How much change in fermentation temperature is needed before you can taste the difference?

[Smiffy]

Since I have had my fermenter/fridge/controller, I have set the temperature to 19.5 C and left it at that.

The data sheet for S-04 says the temperature range is 15 to 24 C, but it also says that if pitching the dry yeast direct into the wort, it should be over 20 C.

So I was thinking I should try exactly the same everything else, but ferment at a different temperature and see what difference it makes to the taste, but do I try at the extreme (e.g. 15 C) or just a couple of degrees different (e.g. 17.5 C)?

The second question is, if intending to ferment cooler, do I chill to 20 C, add the yeast, then chill to the lower temperature, or chill to the desired temperature before adding the yeast. (The yeast will be reclaimed yeast from a previous brew in a "starter" but without leaving it for a day to get going.)

[Smiffy]

I only have the one fermenter, and only one fermenting fridge, so no way to do parallel tests.

[Liam Callaghan]

Thats the word I was looking for, opinionated haha!

More toys needed Smiffy! 

I guess I'm pretty lucky having a meat fridge which I can double up as my second beer conditioning fridge, the only thing is the kegs always smell like salami or smoked bacon.  So I can't pour a pint without eating something.  Sort of explains a few things...  Burp

[Smiffy]

Progress update. I took the yeast slurry from the fridge, allowed it to warm up to 15C, added some wort at 15C, then added the result to the fermenter at 15C. It took 35 hours before the airlock released its first bubble! I was beginning to think that I might have to warm it up a little to get it going. If I do it again, I will make a starter 2 days in advance. After 3 full days it is presently bubbling away nicely, and no yeast sediment yet, showing that all the yeast is happily working.

[Smiffy]

After 12 days, the airlock had stopped bubbling, but the sg was still 1018.

Over the next 4 days I increased the temperature to 20C but the sg was still 1014.

2 days later I added the dry hops, and that also got the airlock bubbling again.

8 days later I kegged it at 1012.

The result: Comparing it with the same everything else but fermented at 20C, it lacks some taste. The malt and the hops are there, but the ale fruitiness is missing. Sort of what is expected, but disappointing because the overall result seems "lacking" to my taste although I'm sure some people would prefer it

I could probably have sped things up by warming it up sooner, and perhaps my "selective breeding" of the yeast (using yeast from a previous 20C ferment) slowed it down even more.

I think I will try a warm ferment next time, say 22C.

[Smiffy]

Just had my first taste of the brew fermented at 22C. It has a slight antiseptic taste which reminds me of the Rex Attitude (which I didn't like). It is quite drinkable, but again, not to my taste. Next brew will definitely be back to 20C.