So...finally have these things going...hopefully I'm using them correctly
Homebrew 101: Call of the Wild…..Yeasts
June 18, 2015
One of the items on my task board of things to get done around the house this week was to take an inventory of the camping, climbing and other outdoor gear in my possession. I had been curious if my tent was still in the basement or whether I would have the perfect excuse to go spend far too much money at REI. This naturally got me thinking about the places I would like to camp this summer and began a checklist of the locales I wanted to which I would venture first. All of this was done whilst sipping on a brett saison, a rather disappointing one though it may have been, a beer that is brewed with a wild yeast variant. During a recent conversation with James from Former Future he told me about his exploits in cultivating some wild fermenters on his own recent adventure (I highly encourage you to pop down to their tap room and ask him or his wife Sara about the trip where this took place and have several pints….and buy a t shirt). Having tasted what these feral yeasts can produce I’ve made it a goal to capture some of my own while out and about in nature. This may at first seem like a laborious and boring task but in truth the process is relatively simple and the results can be spectacular.
What’s the big deal?
As I mentioned in the Homebrew 101 post about Brett (click on the homebrew 101 keyword in the right over there if you haven’t read it…..I’ll just hang out here for a minute while you do that) there are strains of wild yeast like Brettanomyces that can consume sugars and produce alcohols in a way that makes for some tasty beer, wine, cider and mead. Brett isn’t the only bug out there that that uses fermentation to survive and spread, many other strains of yeast and other anaerobic organisms thrive by this process, although not all of these fermentations result in something pleasant. The key is isolating the cultures that do ferment sugars in the desired way and keeping them happy and healthy long enough to produce an awesome brew.
What you will need:
Much as one would want a rod and reel of appropriate size and strength when aiming to catch a particular type of fish, it is equally important that you have the right equipment when on the hunt for wild yeasts. First, it is recommended that you have sterilized canning jars or test tubes with stoppers in which to capture yeast (I’m a canning jar kind of guy but that’s just me). You will also need an airlock and a temperature controlled environment in which to store your bugs after catching them. Of course you will need something for your yeast to consume in your trap, and a sample of wort should be sufficient for that purpose. There are a few other items that you will need once you are culturing the good yeasts from your sample, but we will get to those in a bit.
Capturing your yeast:
There are two primary ways in which to capture wild yeasts. Which method you use is really dependent on what types of yeast you want to cultivate and the location that you will be conducting your effort. Each method has its and pros and cons to take into consideration as well, but that is not to say that one is better than the other.
The first method involves culturing yeasts through submersion of items with natural sugars. Berries, flowers and even bark from sappy trees are particularly good sources from which to collect your bugs in this method as they contain the nutrients yeast naturally consume. Fill your sterile container with a small amount of unfermented wort that has been recently boiled (I generally keep the small amount used to measure the initial specific gravity for this purpose) and submerge your yeast source of choice. Allow the item soak for a bit in the wort but no longer than 24 hours or so as leaving the material in the liquid increases the risk for molds and other contaminants to propagate.
If you’re more of a “throw caution to the wind” type (or just don’t want to dig junk out of your wort sample) you may be more interested in the other collection method that is commonly used. This entails most of the same steps and equipment as above, but where this differs is simply tightly secure cheese cloth over the opening and leave it out in the open air. This is best done in the evening and in highly vegetated areas when the conditions are best suited for microbes and other things to be floating about. Leave your container outdoors for an evening and bring it back in the next morning and poof, your wort should have a full complement of yeast samples.
Propagating and Purifying Your Yeast:
After capturing your yeast sample, it’s important to let it ferment the wort that was used in the process. Rather than the standard two or three weeks of fermenting time that is assigned to most beers, it is important to allow your yeast sample to sit for 30 to 50 days. This may be a trial in patience, but this extended fermentation period allows the desired yeasts to multiply while at the same time reducing the number of potentially contaminating bacteria’s. There is a balance to be struck in this timeframe, as letting it sit for too long can allow the bacteria responsible for lactic acid to increase as well.
Simply allowing the yeast to ferment is not the only step in getting a good yeast culture; it is also important to isolate a pure yeast from the sample. This sounds super science-y, and indeed you will be using some stuff straight out of your high school biology class to do it, but don’t let that trick you into thinking this step is complicated. First you will need to have all of the items needed for purification, specifically an agar plate, a streaking loop (haha, you just said streaking) medical grade alcohol for sterilization and a lighter or more preferably an alcohol lamp. All of these tools an be found on Amazon for relatively cheaply. Heat your loop in the flame from the lighter or lamp for a few seconds then soak it in an additional shot glass of alcohol. Run it through the flame one more time to burn off the remaining alcohol from the soak and poof, you just sterilized your tool.
Next dip the loop in your yeast culture to collect a loopful of yeast, much like collecting ink in a pen. Streak the loop back and forth across the entire agar surface in the plate. Put the lid of the plate on and place it somewhere for a few days to do its thing (I’ve also had folks recommend to me that the plate be flipped over but I’ve yet to hear an explanation as to why). This process dilutes the culture across the agar, allowing for pure yeast strains to develop independently of the other organisms that may be present. After you have noticed a healthy amount of growth in the agar plate it’s time to pick out the good yeasts for your beer.
Identifying the Good Stuff:
When your agar plate is covered in bugs, you are getting close to the end of the process (woohoo, go grab a beer really quick for making it this far into the blog post by the way). Most of what will have grown in the plate will look a bit like the glue you used as a kid to make macaroni pictures, but there are some things to watch out for to make sure what you ultimately use in your brew is safe and delivers the flavors you want.
First, look at the variations in the color of the organisms. The ones that you want to keep an eye out for will be more translucent (or if the agar in your plate was dyed a similar color to that) or white and appear to be relatively smooth. Conversely, unwanted bacteria’s and molds and yeasts will often be different colors and textures and should be a red flag of something to avoid. Some of the more important items to be on the lookout for are Staphylococus aureus (the stuff that causes staph infections) which has a greenish gold color to its colonies, Rhodotorula (a very bad and possibly toxic form of yeast) that has a rusty red color, and the tell tale fuzziness that indicates a mould. There are more identifiers that can allow you to more about the strains of yeast and bugs at a microscopic level, but I don’t have a micro scope and I’m willing to bet most of you don’t either.
And there you have it folks, the super nerdy, semi science filled ultimately rewarding process for hunting down wild yeast. If you are feeling adventurous enough to try this, I recommend seeking out someone with experience to help you determine you aren’t making beer with a nasty bug (quite a few local breweries have folks on staff that are happy to talk shop about yeast). I wish you happy hunting for your new fermenting friend and look forward to seeing the brews that are the result. Cheers everyone!