I brewed a Russian Imperial Stout yesterday. This morning, it was bubbling nicely in the fermenter. I recently purchased some new fermentation gear, specifically a carboy wrap heater, a Johnson A419 temperature controller, and a thermowell for the temp probe. This was my first time using the gear. I hooked the gear up to the fermenter this morning, turned down the temp in the room, set the temp on the A419 for 68 degrees, and headed to work. When I came home this afternoon, the airlock had blown. According to the A419, the temp inside the fermenter was 99 degrees. It took me a while to figure out what was going on. However, after a more careful reading of the instructions for a A419, I figured out that it comes set for “cooling” instead of “heating.” (You have to change the jumpers inside the box to convert to heating.) The A419 was supposed to turn the heater on when the temp dropped below 68. Instead, it was turning the heater on whenever the temp was above 68, i.e., all the time. I have disconnected the heater. The temp in the fermenter is going down slowly. I recognize that the batch could have been contaminated when the airlock blew. I also recognize that the high temp in the fermenter will likely impact the taste and other characteristics of the beer. However, what I really want to know is if the batch is completely ruined. Is the yeast dead? Is there anything I can do to save the batch?
The yeast is probably alright, but I’d say that beer is screwed. At this temp it’ll taste like a mix of rocket fuel and acetone mixed with some wet cardboard.
I’m afraid it’s gone…
90F is the tolerance for yeast. Pitch some new yeast and hope for the best, however there may be off flavors from the high fermentation temp for the day.
[quote=“Dimik”]The yeast is probably alright, but I’d say that beer is screwed. At this temp it’ll taste like a mix of rocket fuel and acetone mixed with some wet cardboard.
I’m afraid it’s gone…[/quote]
+1, dimi is right that beer is toast. You really would not want to drink it. the yeast could be fine but I’d probably pitch that too. time to brew up a new batch.
If you really can’t stomach pouring it down the drain, and have resources(secondary,bottles or keg) try adding a cover-up of coffee beans. I know, it is a stretch, but what the hell. It is already ruined, might as well add some chocolate while you are at it too…!! I dunno… it probably tastes like crap…
My understanding is that it’s closer to 115 F.
Brewers yeast typically becomes inactive between 44-50c, or 112-122f. OP, you probably didn’t kill your yeast. The only way to know if you should drink the batch is to drink it.
A high ferment temp can certainly contribute undesirable flavors, but yeast are only one element of the equation. Off flavors may be masked by hops or sharp malt flavors but you won’t know 'til you try it. The real problem is that some of those rough edges may very well fade with age, but again, you won’t know if you dump it.
My understanding is that it’s closer to 115 F.[/quote]
Yeah, I wasn’t really thinking there. I believe they can actually take about 140 before they’re dead for sure. Over 120 will severely injure though.
It’s all strain-dependent. Lager yeasts usually die in mid 90s while ale strains can go on into the 100s though a lot of them will also suffer.
This is exactly why I’ll be running my chamber for a week or so to make sure all wrinkles are ironed out.
Thank you all for the responses. I did end up dumping the batch. I tried the beer before pouring it out. It did not taste horribly bad. However, the high temperature screw-up was the fourth in a line of things that had gone wrong with this batch, starting with some second degree burns I received from an Erlenmeyer flask boil-over when preparing the yeast starter. With all that had gone wrong, I decided the batch was obviously cursed, and would likely explode in the bottles, or cause severe gastric distress when consumed. No reason to take chances. First batch I have had to dump in nearly 20 years of brewing, but you gotta do what you gotta do. I brewed a replacement batch this weekend.