There's a concept in brewing that doesn't get discussed as often as it should: Establishing a baseline fermentation.
In this article, we'll discuss:
- What exactly a baseline fermentation is.
- How you create one.
- Why you'd want to spend your time on it.
- How professional brewers use them.
- How homebrewers can also benefit from creating one.
What is a Baseline Fermentation?
At its simplest, a baseline fermentation is a set of data that you can look to when producing a particular product. It represents all of the key information that you can use as a brewer to create a consistent brew. Whether it's beer, wine, mead, or cider, there are a lot of variables beyond the recipe alone that develop the profile of the final beverage.
In most cases, the two key pieces of information you'll want are temperature and gravity over time.
At the commercial scale, we also tend to gather pH and dissolved oxygen levels, but this isn't always practical or necessary at a smaller scale.
This data set should represent your favorite version of the beverage since you'll be using it as a baseline against future batches. If a new batch comes along that you prefer, go ahead and use that as your new baseline!
Most brewers will have one for each product, but it can also be very interesting to overlay different batches to see what effect different recipes, yeast, temperatures, etc. have on your production overall.
How Do You Create a Baseline Fermentation?
At home and for the first eight years of our meadery, we captured this data in an Excel spreadsheet. Every day, we'd note the temperature and gravity of the batch.
Advantages of this method:
- It's simple.
- It's inexpensive.
- You don't need any fancy software to look at the data.
- Spreadsheets aren't going anywhere anytime soon (data is future-proofed).
- Making graphs from the data is pretty easy if you don't miss readings.
Disadvantages of this method:
- It's labor-intensive.
- If you're making small batches, it uses a lot of product for hydrometer readings.
- If you miss data it can goof up your graphs.
- You're likely to miss dramatic deviations in your batch when they first occur.
This last point is an important one. We've had two stalled batches that we didn't notice for three days due to the fact that we didn't have a sense of the trend in our gravity readings. This information would have been immediately apparent if we were watching a live graph.
Nowadays we use an absolutely incredible tool called the BrewMonitor.
Here's what we see throughout the fermentation:
You can also do really nifty things like compare two sets of data to look for trends. Here's a dissolved oxygen vs gravity graph:
What this graph is telling us is that our yeast had a very healthy reproductive stage and then got right to work after all of the oxygen was taken up out of the solution, then we had no air entrainment in our pumps since there was no variation in the 02 levels after fermentation started.
If you're a professional brewer, we can't recommend the BrewMonitor highly enough.
Unfortunately, there's nothing like the BrewMonitor available at the homebrewing scale, so Excel will be your best friend.
Why Would You Want to Spend Your Time Making a Baseline Fermentation?
The short answer is consistency.
Temperature, fermentation speed, lags, stalls, and many more factors go into producing the character of the final beverage.
If one batch of your famous Bob's Maryland Special Ice Cream Porter just doesn't have that robust finish you're looking for, you can look for variations between your current batch and your baseline fermentation. Maybe the final gravity was a few points lower. Maybe you had no lag phase and the initial fermentation was faster than usual.
Drop your graphs on top of each other and it's amazing what jumps out!
The other reason to have a baseline data set, especially if you're a commercial brewer, is to catch issues before they become a real problem. It's often easy to correct a stall when it's first starting, but a batch that's been stalled for three days or more can be a real doozy.
How Do Professional Brewers Use Baseline Fermentation Datasets?
As mentioned above, the number one thing we're looking for is variations and deviations.
If something's different (good or bad) we want to know why. For us, it's usually a change in the honey, but sometimes there are other variables that only show up when we drop our current data onto our baseline fermentation set.
Personally, I like to use the data to inform my intuitions. It used to be that I could feel a batch stall coming on with about 85% accuracy, but I had no idea what I was sensing, which made it very hard to teach others. Also, what's going on with that 15% where I was wrong?
Eventually, I was able to see that right around 1.032 there would be a slow-down on fermentations that were heading towards a stall in the 1.020s, but if they were transferred or had additional ingredients added at that stage, the stall never occurred. We changed our brewing system a bit and essentially eliminated stalls (except for the Ancient Collection, which, coincidentally, we can't use the BrewMonitor on).
How do homebrewers use baseline fermentations?
For fun mostly, and to get better at brewing. If you've read this far, you're definitely a brewing nerd. You probably have a closet full of gizmos and bubbling things.
Having baseline fermentation data for your favorite batches can really take your brewing to the next level.
Learn to love Excel!
Enjoy alienating your friends and family by constantly showing them line graphs!
Make the best darn brews you can every time!
