky flavors in beer comes directly from malt and/or hops. Malt is smoky when wood smoke or peat reek, i.e., smoke from a peat fire, infuses malt. Smoked malts can contaminate regular malt in mills and grain handling equipment that are not properly cleaned after use and can even taint regular malt when bags of smoked and unsmoked malts are stacked together. Smoke aromas from hops are extremely rare, but wildfires in Oregon and Washington in 2020 and 2021 did damage some hops. Hop processors kept a very keen nose on bales to prevent smoke-tainted hops from being processed, but there have been a few reports from commercial brewers who have run into the odd lot of smoke-tainted hops. The takeaway from this discussion is to smell malt and hops prior to brewing.

OK, so here are my thoughts on your general problem. Voss kveik is not diastatic and is not reported to be POF+. Your hops were most likely not the source given the quality control on them. So that leaves us with water, excessive boiling (this leads to thermal degradation of ferulic acid into 4VG), microbes, and malt contamination as possible causes. Any of these are possible. There is nothing you can do about this brew, but you may want to review your water and how you are boiling before your next brew.

If you have any malt left, consider doing a hot steep and using your nose to determine if there are any smoky aromas that may come from the malt. Maris Otter is definitely not a malt associated with smoke, but several English maltsters produce both Maris Otter malts and peated malts. Contamination can occur during shipping and storage because of the intensity of peat smoke; it’s called reek for a reason! And microbial contamination is always a possibility. Hopefully this gives you some insight into this foggy topic.

Q I recently bought a pH meter and got some calibration reagents with it. I’m just about finished with my first bottles so I was about to shop around for some new reagents when it hit me . . . do I really need to buy a 7.0 reagent? If I remember from high school chemistry class correctly (it’s been 40 years!), can’t I just use distilled water to calibrate for 7.0?

Jeff Cutler
Redmond, Oregon

A On paper, using distilled water as a pH 7.0 makes sense because the ionization constant is 1 x 10-14 and the concentration of hydrogen ions is 1 x 10-7 molar at 77 °F (25 °C). Converting this to pH by poking 1 x 10-7 into the old calculator and hitting the log key results in -7, and multiplying this by -1 gives us 7; that should be the pH of pure water. I am impressed you remembered that from high school chemistry class. The problem is that water is rarely pure because it is the universal solvent and dissolves all sorts of things, including gases. And even if you were able to keep pure water pure in an environment without CO2, the ionic strength of pure water is too weak for a pH probe to properly function. A pinch of salt could be used to solve that problem.

Although the concentration of carbon dioxide in the atmosphere is only 400 ppm, that’s plenty to affect the pH of water because carbon dioxide sets up a powerful buffer system in water. This same buffering system is present in blood. In the case of water, the carbonate buffer system raises pure water pH up to about 8.2. The takeaway is that you need to buy two buffers to calibrate your pH meter. When you go shopping for pH buffers, you will discover that there are several options, with the most common being pH 4.01, 7.00, and 10.01. Brewers should calibrate their meters using pH 4.01 and 7.00 buffers because brewing biochemistry occurs in the acidic world.

You might be wondering why these pH standards are not affected by carbon dioxide in the atmosphere like water. The answer is because they are buffers themselves. Just in case you were not paying attention during this chapter in chemistry class, buffers are solutions containing a conjugate acid-base pair that are able to resist, or buffer, pH changes. Buffering capacity is directly related to the concentration of these compounds and is limited by how much acid or base can be added before the pH changes. This is why buffers need to be periodically replaced and why they should be stored in closed containers that prevent evaporation. One final point: Don’t ever store your pH meter’s probe in distilled water!

Issue: January-February 2022