Today I took my first shot at harboring wild yeast after recently read some articles at Bootleg Biology, which has great how-to’s on creating your own supply of wild strains from the starters, to selecting individual colonies on plates for isolating a pure strain. The first step, as I mentioned, is beginning/inoculating a starter.
I created a starter wort as you would for a purified culture that you would purchase at your local homebrew shop. Some references may suggest starting with a lower gravity wort than the normal 1.040 SG, but I decided keep it consistent with a normal strength starter. I dissolved 100g of Light Dry Malt Extract (DME) and a pinch of yeast nutrient to 1L of warm water to boil for a minimum of 10 mins.
Here is were the process may differ, although some people may still complete this step in a normal yeast starter. I added enough hops to the liter starter wort to bring the IBUs to around 10-15. The reasoning behind this is hops’ antimicrobial activity, specifically against some bacteria and mold. I weighed out around 0.15 oz of Cascade hops that were grown by my cousin Hunter at Split Rail Hop Farm and added them to the wort in some cheesecloth. I didn’t know the exact AA content of the hops, so I shot for a lower guess around 3% and boiled them for around 10 minutes.
While the wort was boiling away, the next step is to sanitize the 6oz mason jars (with lids) and cheese cloth. Most recommend boiling the jars and lids in a bath for 20 minutes to an hour, but these were brand new in a case so I decided a quick rinse with Star San would work just fine. I screwed the lids over the cheese cloth, gave them a good shake with the Star San, and set them upside down until the wort was finished.
After boiling the wort, I transferred it into each of the 4 mason jars. I made sure to fill the jars about 2/3 full to allow for some headspace for fermentation and culturing. I placed the cheesecloth back over the mouth of the jar and screw down the ring of the jar lid only, this allows the mouth to be exposed to air, but the cheesecloth will prevent large particulate matter from traveling into the starter.
While hot/warm and cooling, I took the jars outside and placed them on some hanging plants on my front porch, There was a chance of rain throughout the night so I wanted to make sure they were out of the way of the water, however, most articles recommend placing each starter in different spots around the yard to give a larger chance for different yeast to enter each culture. These jars will sit outside and cool overnight, and maybe the next day, where I will bring them inside, cover them loosely with a sanitized lid, and wait the days to weeks for fermentation to begin.