Harvest: Aseptically crop yeast into sanitized container and degas.
Harvest yeast immediately after final gravity has been reached. Even if it is kept very cold, yeast should not be stored in the cone or under beer. To yeast, beer is a nutrient-poor waste product, and forcing it to reside there will cause the viability to drop precipitously, no matter how cold it is kept!
- Sterilize valves with 70% alcohol and flame, and sanitize any hoses, utensils and storage containers.
- Catch the middle layer of yeast in a storage container.
- [CONICAL vessels are drained of the bottom trub-filled layer until good color and consistency is seen. Middle layer is captured, then the top trub-filled layer is discarded.
- ROUND vessels require manual harvesting with a paddle, for layers tend to mix if allowed to drain through the valve.]
- Thoroughly degas yeast by shaking storage container and allowing gas to escape through lid.
- If slurry is very thick, dilute the slurry with fresh tap water until it is the consistency of a milkshake.
Diluting the slurry to the proper consistency enhances the “cleaning” effect. Use sterilized and cooled tap water for your dilution.
Clean: Mix chemicals, then add to yeast.
- Add the entire contents of the ACIDIFIED WATER tube to the SODIUM CHLORITE tube.
- Mixture will immediately turn yellow.
- Add mixture to yeast slurry and mix thoroughly.
- Allow to react for a minimum of 30 minutes.
This process is extremely effective at killing brewing bacteria and is gentle enough to use every harvest. It is not effective against wild yeast!
5NaCIO2 (sodium chlorite) + 4H+ (acid) → 4CIO2 (chlorine dioxide) + 4Na+ (sodium ion) + Na+Cl- (salt) + 2H20 (water)
Feed: Add wort concentrate to yeast, then store at 34°F/1°C.
At least 30 minutes after “cleaning” the slurry, add WORT CONCENTRATE.
- No need to mix; the yeast will resuspend in the wort.
- Do not seal lid; pressure built up during storage is harmful to yeast.
- Store at 34°F/1°C.
Yeast will retain high viability for 2 weeks at this temperature. Warmer temperatures will decrease storage times. If your cold room maintains temperatures higher than 34°F/1°C, you must either place the yeast storage container in an ice bath in the cold room (which maintains the proper temperature as long as ice is present), or you must feed the yeast again before 2 weeks has elapsed. If storage times of more than 2 weeks are desired, drain old wort off the yeast bed and replace with fresh wort every 2 weeks.