Wort is like vengeance best pitched lukewarm.
There is a saying in construction, “measure twice cute once,” because once you cut something you can’t un-cut it. This applies to brewing as much as anything in life. There are many points at which a batch of beer can be ruined, but probably one of the easiest ways to ruin a batch is to pitch the yeast in the wart while it is too hot.
Yeast are hearty buggers, they can survive a lot, but too much heat will kill them, and even if it doesn’t, that which does not kill them does not necessarily make them stronger or better. In fact when yeast is pitched in wart that’s not hot enough to kill it, but is still hotter than ideal it can create fusels, which is a German term for bad alcohols, aka rotgut. There’s an ongoing debate as to whether fusels cause us to have bad hangovers, but even if they don’t they can create an off taste, described as hot.
In addition to fusels yeast pitched too warm can cause yeast to produce non-alcohol related chemical compounds such as Diacetyl or Esters that create flavors that are often unwanted in beer and considered to make it taste off. Some beers are prized for their esters, beers made of wheat like hefeweizen are expected to have a hint of banana and clove, but the flavor ins’t necessarily desirable in most beers.
I recently made the mistake of “hot-pitching” a batch of Irish Red Ale. I should have known better, it isn’t the first time i’ve brewed beer, and unfortunately it isn’t the first time i’ve made this rookie mistake, but it’s been a while. After chilling the wart for what seemed like an eternity, taking its temperature and figuring it was close enough, I sloshed and transferred it to the primary fermenter.
Apparently I lack patience in life and apparently this carries over into my brewing. I added cold water to increase the volume, usually this cools the wart to around a sufficient temperature, but instead of taking the temperature to make sure it had cooled sufficiently I dumped the yeast straight in.
Almost immediately I realized my mistake. Feeling the side of the fermenter I could tell it was bad. The thermometer read 100F, which is way too hot for ideal fermentation. I’ve read that Ale yeast can survive temperatures up to 110F, but just because it can survive doesn’t mean it’s going to taste good.
In an attempt to save the batch I added more cold water, iced the fermenter, turned on a fan, and rushed to the internet to see if there was any other way to ameliorate the problem, but as with construction you can’t un-cut something once it’s been cut. I know I should just invest in a wart chiller, they aren’t that expensive, but in addition to being impatient, I’m also lazy and cheap.
Fortunately my mistake wasn’t fatal. I can tell from the bubbling of my air lock that the yeast isn’t dead. It’s happily doing what yeast does, chewing through the sugars in the wart and shitting out alcohol. It may not be very tasty but it will be beer and it will be drunk.