Top Cropping and Yeast Starters

With the brown ale, we fermented it in a bucket in order to try a yeast recycling technique called "Top Cropping." With ale yeast, during fermentation, they gather on top of the beer and form a foam called krausen. So, after about 24 hours of active fermentation, I went an scraped some of the yeast off the top of beer and put it into a mason jar and after a few days in the fridge, the yeast had settled out of the liquid. You can save the yeast in the fridge for up to 6 months, as long as you make a starter before you pitch it again.

For the IPA that we are going to brew on Saturday, we are going to use the yeast that came from the brown. To do this we must make a starter to grow and "wake up" the yeast to ensure viability and proper pitching rates in number of yeast cells. Each normal gravity beer needs about 200 billion yeast cells in order to ferment sufficiently. A small batch of beer (OG 1.030-1.040) is made using dry malt extract and about 2L of water. Once the wort has cooled, I transferred the yeast from the mason jar into the growler with the fresh wort. After about 20 hours, you get a nice fermentation and krausen (above, you can see the krausen on top), and on Saturday we will simply pitch the whole growler into the wort to provide the yeast. For our first attempt at top cropping and making a starter, everything is turning out well so far, but we won't know for sure how viable the yeast are until we see how they react in the IPA.

This top cropping method is very useful in situations where unique yeast strains are used, such as Belgian and Irish ale strains. Normal, all around, dry yeast cost about $3/batch of beer. The unique strains come as a liquid and range anywhere from $7-9/batch. So top cropping and reusing these strains for future use will save a good amount of money in the long run.