Last week I brewed up an all-grain mild (OG 1.036). I didn't make a yeast starter, given the low OG, and just pitched the yeast before the pack fully swelled. It took a few days to get going, and the temp stayed in the low 60s, as it was in my basement. When I took a gravity reading after fermentation looked like it was wrapping up, I was surprised to smell/taste the harsh fusel flavor that I've experienced when a batch ferments too hot... So, two questions here: 1) It is possible that the yeast was underpitched, and does that result in fusels? 2) Will the yeast possibly clean that up somewhat, or is it pretty much a lost batch?
1a) How old was the yeast, and how had it been stored, from the time it was packaged until you used it? Some of that is impossible to know. But yes, it's definitely possible to underpitch 5 gallons of 1.036 wort with a single smack pack. Even a single brand spanking new smackpack could be considered underpitching, depending on your target rate. 1b) Yes, underpitching can cause excessive fusels. 2) Yeast turn fusels into esters. This happens in every batch of beer. Whether they will convert enough fusels to esters to make this beer palatable is unknowable. (That's assuming that what you're tasting is really fusels.) Time will tell.
Vike- I believe that the yeast was a month old, two at the most. I took it out of the fridge and smacked it a few days before brewing. I had intended on making a starter, but had a surprise opportunity to brew with the kids out of the house, so I took advantage of that. I'm 99% sure it's fusels. I've had beers ferment in the summer time get into the low 80s, and this batch tastes just like those. Is there another off-flavor that is similar?
Ethyl Acetate, an ester that exists in all beers, is "solventy" at high levels and is sometimes mistaken for fusel alcohols (and vice versa).
Here's a link to the online version of HowToBrew.com (1st edition) that deals with off-flavors. http://howtobrew.com/book/section-4/is-my-beer-ruined/common-off-flavors I doubt that it is any different from the latest edition (4th) that is available in stores.
Here are the things Palmer said (at least in the original version...can't find my more recent print copy) cause fusels... - too high a fermentation temperature. - excessive amounts of yeast - when the yeast sits too long on the trub I'm not so sure about the second and third things listed above. At least, they aren't consistent with my experience. So I got "Yeast" off the shelf to see what White and Zainasheff had to say. Here are the things they said cause or increase fusels... - Mineral Deficiency - Contamination - Underpitching - High Dissolved Oxygen - High Gravity Wort - High Ethanol Concentration - Incorrect Fermentation Temperature - Dehydration of yeast Interestingly, they don't list excessive yeast or yeast sitting on the trub. I would say that these two things can cause other issues, but not (IMO) excessive fusels.
You got me curious so I looked in my 3rd edition copy of the book where he says to control fusels: increase the pitching rate (which is opposite of the 1st edition) pitch when the wort is cool ferment at lower temperatures in the suggested range (presumably the yeast's range) don't add sucrose or other refined sugars to the wort And Palmer doesn't include the yeast sitting on the trub in this edition. Also, in the text portion (aside from the bullet points) he says, "Fusel alcohol is also increased by warmer temperatures, excesssive aeration, excessive amino acids, and underaeration and a lack of amino acids. Nice eh?" So there are some differences in the editions that we should be aware of when we recommend reading the old online version.
Homebrewing science has advanced quite a bit in the last 20 years or so. Even so, I still think the first edition of "How to Brew" is a whole lot better than nothing for someone contemplating their first brew.
Thanks guys. I also saw that explanation of overpitching, and was obviously confused by it. I guess I'll plan on keeping the beer on the yeast and hope that maybe it cleans it up enough to make it drinkable...
I would also try rousing the yeast a bit, gently swirl the bucket, and even adding a bit more fermentables, either sugar or malt to the yeast active again. The refermentation may clean up the beer a bit. If it's undrinkable in the current state it's worth a shot.
Update: the beer sucks, it's pretty undrinkable. Can I cook with it? I know what alcohols cooks off, so would the nasty fusel flavor do the same?
Alcohol, does cook off, but only partially. Alcohols (including fusels IIRC) form azeotropes with water, so as long as there's any water left in whatever you're cooking, there will be alcohol, even if you boil it.
Sounds like a classic case of contamination to me. Not 100% certain, but likely. More an underpitch problem than overpitch. OP says he pitched before the pack swelled. Even if the yeast is fresh, if the pack didn't swell, and it took several days for fermentation to take off, very likely contaminated by wild beasts. Sorry to say.
No I don't. I am not a microbiologist and have no way of knowing what wild things can get into a brew. All I know is I've experienced this problem more times than I should admit.
I’ve had finger nail polish aromas in very old beers before. I wrote it off as contamination. That might be reminiscent of bad fusels.
When I hear a homebrewer mention “nail polish remover” I first think the issue is the ester Ethyl Acetate: “The main cause of solvent off-flavors is a compound called Ethyl Acetate which is also widely used in glues, nail polish remover and other household solvents. Ethyl acetate is actually an ester produced by the “esterfication” of alcohol during fermentation.” Cheers!
