Alan's Brewery

Harvesting yeast

Recently, Google News popped up an article on harvesting yeast, with plenty of dos and donts . During lockdown, I harvested and used a batch of yeast, and it's nowhere near as painful as they make it sound. (Interestingly enough, because I looked at the article from Google News, Google has decided I must be interested in this, so has since given me three different articles on this topic - and all the articles follow the same recipe.) I certainly have not followed their method.

What I do, as I bottle beer and not keg it, is to collect the yeast from the dregs of each bottle I drink. As I don't like cloudy beer, I normally decant the beer into another container and stop decanting once I see sediment in the neck of the bottle. In a 1L bottle, this normally means about 1cm of fluid in the bottom of the bottle. I then swirl this to get the yeast into suspension, and then pour this into a collection bottle. I leave this collection bottle in the fridge until I have collected enough yeast (about three 20L batches seems to yield about 1cm of yeast). The excess beer, from the collection bottle, I normally decant and use for cooking (what beer drinker uses wine for cooking?).


Collected yeast being prepared for use in the jar one the left, the new collection bottle on the right.

With this yeast batch, I rinsed it twice after I poured it into the jar, before using it in a brew. With rinsing, I poured off the excess liquid, then added about the same amount of filtered water to the jar, shook it vigourously to get the yeast into suspension, and let it rest overnight in the fridge before repeating.

On brew day, I poured off the clear liquid and added about the same amount of tepid water (~30°C) with 1 tsp of table sugar and let it stand at room temperature, while brewing, to check the viability of the yeast. It was not as active as the Safale yeasts I normally use, but showed enough activity for me to be happy to pitch it. It was slow to get going (about 12 hours, whereas the Safale yeasts normally start fermenting immediately). However, once it got going, the reaction was far more vigourous than Safale.


The end product

The brew was a red ale, and the colour is not too bad, slightly browner than red, but not unacceptably so. However, one thing I did find was that the beer was far more cloudy than I am used to with Safale yeasts. This probably means the yeast was not flocculating as well as the yeast it originated from.