Harvesting Wild Yeast
all my invisble friends!!!!
As a person who has found science and brewing to be a wonderful world of interest and excitement, I have recently been going back in time and revisiting some of the lab equipment that I had to use in college. It turns out that a great deal of the science I learned in school is readily applicable to brewing. The first process I wanted to focus on was harvesting wild yeast. This is a practice that was the traditional procedure for brewing beer in history. It can be traced back to the beginning of civilization, when people first started using our micro organism friends as workers. This is still practiced in Belgium and in many of the new craft breweries that are focusing on wild yeast and other micro organisms (Lactobacillus, Pediococcus, and Brettanomyces)
First off, I would like to say that this is a very challenging process, especially for someone who has been accustomed to modern brewing techniques, where sanitation is paramount to making good beer. Harvesting wild yeast is not for the casual brewer, or in many ways, the professional brewer. Controlling this process would be nearly impossible, the daunting amount of variablity would make products that vary from batch to batch. Blending can help, but wild beers are an intense idea. To get pure yeast, it’s really something that dorky scientist’s should to do, like my friend Dave.
He's a Yeast Scientist!!
In order to harvest wild yeast, you essentially have to create an environment that only a few organisms will be happy in (like an alcoholic mixture with a low pH (BEER!)) and expose it to the air. If your lucky, you get S. Cervisae. If your unlucky, you can be harvesting a mixture of mold and dangerous bacteria. It was very challenging to get any success with this, with most of the samples being over run with mold. Let’s see what I got!
This could be due to using a starter what was far too low of a OG. I accidentally made the starter with only .3 grams for a 50 mL sample (OG 1.010???)instead of the 3 grams that was needed. This could have made my results a bit unreliable, but I still got some samples with what should be yeast.
I started with 36 samples, placed randomly both inside a large room and outside by the Verrazano Bridge. I left them for 24 hours on a breezy windy early december night. I then brought the samples in and let them sit covered for 10 days. Out of 36 samples, only 5 looked to have yeast. I put those samples onto petri dishes ( about 18 dishes) and let them incubate for another 5 days. Of the 18 samples. 6 seemed to have yeast colonies. I then put these samples into 6 50 ml starters, then put them onto a stir plate or back into incubator. After 18 days, I took the FG reading on my refractometer. of the 6 samples, 3 had fermented down to the low 1.030’s, from 1.045. The other samples had no difference in gravity (into the garbage!)
- the one on the left! that’s yeast! I hope….
At this point, I’m planning on taking the sample with the most active yeast and get my science friend to tell me whats in it. Then, onto a test batch! MORE TO COME!!
Next time I plan on adding sterilization practices to this as well as making a correct starter