The Wizard explains the impact of lagering in a fermenter as opposed to a keg or bottles, as well as brewing non-alcoholic and low-alcohol beers. Plus, tips for storing kegs and how ascorbic acid may be used at packaging to scrub dissolved oxygen.

Q. How does lagering a beer in a carboy or barrel affect the beer differently than storing the same unfiltered beer in a bottle or keg at the same temperature for the same period of time? 
Chris Patterson
Downers Grove, Illinois

A. This is a great question, Chris, and the answer starts with a quick review of the objectives of lagering. Although lagering is most often associated with lager beer, the process can be applied to all types of beer. Some brewers refer to all aging processes as “lagering,” others use the term “cellaring,” and some simply say “aging.” Naming aside, yeast sedimentation, diacetyl and acetaldehyde reduction, flavor integration, and sulfur scrubbing are among the key changes in beer flavor and appearance that can occur during lagering. In the commercial lager world, lagering may also include partial or complete natural carbonation.

Cask conditioning, while rooted in ale tradition, shares much in common with lagering. One of the key differences between lagering and cask conditioning is volume: Lagering is a bulk process in which the finished beer is later transferred to kegs, bottles, or cans, while cask ales are conditioned in the very vessels from which they are served. Another difference is yeast sediment. Commercially packaged lagers typically do not contain yeast sediment, whereas cask ales generally do.

At home, lagering can be done in containers that do not permit carbonation, such as carboys, or in containers that do, such as kegs or certain pressure-rated small fermenters (such as those included in this homebrew unitank comparison). In both cases, beer clarification, flavor maturation, and sulfur volatilization occur. Lagering in a keg allows homebrewers to mimic commercial practices, including kräusening — adding actively fermenting beer to fully fermented beer to achieve carbonation and speed aging. A key part of this process is venting excess gas. While aging in a carboy also allows sulfur venting, keg aging, where CO₂ is naturally produced and released, is my preferred method.

When lagers are aged in bottles, three important things cannot occur: Sulfur scrubbing, yeast sedimentation, and yeast separation. A practical solution for home lager production is to select a yeast strain that produces clean, low-sulfur lagers within a short fermentation and maturation window. Strains such as SafLager W-34/70 can be used successfully at warmer temperatures (59–68 °F / 15–20 °C) by both home and commercial brewers to quickly produce beers with low diacetyl and sulfur. Others, such as LalBrew NovaLager, have been developed through traditional selection and hybridization to yield strains that produce minimal diacetyl and hydrogen sulfide. 

As long as the beer is cooled to encourage most yeast to drop out before packaging, you can bottle-condition and age for flavor integration. Is the result identical to bulk-aged lager? Probably not, but it can be surprisingly close.

Q. I have been looking for maltose- and maltotriose-negative yeast to brew a low-alcohol Pilsner recipe from BYO. The yeast recommended is White Labs WLP603 (Torulaspora delbrueckii) or SafAle LA-01, and I can’t find those yeasts in a homebrew size. Every maltose-negative yeast is either the 500-g size or unavailable through any online retailer or homebrew shop I have searched. Any tips on what homebrewers can do?
Mike Seward
Barrington, Rhode Island

A. Before I answer this question, I want to say that I sometimes sit on questions because great questions come in waves and this one was sent into the mailbox earlier this year. It’s rarely the case where new information comes about while questions sit in the inbox, but in this case the body of knowledge related to non-alcoholic (NA) brewing is growing at a rapid pace. Bottom line is that this is a timely question and I have some thoughts about this topic.

I am not surprised that you haven’t been able to find a source for these yeast strains because none of these suppliers are selling them into homebrew markets. There is one major challenge when brewing beer with maltose- and maltotriose-negative yeast strains, simply referred to as maltose-negative strains; the biggest risk to stability comes from garden-variety brewing yeast.

Because breweries, both home and commercial, are rife with brewing yeast, the risk of contamination is high. When beer produced using a maltose-negative strain is contaminated with a regular brewing strain, over-carbonation and the possibility of exploding packages is a clear and present danger. The only currently acceptable stabilization process is pasteurization. This may change in the future as alternative approaches are examined, but those currently do not exist. Some breweries and research facilities are serving unpasteurized NA beers fermented with maltose-negative yeast in dedicated draft systems where temperature control is used to minimize the risk of re-fermentation and monitoring is used to check for the signs of re-fermentation.

Another concern with NA beers is the growth of pathogens. That’s the other reason that commercially produced NAs are pasteurized. I will come back to this topic later but want to pivot to some other points first.

If I were writing this answer earlier this year, I probably would not have thought much about the actual alcohol content of the beer as a real concern to homebrewers. However, the alcohol content of these beers is of concern to many of the people who drink them. The term NABLAB is used around the world these days to describe non-alcoholic and low-alcohol beers. Although definitions are not universal, most countries define beers with ABVs between 0.5 and 2.5% as “low alcohol.” When alcohol is less than 0.5% ABV, the term “non-alcoholic beer” is used. The term “alcohol-free” or “zero-alcohol” is reserved for beers with no measurable alcohol.

Consumers who are serious about how they consume or do not consume alcohol must be able to rely upon the producers of NABLABs to properly adhere to these product classifications. Because I drink beer, I am one of those consumers who is not overly concerned about drinking something that may contain 0.7% ABV instead of 0.4% ABV. But brewers cannot make assumptions about others and need to be precise with labeling. If your interest in brewing NA at home is related to brewing beer for a friend or loved one who cannot or does not want to consume alcohol, you really should stick to purchasing these beers from a commercial producer unless you are willing to have your beer analyzed before serving.

You specifically asked about using maltose-negative yeast because that is the method discussed in Kara Taylor’s article. However, there is another method available to homebrewers that does not require special yeast or equipment — high temperature mashing. This method involves mashing in at ~176 °F/80 °C, resting for about 15 minutes, collecting, boiling, and cooling wort as usual, and fermenting with whatever yeast strain you want to use. Because there is essentially no beta-amylase activity, very little if any fermentable sugars are produced during the mash. This very high temperature also quickly stops alpha-amylase activity and results in starchy wort. Halting alpha-amylase is important because alpha-amylase does produce some glucose, maltose, and maltotriose because its action on starch is random.

I recently brewed two beers using this method. Although I knew what I was doing, I was still surprised by the cloudiness of the wort. Not seeing anything during fermentation, although not surprising, was also odd. Although there are compounds in wort that yeast metabolize during the short fermentation, the lack of appreciable fermentable sugars means that alcohol production is all but eliminated and the fermentation appears non-existent. While the beers both finished with a veil, neither are extremely hazy.

Much of the focus of NABLAB production is aimed to eliminate worty aromas and flavors common to these beers. One method that works surprisingly well is kettle souring. Lactic acid bacteria apparently metabolize some of the worty precursors and reduce the concentration of aldehydes in the finished beer. And the interesting thing is that this action occurs in kettle soured wort that is not obviously sour. This means that pH can be monitored and the process stopped with wort boiling before the wort is sour, allowing the method to be used in just about any style.

My recent NA brews used kettle souring. In one brew, a Pilsner-style NA, I dropped the pH to 3.9 (my target was 4.0) and in the second brew, the base for a berry-flavored sour, I dropped it all the way down to 3.2. I used kettle souring in an attempt to reduce worty aromas — this was a success — and to lower pH for safety reasons discussed later.

The 2025 Summit — a joint conference uniting members of the American Society of Brewing Chemist (ASBC) and the Master Brewers Association of the Americas (MBAA) — featured numerous presentations related to NABLAB production. The one topic related to NABLABs that has brewers and industry experts concerned is the risk posed by spoilage and pathogenic microorganisms, especially when it comes to draft beer. Because in-keg pasteurization is not possible and the very real challenges associated with properly cleaning and sanitizing kegs, keg couplers, and draft lines, many brewing experts and brewers believe that NABLABs should only be served from cans or bottles. Although some brewers are conducting research into the use of liquid preservatives, in-package pasteurization is the only preservation method universally accepted for these beverages.

Some small-scale producers use batch pasteurization to process cans and bottles of NABLABs. I can address that process in another column, but for the time being I will just leave you with the knowledge that batch pasteurization is something that can be performed at home. A very conservative level of batch pasteurization for a typical NABLAB is in the 80–120 PU range.

Whether producing low-fermentable wort using the hot and fast mash method or using a maltose-negative yeast strain, I believe that certain practices should always be followed brewers, and others should be avoided when producing NABLABs.

DO:

• Boil wort for at least 30 minutes
• Heat-sanitize the wort cooler
• Reduce wort pH to <4.2
• Adjust finished beer pH to <4.2, if required
• Add all hops before wort cooling
• Heat-pasteurize finished product

DO NOT:

• Dry hop — this simply is an unnecessary risk
• Add unpasteurized fruit purees or any fermentable sugars if your goal is <0.5% ABV
• Barrel age

I know that commercial craft brewers read this column. If you are one, know that I am a big proponent of this growing category of beer. I sincerely want brewers to continue elevating these beers without incident. It’s really amazing how many excellent-tasting products are currently being produced. Brewers are going to do whatever because these products are only regulated by the TTB and the industry does not want to see that change — that’s why producers of these products are so concerned about possible issues in the market.

Caution flags and raised voices, however, will not prevent brewers from experimenting with these beers at home and taking the easy way out by packaging in kegs and not pasteurizing. If you decide to roll the dice, read the literature, understand the risks, clean your kegs by completely disassembling, sanitize your kegs after reassembly, use new draft lines and picnic taps, and store your keg and dispense rig in a cooler at <38 °F/3.3 °C. Finally, have a party and drain the keg asap.

Q. I have a question about storing kegs after they’ve been cleaned and sanitized. I had a bad experience when I had purged a keg with CO₂ and stored it that way for months before using it for kegging. On the day we were going to keg, I popped the lid and got a very strong, pungent odor from the keg. I would say it was even acidic, as if carbonic acid gas had formed over time. How could this have happened? Perhaps I left too much sanitizer in the keg, though I do my best not to do that. Or maybe some other contaminant was present because I didn’t clean well enough? Or perhaps this is a natural process that occurs over several months and the long-term storage of kegs needs to be done differently?
Jeff Vandewinckel
Arlington, Tennessee

A. Your example is an extreme case between sanitizing and use, but the broader question is one I’ve often heard craft brewers discuss when preparing equipment. My preferred method is to clean equipment immediately after use, then sanitize just before use. Fermentation vessels, for instance, are easiest to clean shortly after emptying. Often, a simple water rinse with gentle scrubbing, followed by another light rinse and then a cleaning cycle — either by hand or with a pump and spray ball — is quick and effective. Some brewers then sanitize the vessel and store it closed and under pressure until needed, as you describe.

The real issue with cleaning and sanitizing is that neither process is absolute — sanitized equipment is not sterile. And because no-rinse sanitizers used in brewing and food processing rarely provide residual activity, any surviving microorganisms can grow if nutrients are present. It’s impossible to know exactly what developed in your keg during extended storage, but the sour smell is a clear indicator that something did. Carbonic acid itself is odorless, but when you sniff carbonated beverages, it creates a tingling sensation in your nose. By contrast, organic acids such as acetic, propionic, and butyric have sharp aromas that are easy to detect.

Going forward, I recommend cleaning equipment immediately after use, allowing it to drain, and then storing it. Dust is difficult to control at home and can carry yeasts, molds, and bacteria. A quick rinse followed by sanitization right before use is the best practice.

Q. Can I put ascorbic acid in my cans before I fill them with beer to scrub any dissolved oxygen? Also, how would I dose it?
Darren O’Day
Philadelphia, Pennsylvania

A. Ascorbic acid, also known as Vitamin C, is indeed an antioxidant often discussed in the context of beer stability because of its ability to scavenge oxygen in the headspace of packaged beer. Its mode of action is somewhat different from many other antioxidants. Ascorbic acid does not directly bind oxygen. Instead, it donates hydrogen atoms to reactive oxygen species such as peroxide radicals, thereby neutralizing them. This transfer of electrons is the fundamental chemical process we call oxidation.

However, the behavior of ascorbic acid can be complicated by the presence of transition metal ions, particularly iron and copper (Fe²⁺ and Cu²⁺). In the presence of these metals, ascorbic acid can actually promote the generation of reactive oxygen species rather than prevent it, effectively reversing its antioxidant role and causing oxidative damage. For this reason, successful use of ascorbic acid requires very low levels of these metal ions. Unfortunately, in brewing, keeping metals out can be difficult. Common brewing inputs such as hops, malt, brewing water, and filtration aids can all be sources of copper and iron. But for the sake of discussion, let’s assume a beer with minimal problematic metal ion content.

When used under the right conditions, ascorbic acid is safe for beer, though flavor limits must be respected. At higher concentrations, it imparts a noticeable tartness. The threshold for this effect varies depending on beer style: Light, delicate beers can show tartness at concentrations above about 10 mg/L, while more flavorful or heavily hopped beers can tolerate slightly higher levels. As is often the case in brewing, bench trials are invaluable for determining the appropriate dosage for a specific recipe. A common working range is 5–10 mg/L.

The most practical way to add ascorbic acid is as an aqueous solution. Because the compound itself is reactive toward oxygen, the solution should be prepared in deoxygenated water — ideally water that has been boiled, cooled, and stored in a sealed container to minimize oxygen pickup.

The dosage calculation is straightforward when using metric measurements. For example, suppose you are working with 20 liters of beer and wish to dose at 10 mg/L. That requires 200 mg of ascorbic acid in total. Since the solubility of ascorbic acid in water at 68 °F (20 °C) is about 330 g/L, there is no risk of creating an overly concentrated stock solution. A convenient approach is to prepare a 40 g/L stock solution. 20 mL of this solution will contain the required 200 mg of ascorbic acid for the 20-L batch. Unless you have a highly accurate scale, mixing up 4 g of ascorbic acid in 100 mL of water is easy to measure and gives you plenty for bench trialing and dosing. 

Q: Can I put ascorbic acid in my cans before I fill them with beer to scrub any dissolved oxygen? Also, how would I dose it?
— Darren O’Day • Philadelphia, Pennsylvania

Mr. Wizard says…

A: Ascorbic acid, also known as Vitamin C, is indeed an antioxidant often discussed in the context of beer stability because of its ability to scavenge oxygen in the headspace of packaged beer. Its mode of action is somewhat different from many other antioxidants. Ascorbic acid does not directly bind oxygen. Instead, it donates hydrogen atoms to reactive oxygen species such as peroxide radicals, thereby neutralizing them. This transfer of electrons is the fundamental chemical process we call oxidation.

However, the behavior of ascorbic acid can be complicated by the presence of transition metal ions, particularly iron and copper (Fe²⁺ and Cu²⁺). In the presence of these metals, ascorbic acid can actually promote the generation of reactive oxygen species rather than prevent it, effectively reversing its antioxidant role and causing oxidative damage. For this reason, successful use of ascorbic acid requires very low levels of these metal ions. Unfortunately, in brewing, keeping metals out can be difficult. Common brewing inputs such as hops, malt, brewing water, and filtration aids can all be sources of copper and iron. But for the sake of discussion, let’s assume a beer with minimal problematic metal ion content.

When used under the right conditions, ascorbic acid is safe for beer, though flavor limits must be respected. At higher concentrations, it imparts a noticeable tartness. The threshold for this effect varies depending on beer style: Light, delicate beers can show tartness at concentrations above about 10 mg/L, while more flavorful or heavily hopped beers can tolerate slightly higher levels. As is often the case in brewing, bench trials are invaluable for determining the appropriate dosage for a specific recipe. A common working range is 5–10 mg/L.

The most practical way to add ascorbic acid is as an aqueous solution. Because the compound itself is reactive toward oxygen, the solution should be prepared in deoxygenated water — ideally water that has been boiled, cooled, and stored in a sealed container to minimize oxygen pickup.

The dosage calculation is straightforward when using metric measurements. For example, suppose you are working with 20 liters of beer and wish to dose at 10 mg/L. That requires 200 mg of ascorbic acid in total. Since the solubility of ascorbic acid in water at 68 °F (20 °C) is about 330 g/L, there is no risk of creating an overly concentrated stock solution. A convenient approach is to prepare a 40 g/L stock solution. 20 mL of this solution will contain the required 200 mg of ascorbic acid for the 20-L batch. Unless you have a highly accurate scale, mixing up 4 g of ascorbic acid in 100 mL of water is easy to measure and gives you plenty for bench trialing and dosing. 

Q: I have been looking for maltose- and maltotriose-negative yeast to brew a low-alcohol Pilsner recipe from BYO. The yeast recommended is White Labs WLP603 (Torulaspora delbrueckii) or SafAle LA-01, and I can’t find those yeasts in a homebrew size. Every maltose-negative yeast is either the 500-g size or unavailable through any online retailer or homebrew shop I have searched. Any tips on what homebrewers can do?
— Mike Seward • Barrington, Rhode Island

Mr. Wizard says…

A: Before I answer this question, I want to say that I sometimes sit on questions because great questions come in waves and this one was sent into the mailbox earlier this year. It’s rarely the case where new information comes about while questions sit in the inbox, but in this case the body of knowledge related to non-alcoholic (NA) brewing is growing at a rapid pace. Bottom line is that this is a timely question and I have some thoughts about this topic.

I am not surprised that you haven’t been able to find a source for these yeast strains because none of these suppliers are selling them into homebrew markets. There is one major challenge when brewing beer with maltose- and maltotriose-negative yeast strains, simply referred to as maltose-negative strains; the biggest risk to stability comes from garden-variety brewing yeast.

Because breweries, both home and commercial, are rife with brewing yeast, the risk of contamination is high. When beer produced using a maltose-negative strain is contaminated with a regular brewing strain, over-carbonation and the possibility of exploding packages is a clear and present danger. The only currently acceptable stabilization process is pasteurization. This may change in the future as alternative approaches are examined, but those currently do not exist. Some breweries and research facilities are serving unpasteurized NA beers fermented with maltose-negative yeast in dedicated draft systems where temperature control is used to minimize the risk of re-fermentation and monitoring is used to check for the signs of re-fermentation.

Another concern with NA beers is the growth of pathogens. That’s the other reason that commercially produced NAs are pasteurized. I will come back to this topic later but want to pivot to some other points first.

If I were writing this answer earlier this year, I probably would not have thought much about the actual alcohol content of the beer as a real concern to homebrewers. However, the alcohol content of these beers is of concern to many of the people who drink them. The term NABLAB is used around the world these days to describe non-alcoholic and low-alcohol beers. Although definitions are not universal, most countries define beers with ABVs between 0.5 and 2.5% as “low alcohol.” When alcohol is less than 0.5% ABV, the term “non-alcoholic beer” is used. The term “alcohol-free” or “zero-alcohol” is reserved for beers with no measurable alcohol.

Consumers who are serious about how they consume or do not consume alcohol must be able to rely upon the producers of NABLABs to properly adhere to these product classifications. Because I drink beer, I am one of those consumers who is not overly concerned about drinking something that may contain 0.7% ABV instead of 0.4% ABV. But brewers cannot make assumptions about others and need to be precise with labeling. If your interest in brewing NA at home is related to brewing beer for a friend or loved one who cannot or does not want to consume alcohol, you really should stick to purchasing these beers from a commercial producer unless you are willing to have your beer analyzed before serving.

You specifically asked about using maltose-negative yeast because that is the method discussed in Kara Taylor’s article. However, there is another method available to homebrewers that does not require special yeast or equipment — high temperature mashing. This method involves mashing in at ~176 °F/80 °C, resting for about 15 minutes, collecting, boiling, and cooling wort as usual, and fermenting with whatever yeast strain you want to use. Because there is essentially no beta-amylase activity, very little if any fermentable sugars are produced during the mash. This very high temperature also quickly stops alpha-amylase activity and results in starchy wort. Halting alpha-amylase is important because alpha-amylase does produce some glucose, maltose, and maltotriose because its action on starch is random.

I recently brewed two beers using this method. Although I knew what I was doing, I was still surprised by the cloudiness of the wort. Not seeing anything during fermentation, although not surprising, was also odd. Although there are compounds in wort that yeast metabolize during the short fermentation, the lack of appreciable fermentable sugars means that alcohol production is all but eliminated and the fermentation appears non-existent. While the beers both finished with a veil, neither are extremely hazy.

Much of the focus of NABLAB production is aimed to eliminate worty aromas and flavors common to these beers. One method that works surprisingly well is kettle souring. Lactic acid bacteria apparently metabolize some of the worty precursors and reduce the concentration of aldehydes in the finished beer. And the interesting thing is that this action occurs in kettle soured wort that is not obviously sour. This means that pH can be monitored and the process stopped with wort boiling before the wort is sour, allowing the method to be used in just about any style.

My recent NA brews used kettle souring. In one brew, a Pilsner-style NA, I dropped the pH to 3.9 (my target was 4.0) and in the second brew, the base for a berry-flavored sour, I dropped it all the way down to 3.2. I used kettle souring in an attempt to reduce worty aromas — this was a success — and to lower pH for safety reasons discussed later.

The 2025 Summit — a joint conference uniting members of the American Society of Brewing Chemist (ASBC) and the Master Brewers Association of the Americas (MBAA) — featured numerous presentations related to NABLAB production. The one topic related to NABLABs that has brewers and industry experts concerned is the risk posed by spoilage and pathogenic microorganisms, especially when it comes to draft beer. Because in-keg pasteurization is not possible and the very real challenges associated with properly cleaning and sanitizing kegs, keg couplers, and draft lines, many brewing experts and brewers believe that NABLABs should only be served from cans or bottles. Although some brewers are conducting research into the use of liquid preservatives, in-package pasteurization is the only preservation method universally accepted for these beverages.

Some small-scale producers use batch pasteurization to process cans and bottles of NABLABs. I can address that process in another column, but for the time being I will just leave you with the knowledge that batch pasteurization is something that can be performed at home. A very conservative level of batch pasteurization for a typical NABLAB is in the 80–120 PU range.

Whether producing low-fermentable wort using the hot and fast mash method or using a maltose-negative yeast strain, I believe that certain practices should always be followed brewers, and others should be avoided when producing NABLABs.

DO:

• Boil wort for at least 30 minutes
• Heat-sanitize the wort cooler
• Reduce wort pH to <4.2
• Adjust finished beer pH to <4.2, if required
• Add all hops before wort cooling
• Heat-pasteurize finished product

DO NOT:

• Dry hop — this simply is an unnecessary risk
• Add unpasteurized fruit purees or any fermentable sugars if your goal is <0.5% ABV
• Barrel age

I know that commercial craft brewers read this column. If you are one, know that I am a big proponent of this growing category of beer. I sincerely want brewers to continue elevating these beers without incident. It’s really amazing how many excellent-tasting products are currently being produced. Brewers are going to do whatever because these products are only regulated by the TTB and the industry does not want to see that change — that’s why producers of these products are so concerned about possible issues in the market.

Caution flags and raised voices, however, will not prevent brewers from experimenting with these beers at home and taking the easy way out by packaging in kegs and not pasteurizing. If you decide to roll the dice, read the literature, understand the risks, clean your kegs by completely disassembling, sanitize your kegs after reassembly, use new draft lines and picnic taps, and store your keg and dispense rig in a cooler at <38 °F/3.3 °C. Finally, have a party and drain the keg asap.

Q: How does lagering a beer in a carboy or barrel affect the beer differently than storing the same unfiltered beer in a bottle or keg at the same temperature for the same period of time? 
— Chris Patterson • Downers Grove, Illinois

Mr. Wizard says…

A: This is a great question, Chris, and the answer starts with a quick review of the objectives of lagering. Although lagering is most often associated with lager beer, the process can be applied to all types of beer. Some brewers refer to all aging processes as “lagering,” others use the term “cellaring,” and some simply say “aging.” Naming aside, yeast sedimentation, diacetyl and acetaldehyde reduction, flavor integration, and sulfur scrubbing are among the key changes in beer flavor and appearance that can occur during lagering. In the commercial lager world, lagering may also include partial or complete natural carbonation.

Cask conditioning, while rooted in ale tradition, shares much in common with lagering. One of the key differences between lagering and cask conditioning is volume: Lagering is a bulk process in which the finished beer is later transferred to kegs, bottles, or cans, while cask ales are conditioned in the very vessels from which they are served. Another difference is yeast sediment. Commercially packaged lagers typically do not contain yeast sediment, whereas cask ales generally do.

At home, lagering can be done in containers that do not permit carbonation, such as carboys, or in containers that do, such as kegs or certain pressure-rated small fermenters (such as those included in this homebrew unitank comparison). In both cases, beer clarification, flavor maturation, and sulfur volatilization occur. Lagering in a keg allows homebrewers to mimic commercial practices, including kräusening — adding actively fermenting beer to fully fermented beer to achieve carbonation and speed aging. A key part of this process is venting excess gas. While aging in a carboy also allows sulfur venting, keg aging, where CO₂ is naturally produced and released, is my preferred method.

When lagers are aged in bottles, three important things cannot occur: Sulfur scrubbing, yeast sedimentation, and yeast separation. A practical solution for home lager production is to select a yeast strain that produces clean, low-sulfur lagers within a short fermentation and maturation window. Strains such as SafLager W-34/70 can be used successfully at warmer temperatures (59–68 °F / 15–20 °C) by both home and commercial brewers to quickly produce beers with low diacetyl and sulfur. Others, such as LalBrew NovaLager, have been developed through traditional selection and hybridization to yield strains that produce minimal diacetyl and hydrogen sulfide. 

As long as the beer is cooled to encourage most yeast to drop out before packaging, you can bottle-condition and age for flavor integration. Is the result identical to bulk-aged lager? Probably not, but it can be surprisingly close.

Q: I have a question about storing kegs after they’ve been cleaned and sanitized. I had a bad experience when I had purged a keg with CO2 and stored it that way for months before using it for kegging. On the day we were going to keg, I popped the lid and got a very strong, pungent odor from the keg. I would say it was even acidic, as if carbonic acid gas had formed over time. How could this have happened? Perhaps I left too much sanitizer in the keg, though I do my best not to do that. Or maybe some other contaminant was present because I didn’t clean well enough? Or perhaps this is a natural process that occurs over several months and the long-term storage of kegs needs to be done differently?
— Jeff Vandewinckel • Arlington, Tennessee

Mr. Wizard says…

Your example is an extreme case between sanitizing and use, but the broader question is one I’ve often heard craft brewers discuss when preparing equipment. My preferred method is to clean equipment immediately after use, then sanitize just before use. Fermentation vessels, for instance, are easiest to clean shortly after emptying. Often, a simple water rinse with gentle scrubbing, followed by another light rinse and then a cleaning cycle — either by hand or with a pump and spray ball — is quick and effective. Some brewers then sanitize the vessel and store it closed and under pressure until needed, as you describe.

The real issue with cleaning and sanitizing is that neither process is absolute — sanitized equipment is not sterile. And because no-rinse sanitizers used in brewing and food processing rarely provide residual activity, any surviving microorganisms can grow if nutrients are present. It’s impossible to know exactly what developed in your keg during extended storage, but the sour smell is a clear indicator that something did. Carbonic acid itself is odorless, but when you sniff carbonated beverages, it creates a tingling sensation in your nose. By contrast, organic acids such as acetic, propionic, and butyric have sharp aromas that are easy to detect.

Going forward, I recommend cleaning equipment immediately after use, allowing it to drain, and then storing it. Dust is difficult to control at home and can carry yeasts, molds, and bacteria. A quick rinse followed by sanitization right before use is the best practice.

There are plenty of food sources that may be used for souring beer, from kimchi to soured dill pickles. Learn more about why these sources could save brewers money and result in flavorful brews. Plus: How to calculate the carbs in your homebrews and advice on how long you should hold onto those hops in your freezer.

Q. I recently watched one of your BYO+ videos about making sour beer. The suggestion to use kimchi for souring beer blew my mind! I’m already making my own kimchi, so I will definitely try this. Here are my questions: 1. Is there any taste difference between using kimchi and the Lactobacilli that I can purchase from a lab? 2. If kimchi works, what about traditionally soured dill pickles, e.g., Strubbs?
Gord Maxwell, via Live Chat

A. I recently talked about this during a BYO Live Chat and thought it would be worthwhile to share some expanded thoughts in writing. Let’s start with the idea of using kimchi as a source of bacteria for making sour beer. As a probiotic-rich food, kimchi is a well- established source of various microorganisms believed to promote gut health (Indigenous Fermented Foods for the Tropics is a great reference on this). These microbes, many of which are lactic acid bacteria, also happen to be useful in the production of sour beer.

The primary organisms responsible for kimchi fermentation belong to the gram-positive, acid-producing Lactobacillaceae family of bacteria, often referred to more simply as lactics. This large and diverse group of bacteria is naturally found in many places, including grains, fruits, vegetables, and even in puddles of fermenting spilled milk. One particularly interesting trait of lactics is that many are heterofermentative, meaning they produce multiple byproducts during fermentation. Depending on fermentation conditions, these byproducts typically include lactic acid, ethanol, and acetic acid. This contrasts with homofermentative lactics, which mainly produce lactic acid. That’s enough nerding out for now. 

These days, most sour beers are produced using one of two general approaches: Either by purchasing lab-grown cultures or by channeling your inner Tarzan and wrangling wild bugs. Traditional sour beers rely heavily on the Tarzan method, where wort is naturally inoculated by airborne microbes, ingredients, and the unique microflora found in the brewing environment. One of the best-known examples of this method is used by Brasserie Cantillon in Brussels, Belgium. They are legendary for their exceptional wild ales, which have been brewed using largely unchanged techniques for nearly a century. Their brewery sits tucked away in a charming neighborhood surrounded by butcher shops, cafés, and rows of townhouses, blending the old-world craft of spontaneous fermentation with the bustle of modern life. 

In more recent years, brewers have adapted this traditional approach by using fermented foods — especially yogurt and kefir — as alternative sources of bacteria for kettle sours. Although these cultured dairy products are often made with blends of commercially available bacteria, to the brewer they are still considered somewhat wild, since the exact composition of the cultures isn’t usually known when added to wort. This adds a layer of unpredictability, which can be both exciting and risky. 

Over the past 25 years or so, access to specialty cultures of bacteria and yeast has grown dramatically. Today, brewers looking for consistency and control in their funky beers have a wide range of commercial options. In the early days, most of these lab cultures were blends of organisms found in traditional Belgian lambics or blends intended to approximate bugs found in lambics. As time went on, the push for more predictable and faster souring methods led to the rise of kettle souring. This process is popular because it allows brewers to keep the souring bugs contained in the brewhouse, rather than introducing them into the fermentation cellar where cross-contamination is a concern. 

Because malt is such a rich source of lactic acid bacteria — including Lactobacillus delbrueckii, which is homofermentative, and Lactobacillus plantarum, which is heterofermentative — many early kettle souring techniques relied on bugs cultured directly from malt. Today, however, brewers can easily purchase pure lactic cultures from yeast labs. These have largely replaced wild-cultured sources, especially for brewers seeking repeatability and ease of use. 

More recently, lactic acid–producing yeast strains have gained popularity. Lachancea thermotolerans is a naturally occurring yeast that produces both lactic acid and ethanol and is now available to homebrewers and commercial brewers from yeast labs such as Escarpment Labs and Lallemand. Lallemand also offers a genetically modified Saccharomyces cerevisiae strain known commercially as Sourvisiae. This strain has been engineered to express the gene for lactate decarboxylase, an enzyme that converts pyruvate to lactic acid. The main advantage of using Lachancea or Sourvisiae in sour beer production is the simplified process compared to kettle souring, with no bacteria introduced into the cellar. 

All of this helps explain why the idea of going Tarzan with kimchi as a source of lactics is so appealing for brewers looking for an adventure. Fresh kimchi juice contains a healthy population of lactic acid bacteria. According to the kimchi chapter in Indigenous Fermented Foods from the Tropics, cell densities in kimchi typically range from 100 million to 1 billion cells per milliliter. That’s an ideal range for brewers looking to propagate a strong bacterial culture for use in beer. You’ve got plenty of biological firepower in even a small splash of kimchi juice to propagate for use in brewing. 

Kimchi is just one of many fermented foods that can be used to wrangle bugs for making sour beer. My general advice is to start with foods that taste good to you. If you wouldn’t eat it, don’t brew with it. Live sauerkraut, buttermilk, and dill pickles are all viable sources of lactics. 

One final, important tip: If you’re working with heterofermentative lactics, avoid creating conditions that lead to the production of acetic acid (aka vinegar). These bacteria only make acetic acid in the presence of oxygen, so be sure to minimize oxygen exposure during the souring phase. A sealed vessel and a good dose of CO₂ headspace can help you keep things clean and crisp.

Q. Two nutrient analytics labs tested my first attempt at a low-carb beer and showed all sugars and carbs as less than 1 g per 100 mL. Yet it does spike my blood sugar severely. According to Brewfather, my recipe should have 3.6 g of carbs per 100 mL. Are the labs missing some type of sugar or carbs? 
Pieter de Weerdt
Via Live Chat

A. This is a great question that affects beer lovers of all sorts, especially those of us who keep a watchful eye on our blood glucose levels. Unfortunately, I cannot provide any specific details about the data you received from the labs who ran your testing with the available information. It does seem unusual that beer with 1 gram of carbs per 100 mL would cause a spike in your blood glucose. As a comparison, commercially produced light/low carb beers brewed in the U.S. contain between 0.7 – 1.9 grams of carbs per 100 mL of beer. Although I cannot provide information about the past, I can comment on differences between expectations and measured values, how to estimate carbs, and a few ways to reduce them in beer. Let’s begin with predictions.

Recipe calculators use predictive equations to estimate alcohol and residual extract based on the original gravity and predicted final gravity. Because malt specifics, mashing particulars, and water chemistry can all affect wort fermentability, predicting final gravity is not much more than a guess. Furthermore, yeast strain, pitching rate, and yeast nutrients influence residual carbohydrates left behind after fermentation. In my experience, making assumptions about fermentation is not as approximate as assumptions about wort composition. That said, predicting final gravity is approximate.

A better way to estimate alcohol and residual carbohydrates is to use a model that uses both original extract/gravity, and apparent extract/gravity. Two estimates I feel comfortable using are the following developed by Gary Spedding because I bumped these calculations against known beer data and they provide solid estimates. Although the original publication in Brewers Digest cannot be found online, this article in Brewers Journal contains Spedding’s calculations. There are two equations in this article for alcohol by weight (ABW) and it is the second that should be used (I converted equations from the original reference into a spreadsheet years ago and know that there was some sort of editorial confusion in the referenced article).

Real Extract = (Original Extract × 0.1948) + (Apparent Extract × 0.8052)

Alcohol by Weight = 0.8052 x (Original Extract-Real Extract) / 2.0665 – (1.0665 x Original Extract / 100)

Here is what the math above reveals about a typical beer-flavored beer with a wort gravity of 11 °Plato and a final gravity of 2 °Plato. Note that I have not included specific gravity equivalents because the equations above use Plato for the calculations, but for those curious we are talking about 1.044 OG and 1.008 FG. Also note that the units on Plato are grams extract per 100 mL of beer or percent by weight.

Real Extract = (11 x 0.1948) + (2 x 0.8052) = 3.74 °Plato

Alcohol by Weight = [0.8052 x (11 – 2)] / [2.0665 – (1.0665 x 2/100)] = 3.5% ABW (g/100 mL)

Alcohol by volume is equal to ABW / 0.79 (the density of ethanol), and 3.5% ABW equals 4.5% ABV. I only show ABV because it is the most common unit used to express alcoholic strength in beer, wine, and spirits. However, when it comes to calculating grams of residual extract and calories, percent by weight is the value to use.

The term real extract is used to define dissolved solids in beer, which are mainly comprised of carbohydrates but also include protein, minerals, and hop acids. For your inquiry, it is safe to assume that 100% of the real extract can be attributed to carbs because that slightly overestimates the value.

We have determined that beer with an OG of 11 °Plato and a final gravity of 2 °Plato contains 3.7 grams of carbs per 100 mL of beer and 3.5% ABW. Carbs contain 4 kcal/gram and alcohol contains 7 kcal/g, giving the beer in this example 39.3 kcal/100 mL of beer or 140 kcal per 12-oz. (355-mL) serving.

In my experience, a lab analysis should provide data that is similar to what is calculated above provided you are producing beer that falls into the typical range of beers found in the market. Spedding’s calculations are based on beer data and do not work for completely fermentable solutions. Without knowing the original extract and apparent extract of your beer, I don’t know if the Brewfather prediction is off or if the labs are off. Run the numbers to see which set of data seems most plausible.

I am guessing from your question you may use a continuous blood glucose monitor. I use one of these devices and have learned a lot about how different foods and beers affect my blood glucose. I feel fortunate to have discovered that my blood glucose was abnormally high a few years ago and to be successfully controlling things with a combination of diet, medication, and monitoring. One thing I learned is my body reacts differently to some beers. When I drink non-alcoholic beers produced using maltose-negative yeast strains, for example, my blood glucose usually spikes because these beers contain all of the maltose and maltotriose that comes with mashing. I also have noted spikes when drinking “normal” beers that have above average final gravities. One hunch that I have with some of these beers is that they have been fermented with yeast strains that do not ferment maltotriose. Unfortunately, this property of yeast strains is not widely published. It is known, however, that many English strains popular among the haze-crazed crowd do not ferment maltotriose.

Methods to lower carbs in beer include extended mash rests in the 140–145 °F (60–63 °C) range, the use of exogenous alpha amylase or amyloglucosidase in the mash or fermenter, substituting sucrose or dextrose/glucose for a portion of malt or malt extract to increase wort fermentability, brewing lower gravity beer styles, selecting high-attenuating yeast strains, and taking advantage of hop creep to dry beers out. 

Q. What is the longest you would store Hops in the freezer? Would the max storage time be different for bittering vs. aroma hops?
Ken Grace
Via email

A. This question has two very different answers depending on the source of the hops. Let’s start with pelletized hops sold to commercial breweries. These hops begin their journey at the farm, where tall bines are cut from the fields and the cones are separated using a picking machine. Although a small number of farmers now use hop combines that cut, pick, and separate leaves and bines from cones, most still use picking machines housed in buildings typically referred to as picking sheds. Once the picker has disassembled the cones, leaves, and bines, a system of belts and blowers separates out the cones.

The next step is hop kilning, where hot, dry air reduces the moisture content to below 8%. After kilning, the dried hops are stored in large piles to allow the moisture to equilibrate. In most parts of the world, the hops are then compressed into bales. Before pellets became the norm, this was the end of the line for most hops: Bales would be stored in warehouses — often warm ones — before being shipped to breweries. It was U.S. brewers who demanded refrigerated hop storage. In fact, U.S. hop processors routinely store bales in freezers, whereas German processors typically store them in refrigerators at 36–41 °F (2–5 °C).

Because most hops today are pelletized, bales destined for pellet production are usually stored only briefly before being broken apart using a piece of equipment called a bale breaker. The cones are then milled into powder using a hammer mill. The powder is typically blended in a ribbon-style mixer to reduce variability between bales, then compressed into pellets using a forming die. These days, forming dies are cooled with liquid nitrogen and some processors even cool the hop powder prior to forming. Finally, the pellets are packaged in foil bags. The current standard is to flush these bags with nitrogen gas to create a modified atmosphere that reduces oxidation during storage. For many years, vacuum packing was common, but this method makes the bags prone to damage and can cause pellets to clump together into hard-to-handle masses.

The foil bags of hop pellets are then boxed, palletized, transferred to cold storage, and kept there until shipped to breweries or into distribution channels. Depending on the variety — some hops have better storage properties than others — and the intended use, hop pellets can be stored cold for up to six years. In general, pelletized aroma hops start to fade after 2-3 years of storage and bittering hops can hold their brewing value up to about six years. Breweries equipped with lab instruments and trained sensory panels routinely sample and analyze their inventory to determine how best to use it. Because hops are used exclusively in beer, breweries contract with growers to ensure a reliable supply. When aroma hops become unsuitable for brewing, brewers may repurpose them for bittering or take the loss. One major advantage of hop extracts is extended shelf life, which is why many larger breweries convert a portion of their inventory into extracts shortly after pelletizing (most extract facilities are designed to process pellets, which are more compact than cones).

I know I haven’t answered your question yet, but it’s important to understand how pellets are produced and packaged. The issue is this: Pellet bags typically contain 11, 22, or 44 pounds (5, 10, or 20 kg) of hops. Hops sold in the homebrewing market, by contrast, usually come in 1-oz. (28-g) packages. So the obvious question is: How are these 1-oz. (28-g) bags produced?

Typically, they are repackaged from larger bags that are labeled with critical information such as the harvest year, the processor (the company that converts bales into pellets), a lot number, and sometimes a QR code linking to hop analytics. However, not all repackaged pellets retain this vital information. For example, a commercial-sized bag of 2024 Cascade hops labeled with 8.5% alpha, 6% beta, and 1.5% oil might simply become a bag labeled “U.S. Cascade Hops” with a general alpha acid range of 5–9%.

Hops sold to homebrewers are somewhat analogous to growlers or Crowlers^TM of beer. While it is entirely possible to repackage hops without increasing oxygen exposure, the risk is higher. This alone likely shortens the shelf life of homebrew hops compared to those sold to commercial brewers. Another issue is the packaging. Foil bags offer excellent gas barrier properties assuming the seal is perfect and there are no pinholes. Plastic bags, on the other hand, offer poor barrier protection, meaning that even a vacuum-sealed plastic bag can still allow oxygen ingress over time.

My advice is to use hops as soon as possible after purchasing, unless they are packed in foil and clearly labeled with the crop year and processor. The challenges of repackaged hops are well understood, and many hop processors serving the homebrew market have responded by labeling their products with the same information as packs sold to commercial brewers.

Hops do go on sale, and good deals can be found. I love a bargain and feel confident buying discounted hops if I know they were packaged by a reputable processor and properly stored throughout their life. That last piece, storage history, is nearly impossible for any buyer to verify, whether homebrewer or pro. That’s why it’s good brewing practice to smell your hops before use. If you open a bag and something seems off, it’s your call: Repurpose the hops for bittering or make the executive decision to toss them.

Q: What is the longest you would store hops in the freezer? Would the max storage time be different for bittering vs. aroma hops?
— Ken Grace, via email

A: This question has two very different answers depending on the source of the hops. Let’s start with pelletized hops sold to commercial breweries. These hops begin their journey at the farm, where tall bines are cut from the fields and the cones are separated using a picking machine. Although a small number of farmers now use hop combines that cut, pick, and separate leaves and bines from cones, most still use picking machines housed in buildings typically referred to as picking sheds. Once the picker has disassembled the cones, leaves, and bines, a system of belts and blowers separates out the cones.

The next step is hop kilning, where hot, dry air reduces the moisture content to below 8%. After kilning, the dried hops are stored in large piles to allow the moisture to equilibrate. In most parts of the world, the hops are then compressed into bales. Before pellets became the norm, this was the end of the line for most hops: Bales would be stored in warehouses — often warm ones — before being shipped to breweries. It was U.S. brewers who demanded refrigerated hop storage. In fact, U.S. hop processors routinely store bales in freezers, whereas German processors typically store them in refrigerators at 36–41 °F (2–5 °C).

Because most hops today are pelletized, bales destined for pellet production are usually stored only briefly before being broken apart using a piece of equipment called a bale breaker. The cones are then milled into powder using a hammer mill. The powder is typically blended in a ribbon-style mixer to reduce variability between bales, then compressed into pellets using a forming die. These days, forming dies are cooled with liquid nitrogen and some processors even cool the hop powder prior to forming. Finally, the pellets are packaged in foil bags. The current standard is to flush these bags with nitrogen gas to create a modified atmosphere that reduces oxidation during storage. For many years, vacuum packing was common, but this method makes the bags prone to damage and can cause pellets to clump together into hard-to-handle masses.

The foil bags of hop pellets are then boxed, palletized, transferred to cold storage, and kept there until shipped to breweries or into distribution channels. Depending on the variety — some hops have better storage properties than others — and the intended use, hop pellets can be stored cold for up to six years. In general, pelletized aroma hops start to fade after 2-3 years of storage and bittering hops can hold their brewing value up to about six years. Breweries equipped with lab instruments and trained sensory panels routinely sample and analyze their inventory to determine how best to use it. Because hops are used exclusively in beer, breweries contract with growers to ensure a reliable supply. When aroma hops become unsuitable for brewing, brewers may repurpose them for bittering or take the loss. One major advantage of hop extracts is extended shelf life, which is why many larger breweries convert a portion of their inventory into extracts shortly after pelletizing (most extract facilities are designed to process pellets, which are more compact than cones).

I know I haven’t answered your question yet, but it’s important to understand how pellets are produced and packaged. The issue is this: Pellet bags typically contain 11, 22, or 44 pounds (5, 10, or 20 kg) of hops. Hops sold in the homebrewing market, by contrast, usually come in 1-oz. (28-g) packages. So the obvious question is: How are these 1-oz. (28-g) bags produced?

Typically, they are repackaged from larger bags that are labeled with critical information such as the harvest year, the processor (the company that converts bales into pellets), a lot number, and sometimes a QR code linking to hop analytics. However, not all repackaged pellets retain this vital information. For example, a commercial-sized bag of 2024 Cascade hops labeled with 8.5% alpha, 6% beta, and 1.5% oil might simply become a bag labeled “U.S. Cascade Hops” with a general alpha acid range of 5–9%.

Hops sold to homebrewers are somewhat analogous to growlers or Crowlers^TM of beer. While it is entirely possible to repackage hops without increasing oxygen exposure, the risk is higher. This alone likely shortens the shelf life of homebrew hops compared to those sold to commercial brewers. Another issue is the packaging. Foil bags offer excellent gas barrier properties assuming the seal is perfect and there are no pinholes. Plastic bags, on the other hand, offer poor barrier protection, meaning that even a vacuum-sealed plastic bag can still allow oxygen ingress over time.

My advice is to use hops as soon as possible after purchasing, unless they are packed in foil and clearly labeled with the crop year and processor. The challenges of repackaged hops are well understood, and many hop processors serving the homebrew market have responded by labeling their products with the same information as packs sold to commercial brewers.

Hops do go on sale, and good deals can be found. I love a bargain and feel confident buying discounted hops if I know they were packaged by a reputable processor and properly stored throughout their life. That last piece, storage history, is nearly impossible for any buyer to verify, whether homebrewer or pro. That’s why it’s good brewing practice to smell your hops before use. If you open a bag and something seems off, it’s your call: Repurpose the hops for bittering or make the executive decision to toss them.

Q: Two nutrient analytics labs tested my first attempt at a low-carb beer and showed all sugars and carbs as less than 1 g per 100 mL. Yet it does spike my blood sugar severely. According to Brewfather, my recipe should have 3.6 g of carbs per 100 mL. Are the labs missing some type of sugar or carbs?
— Pieter de Weerdt, Via Live Chat

A: This is a great question that affects beer lovers of all sorts, especially those of us who keep a watchful eye on our blood glucose levels. Unfortunately, I cannot provide any specific details about the data you received from the labs who ran your testing with the available information. It does seem unusual that beer with 1 gram of carbs per 100 mL would cause a spike in your blood glucose. As a comparison, commercially produced light/low carb beers brewed in the U.S. contain between 0.7 – 1.9 grams of carbs per 100 mL of beer. Although I cannot provide information about the past, I can comment on differences between expectations and measured values, how to estimate carbs, and a few ways to reduce them in beer. Let’s begin with predictions.

Recipe calculators use predictive equations to estimate alcohol and residual extract based on the original gravity and predicted final gravity. Because malt specifics, mashing particulars, and water chemistry can all affect wort fermentability, predicting final gravity is not much more than a guess. Furthermore, yeast strain, pitching rate, and yeast nutrients influence residual carbohydrates left behind after fermentation. In my experience, making assumptions about fermentation is not as approximate as assumptions about wort composition. That said, predicting final gravity is approximate.

A better way to estimate alcohol and residual carbohydrates is to use a model that uses both original extract/gravity, and apparent extract/gravity. Two estimates I feel comfortable using are the following developed by Gary Spedding because I bumped these calculations against known beer data and they provide solid estimates. Although the original publication in Brewers Digest cannot be found online, this article in Brewers Journal contains Spedding’s calculations. There are two equations in this article for alcohol by weight (ABW) and it is the second that should be used (I converted equations from the original reference into a spreadsheet years ago and know that there was some sort of editorial confusion in the referenced article).

Real Extract = (Original Extract × 0.1948) + (Apparent Extract × 0.8052)

Alcohol by Weight = 0.8052 x (Original Extract-Real Extract) / 2.0665 – (1.0665 x Original Extract / 100)

Here is what the math above reveals about a typical beer-flavored beer with a wort gravity of 11 °Plato and a final gravity of 2 °Plato. Note that I have not included specific gravity equivalents because the equations above use Plato for the calculations, but for those curious we are talking about 1.044 OG and 1.008 FG. Also note that the units on Plato are grams extract per 100 mL of beer or percent by weight.

Real Extract = (11 x 0.1948) + (2 x 0.8052) = 3.74 °Plato

Alcohol by Weight = [0.8052 x (11 – 2)] / [2.0665 – (1.0665 x 2/100)] = 3.5% ABW (g/100 mL)

Alcohol by volume is equal to ABW / 0.79 (the density of ethanol), and 3.5% ABW equals 4.5% ABV. I only show ABV because it is the most common unit used to express alcoholic strength in beer, wine, and spirits. However, when it comes to calculating grams of residual extract and calories, percent by weight is the value to use.

The term real extract is used to define dissolved solids in beer, which are mainly comprised of carbohydrates but also include protein, minerals, and hop acids. For your inquiry, it is safe to assume that 100% of the real extract can be attributed to carbs because that slightly overestimates the value.

We have determined that beer with an OG of 11 °Plato and a final gravity of 2 °Plato contains 3.7 grams of carbs per 100 mL of beer and 3.5% ABW. Carbs contain 4 kcal/gram and alcohol contains 7 kcal/g, giving the beer in this example 39.3 kcal/100 mL of beer or 140 kcal per 12-oz. (355-mL) serving.

In my experience, a lab analysis should provide data that is similar to what is calculated above provided you are producing beer that falls into the typical range of beers found in the market. Spedding’s calculations are based on beer data and do not work for completely fermentable solutions. Without knowing the original extract and apparent extract of your beer, I don’t know if the Brewfather prediction is off or if the labs are off. Run the numbers to see which set of data seems most plausible.

I am guessing from your question you may use a continuous blood glucose monitor. I use one of these devices and have learned a lot about how different foods and beers affect my blood glucose. I feel fortunate to have discovered that my blood glucose was abnormally high a few years ago and to be successfully controlling things with a combination of diet, medication, and monitoring. One thing I learned is my body reacts differently to some beers. When I drink non-alcoholic beers produced using maltose-negative yeast strains, for example, my blood glucose usually spikes because these beers contain all of the maltose and maltotriose that comes with mashing. I also have noted spikes when drinking “normal” beers that have above average final gravities. One hunch that I have with some of these beers is that they have been fermented with yeast strains that do not ferment maltotriose. Unfortunately, this property of yeast strains is not widely published. It is known, however, that many English strains popular among the haze-crazed crowd do not ferment maltotriose.

Methods to lower carbs in beer include extended mash rests in the 140–145 °F (60–63 °C) range, the use of exogenous alpha amylase or amyloglucosidase in the mash or fermenter, substituting sucrose or dextrose/glucose for a portion of malt or malt extract to increase wort fermentability, brewing lower gravity beer styles, selecting high-attenuating yeast strains, and taking advantage of hop creep to dry beers out. 

Q: I recently watched one of your BYO+ videos about making sour beer. The suggestion to use kimchi for souring beer blew my mind! I’m already making my own kimchi, so I will definitely try this. Here are my questions: 1. Is there any taste difference between using kimchi and the Lactobacilli that I can purchase from a lab? 2. If kimchi works, what about traditionally soured dill pickles, e.g., Strubbs?
— Gord Maxwell, via Live Chat

Mr. Wizard Says…

A: I recently talked about this during a BYO Live Chat and thought it would be worthwhile to share some expanded thoughts in writing. Let’s start with the idea of using kimchi as a source of bacteria for making sour beer. As a probiotic-rich food, kimchi is a well- established source of various microorganisms believed to promote gut health (Indigenous Fermented Foods for the Tropics is a great reference on this). These microbes, many of which are lactic acid bacteria, also happen to be useful in the production of sour beer.

The primary organisms responsible for kimchi fermentation belong to the gram-positive, acid-producing Lactobacillaceae family of bacteria, often referred to more simply as lactics. This large and diverse group of bacteria is naturally found in many places, including grains, fruits, vegetables, and even in puddles of fermenting spilled milk. One particularly interesting trait of lactics is that many are heterofermentative, meaning they produce multiple byproducts during fermentation. Depending on fermentation conditions, these byproducts typically include lactic acid, ethanol, and acetic acid. This contrasts with homofermentative lactics, which mainly produce lactic acid. That’s enough nerding out for now. 

These days, most sour beers are produced using one of two general approaches: Either by purchasing lab-grown cultures or by channeling your inner Tarzan and wrangling wild bugs. Traditional sour beers rely heavily on the Tarzan method, where wort is naturally inoculated by airborne microbes, ingredients, and the unique microflora found in the brewing environment. One of the best-known examples of this method is used by Brasserie Cantillon in Brussels, Belgium. They are legendary for their exceptional wild ales, which have been brewed using largely unchanged techniques for nearly a century. Their brewery sits tucked away in a charming neighborhood surrounded by butcher shops, cafés, and rows of townhouses, blending the old-world craft of spontaneous fermentation with the bustle of modern life. 

In more recent years, brewers have adapted this traditional approach by using fermented foods — especially yogurt and kefir — as alternative sources of bacteria for kettle sours. Although these cultured dairy products are often made with blends of commercially available bacteria, to the brewer they are still considered somewhat wild, since the exact composition of the cultures isn’t usually known when added to wort. This adds a layer of unpredictability, which can be both exciting and risky. 

Over the past 25 years or so, access to specialty cultures of bacteria and yeast has grown dramatically. Today, brewers looking for consistency and control in their funky beers have a wide range of commercial options. In the early days, most of these lab cultures were blends of organisms found in traditional Belgian lambics or blends intended to approximate bugs found in lambics. As time went on, the push for more predictable and faster souring methods led to the rise of kettle souring. This process is popular because it allows brewers to keep the souring bugs contained in the brewhouse, rather than introducing them into the fermentation cellar where cross-contamination is a concern. 

Because malt is such a rich source of lactic acid bacteria — including Lactobacillus delbrueckii, which is homofermentative, and Lactobacillus plantarum, which is heterofermentative — many early kettle souring techniques relied on bugs cultured directly from malt. Today, however, brewers can easily purchase pure lactic cultures from yeast labs. These have largely replaced wild-cultured sources, especially for brewers seeking repeatability and ease of use. 

More recently, lactic acid–producing yeast strains have gained popularity. Lachancea thermotolerans is a naturally occurring yeast that produces both lactic acid and ethanol and is now available to homebrewers and commercial brewers from yeast labs such as Escarpment Labs and Lallemand. Lallemand also offers a genetically modified Saccharomyces cerevisiae strain known commercially as Sourvisiae. This strain has been engineered to express the gene for lactate decarboxylase, an enzyme that converts pyruvate to lactic acid. The main advantage of using Lachancea or Sourvisiae in sour beer production is the simplified process compared to kettle souring, with no bacteria introduced into the cellar. 

All of this helps explain why the idea of going Tarzan with kimchi as a source of lactics is so appealing for brewers looking for an adventure. Fresh kimchi juice contains a healthy population of lactic acid bacteria. According to the kimchi chapter in Indigenous Fermented Foods from the Tropics, cell densities in kimchi typically range from 100 million to 1 billion cells per milliliter. That’s an ideal range for brewers looking to propagate a strong bacterial culture for use in beer. You’ve got plenty of biological firepower in even a small splash of kimchi juice to propagate for use in brewing. 

Kimchi is just one of many fermented foods that can be used to wrangle bugs for making sour beer. My general advice is to start with foods that taste good to you. If you wouldn’t eat it, don’t brew with it. Live sauerkraut, buttermilk, and dill pickles are all viable sources of lactics. 

One final, important tip: If you’re working with heterofermentative lactics, avoid creating conditions that lead to the production of acetic acid (aka vinegar). These bacteria only make acetic acid in the presence of oxygen, so be sure to minimize oxygen exposure during the souring phase

Q. I monitor my fermentation with a Tilt hydrometer, but back it up with a standard hydrometer. The two are always a little off but are good checks. My final gravity (FG) is always high, no matter what style I am brewing. If the target is 1.018, I’m usually finishing at 1.022. Although I calibrated my Tilt, the hydrometer reads 2–4 gravity points higher for final gravity even when adjusted for temperature. What am I doing wrong to always have higher gravity at the end of fermentation?
Barney Heller
North Wales, Pennsylvania 

A. Well, Barney, this question touches on two separate pain points in brewing — measurement challenges (calibration) and final gravity issues.

One of my brewing touchstones is to always give instruments a serious side-eye. I don’t recall when I began questioning instruments, but know that mistrust is an asset. You have two instruments that are supposed to measure the same thing and have two different results. You have two options: Compare your Tilt and your hydrometer against standards (and when you say you calibrated the TIlt hydrometer, I’m guessing this is what you have already done) or add a third instrument to the party. Although the second option is not a terrible idea, unless the third instrument has been certified all you will do is add more confusion to things. So, what about bumping these up against a standard?

The gold standard for specific gravity is pure water with a density of 1.000 kg/L or a specific gravity of 1.000 (SG is unitless as it compares the density of one liquid to that of water). For many instruments, a single-point calibration is insufficient and a second or third calibration standard is required. Examples of multi-point calibrations include pH, temperature, and mass. This is also true of density, but once a hydrometer of a given length and weight is calibrated over a range using at least two calibration standards, the calibrated scale can be replicated. The takeaway is that you have completed the first step in sleuthing out the measurement by dropping your hydrometer and your Tilt into pure water and measuring the density. They both should read 1.000 at the water temperature your hydrometer is calibrated (your Tilt has a built-in correction).

My distrust of instruments is generally related to devices with “black boxes” that bring in some sort of input and return a value. Measurement errors often result from something awry with the black box input. This could be a dirty sensor, something touching a sensor, or interference with moving parts. The Tilt is a clever device where density is determined by the angle that the Tilt device floats in liquid. As density drops, so does the Tilt device. And as the Tilt hydrometer sinks, it becomes more vertical. Drop the same Tilt hydrometer into a high-gravity wort, and it will lean more horizontal.

Both of your devices have simple measuring principles, although the inner workings of the Tilt are nifty. And both devices will be affected by deposits on the surface that change the weight of the device; make sure they are both clean. My money is on the Tilt for being correct and your hydrometer for being off. I guess this is a good time to mention that you are probably not the problem.

Hydrometers rely on the proper placement of a slip of paper for proper calibration. Misplacement by a couple of millimeters in a short hydrometer can result in significant errors. This is why it is critical to always test hydrometers in standard solutions. For those of us using sets of tall hydrometers with relatively narrow ranges, for example 1.000–1.034 SG, 1.032–1.068 SG, and 1.065–1.101 SG (or 0–8.5 °P, 8–16.5 °P, and 16–24 °P), calibration is easier said than done. Suffice to say, don’t trust a hydrometer further than you can drop it before first checking it out.

Missing your FG is a deep topic that I will simply dip my toe into. For starters, the FG of a brew has a lot to do with malt, mashing, and yeast. Change any of these things and expect a change in FG. But then there is the published FG. What does this mean? Is it a value plucked from the performance of a single batch of beer or is it the average FG of many, many brews of the same recipe? Here is the thing with FG . . . it usually contributes less to body and flavor than brewers think. The one exception to this is when a beer finishes high because of unfermented sugars that are sweet.

Details aside, if you want a drier beer, there are a few easy things to try. The first is extending your mash temperature in the 149 °F (65 °C) range. Sixty minutes is long enough to produce highly fermentable wort. Another thing to consider is to back off specialty malt additions, like crystal and caramel malts, that boost FG. And then there is yeast strain; yeast strains that are either unable to ferment maltotriose or those that do so poorly will leave higher finish gravities compared to strains that do ferment maltotriose. For the latter, most lager strains and ale strains like Chico gobble up maltotriose like nobody’s business.

Q. By reading one of your explanations on “simplifying brewing” I understand that you use a Grainfather all-in-one brewing system. I have used the Grainfather G30 for about eight years. From the very beginning I was upset with the non-homogeneity of temperature during mashing. Because the temperature measurement position is located under the false bottom, I have concluded that the wort atop of the grains is much cooler (confirmed by measurements with an external thermometer).

I saw that the grain tube in the new Grainfather model has perforations on its cylindrical surface, so I am updating my system with a new basket. Though I question whether part of the wort will not be flowing through the grain with this design and the efficiency will be severely reduced. What is your opinion on this?
Luiz Rebouças
Via email

A. Luiz, thank you for the great question. I do brew using a Grainfather G30 and am familiar with how the original system is designed, as well as the new basket. For those of you who are not familiar with these systems, there are two main parts of the Grainfather and other systems based on the same basic all-in-one design (see diagrams shown in Figure 1).

The brew kettle is heated from the bottom using an electric heating element positioned on the bottom of the kettle from the exterior. When looking down into the kettle, the heater is not visible. When used for mashing, a smaller mash basket is inserted into the kettle to hold the mash. In the original basket shown on the left in Figure 1, wort flows down through the bottom screen, into the pump and is returned to the mash basket onto the top screen. Wort pooling above the top screen flows directly to the bottom of the vessel through an overflow pipe to prevent the pump from exerting too much pull on the mash and from starving after all wort outside of the basket has been pumped to the top.

In my experience, the original design works best when using coarsely milled malt or more finely milled malt in conjunction with rice hulls because the mash bed is more permeable. The issues I have experienced with the original design are variable yields, occasional long wort collection times, and difficulty with uniform mash temperature. This sounds like your experience.

One thing that works for me is to start my mash at about 140 °F (60 °C), periodically stir for about 15 minutes, then install the top screen, and start the recirculation pump and the mash profile. If I am using a single mash temperature, I start my mash at about 149 °F (65 °C), periodically stir for 15 minutes, install the top screen, and start the pump and simply set my mash temperature at 149 °F (65 °C) to maintain temperature. Mash stirring during the beginning of the mash really helps with thorough hydration of the malt while also moving things around to improve extraction. I spent my commercial brewing days using stirred mashes and really like the yield improvement and increased consistency between batches that stirring provides.

To answer your questions, I contacted Aaron Hyde with RahrBSG to get some information about the new basket design used in all new Grainfather systems. Aaron is currently RahrBSG’s Director of Product and Portfolio and the former General Manager of Portfolio and Strategy for Bevie, the New Zealand-based company that produces the Grainfather. The basket redesign was Aaron’s brainchild. 

“I suspected side perforations would improve temperature control because the perforations improve wort flow through the mash, even when thick and sticky, which is why the overflow pipework on the old system was needed.” Aaron also felt that adding side perforations would not decrease efficiency because liquid tends to flow down through the grain bed during draining. In practice, users of the new design report higher yields in comparison to the old design and find the new design to perform more consistently from brew-to-brew.

One thing to consider is sparging technique. Some brewers like to keep a small volume of water above the mash bed during sparging and time additions or the flow rate of continuous sparge additions to maintain a consistent level of water. With the new design, that method would indeed result in water flowing out of the side perforations. The best approach to sparging is to add sparge water in batches until it just begins to pool. After a couple of minutes of draining, add more sparge water.

The larger models are equipped with a sight tube showing wort volume in the kettle, while the G30 does not have this feature. I use a calibrated wooden stick (flat yard stick purchased at the hardware store) with my G30 to monitor how much wort I have collected and use this information to gauge when more sparge water is needed (to use this stick, I slip it between the kettle and grain basket wall and look for the top of the wetted portion). For example, if adding sparge water in 2-quart (2-L) increments, waiting for the kettle volume to increase by 2-quarts (2-L) indicates when the next addition can be made.

I do think that the questions posed make sense, but at the end of the day, the improved liquid flow through the bed during wort recirculation outweigh the small volume of wort flowing outward from the perforations. 

Q. I am watching John Palmer’s water presentation on the BYO website and he got into pH a little bit. I have always been confused about the change in pH when taking a sample. If I am understanding what John is saying, mash pH is 0.3 lower than the pH meter reading at room temperature or below? If that is the case, to ensure my mash pH is 5.2, the reading on my pH meter should be 5.5, correct? 

Sometimes when I take a sample, I put it into an ice bath to quickly cool it down. If I am not careful, sometimes the temperature drops down to ~63 °F (17 °C) or so. What impact does measuring at this temperature have on calculating the mash pH?
Rick Bray
via email

A. I think the best way to explain this is to start with a brief discussion about pH and why temperature affects it. pH is a measure of hydrogen ion concentration using a logarithmic scale, where pH = -log [H⁺]. The pH of pure water is 7.0 at 77 °F (25 °C) because the concentration of hydrogen ions is 10-7 moles per liter — noted as [10^-7] using standard chemistry shorthand — because of the equilibrium of water with its dissociated ions as shown below:

H²O  H⁺+ OH^–

The equilibrium of molecules is governed by an equilibrium constant at a specific temperature. The equilibrium constant of water (written as K^w) is 10^-14 at 77 °F (25 °C). As temperature increases above 77 °F (25 °C), or standard temperature used in chemistry, dissociation increases as does the concentration of hydrogen ions. Because pH is defined as the -log [H⁺], an increase in [H⁺] corresponds to a lower pH. Acidic solutions have a higher concentration of hydrogen ions than pure water and bases have lower hydrogen ion concentrations compared to pure water.

The graph shown in Figure 2 illustrates that water pH ranges from 7.5 to 6.1 over the temperature range from 32–212 °F (0–100 °C). 

Using water as the topic of discussion, Figure 2 shows that water with pH 6.5 measured at 140 °F (60 °C) will increase to pH 7.0 when cooled to 77 °F (25 °C). However, this assumption becomes invalid if there is anything in the water that acts as a pH buffer. Buffers are systems of organic acids that can bind hydrogen ions through their own equilibria. For example, carbon dioxide readily dissolves in water and exists in three forms — carbon dioxide, bicarbonate, and carbonate, as shown in the following equation:

H²O + CO²  HCO^3– + H⁺   CO^3–2+ 2H⁺

Back to the assumption that water at 140 °F (60 °C) with pH 6.5 has a pH of 7.0 at 77 °F (25 °C). This is a poor assumption because the atmosphere contains about 0.04% carbon dioxide. Mashes contain much more buffering compounds compared to the small amount of carbon dioxide contributed by the atmosphere. These buffers include proteins, amino acids, phosphates, and nucleic acids from malt, plus carbonate from brewing water. To further complicate things, calcium and magnesium from brewing water both cause a reduction in mash pH because they react with malt compounds. In practical terms, this means that the mash system is heavily buffered and that changes in mash pH as a function of temperature are not as big as changes in pure water pH.

Life is full of approximations. The typical thumb is about an inch (2.5 cm) wide. A stone fetched from a pile of standard stones weighs 14 pounds (6.4 kg). A hand is 4 inches (10 cm) measured from thumb to opposite side of palm. And mash pH drops by about 0.30 pH units when cooled from mash to room temperature. One thing we know about these approximations is that they are indeed approximate!

The best way to consistently monitor mash pH is to either cool it to 68 °F (20 °C) — not 77 °F (25 °C) because biochemists use a different set of rules than physical chemists — or measure mash pH hot. If you prefer measuring mash pH at 68 °F (20 °C), you should use published pH ranges that are associated with cooled samples for your target range. Although the ranges vary by source, 5.45–5.65 at 68 °F (20 °C)  agrees with textbook information. Some references, most notably Malting & Brewing Science by Hough, Briggs, Stevens, and Young, provide mash pH at mash temperature and at room temperature. The true confusion with this subject comes from the lack of temperature reference in nearly all published data about mash pH. Given the well-known effect that temperature has on pH, it’s appalling that brewing scientists and academics have omitted this important detail.

Hopefully the background about pH and temperature is useful. Now let’s apply this information to your specific questions. You correctly understand what John is saying. The mash pH is lower than the pH measured in a cooled sample. Is it 0.3 pH units lower? The only way to know is to measure the pH at two temperatures because the mash buffering systems are too numerous and variable to predict the temperature effect.

Yes, if you are targeting pH 5.2 for your mash pH, then you want your reading to be higher when measuring a cooled sample. I will come back to this in a moment.

If you cool your sample to 63 °F (17 °C) instead of 68 °F (20 °C), you cannot use the same approximation for the offset. Instead of the difference being ~0.3 pH units, it may be closer to 0.32 pH units. Is this difference going to change your beer? Probably not, unless you are brewing the same beer many times a year on a commercial scale.

Now that I have answered your questions, let’s muddy things up a bit! pH 5.2 likely became a target for mash pH because of the following excerpt from Malting & Brewing Science:“ An infusion mash is best carried out at pH 5.2–5.4. Consequently, the pH in the cooled wort will be 5.5–5.8.” I think the first sentence became part of the homebrewing zeitgeist while the values in the second sentence were forgotten! I suggest changing your target pH at 68 °F (20 °C) to be in the 5.5–5.8 range.