The Giga Guide to Harvesting and Re-Pitching Yeast

One of the biggest steps a brewer can take toward better beer and business is to routinely re-pitch yeast. Optimal pitch rates of healthy yeast protect your beer from spoilers, ensuring beer remains consistent and free of off-flavors. It also makes good business sense. Averaging the cost of a single lab pitch across seven to 10 brews will reduce the cost of yeast to just $35–$45 per batch for a 10-barrel brewery, or less than one-tenth the cost of malt alone. Whether you are just starting out or want some tips to improve your process, here is our little guide to harvesting, storing, and re-pitching yeast like a pro.

Harvesting yeast

To get the biggest yield of healthy yeast, follow these tips:

1. Once fermentation is complete, cold crash to 34–40°F (1–4°C).
2. Collect yeast 24–72 hours after reaching desired temperature. Leaving yeast in the cone for more than 72 hours, or harvesting too soon, may lead to lower viability/yields.
3. Sanitation is of the utmost importance when harvesting yeast. Start with a well-sanitized hose and fittings. A sanitized brewery hose from that day's SIP is a good option. Alternatively, a short length of reinforced vinyl tubing dedicated to yeast harvest can be fitted with TC x HB fittings and sanitized in a bucket. Try using this simple method to sanitize the tank valve: Attach a 90-degree elbow to the valve and fill with sanitizer (i.e. PAA or similar). Let the valve soak for 10 minutes, and then remove the elbow and attach your sanitized hose. Now you are ready to begin harvesting.
4. Run off the initial slurry into a waste bucket or drain until the yeast is a light cream/tan color and feels smooth and silky between the fingers. Collect the good slurry and stop as soon as it begins to run thin. For most yeast strains, this method yields enough yeast to pitch two beers of the same size.
5. Harvesting from beers over 17° Plato may lead to unhealthy yeast. Try to harvest and re-pitch yeast only from lower gravity brews.

Harvesting yeast from dry-hopped beers

Many brewers dry hop near the end of fermentation. Although harvesting yeast after dry hopping is not a good option, try lowering the temperature to 60°F (15°C) for 24 hours and harvesting before dry hopping. This method works well enough to re-pitch several times, but pay close attention as the quality and quantity of yeast can be affected by harvesting without a proper cold crash.

Storing yeast

There are many options for yeast storage vessels (referred to as a yeast brink). A brink can be as simple as a bucket or a keg modified to have a 4-inch TC port for easy access and a 1.5-inch TC port for pitching. Using a standard keg may seem appealing, but trying to pitch yeast through a ball lock or similar keg valve will lead to clogging and frustration. Regardless of your choice, make sure your yeast brink has the core attributes listed below:

1. Your brink must be sanitary and easy to clean—avoid containers with potential for microbial harborage and narrow openings that don’t allow easy access for cleaning and inspection. Think smooth surfaces with no internal parts or grooves for things to hang up in. Stainless steel is preferable to plastic because of its non-porous surface and high heat tolerance. That being said, many brewers successfully use plastic brinks if the container is dedicated solely to yeast and is carefully cleaned and sanitized after each use.
2. Your brink needs to have a way to relieve pressure while yeast are stored—air locks, blow off hoses, and check valves are all good solutions. Yeast subjected to CO2 pressure during storage may lose viability and activity. At a minimum, the brink should be “burped” once or twice a day during storage to relieve pressure.
3. Think about how you will pitch the yeast. For example, buckets may be more awkward than modified kegs that can be pressurized.
4. Whatever brink you use, store yeast at 35–40°F (2–4°C). Storage for less than a week is ideal. Yeast stored for more than three weeks will have poor viability.
5. Cleaning and sanitizing your brink after each use is essential!

How much yeast should I pitch?

Below are three options for ensuring a consistent pitch rate of your harvested yeast. All of them assume that an average yeast slurry harvested from beer is 1–2 billion cells per ml and 90 percent viable. Of course, the ideal pitch rate depends on the beer style, yeast strain, and your process, so use the numbers below as a starting point. Once you get it dialed in, you can stick with it for consistent fermentation.

1. Pitching by Volume: Although this is the least accurate method due to air retention in the yeast slurry, many brewers successfully pitch by estimating slurry volume. For beers up to 17˚P, pitch 0.3–0.5 gallons of yeast per barrel (31 gallons) of wort. For example, for 10 barrels of wort, use 3–5 gallons. (Note: For homebrewers, that is about 1.2–2 ounces per gallon, or 6–10 ounces of slurry for a typical 5-gallon batch.) For beers greater than 17˚P, pitch more: 0.6–0.8 gallons per barrel.
2. Pitching by weight: Preferred over pitching by volume, because it avoids any issues with air retention. Use a floor scale to weigh the empty brink, and then weigh again after filling with slurry. The difference is the net weight of yeast. For beers up to 17˚P, pitch 2.6–4.4 lb (1.2–2 kg) of yeast per barrel of wort. For example, for 10 barrels of wort, use 26–44 lbs (11.8–20 kg). For beers greater than 17˚P, pitch 5.3–7 lbs (2.4–3.2 kg) per barrel.
3. Pitching by cell number: This method requires you to determine the yeast cell concentration—typically measured in cells per ml using a hemocytometer. For beers up to 17˚P, pitch 1.2–1.5 trillion yeast per barrel of wort. For example, for 10 barrels of wort use 12–15 trillion. For beers greater than 17˚P, pitch 2.3–2.5 trillion per BBL. See our detailed guide to using a hemocytometer here.

About GigaYeast

GigaYeast, Inc. was founded in 2011 to produce perfect yeast for brewers. And by perfect we mean the right yeast, the right pitch rate, and no contamination. We are known for the best customer service in the industry and providing free education to brewers on all things fermentation. Visit us at GigaYeast.Com to learn more.