Ok, so the last 3-5 batches I’ve done (all grain) have finished fermenting at least 3 points below what my brewing software estimated for FG. I’ve brewed a stout with wlp002, an IPA and a pale ale with wlp001, and all have finished 3-5 points low.
I have a thermapen that I use to measure my mash temps, and I have verified that it is calibrated correctly. I know that my mash tun cooler maintains temps very well, within 1-2F of starting mash temp, so I’m reasonably certain I’m not having a 152F mash ending at 146F.
It seems to be more common across all batches now than it was earlier in the year. I have in the last 5 batches begun oxygenation and fine-tuning my process for starters. Is it possible that a generally healthier more appropriate pitch of yeast is the “culprit” here?
In my limited experience, I would say that that can definitely be a big part of it. Another consideration is your software: I know in Beersmith, they attenuation figures for yeasts are all in manufacturers’ ranges, but you may likely get better than the average of those limits. You can adjust the setting by editing your yeast. I know I regularly get WLP001 to finish above 80% when that is the top of the range from White labs, and that is fresh pitches from a starter, no re-pitching. Everyone else can add more, and will likely say it is your better yeast management practices, and I don’t disagree
Most of my batches finish low. It’s part of the game. As I understand it, not performing a mash out can affect then fermentabilty by breaking longer chain sugars into smaller chains. I don’t mash out because I am lazy.
how dry we talking? well since you seem fairly certain of the mash temp, we’ll leave that aside. possibilities:
water to grist ratio- thinner mashes can enhance the maltose production and increase the wort’s fermentability and attenuation.
higher % base malt and less specialty grains can make a more fermentable wort.
wlp01 attenuates very well for me.
-fermentation temp- higher temps can increase attenuation
yeast health plays a role in attenuation-good or bad both directions
-keep in mind the software is just a gauge or estimation. the beer will do what it wants based upon any combination of the above variables.
Those software estimates are just that - estimates. There are just too many variables in the process to finish where the software estimates with any regularity. Your FG is a combination of yeast strain/health/quantity, grist and mash temp. Not to mention the accuracy of your FG readings. Are you using a hydrometer, and is it calibrated and reading accurately (including temp correction)? If using a refractometer, FG readings are off because of the alcohol present , so there is a correction to use to make your reading accurate. If you’re confident in your readings, mash a little higher or make your grist a bit less fermentable. Good luck !
EDIT - Aside from mash temp you would make your grist less fermentable by increasing specialty malts a bit. Mashing a couple degrees warmer and using a couple % more crystal for example could raise your FG by the 3 points or so.
–My standard mash ratio is 1.25 qts per lb of grain.
–I think you got that reversed…lower mash temps will lead to a more fermentable wort…
–yeah, good points on the software. I use beeralchemy and it has been pretty accurate but has become less so earlier this year after I started doing starters religiously, and even more inaccurate after I began oxygenating.
–tools…I use a refractometer most often, but have lately begun using my hydrometer also to double check readings. I’ve found my FG adjustment for the refractometer to be yield a value in line with the hydrometer reading. I use BA’s sean terrill’s FG calculator most often, I’ve found it to yield pretty accurate FG figures.
correct on lower mash temp-but i didnt say that. i did reference fermentation temp. seems like you’ve ruled out mash temp and mash thickness. i’d look at the grain bill, the yeast choice, and as mentioned by another, possibly increasing your mash temp if you’re looking for a less dry result.
I assume you’re mashing for 60 to 90 minutes? You could try mashing for just 35-45 minutes and see if that helps. I only mash for 40 minutes because I find that attenuation is fine at that point. I know that if I mashed longer I could gain a couple 2-3% attenuation, which to me is no big deal, but to you, maybe this would make you happy and every little bit might help.
If you haven’t done so already, ensure your mash thermometer is calibrated at boiling. The boiling point of water is different depending on your elevation so be sure to look this up for wherever you are located. Then boil some water and see if your thermometer is a little off. It might also help to check temperature against a couple of other thermometers and pick out the one that is most accurate to use as your mash thermometer.
I use brewers friend which has the ability to enter a custum attenuation number. When I brew a new recipe, if im going to keep the recipe I go in and enter the correct attenuation for my brewery. For me that normally means raising the attenuation percentage as I usually finish lower than expected. For example I repeat brew my Scottish quite often and that beer always finishes within a point of where I expect it to. New recipes usually finsh about 3-5 points lower that estimated.
First of all, does it even matter? Are you dissatisfied with something about these beers that makes you want to change your brewing process? If the answer is no then who cares what the software says. Or, for that matter, what the FG is.
Healthy yeast are definitely driving better attenuation but you don’t want to get away from healthy fermentation. Look at raising mash temperature and/or shortening your mash to keep more dextrins for body.
It does matter more to me when brewing lower gravity beers. Not as big a deal to be .5 to .8% abv off with a 7 or 8 percenter, but its a much bigger deal to be off like that on a 3.1% mild or bitter. Those types can be light enough that that much additional alcohol can throw off the balance of the beer.
has the beer tasted unbalanced? again, the point is that what matters is the perception of the beer and conformance to any particular set of theoretical numbers doesn’t necessarily equal any particular flavor profile.
so if the problem is that the beer tastes a little off balance due to alcohol then I would say you should attempt to change the fermentability of the wort or choose a less attenuative yeast or a yeast that leaves a better mouthfeel to balance the impression.
Crystal malt is good for this as is flaked barley, rye, or similar semi-raw glucan rich adjuncts.
You can also play around with yeast handling. I would say that pure o2 is not appropriate for low OG ales. try aerating by hand with a whisk or mix stir. try keeping the ferm temp even lower and/or raising the mash temp to 162.
