Yeast Management in the Brewery
Proper yeast management is key to consistent beer. Optimal pitch rates of healthy, uncontaminated yeast protect your brew from beer spoilers and ensure beers remain consistent and free of off flavors. Read this short, simple guide to learn the basics of harvesting, storage and re-pitching.
Harvesting from Conical fermenter:
Time and Temp are important: Yeast should be harvested after fermentation is complete and the tank is at 34˚F to 40˚F. Ideally, begin collecting yeast 48-72 hrs after crashing. Leaving yeast in the cone for extended periods of time will lead to poor viability. Harvesting before 48hrs may lead to poor yields.
Where to put the Yeast:
There are many options. Here are two that are simple and affordable. A well sanitized covered bucket dedicated to yeast (must be pitched through a man-way). A keg with sanitary fittings. The keg needs a TC/dip tube for filling and dispensing, a vent to allow filling and emptying and a way to pressurize for re-pitching the yeast via a TC connection.
Start with a well sanitized hose and fittings. Sanitize the harvest valve using this simple method: Attach a 90 degree elbow to the valve and fill with sanitizer (i.e. PAA or similar). Let the valve soak for 5-10’ and then remove the elbow and attach your sanitized brewery hose. Now you are ready to begin harvesting.
First, run off slurry into a waste bucket or drain until the yeast is a light cream/tan color and feels smooth and silky between the fingers. Begin collecting the good slurry and stop as soon as it begins to run thin. You may want to do this a few times over the course of a couple days to get the best harvest.
Always avoid taking the initial rough trub and the final thin runnings. You want the smooth creamy middle fraction. Always harvest from low gravity beer. Yeast harvested from high gravity beer has low viability and activity.
Store yeast at 35-40˚F. If storing for more than 48hrs make sure to bleed excess pressure from storage container on a regular basis or install a check valve. Excessive pressure will build up over time and reduce viability. Yeast should be pitched as soon as possible. Storage for no more than a week is ideal. Yeast stored for more than 3 weeks will have poor viability. Please don’t pitch yeast stored for more than 4 weeks.
Concentration and Viability: An average yeast slurry harvested from a conical fermenter is between 1-2 billion cells per ml. Ideally yeast should be greater than 90% viable. If viability is less than 80% please don’t pitch it*.
Pitch Rates: Below are three options for ensuring a consistent pitch rate. The ideal pitch rate depends on the beer style, yeast strain and your particular process. Use the numbers below as a guide starting with the mid range and adjusting up or down as needed. Once you get it dialed in stick with it for consistent brew. Always allow yeast to come up to room temperature before pitching.
- Pitching by Volume: For beers up to 17˚P Pitch 0.3 to 0.5 gallons of yeast per BBL of wort. For example, 10 BBL of wort use 3 to 5 gallons. For beers greater than 17˚P pitch 0.6 to .8 gallons per BBL.†
- Pitching by weight: For beers up to 17˚P Pitch 2.6 to 4.4 lbs of yeast per BBL of wort. For example, 10 BBL of wort use 26 to 44 lbs. For beers greater than 17˚P pitch 5.3 to 7 lbs per BBL.
- 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 to 1.5 trillion (that’s 1012) yeast per BBL of wort. For example, 10 BBL of wort use 12 – 15 trillion. For beers greater than 17˚P pitch 2.3 to 2.5 trillion per BBL.
†Flocculent yeast trap a large amount of gas. This can make the actual volume much smaller than the apparent volume. Degas flocculent yeast by diluting it with ¼ volume of cool sanitary water (i.e. 0.25 gal water for every gallon of yeast). Water can be prepared by boiling for 30 to 60 minutes and cooling to 35-40F overnight. Place the cool water in the storage vessel before harvesting and gently swirl the container to degas the yeast as it is harvested from the fermenter. Alternatively you can estimate the volume of slurry that is due to trapped air and pitch accordingly. To estimate the real slurry volume pull a small sample from your yeast brink into a pint glass and mark the starting volume and the volume after it settles for several hours. For instance, if the settled volume is ½ the starting volume then pitch twice the volume needed.