Is there ever a need or benefit to raising fermentation temps towards the end of fermentation? In my case, I am talking about a change from ~65 to around 69 to 70 (upper limit for this particular yeast).
Indeed. It can help yeast attenuate and clean up fermentation off flavors. Though at 65 most stains will be fine anyway.
Yes, and as Jimmy mentioned, typically more necessary in lagers, hybrids or cold fermented (cooler than 65*) ales when diacetyl is detected. That’s why the process is often referred to as a D-rest, for Diacetyl.
I like to do it for most beers because even if you are fermenting at 65, the temperature can start to drop on its on because the yeast activity has slowed down near the end of fermentation. Lower temperatures equal slower yeast activity as well so they can kind of work together to stop the yeast activity a little earlier than you might like, which would affect your attenuation.
I find it especially helpful with strains that are highly flocculant like 1968, it really helps them finish up nice and clean
stains?
Strrrains
I read this today under a particular yeast strain description…
“In order to achieve high attenuation, we recommend fermenting at 67-69 ºF for 3-4 days, and then raising the temperature to 72 ºF until a stable gravity is reached.
Temperature: 66 - 70 ºF”
Wouldn’t this hurt the yeast if you raised the temp outside of the temp range listed?
Is high attenuation associated with how vigorous fermentation seems?
1.) Nope
2.) Not really. It’s more determined by the fermentability of the wort. Of course, you need healthy, active yeast to go with that, but if your wort is low in fermentability it won’t really matter how active the yeast is.