Harvesting Yeast for the Pro Brewer

Harvesting Yeast for the Pro Brewer

Why should I harvest yeast?

The No.1 reason you should be harvesting yeast is simple: saving money. Commercial brewers can significantly reduce their production cost-per-BBL by harvesting their yeast just once – which often provides enough slurry for two subsequent batches. The savings pile up with each reuse.

This is the main advantage liquid yeast has over dry yeast. Dry yeast manufacturers do not recommend harvesting and repitching their product, which ends up making it more expensive than liquid over time.

We’ve laid out a simple harvesting procedure with guidelines for storage to help you get the most value for your pitch

Is my yeast suitable for harvesting?

The best yeast to harvest comes from low-to-moderate Original Gravity (OG) beers that are around 12-13 Plato (P) or 1.050 Specific Gravity (SG). This yeast will be healthier and have a higher density of cells compared to yeast from a high gravity fermentation, where the yeast would have been exposed to higher levels of ethanol and experienced osmotic stress. 

Yeast will store better and provide higher counts if it comes from a beer that has not been dry hopped, or it is harvested prior to dry hopping. 

GUIDE

Step 1: Soft/Cold Crash. 

Lower the temperature of your fermenters for at least 24 hours to encourage the yeast to settle to the bottom of the cone. Some yeasts will settle – or flocculate out – quickly, while others will take longer. Typically, English- and American- style ale strains will flocculate quicker than saisons, Belgian ales, lagers and Brettanomyces.

Chill to a temperature below the yeast’s primary fermentation range, typically below 58F (14C) for ales and below 48F (9C) for lagers. After 24 hours, you should be ready to harvest most strains. If longer flocculation time is needed, maintain cold temperatures. 

Step 2: Attach brink 

**Note: Sometimes you’ll have a new fermenter ready for wort, and can harvest from conical to conical. The process will largely be the same, making sure to CIP and pressurize the receiving conical beforehand.

Using a clean brink and hose, you can pasteurize before harvesting for sanitary redundancy. This step is vital as any wild, environmental microbes could survive in your yeast and infect subsequent batches. Run 180F (82C) water through the hose and brink for 25 minutes. When done, flush excess water from the hose and brink using CO2. Rinse the outside of the brink with cold water to get it closer to the temperature of the yeast (a brink over 100F or 38C would be detrimental to many strains).

Pressurize the tank and brink to 10 PSI. Connect the brink to a T valve stemming from the bottom of your conical. Fill the brink from the bottom up. 

Step 3: Harvest

First, open the T and run off slurry until the slurry coming out looks milky and creamy. Once the yeast looks good, begin running it into the brink. 

While filling the brink, try to keep the pressure stable by keeping it constant (10 PSI) on the tank and slowly releasing pressure as needed from the brink. You may need to release brink pressure carefully via the valve on top if there is no separate pressure relief valve. This process of keeping a steady flow is to help ensure you’re only collecting yeast and don’t have beer from the conical punching through the cake –  which can foam in the brink and lower your cell density drastically. 

It can take up to 15 minutes to fill the brink depending on the yeast strain. You will know it’s full when yeast begins to come out of the top valve. 

Step 4: Storage

Store the yeast as close to 32F (0C) as possible to lower the fermentation activity. For many brewers, this will be in their walk-in refrigerator. 

While storing, the yeast’s main enemies will be pressure and heat generated from fermentation in the brink. It’s advisable to vent the brink of CO2 daily to reduce the pressure as much as possible. For longer storage, some brewers attach an airlock to the top of the brink.

How long you can store the yeast will vary by strain. Generally, you will start to see significant loss of viability after one week. Even with some viability loss, however, performing a proper viability check and cell count prior to re-pitching will ensure you pitch the right amount of slurry. 

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