January 21, 2019

One Gallon Spontaneous Fermentation Batch #3

Although this is my third attempt to successfully brew a small batch spontaneously fermented beer, it's my first attempt in Colorado. I'm closing in on two years since I brewed the first two attempts so I've had a chance to see how they developed and adjust processes. As I discussed in this update post on those two batches, I never saw much sourness develop. The post was briefly discussed on milk the funk and a few people commented that the hopping rate was really high which certainly could be a reason. I've had some time to think on these beers and how I want to adjust the process and recipe going forward. I don't want to create acid bombs but at the same time some acidity is an important part of the flavor and structure of these beers.

Changes to Batch #3 from batches #1 and #2


This batch will take on two changes from the prior batches to test increasing the acidity of these beers. First, I will reduce the hop rate. I think the commentors on Milk the Funk are at least partially correct that the hopping rate has a negative effect, even using aged hops. I've been using aged American hops which are higher in alpha acids and it's easily possible these hops still have a lot more alpha acid left behind than online calculators state. I will cut the volume in half and see how that affects the beer. My suspicion is that this is not a complete answer for the lack of acidity. I expect that some amount of hop tolerant lactic acid bacteria should have found their way into the beer even if they are late bloomers like pediococcus. 

My other thought here is that the first two spontaneous fermentations cooled too quickly and landed at too cool of a temperature by the time I racked them into fermenters in the house. Each batch was cooled for about eight hours in temperatures running from 35-45F and the beers cooled down to the forties fairly quickly. By comparison, lambic brewers tend to land in the sixties overnight although ambient temperatures are comparable. This difference is easily explained by the difference in volumes. By cooling down to a lower temperature and staying there for several hours I wonder if the bacterial load collected as the wort cools is not getting a necessary opportunity to multiply. If their numbers are low then they might lose the competitive battle for resources as the beer warms back up inside the house. To deal with this issue I will brew this batch during warmer temperatures when the ambient environment is in the upper fifties so the beer will cool to the sixties and cool a little slower. 

Otherwise this batch will keep all the attributes of the prior batches. I'll follow the recipe outlined for batch 1 but reduce the blend of aged American hops down to a mere 0.30 ounces. I will also use pils malt from local maltster Root Shoot rather than the pale malt used in batch #1.

Spontaneous Fermentation Batch #3 Brewday

Brewed 12.14.18.

Turbid mashes are one of those processes in brewing that gets a little easier and quicker with experience. I recall that first turbid mash feeling like I was constantly juggling temperatures and not really sure how to extract runnings from those early infusions. Now I know what to expect and these brew days run smoother but not necessarily faster. It's still several hours of mashing and not just a set it and forget it kind of mash. Nevertheless everything ran smoothly. 

Those milky first runnings
With the mash and sparge finally complete after four hours it's time to get the boil moving. As with the earlier batches of spontaneous beer and the last three years of my solera, I'm using aged hops. I've cut back from using 0.70 oz./gal. to 0.30 oz./gal. for this batch to hopefully develop more acidity than the last two batches. This batch has a combination of 2013 homegrown Cascade and 2011 Belma.

Aged hops waiting to join the boil

At the end of the ninety minute boil the wort makes its way out to my backyard to cool. I decided the best place available on my property for inoculation is the small patio outside my bedroom. It sits beneath two aspen trees near a wooden fence and a pergola so between all this wood there should be plenty of opportunity to pick up a healthy blend of microorganisms.

The wort took exactly three hours to drop from boiling to 59F. In the past two batches I moved the wort between vessels to try to slow cooling and left the wort out for a long period of time. As mentioned above, one of my concerns about the lack of acidity is that I left the wort in cool temperatures for too long which may have stunted early bacterial growth and resulted in insufficient acidity. I tracked the cooling temperature in fifteen minute increments which produced an expected cooling curve.


TimeWort (F)Ambient (F)
7:00pm18340
7:15pm14540
7:30pm12040
7:45pm10940
8:00pm9942
8:15pm9038
8:30pm8238
8:45pm7740
9:00pm7240
9:15pm6739
9:30pm6439
9:45pm6139
10:00pm5939



The cooled wort was then transferred into a 4l carboy while filtering out the hops. I added roughly eight ounces of distilled water to top up the batch to one gallon. I sent it to the fermentation chamber with the temperature set to 69F. I'll keep it at that temperature for a few days to ensure it doesn't get too cool in the basement then cut the heat and let it work at ambient, which is in the low 60s/upper 50s right now.


Fermentation Notes

Day 3: Already showing signs of fermentation. I'm holding the temperature at 72F right now to get things moving.



Day 15: Activity has dropped off and the beer has dropped fairly clear. The aroma is musty, old wet sponge and rotting fruit with an underlying bright navel orange that is nice despite all the weird aromas around it. Although old wet sponge and rotting fruit doesn't sound like a good direction for a beer, this does not strike me as terribly different from other spontaneous experiences.



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