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.)

[Dougal]

The cleanest tasting beers I made with S-04 used 3rd gen slurry fermented at 15C.
I can't remember if I pitched cool then, but I've since found that generally it's better to pitch cool and rise to ferment temp rather than the other way round (if you have the time). At 15C I'd probably pitch and ferment at that temp. S-04 is pretty bulletproof and will finish your beer happily, but some of the other English strains like 1968 don't take well to cooling and tend to drop out quickly if you don't keep increasing the temperature throughout the ferment. 

[Liam Callaghan]

Nice study Smiffy!   Seems to be a very handy thing to do with each strain of yeast your looking to use often.

I'm about to do a similar thing with a new saison yeast.  Just ran the first one at 26 degrees and will run next weeks at 20 and see how they go.  The one at 26 seems to have an amazing smell at this stage, I hope it stays through the conditioning stage.  Seems wierd brewing at such a high temperature.

From memory you chill to below your ferment temp and let it slowly rise to the temp you want to ferment at.  I just read this in Yeast.  Unfortunately for me I read it after I made my Helle and I pitched them at 2-3 degrees warmer and cooled it.  It did help the starter go which was my intention but as the yeast makes most of its flavour compounds in the first 72 hours or so I will probably have more than I want.  Kegging this week so I'll have a taste and find out I guess. 

That might be for lager yeast only, I am still far from having a full understanding of it...  I'll check tonight.

Very interesting topic to read up on though, a great book if you have the time.  Cheap as from the www.thebookdepository.co.uk , free post for any order.

 

You splitting the batches or making a new one each test?

[Smiffy]

Do you mean splitting the yeast? Yes, I used about half of what I collected two brews ago in the last one, and I'll use the other half in the next one.

Pitching the yeast below the desired fermentation temperature makes sense as when the yeast gets going the heat generated might otherwise raise the temperature too high, but if working at the bottom of the range for a particular yeast it may stop the yeast. Is the book talking about a temperature controlled fermenter or talking about the ambient temperature where the fermenter is? (Not having seen the book, I don't know whether it is aimed at home-brewers or pros.)

Still undecided whether to try the coolest temp as I do like the result of 20C fermentation and I don't remember ever hearing of traditional English bitter being kept at 15C during fermentation.

[jt]

I remember reading a piece from Chris White, Whitelabs, saying to pitch ale yeasts at 15c and let the yeast bring the temperature up by itself. Not that I often get my own wort to 15 before pitching . . . But the thought is there.

[Dougal]

Give 15C a go. You'll get a stronger malt presence (or maybe just more perception of malt with the reduced fruitiness). I first did it at the advice of Coop from Wigram Brewery. His Bristol Best Bitter is a pretty good drop made with S-04 fermented cold.

I think the other reason that pitching cold is often suggested is that there are less precursors for diacetlyl etc. produced, so in theory the beer needs less conditioning. In practice most of us knock out pretty good beers in a 2-3 week period, so who's to say?   

[jt]

So start at 15 and then bring it upto 20 ?

[Dougal]

Yep. Given that  most of the esters and such are produced in the first couple of days, I'd pitch and hold at 15C for 2-3 days, then ramp up a degree a day till you get to 20-22C. Maybe ramp faster if it looks like fermentation is finished and the yeast is starting to drop.

[Smiffy]

If it ferments down to a reasonable gravity at 15C, I don't understand why would I want to increase the temp after that?

[Dougal]

So, what you're doing by starting cool is restraining ester and diacetyl precursor production. Then, after the first few days you can actually speed things up by slowly increasing the temperature. The beer will finish out fully (you'd never get a beer with 1968 to finish if you started at 16C and didn't raise the temp, it's just too temperature sensitive).  Also, after active fermentation is complete, the yeast eats up some of the compounds it produced during fermentation, and it does this especially well at warmer temperatures.

It's up to you. If you like fruitier ester profiles in your beer then pitching and fermenting warm can be a good idea. You'll be surprised at the difference in flavour profile from a cool ferment though. I tend to use a cool ferment for hoppy styles where I don't want the hops to be obscured by esters, and for an ESB or similar I'd go a bit warmer to get some fruitiness. All relative to your chosen yeast of course. 

[Smiffy]

Sounds like the planned one or two experiments have at least doubled.

I'll start with the "pitch and hold at 15C for 2-3 days, then ramp up a degree a day till you get to 20-22C" keeping an eye on s.g. and rate of yeast dropping.

[Liam Callaghan]

I meant splitting the batch of wort, so if you make say 30 litres you can split it into two 15 litre batches and then pitch your yeast into them.  You can then test each 15 litre batch at different temps with the same yeast strain, compare how they perform.  Half your test time.

Its a great book mate, I would recommend it to anyone thats brewing.  Some hard reading (for me anyway) on the biology front but keep plugging away, it does seem to sink in and when you get the bits that are relevent to what you are doing it will make sense.  Its for pro and amatures I believe.  Damian let me borrow his copy but I have since been and bought my own, I think its one of those books you will keep returning too.  Best find of the year for me, a real eye opener.

http://www.bookdepository.co.uk/Yeast-Chris-White/9780937381960

The book is assuming you have a controlled fermentation temperature btw and I wouldn't be concerned about pitching in a few degrees below its working range, its not going to run dormant on you.  You might want to make sure your starter is close to your pitching temperature before hand too. 

I'd follow what Douglas said, he is a bit of a demon when it comes to making beer and understanding yeast, he seems to have done alot of the hard yards.  Certainly knows his stuff and is happy to share.  If we did knighthoods for promoting quality beer making at home, he'd be in the running :p

 

Ps.  I don't have shares in "Yeast"

[Dougal]

I'd follow what Douglas said, he is a bit of a demon when it comes to making beer and understanding yeast, he seems to have done alot of the hard yards.  Certainly knows his stuff and is happy to share.  If we did knighthoods for promoting quality beer making at home, he'd be in the running :p

I think what Liam's trying to say is that I'm opinionated :P

I have, however, played host to Captain F*ckup on occasion, and read up a bit and tried to learn from the experience. I'm a big fan of pitching cool and ramping, as you seem to decrease the need for conditioning. Recently turned out a wit beer fully carbed in the bottle and tasting great in under two weeks by applying that principle.