Yeast is obviously the workhorse of any brewery, but what are some of the ways a small-scale brewery can get the most out of your yeast? Learn about the keys to properly managing your yeast in a small-scale brewery from best practices with re-pitching, yeast storage, propagation, as well a low-budget fermentation tests you should be using. Learn how to take care of your yeast for predictable tank turn times, consistent fermentations, and reduction of off-flavors.

PDF of Presentation Slides: https://byo.com/wp-content/uploads/LauraBurns_2024_Nanocon.pdf

Although the first hydrometer was described more than 1,600 years ago, its use in brewing dates only to the late 1700s. More than 250 years of data collection show that beer strength has historically been moderate by modern standards. Strong beer styles intended for storage, shipment, or sipping at higher alcohol levels are the obvious exceptions. Even today, most beers remain within a moderate range when compared to other alcoholic beverages.

Brewing history also shows that malted grains were the dominant ingredient in beer until the late 1800s, when German-American brewers began using corn (maize) and rice adjuncts to dilute malt protein and husky tannins from Midwest barley varieties of the time. Contrary to popular belief, adjunct use aimed to improve beer quality, not to reduce production costs.

You may be wondering: What do wort gravity, beer strength, and adjunct use have to do with yeast nutrition? These historical details reveal that brewers have been fermenting normal-gravity, high-malt worts for centuries. They also suggest that beer has been popular enough to sustain a continuous brewing tradition for thousands of years without the use of yeast nutrients until quite recently.

The modern biochemical argument for the rise of yeast nutrients is rooted in our growing knowledge of zymurgy. Without that scientific framework, how could brewers have known when or how to supplement fermentation? And yet, they developed the complex triple decoction mash — without any understanding of enzymes and without thermometers — crafting a reliable process from inconsistent, poorly modified malts.

The more practical explanation for the recent widespread use of yeast nutrients is simple: They weren’t necessary for brewing the kinds of beers that dominated most of brewing history. So why are yeast nutrients now ubiquitous among both home and commercial brewers? Before exploring that question, let’s review how nutrients are used by our fungal friends.

Zinc is a critical cofactor for alcohol dehydrogenase, the enzyme that converts acetaldehyde to ethanol. It also supports yeast cell membrane integrity. Adequate zinc levels promote faster fermentation, better attenuation, and cleaner-tasting beer. Because wort is often zinc-deficient, supplementation in the range of 0.1–0.3 ppm can be beneficial. Although many references, often without citation, state that excess zinc is toxic to yeast, this concern is usually overstated. Problems typically arise when the zinc concentration is around 3 ppm or greater, roughly ten times the upper limit of normal additions.¹

B vitamins (including thiamine, riboflavin, niacin, pantothenic acid, biotin, and folic acid) act as coenzymes in glucose metabolism, energy production, and fatty acid synthesis. They are essential for yeast growth, reproduction, and complete attenuation. Most are present in sufficient quantities in wort, though high-adjunct worts may be deficient.

Amino acids (organic nitrogen from raw materials) and diammonium phosphate (DAP, an inorganic nitrogen from nutrient supplements) supply yeast with nitrogen for protein, enzyme, and structural component synthesis. Both forms promote faster yeast growth and more vigorous fermentation.

Nitrogen in wort is measured as free amino nitrogen (FAN) and comes primarily from malt and, to a lesser extent, from protein-rich adjuncts, except when DAP is added directly as a nutrient. Because proline is a major component of FAN but is not assimilated by yeast, a wort with high FAN can still lack certain essential amino acids.

Magnesium stabilizes metabolic enzymes, is critical for ATP production, and helps regulate intracellular pH during fermentation. It improves yeast vitality, enhances stress resistance, and supports consistent fermentation performance. Malt typically provides sufficient magnesium.

Manganese serves as a cofactor for antioxidant enzymes such as superoxide dismutase and plays a role in carbohydrate metabolism. It protects yeast from oxidative damage and supports cell health throughout fermentation. Malt usually supplies enough manganese.

Phosphorus is essential for ATP formation, phospholipid synthesis, and nucleic acid production. Malt is a rich source of phosphorus.

Potassium boosts metabolic enzyme activity and helps regulate intracellular pH and osmotic pressure. Malt typically contains sufficient potassium.

Calcium stabilizes yeast cell walls, aids flocculation, and influences enzyme activity. It can improve beer clarity but, in excess, may slow yeast growth. Mash additions for pH control and alpha-amylase stabilization typically meet fermentation needs.

Sulfur, usually in the form of sulfate, is required for the synthesis of sulfur-containing amino acids such as methionine and cysteine, as well as certain vitamins. Wort sulfate comes primarily from brewing water, as malt and other carbohydrate sources contribute very little. Many nutrient blends supply sulfate via salts such as zinc sulfate, magnesium sulfate, manganese sulfate, and potassium sulfate.

Lipids and sterols are necessary for maintaining yeast cell membrane fluidity and function. They improve ethanol tolerance, ensure complete fermentation, and enhance yeast vitality in harvested crops. Although wort contains little lipids or sterols, yeast can synthesize them if sufficient oxygen is available. Dried yeast typically contains ample lipids and sterols, eliminating the need for wort oxygenation.

In short, all-malt wort is almost the perfect source of everything a yeast cell needs to thrive. The one exception is zinc, which is often deficient. Unless you strictly follow the Reinheitsgebot, many options exist to correct zinc deficiency. If the Reinheitsgebot is your jam, consider biological acidification using spent grains as a zinc source (much of the malt zinc leaves the brewhouse with spent grains) or Servomyces. Because few homebrewers strictly adhere to the Reinheitsgebot, I’ll avoid the rabbit hole on the horizon!

So why are nutrients commonly used if all-malt wort is so nutrient-rich? The most common reason is dilution of malt-derived nutrients by unmalted adjuncts such as corn/maize and rice. Because malts from most regions are now well-modified and often contain excess nutrients, dilution is generally not an issue until adjunct levels exceed about 20%.

Another common use, especially in commercial brewing, is in high-gravity brewing, where high-alcohol beer is diluted with brewing water after fermentation. Home and craft brewers face similar challenges when brewing big beers, with or without sugar adjuncts. These strong worts cause greater osmotic stress on yeast at fermentation onset and more ethanol stress as fermentation progresses. Nutrients help improve metabolic efficiency and enable yeast to synthesize membrane components that cope with these harsher conditions.

Finally, there is hard seltzer — the beverage that has opened many brewers’ eyes to the importance of yeast nutrients. Proper nutrient additions allow yeast to quickly and cleanly ferment “worts” made entirely from glucose (dextrose or corn sugar), sucrose (cane or beet sugar), and/or fructose (fruit sugar).

The underlying commonality of these cases is speed and reliability. When nutrients are added to deficient worts, fermentation is faster, cleaner, more consistent, and generally less stressful for brewers hoping that a fermentation makes it to the finish line and tastes as expected after the long wait.

Now that we’ve covered some background and identified the beer styles most likely to benefit from nutrient additions, the obvious question is: How much should I use? Unfortunately, that’s not an easy one to answer. Brewers often use FAN as a nutritional metric because it measures the pool of amino acids and small peptides in wort that yeast can readily assimilate for protein and enzyme synthesis. While FAN is useful for gauging nitrogen availability, it tells only part of the story. Yeast also requires vitamins, minerals, lipids, and other cofactors for optimal health. FAN measurements do not capture these other essential nutrients or account for amino acid imbalances. Because most brewers are not equipped to analyze a wort’s complete nutrient profile, they rely on general guidelines and trial-and-error adjustments to determine dosage rates. Table 1 offers guidance on which nutrients to consider for different wort types.

If you’ve read about nutrients in winemaking or cidermaking, you may already be familiar with YAN (Yeast Assimilable Nitrogen) and wonder how it differs from FAN. YAN measures all amino acids except proline, along with ammonia — the form of nitrogen supplied by DAP and urea (the latter not discussed earlier since it is rarely used in brewing). While YAN is a more complete metric than FAN, maltsters and brewers generally do not measure it because two separate analyses are required.

This seems like a logical point to introduce the nutrients available to homebrewers and show how they fit into the framework outlined earlier. The challenge is that while there are many products available to the brewer, most provide limited technical detail about their actual composition. Suppliers tend to sell performance while treating formulation as proprietary. Still, ingredient lists can offer valuable clues.

For example, products without zinc should be assumed to contain no zinc unless the nutrient is specifically marketed as a zinc source, such as Servomyces. Those containing yeast extract or yeast cells provide organic nitrogen along with B-vitamins and micronutrients. Soy flour also supplies organic nitrogen. Nutrients made with DAP or urea (more common in distilling or very high-alcohol fermentations than in brewing) deliver inorganic nitrogen. Some labels simply mention “trace minerals,” while others list specific salts such as magnesium sulfate, manganese sulfate, or potassium sulfate. The real difficulty lies in knowing how much of each nutrient is delivered at the recommended dosage — an area where comparing notes with fellow brewers can be especially helpful.

In summary, yeast nutrients have become important not because traditional malt worts were lacking, but because modern brewing practices often create new stresses for yeast, including shorter fermentation windows. High-gravity fermentations, heavy adjunct use, and sugar-based beverages like seltzer reduce nutrient availability and increase fermentation challenges. Supplements such as zinc, amino acids, vitamins, and trace minerals help maintain yeast vitality, improve stress tolerance, and support clean, consistent attenuation. By recognizing when supplementation is most beneficial, brewers can adapt to today’s diverse styles while ensuring fermentation reliability. Thoughtful nutrient use ultimately strengthens yeast performance and enhances the quality of the finished beverage. 

References:

¹ Yun-ying Zhao, Chun-lei Cao, Ying-li Liu, Jing Wang, Jie Li, Shi-yun Li, Yu Deng, Identification of the Genetic Requirements for Zinc Tolerance and Toxicity in Saccharomyces cerevisiae, G3 Genes|Genomes|Genetics, Volume 10, Issue 2, 1 February 2020, Pages 479–488.

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.

Yeast isn’t just an ingredient, it’s a living, flavor-producing powerhouse of an organism. What other ingredients are still thrivin’ and dividin’ when it comes time to brew another beer? And because of this, brewers are afforded a massive opportunity to be their own propagators. Keep that culture healthy and viable; it will reward you in return. You need it, and it needs you, so why not make it a major focus in your operations? Every brewer should understand the nuances of their yeast cultures’ flavor, smell, appearance, and behavior in fermentation. This makes you proactive rather than reactive, having a strong grasp on consistency and quality. 

Today, breweries need to find savings in all aspects of their business. One of the biggest ways to save money when it comes to yeast is from maximizing each culture’s potential. Step one? Set a yeast budget. Know your targets, track your spending, and make data-driven decisions. This is absolutely critical because you cannot make informed, data-driven decisions and achieve the greatest success if you do not have a starting place. What’s too expensive? What cellar practices aren’t worth the effort? We can use this information to identify what products to use, how often these products need to be repitched, and what methods may need to be employed for success. So, what does this look like for nanobreweries?

Nanobreweries may be quick to point out that the lack of frequent brew days or cellar space negates their ability to get much use out of a yeast culture. Combine that with a desire to frequently use different yeast strains and the fact that taprooms and brewpubs often achieve higher margins on pints served over the bar, you may ask how any of this applies. I implore you to reflect on your current standard operating procedures and look for opportunities to increase quality. For nanobreweries, frequent strain changes or limited cellar space might make yeast management seem impractical. But with smart planning, even small breweries can improve quality and cut costs. Over time, these savings add up, whether it’s $50 saved today or thousands over years. So, continue on as we discuss strategies for scheduling, harvesting, and repitching while quantifying cost and methods to save on yeast.

Scheduling and Planning

I can’t emphasize enough that a little foresight goes a long way. Plan and strategize the use of cultures being brought into the brewhouse. A tentative schedule of future batches and styles is an easy-to-implement strategy that can lead to immediate cost savings. Ask yourself which upcoming beers can be fermented with this culture. And how often or frequently will these batches occur? This will help you identify an opportunity for scheduling fermentations so you can capitalize on harvests by minimizing storage time. Using a more flavor-neutral strain makes scheduling easy, but it can be more difficult with seasonal or “one-off” brands. But you can still get creative and schedule a second or even third sequential batch that can utilize any strain. If you’re using a hefeweizen strain, think of other styles that can utilize this strain (dunkelweizen or weizenbock, for instance), and because two banana-flavored beers may not be the best sales strategy, adjust fermentation parameters to make a “cleaner,” reduced-ester version. Think overpitching, spunding valves and pressure, or lowering the fermentation temperature. 

When planning new cultures, always document the batch, its original gravity, and the yeast culture generation (if re-pitching). A key strategy for reducing your cost is to use early generations in lower-gravity batches and pitching harvested yeast into higher-gravity beers requiring a larger pitch of yeast. You are your own propagator! High-gravity fermentations present a compounding financial challenge that many brewers overlook. When pitching into wort above 17–18 °Plato (1.070–1.074 specific gravity), breweries face both the immediate cost of doubling their yeast quantity and the hidden expense of losing repitching potential. The extreme conditions of high osmotic pressure and alcohol stress typically degrade yeast health to the point where reuse becomes inadvisable. A more strategic approach begins with mid-gravity wort in the 12–15 °Plato (1.048–1.061 SG) range. These gentler fermentations allow yeast to build biomass and vitality, creating opportunities for extended use. For example, a brewery could pitch fresh yeast into a 15 °Plato (1.061 SG) IPA, harvest healthy cells, and then deploy them in a subsequent 20 °Plato (1.083 SG) imperial stout. This progression not only stretches the initial yeast investment across multiple batches but also ensures the culture is at peak health when facing its most challenging fermentation. 

Ensuring Healthy Fermentations

Once you’ve established your yeast strategy, the focus shifts to maintaining optimal fermentation conditions. Malt naturally provides most of the essential nutrients yeast needs — like carbohydrates for energy, vitamins for metabolic function, and amino acids for cellular functioning. These components are rarely deficient in standard all-malt worts, but brewers should remain vigilant in recipes with higher adjunct percentages, low original gravities, or poorly modified malts, as these can create nutritional gaps. Two elements demand particular attention: Oxygen and minerals. 

Proper aeration at pitching is critical with liquid cultures because without adequate oxygen, liquid yeast struggles to synthesize sterols and fatty acids for building cell membranes during the growth phase (0–48 hours). This can result in sluggish fermentations and poor attenuation. Adequate oxygenation at pitching is less of a concern if using a dried culture due to sufficient sterol and unsaturated fatty acid reserves to support cell division.

Minerals like zinc and magnesium play equally vital roles as enzyme cofactors, influencing everything from flavor development to cell replication. Zinc deserves special consideration because it readily binds to trub during wort production and fermentation, often leaving insufficient amounts available for yeast metabolism. Over successive generations, this deficiency can progressively weaken cell health and reduce fermentation performance. The financial incentive is clear: Healthy yeast means more reliable fermentations and greater generational longevity, all resulting in high-quality beer. Each additional batch you can brew from a single yeast purchase directly lowers your per-batch cost, transforming what might seem like a minor process detail into a meaningful opportunity for savings. By prioritizing these fundamentals, you’re not just nurturing your yeast, you’re protecting your bottom line.

Monitoring Yeast Health

Do I need to run tests to ensure my parameters are in spec for fermentations? In a perfect world, that would be great, but as a nanobrewery this is not always possible nor absolutely necessary. There are a few key parameters that are cheap and easy to monitor and will give you enough information to make informed decisions about your yeast culture. 

Let’s start with recording simple gravity and pH readings, as entry-level equipment is both inexpensive and capable of producing accurate results. The key lies in tracking trends, not just numbers. Daily gravity and pH readings during active fermentation tell a more valuable story than any single data point. Focus on the pH drop within the first 48–72 hours as a reliable indicator of yeast activity and vitality. Healthy fermentations’ pH steadily declines during this time before slightly rising through the end of fermentation. Sluggish drops in these initial hours typically signal trouble and poor yeast health. A tip for identifying poor health early is to closely monitor pH drops about 12–16 hours after pitching because inactivity is easier to correct at this time. It may allow you to employ batch-saving techniques like raising the temperature, adding more dissolved oxygen, supplying yeast nutrients, rousing the yeast with CO₂, or pitching actively fermenting cultures from other batches. Document these patterns for each strain to create benchmarks; plot them on a simple Excel graph, and over time you’ll recognize normal behavior versus potential issues. 

These observations cost nothing but attention, yet provide critical insights into your yeast’s condition. Consistency matters beyond fermentation metrics. If you want added verification that a culture is healthy, invest in a microscope ($250–$300) and the items necessary to perform cell counts and viability testing. Track and aim for consistent harvest sizes using weight (lbs./kgs) or volume (gal./L), and monitor slurry density by eyeballing a slurry through a sight glass or performing a cell count. Any substantial variations in collected yeast may indicate changing culture health. But remember, even without advanced equipment, consistent tracking of basic parameters gives you most of what you need to produce excellent, consistent beer. 

The bottom line? You don’t need a lab to make smart decisions. You just need good habits, basic tools, and an understanding of what “normal” looks like for your yeast.

Harvest and Storage

The culture just fermented a batch exactly to specifications and is ready to be harvested and stored until future use. This is a critical step because you don’t want to negate the success you just observed in fermentation by improperly storing the yeast and impacting its health. Let’s discuss a few key recommendations to ensure you maintain the highest viability and vitality between batches. 

Aim to collect your yeast when the beer sits about 1 °Plato (5 gravity points) above terminal gravity, just before initiating a diacetyl rest. At this stage, the most flocculent cells have already settled in the cone, contributing little to finishing fermentation, and the remaining suspended cells will handle the final gravity drop and diacetyl cleanup. By harvesting now, you rescue your yeast from the increasingly harsh conditions of the fermenter, where mounting pressure, rising alcohol levels, and insulating heat can rapidly deplete their energy reserves. This stored energy within the cell, glycogen, is needed when the cells are in storage to maintain their health until the next batch.

Perform standard transfer techniques, keep things clean, and slowly open the valve as you dump trub and transfer yeast into a storage vessel to avoid tunneling. Tunneling occurs when yeast remains impacted on the sides of the cone and prevents the entire slurry from being harvested. Trub dumps are key and can be performed daily during fermentation or when harvesting to avoid capturing dead or compromised yeast cells, hop matter, and coagulated proteins. Once collected, treat your stored yeast with the same care you’d give finished beer: Keep it cold (33–38 °F/1–3 °C) in a sanitized, CO₂-purged vessel to minimize oxidation and unwanted metabolic activity. Remember to vent storage vessels daily to prevent CO₂ buildup from stressing the cells. Storage time can be a concern for nanobreweries. Aim to repitch as soon as possible, but a rough rule of thumb is to store no more than 2–3 weeks after harvesting a healthy culture, as viability declines noticeably with most strains beyond this window. Note that different strains vary in their ability to maintain health in storage. The only way to truly know how long you may store a culture is by recording daily viability readings and identifying an average length for when declining viability occurs. One last tip: Avoid oxygen and warm temperatures because both will trigger metabolism and cause the yeast to begin consuming its stored energy reserves (glycogen). 

Repitching Yeast

Repitching yeast at a consistent pitching rate is one of the best ways to improve your quality, flavor consistency, and generational use. The most accurate way to do this is to pick up a microscope and learn to perform viability and cell counts. However, excellent results can still be obtained through careful estimation and documentation. The foundation lies in establishing three key parameters: Your target pitching rate (typically 7.5–15 million cells/mL or 0.75–1.5 million cells/mL/°P), your estimated slurry concentration (generally 1–2 billion cells/mL), and your estimated viability (usually 80–95% for healthy cultures).

Without a microscope, the key here is that these are estimated values, and below are the steps to perform your own estimated repitching calculations. The calculations follow a straightforward approach: First, determine your total cell count needed to pitch based on batch volume and gravity, then divide by your slurry concentration to find the required volume, and finally, convert to weight, if necessary, using the approximate density of yeast slurry (1.15 g/mL). 

Step 1

Calculate the total number of cells for the batch.

1 BBL = 117,348 mL

Pitch Rate (cells/mL) x Starting Gravity (Plato) x Batch Size (mL) = Total Cell Population (cells/mL)

Step 2

Calculate the volume of stored yeast to pitch.

Total Cell Population (cells/mL) / Slurry Density (cells/mL)  = Volume of Slurry Density (mL)

Step 3

If necessary, convert to weight.

Volume of Slurry Density x 1.15 (g/mL) = Weight of Slurry (g)

The following table shows examples already calculated for a 7.5-million cells/mL repitching rate. 

Methods to Maximize Value

As a brewer, you are a propagator of yeast, so reap the bounty of your efforts and maximize the value of your yeast expenses by strategizing the movement of yeast through your cellar. A simple strategy is to split yeast harvests into two subsequent repitches. The yeast divides anywhere from 3–6x, depending on factors like fermentation temperature, strain, gravity, etc., providing you with much more yeast than initially pitched. You can split these into “cousin” lineages and track them separately as they move through the brewery. Nanobreweries are limited in brewhouse capacity, but utilizing this strategy even once can show worthy savings over time. 

Example: Think about a month where you harvest week one, pitch half the harvest into a core high-ABV beer week 2, and pitch the other half into a second core beer week 3. That’s a minimum of three batches with a single purchase, reducing your overall expense to a third of its original cost. It’s not hard to imagine that over the course of a year we are talking about significant savings on yeast expense.

Double batching is another powerful savings tool. By brewing half your fermenter volume one day and completing the fill the next day, you leverage the yeast’s 24-hour growth period to avoid a second pitch. Just pitch to the day-one fill volume. This halves your yeast costs immediately, with compounding savings across generations. 

Last, pressurized lager fermentations are becoming more popular, especially with the rebirth of demand for lager brewing in many craft breweries. The concept is that warmer temperatures allow for greater metabolic activity and promote cell division in the initial growth phase. Traditional cold pitching (48–55 °F/9–13 °C) requires nearly double the yeast, but starting at 65–70 °F (18–21 °C) with 1 bar pressure (or 14.5 PSI) promotes natural cell growth while maintaining clean profiles through pressure-induced ester suppression. The benefits multiply: Lower pitch rates, faster fermentations (6–8 days versus 2–3 weeks), and reduced tank time, all while achieving lager character. 

Implement, Document, & Save

Don’t cut corners for convenience or upfront savings. Invest in quality yeast, track performance, and stick to your strategy, even if results take 6–12 months to materialize. Document every batch, generation, and cost to refine your process.

Yeast management isn’t just about saving money, it’s about brewing better beer. By treating your cultures as partners, not commodities, you will unlock consistency, creativity, and long-term profitability. 

You’ve certainly heard the anecdote: Brewers make wort, but yeast makes beer. It’s the key to fermentation — the transformation of one thing into another delicious thing. The trouble is a side effect of a great problem to have, which is that we have so many yeast options available to us that choosing the right one feels just as hard as ordering wine off a pricey wine list. Let’s talk about considerations when choosing a yeast and then review the key numbers and terms that process includes.

Yeast Manufacturers and Selection

The first elephant in the room is manufacturer selection. When you order a beer ingredient kit from one of the big homebrewing retailers, there’s usually a drop-down list to pick a yeast. The beginner homebrewer may simply default to whatever the cheapest option is (not a bad reason!), but there could be five or more options for that particular style, including multiple options from each manufacturer! The main companies making homebrew-sized quantities are liquid yeast manufacturers Omega, White Labs, Wyeast, and Imperial, and dry yeast manufacturers Lallemand, Fermentis, and Mangrove Jack’s (though some liquid yeast suppliers are starting to roll out dry versions of their most popular strains as well). All of these have impeccable quality control and consistency. Some of us pick one and stick with it like we would a car manufacturer, but you really can’t go wrong with any of them if you take the rest of the considerations we’ll discuss next.

Liquid vs. Dry Yeast

The main distinction to navigate when selecting yeast is picking between liquid and dry yeast. 

Liquid yeast offers more options so you’re able to find a variety of yeast choices for any style of beer you want to brew. Whereas you find one or two strains suitable for a saison from each dry yeast manufacturer, you’ll find a small handful from many of the liquid yeast labs, each bringing unique characteristics to the resulting beer. However, liquid yeast requires careful handling and near-constant refrigeration. Those are live cells living in suspension, patiently waiting to be fed! If you receive a swollen liquid yeast pouch, it doesn’t mean it’s bad — it just means the cells have come out of “hibernation” from the cold and have started multiplying and creating CO₂ inside the pouch. However, without a microscope and hemocytometer to count cells, you’re pretty much guessing about whether it’s still good to use. You could propagate the slurry in a yeast starter, but if that pouch sat in the back of a delivery van during a 104 °F (40 °C) California summer for two days, then it’s probably not worth pitching.

Dry yeast, on the other hand, is more convenient, generally costs less, and has a much longer shelf life. The technology for concentrating and drying yeast has come a long way and has become readily available to manufacturers, so homebrewers today benefit on both price and options from dry yeast labs. These packets are moisture-proof and vacuum-sealed or packed under an inert atmosphere to protect the yeast from contamination, air, humidity, and spoilage, which gives us an easy go-to option we can always keep on hand. I keep my dry yeast refrigerated, but not all brands require that and even those that suggest it should be OK if left at room temperature for a few days.

Yeast Nutrients and Proper Handling

It’s best practice to check the yeast manufacturer’s suggestions regarding nutrient additions at pitching time and during fermentation. While some yeasts may come with nutrients, most do not. High-gravity beers and lagers often require additional yeast nutrients to ensure a healthy fermentation.

One of the best ways to ensure a healthy fermentation is to properly oxygenate your wort before pitching if using a liquid yeast; dry yeast generally doesn’t require additional oxygenation. Yeast requires oxygen to multiply during the initial growth phase. For homebrewers, shaking the fermenter vigorously or using an aquarium pump with a diffusion stone can effectively oxygenate the wort. Professional brewers often use filtered air or pure oxygen injection to ensure adequate oxygen levels. Many homebrew equipment manufacturers have some pretty cool carbonation stone options when using stainless conicals with tri-clover ports. 

Choosing the Right Yeast Strain

Twenty years ago, we were lucky to have one, maybe two, options for each style. Most beginner ale ingredient kits just come with the dry, shelf-stable SafAle US-05 because of its stability and consistency. Nowadays you could pick from more than a dozen strains, choosing one over another because of the final product outcomes you are seeking.

Yeast strains vary in their ester production and temperature preferences due to differences in their genetic makeup and metabolic pathways. Esters, which contribute fruity and floral aromas to beer, are primarily created through the enzymatic reaction between alcohols and acids during fermentation. Different yeast strains contain unique sets of enzymes that regulate ester formation, which is why a Belgian yeast might produce pronounced banana and clove notes while a clean American ale yeast generates minimal ester content.

Temperature plays a key role in ester production because it directly influences yeast metabolism. Higher fermentation temperatures accelerate yeast activity, leading to increased production of esters and other volatile compounds. This means that fermenting with the same yeast at the lower end of the manufacturer’s recommended temperature range will result in a different tasting beer than fermenting at the upper end of the recommended range. This is just another way to influence the final outcome of your beer that brewers must consider. The yeast cell membrane’s fluidity and stress tolerance also differ between strains, affecting their optimal temperature range. Some ale yeasts, like White Labs WLP090 (San Diego Super Ale), are selected for high-performance fermentation at warmer temperatures while maintaining a clean profile, whereas traditional lager strains require cold fermentation to suppress ester formation. Understanding these characteristics allows brewers to harness yeast behavior for precise flavor control.

Looking for a more estery profile with a hint of fruitiness? Omega’s OYL-011 (British Ale VIII) has got you covered. If you want a clean and crisp hop-forward beer, then Imperial’s A07 (Flagship) is your pick. When I’m seeking a fast turnaround and clean finish, then White Labs WLP090 is my go-to.

Those are just a few liquid options for pale ale, but the point is that yeast plays a big factor in the finished product, so the key to knowing which option to pick is by learning how they behave. Reading the manufacturer’s description is a great place to start, though it isn’t enough guidance for me. I frequently split batches and try two different yeasts on the same wort so I can compare the appearance, aroma, flavor, and finish and make my own opinions about the outcomes. When doing this, take notes of how the fermentation behaved and your evaluation of the finished beer so you have this information when selecting yeasts for future batches.

After experimenting for years, I’ve settled on specific options for my “house beers” that I keep in rotation.

Temperature Control: Yeast’s Goldilocks Zone

Yeast is like Goldilocks — it wants everything to be just right. Temperature control during fermentation is one of the most important factors in achieving consistent results. Too warm, and you can get excessive ester production, fusel alcohols, and off-flavors. Too cold, and the yeast may become stressed or sluggish, resulting in an incomplete fermentation.

For most ale yeasts, the ideal fermentation temperature is between 65–72 °F (18–22 °C). Lager yeasts typically perform best between 45–55 °F (7–13 °C), requiring additional equipment like temperature-controlled fermentation chambers to maintain steady conditions. Even when fermenting in these ideal temperature ranges, the outcome will differ depending which end of the spectrum the beer is fermented. Temperature is ideally measured using the internal temperature of the fermenter. We can achieve that with a thermowell or a temperature probe mounted to a tri-clover port or through a two-hole bung. 

Understanding Yeast Numbers and Terms

There are a number of factors yeast manufacturers will list for each strain that are important to understand when choosing a yeast that will offer the desired outcomes, which we’ll dig into next: 

Attenuation

Attenuation can be thought of as the yeast’s work ethic. This number quantifies the density change in the wort as the yeast converts sugars into alcohol and CO₂. The level of attenuation has a direct impact on the beer’s dryness. Yeast strains can have varying levels of capability to ferment maltotriose — low-attenuating yeasts typically ferment none. 

Low attenuation (65–70%): Common for malt-forward beers like stouts and porters, leaving more residual sweetness.

Medium attenuation (70–75%): Common in ales and lagers for a balanced finish.

High attenuation (75–80%): Ideal for drier beers, where we want hops to shine, such as West Coast IPAs.

Extreme attenuation (85–95%): These high levels of attenuation to ferment beer are only possible when using diastatic (STA1) strains, such as those used to ferment saison, and are only used when trying to achieve an extremely dry finish. Another way to get an ultra dry beer would be to pitch enzymes (e.g., amyloglucosidase) in addition to yeast. 

Flocculation

Flocculation refers to how well yeast cells clump together and settle out of the finished beer. High-flocculating yeasts lead to clear beer, while low-flocculating yeasts stay in suspension longer, ideal for hazy styles like New England IPAs.

Temperature

The listed temperature is the ideal range the yeast should be fermented. We’ve already covered the impact of fermenting at one end of this range from the other.

Viability and Cell Count

Yeast viability refers to the number of live yeast cells available for fermentation. This number is indicative of new yeast when it is packed, so keep in mind that older yeast packets may have lower viability. A proper pitch rate ensures healthy fermentation. Yeast calculators, like those from Brewfather or BeerSmith, can help homebrewers determine the correct number of cells needed for their batch. We’ll dig more into pitch rates later.

STA1

Some yeast manufacturers list whether a yeast strain is Saccharomyces cerevisiae var. diastaticus (containing the STA1 gene). These strains are capable of fermenting residual carbohydrates that are unfermentable to most Saccharomyces strains.

Pitching Enough Yeast

Getting the right pitch rate is essential for a successful fermentation, and it depends on factors such as wort gravity, beer style, and fermentation temperature. Underpitching can lead to stressed yeast, sluggish fermentation, and excessive ester or diacetyl production. Overpitching, while less risky, can sometimes result in fewer flavor compounds or an overly clean beer that lacks character. That said, there is no hard and fast “ideal” pitch rate. Fermentations can successfully ferment over a range of pitch rates, but different pitch rates can, and often do, influence beer flavor. Some brewers prefer using low pitch rates for weizen yeast and others prefer higher pitch rates. Trialling different rates and learning from the results to determine your preferences is worthwhile. Don’t forget to take notes as you test!

The standard pitch rate guidelines vary depending on the author or manufacturer, but we generally land on these numbers when using liquid yeast:

Ale Fermentation: 0.75 million cells per milliliter per degree Plato 

Lager Fermentation: 1.5 million cells per milliliter per degree Plato

To calculate the number of yeast cells needed for a 5-gallon (19-L) batch of wort, use this formula:

Cells needed = wort volume (in gallons) × wort strength in ˚Plato × pitch rate × 3,785 (mL in a gallon)

As an example, for a 12.5 ˚Plato ale: 5 × 12.5 × 750,000 × 3,785 = 177 billion cells.

A fresh liquid yeast pack typically contains around 100 billion cells, meaning that a standard ale at 1.050 would require about one pack with a yeast starter or two packs without a starter to ensure a proper pitch. A lager would likely need two to three packs or a large yeast starter to reach the necessary cell count. Imperial Yeast is one manufacturer that has a broad range of options and their liquid yeast comes in 200 billion cell pitches. Personally, I love that because I know I just need one pouch for a 5-gallon (19-L) batch, and second, if a pouch sits in my fridge for several months I can still safely pitch it because it started with more cells than I needed. 

Dry yeast packets (11.5 g) generally contain 100-115 billion cells and are a convenient option for single-pitching standard gravity ales. However, for higher-gravity beers (above 1.060), additional packs are recommended to avoid fermentation stress.

Online pitch rate calculators simplify this process by allowing brewers to enter their wort gravity and yeast viability to get precise yeast pitching recommendations.

Troubleshooting Common Yeast Issues

Stuck Fermentation: Could be due to underpitching, low fermentation temperature, or poor yeast health. Solutions include raising the temperature or pitching fresh yeast.

Off-Flavors: Acetaldehyde (green apple) or diacetyl (buttery) off-flavors may result from stressed yeast or improper fermentation temperatures.

Think of brewing as starting a rock band. You, the brewer, are the manager, setting the stage and getting all the equipment (malt, hops, water) ready. But the real star of the show — the one who determines the style, energy, and final sound of your beer — is the lead singer. That’s your yeast.

Do you want a smooth, clean performance? Pick a yeast like US-05 or WLP001, the brewing equivalent of a classic rock singer – reliable, crisp, and won’t subject your wort to too many surprises.

Looking for some personality and flair? A British ale yeast like Omega’s OYL-011 is your Mick Jagger, adding fruity esters and making your beer a little more dynamic.

Going for high-energy and big flavors? A Belgian yeast strain will bring the stage presence of Freddie Mercury — bold, expressive, and impossible to ignore.

Need something technical and precise? Lager yeast is like a classically trained opera singer, slow and steady but delivering a refined, clean performance when given the right environment (cold fermentation).

Now, if you don’t give your singer the right setup — good stage conditions (proper fermentation temperature), enough oxygen (healthy yeast handling), and the right-sized crowd (proper pitch rate) — they’re going to struggle, forget the lyrics, and maybe even storm off stage (stuck fermentation). But if you set them up for success, they’ll deliver a flawless performance, and the crowd (your taste buds) will go wild.

So, when picking your yeast, don’t just grab the first one you see — think about the kind of beer you want to make and pick the right front man for the job. Rock on with your yeast selection, brewers! 

Proper nutrition of brewing yeast is critical for yeast to grow unimpeded and ferment our wort without limitation to produce all the flavors and byproducts we desire in our beer. Adding supplemental yeast nutrient to every batch of wort is an inexpensive hedge against a stuck, incomplete or otherwise substandard fermentation. Most of the time, wort will be adequately nutritious to the yeast. However, not all of what yeast need are always present in adequate amounts for them to reach their full potential of growth, reproduction and metabolism necessary to make great beer. BYO’s Technical Editor Ashton Lewis walks you through the world of yeast nutrients and when and how to give your yeast a helping hand.

Q: I use dry yeast for my hefeweizens. I hear one should stress the yeast for more phenolics. If I have an 11-gram packet, should I only use part of it or increase the fermentation temperature to boost aromatics?
— Edward O’Neill • Saint Louis, Missouri

A: This is a great question that is perfect for a short answer. Contrary to my love of marching to my own beat, I do believe in following supplier suggestions. I would start out by doing what the yeast manufacturer suggests for weizen beer. The best place to find this information is usually on the supplier’s website. If you don’t get the desired results, there are two paths to follow. One is to choose a different yeast strain and the second is to start adjusting your mashing, pitching, and fermentation set points. Because I am a simple brewer, I would start with Door #1 if I were unhappy with my fermentation results; change yeast strains.

But if you want Door #2, there is a whole lot of stuff to consider. Adding a ferulic acid rest (see my column in the July-August 2024 issue for more information), decreasing pitch rate, decreasing wort aeration, adjusting temperature (up and down both have their merits), and adjusting your grist bill are all options. The challenge with Door #2 is that you have just entered the hall of mirrors and it can take a very, very long time to figure out the best path forward.

And then there is Door #3 — which is following my homebrew hefeweizen recipe. The grain bill is made up of 50% German pale malted wheat, 48% Pilsner malt (brewer’s choice), and 2% light crystal malt for a touch of color. Wort gravity should be 1.050 (12.5 °Plato) and the bitterness should be ~12 IBU using a single addition of a German noble hop variety. Mash in at 122 °F (50 °C) and hold for 20 minutes, then heat to 154 °F (68 °C) and hold for 30–45 minutes. Collect wort, add hops at the start of the 60-minute boil, cool to 64–68 °F (18–20 °C), pitch SafAle W-68 per the pitch rate for your batch size (printed on pack), and ferment at 68 °F (20 °C). 

Being this specific with brewing suggestions is something I rarely do, but I am really loving having a dried source of Weihenstephan 68 for my weizen brewing. This strain is the classic weizen yeast for those fruity and clove aromatics found in quintessential Bavarian wheat beers. Prost! 

At the bottom of my freezer lies a homebrewer’s treasure trove: Dozens of small vials containing frozen yeast. These vials are organized in groups of five or six, each cluster representing a different yeast strain. My collection includes popular varieties like Chico and seasonal favorites such as British Bedford Ale.

At any time, I can select a vial or two, revive the yeast in a starter, and have it ready to pitch into a fresh batch of wort. The best part? Some of these frozen vials are over five years old and still perform well when reactivated.

The secret lies in proper freezing techniques. When managed correctly, frozen yeast can maintain its viability for an impressively long time, offering homebrewers a convenient and cost-effective way to always have their favorite strains on hand.

Understanding the Basics

Freezing yeast is a relatively straightforward way to keep various strains on hand without taking up much space. The basic process involves creating a protective solution called a cryopreservative using food-grade glycerin and water. When combined with yeast, this solution helps prevent ice crystals from damaging the yeast cells during freezing. 

After sterilizing the solution, you mix it with a small amount of yeast (either fresh yeast or from a slurry) and store it in small vials in the freezer.  This method slows down the yeast’s biological activity, keeping it viable for years. With careful handling, you can easily revive the yeast by thawing out a couple of vials and adding them into a starter a day or so before brew day.

The Benefits of Frozen Yeast

Purchasing fresh yeast for every batch can get expensive, and since the viability of yeast cells decreases over time, it requires careful planning to ensure you have fresh yeast just in time for brew day. For years, my favorite way to address these concerns was to overbuild starters.

Here’s how overbuilding starters works:

A day or so before brew day, take a packet of fresh liquid yeast and pitch it into a yeast starter that’s about 50% larger than needed for the intended batch.

After a day or two of spinning the starter on a stir plate, collect a third of the starter in a sanitized vessel — such as a pint-size Mason jar — and store it in the fridge.

The rest of the starter is pitched into your wort as usual.

When it’s time to use that yeast again, take it out of the fridge a couple of days before your next brew day, overbuild another starter, and again split that starter between your new brew and another sanitized vessel.

This method allows a single packet of yeast to be used multiple times without the added steps of harvesting yeast from the bottom of your fermenter post-fermentation. However, freezing yeast overcomes several limitations of the overbuilt starter approach:

Extended Viability

A yeast slurry stored in the fridge can retain some viability for months, though it is often recommended to use it within a week or two. With each passing day, more yeast cells die, and after a few months, the slurry may contain very few viable yeast cells. By freezing yeast, the yeast cells’ biological activity is significantly slowed down, preserving their viability, potentially for years.

Reduced Generational Mutation

Freezing yeast also reduces generational mutation. With the overbuilt starter approach, each use of the yeast slurry results in a new generation of yeast. Repeating this process more than a handful of times can lead to significant mutations not present in the fresh yeast received from the yeast lab. In contrast, freezing yeast allows you to split a single starter or packet of fresh yeast (let’s call it generation 0) into 10 vials. When you have only a few vials left, you can build a starter with the remaining vials to create another 10 vials of what is now generation 1 yeast. This cycle means many more batches of yeast are available from each generation, resulting in fewer mutations over time.

Step-by-Step Guide

The process to freeze yeast takes a bit of preparation but with some minimal equipment is easy enough to follow and is something I’ve repeated dozens of times.

Step 1: Prepare a cryopreservative solution

Yeast cannot simply be stored in the freezer as ice crystals will form and rupture the cell walls, killing the majority of the yeast. A cryopreservative is needed to protect the yeast cells during freezing. Here is how to make the cryopreservative: 

Required Equipment 

Pressure canner
Food-grade glycerin
Measuring cup
Mason jar (preferably with a wide mouth)

Instructions

Measure out 2.5 fl. oz. (75 mL) of glycerin and 7.5 fl. oz. (225 mL) of water. I’ll typically use filtered or bottled water. This creates a 25% glycerin, 75% water solution.

Combine the glycerin and water in the Mason jar.

Place the jar in a pressure canner and process for 10 minutes following your canner’s instructions. This will sanitize the cryopreservative and make it shelf stable. 

After processing, remove the canner from heat and allow it to depressurize naturally.

Once it’s safe to open the canner, remove the jar and let it cool to room temperature. Do not rush this process by running it under cool water or placing it in a water bath, as rapid temperature changes could cause the jar to shatter.

Once cooled, your cryopreservative is ready for use. This solution can last for a good while — typically enough for six batches or about 60 15-mL tubes.

Step 2: Prepare your yeast

You have two options for preparing your yeast: Using a fresh packet or creating a yeast starter. Both methods are valid and have their own advantages.

Required Equipment

Sanitizer spray bottle
Wide-mouth Mason jar 

Option A: Using a fresh yeast packet

Purchase a fresh pouch of your desired yeast strain. I’ve only ever used liquid yeast for this process, although dry yeast should work as well. Check the manufacture date on the yeast pouch — the fresher, the better to maximize viability.

Sanitize the outside of the pouch thoroughly using your sanitizer spray bottle.

Carefully open the packet and pitch the yeast into a sanitized Mason jar. This will make it easier to extract in the next step. 

Option B: Creating a yeast starter

Alternatively, prepare a yeast starter 24–48 hours before you plan to freeze your yeast, following your preferred starter recipe.

Once fermentation is complete (usually 24–36 hours), place the starter in the refrigerator for a few hours to cold crash. This helps the yeast settle to the bottom.

Carefully decant most of the liquid from your starter, leaving behind the yeast slurry at the bottom.

Transfer the remaining yeast slurry to a sanitized wide-mouth Mason jar.

Step 3: Mixing yeast with cryopreservative

Now we are ready to combine the yeast and cyropreservative into test tube vials. Each vial will contain approximately 5–20 billion yeast cells, depending upon the viability of the source yeast. 

Required Equipment 

Sterile test tube vials (15-mL capacity, 10 per batch)
Oral syringes (6-mL capacity)
Sanitizer spray bottle

Instructions

Sanitize both the oral syringe and test tubes using a sanitizer spray bottle. 

Using a sanitized 6-mL oral syringe, extract 5–6 mL of yeast and gently squirt the yeast into each test tube. One pouch of fresh yeast or a yeast slurry should easily be able to fill 10 vials. 

Sanitize the syringe again and then extract an equal 5–6 mL of cryopreservative solution and add to each test tube. 

Once all tubes have yeast and cryopreservative, close each tube and shake to mix the yeast and cryopreservative thoroughly.

Be sure to label the test tubes with the yeast strain added, the date, and the yeast generation.

Step 4: Freezing the yeast samples

We are now ready to freeze the yeast vials, but rather than just tossing the samples into the freezer, we’ll need to use an isopropyl alcohol bath. This will slow down the freezing process, which helps prevent damage to the yeast cells from ice crystal formation.

Required Equipment

Freezer-safe, leak-proof plastic bin
High purity (>90%) isopropyl alcohol
Freezer

Instructions

Take a freezer-safe plastic bin and place all of your prepared yeast sample test tubes in it.

Pour high purity (>90%) isopropyl alcohol into the bin until the yeast samples are fully submerged.

Securely cover the bin with its lid.

Place the sealed bin containing the alcohol and yeast samples into your freezer. Leave the bin in the freezer for a minimum of 24 hours.

The yeast samples can be removed from the alcohol after this period and stored in the freezer in a container of your choosing.

Step 5: Using your frozen yeast samples

When your next brew day arrives, the process of thawing and putting the yeast to work is straightforward.

Required Equipment 

Yeast starter calculator
Yeast starter equipment (wort, flask, stir plate)

Instructions

Use a yeast starter calculator to determine your pitching needs. Enter your wort details (original gravity, volume, target pitch rate, and enter 20 billion as the starting yeast count for each tube you plan to use). 

Once you’ve determined the correct number of tubes and starter specifications, remove the required number of yeast sample tubes from your freezer. I will typically only use one or two vials. Let them thaw slowly at room temperature.

Prepare your yeast starter following standard practices.

Use the thawed yeast samples as you would a commercial yeast packet when making your starter.

Once you are down to three tubes in the freezer of a given yeast strain, use them to make a new starter of this yeast to replenish your stock. Then follow the previously outlined steps again to create the next generation of your frozen yeast bank. I will typically go through three generations before purchasing new yeast, which is enough for dozens of batches of beer.

And that’s all there is to establishing your own private yeast bank, allowing you to keep your favorite yeast strains viable and on-hand whenever you need them. 

Sources:
• www.homebrewnotes.com/making-a-frozen-stock-yeast-bank/

• www.homebrewtalk.com/threads/maintaining-a-healthy-yeast-bank-long-term.678997

Q: I’ve homebrewed for many years but shifted to small batches these last 5 years. I’ve always brewed with dry yeast due to cost. But I want to expand beyond English ales and S-04. I’m getting ready to start my yeast bank and am trying to find information on pitch rates and small-scale yeast starters. I brew batch sizes between 1–2.5 gallons (4–10 L). I’m thinking I can buy a package of liquid yeast, make 7 or 8 slants, and pitch in a 2-gallon (8-L) batch and have enough to brew all year with those slants.
— Lee Nagel • Branson, Missouri 

A: I think I am following your plan and will rephrase so that what follows is clear. You want to buy a single liquid pack, “borrow” a bit to prepare 7–8 slants, and use the balance for your first brew. When you go to brew again, you will take a slant, make a propagation, and then pitch. This is the part that is a bit unclear. Slants are typically used multiple times where an inoculation loop is used to transfer a bit of yeast into a flask with wort or onto a Petri dish. You could use fewer slants, but I will roll with one slant for each brew and offer a hack on saving a step when using the slant.

The short answer is yes; you have a solid plan to reduce yeast costs per brew. For what it’s worth, you can also make slants by starting with a slurry made from dried yeast and treating the same as a liquid culture. This answer may be all the information you need to confirm your plan, but I will take the opportunity to provide more information about what this method looks like to brewers who have not made slants and who may want to give this a try.

Let’s start by defining a slant. In micro jargon, a slant refers to some sort of solid growth media prepared in a test tube that is allowed to solidify at an angle. The growth media is usually made by purchasing powdered media that include nutrients, agar (a carbohydrate that forms a gel after boiling and cooling), vitamins, and minerals. Specialty growth media may contain selective compounds that select for certain organisms, inhibitors that prevent growth of certain microbes, and/or indicators, such as pH indicators and stains, that help microbiologists understand more about what is growing on the media.

In the brewing world, slants are primarily used to store yeast for intermediate durations by applying cells to the surface of the slant with a loop, allowing a “lawn” to grow on the surface of the slant, then transferring to a refrigerator for storage. Slants are often covered with sterile mineral oil to prevent water loss from the media during prolonged storage; this method allows slants to be stored for many years without issue. Because the yeast applied to a slant is typically taken from a pure culture, the most common growth media is wort agar, a general-purpose media commonly used to grow yeast and mold.

A good rule used to determine propagation volume is for the final wort volume to contain 10% yeast slurry. Discussions about microbiology are always done using metric terms, so I will stick to milliliters and liters for clarity. In your case, you will want a prop volume of about 750 mL to pitch a 2-gallon (8-L) batch. I brew 5-gallon (19-L) batches and would need a prop volume of about 2000 mL. I round to convenient volumes because it’s much simpler to use increments of 100 or 250 mL when assembling basic lab supplies and these are indeed rules of thumb where close enough works well enough.

I like starting with the pitch volume because that helps plan the propagation schedule. The general method followed for yeast propagation is to use 1:10 dilution steps. In your case, that final 750-mL propagation volume is made by adding 75 mL of growing yeast slurry to 675-mL wort. A quick start to yeast activity is important when propagating yeast, just like it is during beer fermentation, because maintaining sterile conditions is impossible without specialized microbiological equipment and methods. This is true at home and in most yeast labs because of the transfer steps involved. The bottom line: Don’t make the first step too dilute because it risks the chance of growing unwanted microbes.

Adding a single colony from a Petri dish to 10–25 mL wort is a typical first step. However, slants have a lawn of yeast, not single colonies. This works to your favor because you can make your first step from slant to wort into 75 mL by picking up the equivalent of about one peppercorn-sized “scoop” of yeast from the lawn. At this point, you can save your slant for another prop or throw it away. You should see yeast activity in your flask within 1–2 days and will want to transfer the entire 75 mL into your 675-mL flask in two to three days. At the end of day five, it’s time to pitch into your 2 gallons (8 L) of wort.

For 5-gallon (19-L) brewers like me, our prop volumes are 200 mL and 2000 mL. Going from a slant to 200 mL is too big of a jump, so we need to start out with 20 mL. One way to do this is to make up a 20-mL starter in a flask. Another way is simply pouring 20 mL of wort on top of the slant. For this to work, properly sized test tubes (~50 mL) containing ~15 mL of media are required. This is the time savings hack mentioned earlier.

That’s about all the specifics I think are needed to answer your question, though key techniques omitted that readers should be aware of are media preparation, wort/media sterilization, proper use of inoculation loops, and proper transfer techniques. These are all critical for successful micro work. The good news is that none of these methods require much specialized equipment, and they are all relatively easy to perform at the proficiency required for success in the homebrewery.

Q: I read an article on saving yeast and started to think about long-term storage. I have a small freeze dryer from Harvest Right that I use for storing food for camping and hiking. Those foods rehydrate pretty well. What are your thoughts on actually freeze-drying, not just freezing, the yeast for use later on? Do you think it will work or has anyone tried this at home?
— Don Foster

A: Freeze-drying, or lyophilization, has been used for drying bacteria and yeast for nearly 100 years. The process begins by freezing, followed by subjecting the sample to a vacuum. The low pressure results in sublimation, where solid water, aka ice, directly changes phases into water vapor without moving through the aqueous phase; totally sublime. Although freeze-drying works well for food products, it is a stressful process for living cells and tissues. One of the earliest references investigating the application of freeze-drying to brewing yeast is the work of Wickerham and Andreasen of the Wallerstein Laboratory (NYC) in 1942. While brewing yeast can be freeze-dried, two complications are relatively high loss in viability and a change in the population of cells.

A study by Jean Wynants, titled “Preservation of Yeast Cultures by Lyophilization,” published in 1962 in the Journal of the Institute of Brewing showed a population increase in respiratory deficient mutant cells, known as petite mutant, after freeze-drying. Wynants concluded that the freeze-drying process led to low cell survival rate selected for petite mutants, thereby skewing the population of cells after rehydration. He also concluded that freeze-drying requires a selection step following rehydration, then propagation using the standard method of the time where a colony is transferred into a small volume of wort to begin a series of propagation steps. This method is still the norm today.

Freeze-drying is used to preserve yeast and does indeed allow for long-term storage of cells. Many yeast labs around the world send freeze-dried cultures by mail to labs and commercial users (breweries, wineries, bakeries, etc.) because of its convenience. One of the keys to the method is using a lyoprotectant agent to add protection to the culture before freeze-drying. Examples of lyoprotectants include blood serum and disaccharide solutions made from sucrose or trehalose.

You have a freeze dryer and are interested in trying it with yeast. My suggestion is to read more about how this technology is used to dry living cultures and give it a try. The worst thing that can happen is that you end up with dry, dead yeast!