I have been reading Jamil Zainasheff and Chris White's (from White Labs) new book called Yeast: A Practical Guide to Beer Fermentation. The book is supposed to be more of a brewer's handbook on yeast than a text book. It is informative but not really captivating, that is, not for the non-brewing geek.
The book advocates shifting focus of brewing away from the processes of mashing and boiling and hop or other additions and to the science of yeast culturing (or whispering or wrangling if you prefer) as the Zen path to good beer. The book makes the case that focusing your efforts on techniques that cultivate a healthy yeast environment produces better beer. The techniques involved are precisely all of the things I have been ignoring in my brew day, or haphazardly/halfheartedly doing as a byproduct of my current techniques.
I have never experimented with improving yeast health, nor really experienced the wrath of ignoring the yeast. Of course I keep my brewery clean (which is the number one thing), but I kind of ignored issues of proper pitch rates (unless I was hot bunking yeast), aerating the wort before pitching, properly cooling the wort (we usually pitch a little high), and have not until recently had any control over my fermentation temperatures (and still don't when the brewery is at my brother's house, although our basements work at a decent 68F by luck). I have never had a stuck fermentation, and in 15 years only one noticeably contaminated beer....Well, until now.
Over the weekend before Thanksgiving we bottled our fresh hopped West Coast Red and repitched our wort for our Porter. I inadvertently got a healthy dose of the yeast and trub in the bottling tank while siphoning (carelessness by my part) and ended up with a super cloudy sample of wort to take our final gravity readings. Despite giving the sample ample time to cool and settle, it never did. The yeast is a low flocculator (the amount the yeast settles out of the beer), but the gravity reading on a beer was 8 points higher than the computer program I use predicted (my ferments often come in within a point or two either way). The yeast we used is a lower attenuator (the amount of sugar it ferments), but by my calculations my ferment was 8-12% lower than the low range the yeast producer states. The calculation of apparent attenuation is easy. The formula is (OG-FG)/OG. In my case, (48-18)/48 equals 62% where I expected around at least 70-72%.
So, I have a low attenuation problem and guess what would help that? So, luckily I am reading the Yeast Book. I skipped to the Troubleshooting Chapter at the end (I haven't read that far yet), and on page 272 it states "wort composition trumps all when it comes to getting yeast to attenuate a desired amount" and goes on to say if your fermentation test shows that the beer will only attenuate down to 1.020 with the yeast you are using, it is unrealistic to expect the beer to drop to 1.012. Ironically, these are the numbers I was dealing with. I don't yet know what a forced fermentation test is (I haven't read that far) and thus haven't done said test to see if this is normal. Considering that higher gravity worts tend to miss the full expected attenuation (my 1.048 wort isn't really considered high gravity) of a fermentation test, this could be in my margin of error right there. But if everything else was normal, the other usual suspects are:
Too low fermentation temps: Our basement breweries are pretty constant in the high 60's and the weather outside was warmer than normal for the year.
Lack of Oxygen: Considering we never aerate, but do pass our wort through our pump on its way to the basement these days (acting as a sort of will o wisp). While this may be our problem because we can be considered chronic under aerators, we are probably aerating more than we ever have.
Underpitching: We are chronic underpitchers. We never make starters and we use the 100 billion cell Wyeast smack packs (which are wonderfully fresh at my two local homebrew shops, and horribly old at the one near my brother's...we use fresh) which is enough for 1-5 gallon batch of moderately low gravity wort (according to the book and prevailing experts and current research). We make 12 gallons, so we are usually underpitching by at least 50% but according to the author's online yeast calculator we should have used 4 smack packs.
Underpitching is the most likely culprit. We often repitch our yeast slurry on successive batches, so not every batch is chronically underpitched, but it is interesting to note. My record keeping just got good enough to start comparing the beers that we chronically underpitched to ones where we repitched.
1.050 WCR, underpitched, 6-8 points high.Brother's basement.
1.052 Brown, underpitched, finished 6 points higher than predicted. Brother's basement
1.054 Watermelon, repitched, came within 1 point (high) of predicted. My fermentation chamber
1.0xx Blonde (broke hydrometer but predicted og was 52), underpitched, finished 2 points lower. My Ferm
1.054 Wit, underpitched, finished 5 points lower than predicted. My Ferm
1.060 Scottish, underpitched, finished 2 points high. My basement? not sure where or what fermenter.
1.060 Oktoberfest (way underpitched lager), finished 1 points low. Brother's window well
1.044 APA (4th gen repitch), finished 4 points low My basement
1.038 WCR (3rd gen repitch), finished 1 point low. My basement
1.050 Porter (2nd gen repitch), nailed predicted My basement
1.067 Winter Ale (1st gen), 4 points low. My basement
So, in comparing the last 12 months of brewing, I was mostly lower than my computer program predicted, even when underpitching. The most recent outliers are the brown where we underpitched british ale yeast and our recent west coast where I mistakenly used and underpitched American Ale (I usually use American Ale II). If the Porter comes in on target or lower, I can infer that underpitching is a major contributer. If it comes in higher, while underpitching can also be a factor, it is more due to other environmental conditions or practices at my brother's brewery. It is important to note that we also switched to a single open keg fermentation from two carboys at my brother's house. We adopted the single open fermenter when I switched to the controlled temp fermentation cabinet. We also have been having more control of our mash temperatures (higher). We used to mash in at a temp and let it cool from there. It just could be the American Ale and British Ale yeast (with all the conditions we provide).
I have been told by a grand master level beer judge that underpitching and under aerating makes a difference in the taste of beer. I have no idea if I could personally taste the differences or if it is only perceptible to higher tasters (like the big time judges). There is also a lot of science to back it up. I have the problem of not wanting to spend more on my brewing sessions, and the issue of not really having a clean room lab to propogate yeast in, and buying more equipment (Oxygen bottle, aeration stone, stir plate, lab flasks, etc.) that doesn't meet my current goals of shortening my brew day or make it safer/easier to brew.
Perhaps a future phase of the brewery will include these steps and focus on the effort of making the yeast perform better. I do hope to someday find a space that we can brew in that is clean (our garages are filthy). I have crazy dreams of renting space to brew in, or building a shed for the sole purpose of brewing (so I can control the cleanliness, temperature, and process/procedure) while easing the clean up and keeping everything close. I don't think I would mind adding more procedure and equipment at that point. It is just such a pain to unpack, set up, and clean spread out all over a house and garage. It is almost as if I am moving towards pro-level brewing without the license. I already make more than I can drink.