How to Harvest and Reuse Yeast: A Step-by-Step Brewing Guide

by Dane Wilson | Last Updated: September 26, 2025

Hey there! This site is reader-supported and we earn commissions if you purchase products from retailers after clicking on a link from our site.

Buying fresh yeast for every brew session means spending eight to twelve bucks per batch. Brew twice monthly, and that’s over $200 annually on a perfectly reusable ingredient. Beyond the cost savings, yeast harvesting and reuse lets you develop your own house culture, delivering consistent, professional-level results batch after batch. Pro breweries have been doing this forever, and there’s no reason homebrewers can’t master the same technique. The process is simpler than most brewers realize. From selecting the right batch to storing your slurry properly, you’ll learn the step-by-step process that’ll have you tracking yeast generations like a seasoned brewer in no time.

Table of Contents

• Why Bother With Yeast Harvesting?
• Preparing Equipment
• Selecting the Right Batch
• Harvesting Yeast from Fermenter
• Washing the Yeast (Optional)
• Storing Yeast
• Preparing Yeast for Reuse
• Reusing Yeast in Brewing
• Troubleshooting Common Issues
• Stop Buying, Start Harvesting
• FAQs

Why Bother With Yeast Harvesting?

Think of yeast as the hardest-working employee in your brewery – one that’s willing to clock in for multiple shifts without demanding a new paycheck every time. When you’re buying fresh yeast packets for every brew session, those costs add up faster than tabs at your local brewpub. We’re talking anywhere from three to twelve bucks per batch, and if you’re brewing regularly, that’s serious money left on the table.

But here’s the thing – harvesting and reusing yeast isn’t just about being thrifty. When you cultivate a relationship with your Saccharomyces cerevisiae (that’s the fancy Latin name for brewer’s yeast), you’re essentially creating your own house culture. This practice helps maintain consistency across batches and can even preserve hard-to-find strains that you’ll want to use again and again. Professional breweries have been doing this forever, and honestly, there’s no reason you shouldn’t jump on board.

The sustainability angle is worth mentioning, too. Every time you harvest yeast instead of tossing that creamy slurry down the drain, you’re reducing waste and keeping perfectly viable organisms in rotation. It’s the brewing equivalent of composting – good for your wallet and good for keeping things green.

Related: How and When to Harvest Hops

Preparing Equipment

Before you dive into harvest mode, let’s talk gear. You can’t just wing this part – contamination’s your worst enemy here, and a little prep work goes a long way toward keeping your yeast pure and your beer delicious.

Essential Tools for the Job

Grab some sterilized mason jars – they’re perfect because you can see through them to check on your yeast layers later. You’ll want at least three or four large ones (think 500ml or bigger). Don’t skimp on the sanitizer either – whether you’re team Star San or prefer another no-rinse option, make sure everything’s properly sanitized. We’re talking the jars, the lids, any funnels, tubing, spoons – everything that’ll touch your precious yeast.

Here’s a pro tip that’ll save you headaches: heat sterilization beats chemical sanitizers when you’re working with yeast. Boiling your equipment or giving it a pass through flame provides an extra insurance policy against sneaky bacteria. Some brewers spray rather than soak their gear, but honestly, boiling’s your safest bet.

Setting Up Your Workspace

Clear off a clean surface and give it a good spray-down with diluted alcohol or Star San. You want to work away from any drafts that could blow bacteria into your setup. Think of bacteria like dust particles – they’re just waiting to hitch a ride and crash your yeast party. If you’ve got a flame source nearby, even better – hot air rises and takes bacteria with it.

Selecting the Right Batch

Not every fermentation’s a good candidate for yeast harvesting. It’s like trying to adopt out puppies – you want the healthy ones that’ll thrive in their new homes.

The Sweet Spot: Mid-Generation Magic

Professional brewers typically reuse yeast for five to ten generations, depending on how well they handle it. Your second or third-generation yeast? That’s often the sweet spot where you’ll see the best performance. The yeast has flexed its muscles, learned the ropes, but hasn’t been through the wringer yet.

Beer Style Matters

Always harvest from low-gravity and low-hopped beers. That means your sessionable blonde ale or straightforward brown ale makes a way better donor than your double IPA or imperial stout. High-gravity beers stress yeast out (imagine working double shifts every day), and excessive hops can be harsh on yeast cells. You want happy, healthy yeast that’s had a relatively easy fermentation.

Clean fermentations are your friend here. If your beer had any weird smells, stuck fermentation, or other drama, skip harvesting from that batch. Save the harvest for when everything went smoothly and your wort fermented like a dream.

Harvesting Yeast from Fermenter

Time to get hands-on. The actual collection process isn’t rocket science, but timing and technique matter.

Top Cropping vs. Bottom Cropping

You’ve got two main approaches here. Top cropping involves skimming that beautiful krausen – the foamy yeast head – from the top during active fermentation. It’s cleaner and gives you more predictable results, though it requires catching the fermentation at just the right moment.

Bottom cropping is more common for homebrewers because it’s easier timing-wise. After you’ve siphoned off your beer, grab that yeast sediment at the bottom as quickly as possible using a sterile spoon or by carefully pouring. If you’re using a conical fermenter, you’ve hit the jackpot – just open that bottom valve and let gravity do its thing.

The Three-Layer System

Here’s where it gets interesting. When harvesting from a conical tank, the best yeast settles into a middle layer between the trub (that first layer of dead cells and gunk) and the top layer of less-viable yeast. You want that middle section – it’s the Goldilocks zone of yeast harvesting.

Drain off that first dark, chunky stuff. When you see creamy, tan-colored yeast flowing, that’s your cue to start collecting. Once it starts getting thin or discolored again, stop. You’re shooting for that dense yeast slurry that looks like melted peanut butter – appetizing comparison, right?

Related: How To Make Alcohol Without Yeast – It’s Possible!

Washing the Yeast (Optional)

Let’s clear something up real quick: washing and rinsing yeast aren’t quite the same thing, even though most homebrewers use the terms interchangeably. Rinsing (what we’re doing here) separates healthy yeast from leftover trub and hop matter. True washing involves chemicals to knock out bacteria – that’s more pro-brewer territory.

The Simple Rinse Method

Fill your container about 20% full with the yeast slurry, then add sterile water to bring it up to 85-90% volume, leaving some headspace. Shake it like you’re making a cocktail (minus the ice and vermouth), then let it sit for at least 20 minutes.

Hold your container up to the light – you should see three distinct layers forming. The top layer is mostly water and can be dumped. Middle layer? That’s your money shot – healthy yeast that’s ready to party in your next batch. Pour that carefully into another sterilized jar. Bottom layer’s trub and sediment, so that gets tossed too.

Want to concentrate things even more? Run through this process again. Each rinse gets you cleaner yeast, though there’s a point of diminishing returns where you’re just making extra work for yourself.

Storing Yeast

You’ve done the hard part – now don’t blow it on storage.

Fridge Life and Labeling

Pop those jars in your fridge right away. Keep them at 34-36 degrees in a dark, oxygen-free space. The cold puts your yeast into hibernation mode, slowing down its metabolism and keeping it viable longer.

Label everything. I mean it – write the strain, the generation number, and the harvest date on each jar. Three months from now, when you’re staring at mystery jars in your fridge, you’ll thank yourself. Trust me on this one.

How Long Can You Store Yeast?

If you’re storing for less than two weeks, you’ll usually have no problems reusing yeast. After four weeks, viability typically drops to 50% or lower. Ideally, you want to use your harvested yeast within a week for the best results.

Keep an eye on your stored yeast. If CO2 builds up, crack the lid occasionally to relieve pressure. Some brewers do this a few times daily. The yeast is still alive in there, just taking a nap, and occasionally it needs to exhale.

Preparing Yeast for Reuse

Your yeast has been chilling (literally) in the fridge. Now it needs a gentle wake-up call before diving into a new batch.

Making a Starter: The Yeast Alarm Clock

A yeast starter is essentially a mini-batch of beer where you’re boiling and fermenting a small volume. You’ll need an Erlenmeyer flask (or just a large jar), some dried malt extract, water, and yeast nutrient.

Here’s the play-by-play: Mix about 150 grams of dry malt extract in 1.5 liters of water, aiming for roughly 1.037 specific gravity. Boil it for 20 minutes to sterilize, then cool it down to room temperature. Once it’s cooled, pitch your harvested yeast slurry into the flask. Cover with sanitized foil and let it do its thing at around 72°F.

The Stir Plate Advantage

If you’ve got a stir plate, use it. That constant agitation keeps oxygen flowing to the yeast, which is crucial for cell reproduction rather than alcohol production. No stir plate? Just give the flask a good swirl every few hours. You’re aiming for 24-48 hours of starter time, though some strains (especially lager yeasts) might need a bit longer.

The starter should look milky and smell yeasty, not worty. When you see a thick layer of yeast at the bottom and the liquid’s clearing up, you’re golden. You can pitch the whole thing, or cold-crash it in the fridge for a few hours, pour off most of the liquid, and just pitch the concentrated yeast slurry.

Reusing Yeast in Brewing

Game time – you’re ready to pitch that reused yeast into fresh wort.

Pitch Rates and Generational Limits

Remember that roughly one milliliter of dense yeast slurry contains about one billion viable yeast cells. Use this as your baseline for pitch rate calculations. Most online calculators can help you nail the exact amount you need based on your wort volume and gravity.

Depending on strain, harvesting practices, and quality control, yeast can be successfully repitched for 5-10 generations. Some strains (looking at you, German hefeweizen yeasts) mutate faster and lose their desirable characteristics after just a few generations. Others, like Scottish or Irish ale strains, are tougher and can handle more repitches.

The Consistency Factor

Here’s what makes harvesting worth the effort: when you pitch the same yeast generation after generation, you develop familiarity with how it performs. You’ll know its fermentation timeline, its flavor profile, and its quirks. That consistency helps you dial in your recipes and brew more predictable beer.

Keep notes on each generation. How quickly did it take off? What was the final attenuation? Any flavor drift? This information becomes your personal yeast playbook.

Troubleshooting Common Issues

Even with perfect technique, things can go sideways. Let’s troubleshoot the usual suspects.

Contamination: When Bad Bugs Crash the Party

Bacterial infection is the nightmare scenario. Your yeast slurry should smell clean and yeasty, maybe a little beery. If it smells sour, like rotten eggs, or has any funky off-aromas, don’t use it. Period. Phenolic off-flavors, often described as Band-Aid or plastic-like, typically indicate wild yeast contamination.

Prevention’s your best defense here. Sanitize religiously. Work in a clean space. Don’t harvest from questionable batches. If you’re ever uncertain about a yeast sample’s quality, err on the side of caution and grab a fresh packet.

Low Viability and Weak Fermentations

If your repitched yeast takes forever to start fermenting or never quite finishes the job, viability’s probably tanked. This happens when yeast sits too long in storage or when you’ve pushed a strain beyond its limits.

The fix? Make a bigger starter next time to wake up more cells. Or just recognize that this particular batch of harvested yeast has reached retirement age and start fresh.

Autolysis: The Self-Destruction Problem

Autolysis happens when yeast cells burst open, releasing enzymes that create sharp, bitter tastes with meaty and sulfurous notes. It sounds dramatic, and it kinda is – think of it as yeast cells going out in a blaze of glory.

The good news? Autolysis typically takes several months to occur, and it’s mainly a concern for beers with extended aging on the yeast cake. For most homebrewers, if you’re harvesting reasonably soon after fermentation wraps up and not letting beer sit on yeast for months at warm temperatures, you’ll probably never deal with autolysis.

High temperatures accelerate autolysis, as does osmotic shock (like pitching yeast into super-high-gravity wort). Old yeast and insufficient aeration can also trigger excessive ester production and soapy off-flavors through autolysis. The solution? Harvest promptly, store cold, and treat your yeast right from the start.

Stop Buying, Start Harvesting

There you have it – harvesting and reusing yeast isn’t some mysterious dark art reserved for brewing wizards. It’s a practical skill that’ll save you money, improve your brewing consistency, and make you feel like a legitimate brewery operator (even if your “brewery” is just a corner of your garage). Start with one harvest and see how it goes. Before you know it, you’ll be tracking yeast generations like a pro and wondering why you ever bought a new packet for every brew day.

FAQs