Calculating the sweet spot for yeast fermentation temperature?

[trustyrusty]

Hi There,
I posted about the temp of yeasts before, and people sent links to manufacturers, particularly kit yeasts. Yeast providers have more accurate ranges.

I was wondering if there was site that or any book that has a way of working out the opitinum yeast temp. Some kit makers say between 22 - 28 or so. (Ales and lagers they don't seem to say much different as I assume not a true lager yeast). Seems high to me and as I read it generally 17/18 degrees is a good mark for most yeasts but is there a way of working it out, or just through experience. I have a Blue Mountain Lager that I want to do at 18 deg, (not what it says on the can). I believe making a beer at 18 deg. can be very different to a beer at 22 deg? The last few brews I have done with kit yeast because I have been able to control temp better and I want to build knowledge understand the taste of the yeast - before I change to other yeast, so I know what the difference is.So I am interested in getting the correct results for each yeast or at least a spot where the results are best.

I don;t expect people to search google for me I can do that, I am interested in your experience or if know knowledge of.

There was a website that compared brewing methods -- kept every variable the same except they change the factor they wanted to test, I am sure they would have done this, but I cannot remember the name. Quite a good site actually.

Thanks

 

[MHB]

Crikey - Pick an easy question why don't you.
Temperature is one of the big influences on how a yeast preforms, but far from the only one.
With increasing temperature (up to a point) yeast works faster and makes more metabolic side issues (mostly esters), some yeasts are very low ester formers even at fairly high temperatures (Mauri 514 (common kit yeast) being a good example) some very high (Wheat yeasts being a very good example)

Other big influences on how a yeast will preform
Wort Quality - Fermentable sugars, protein content, minerals, vitamins, lipids
Dissolved Oxygen - If low the yeast wont reproduce as much, will consume less of the above, will take longer to finish, (will be under more stress and make more flavours)
Pitch Rate - More yeast makes less flavour, lower pitch rates lead to more flavour.
Temperature - the colder it the slower yeast works, in general you need more yeast to get the job done. Choose the middle of a manufacturers recommended range as a starting point (adjust from there to taste).
There will be a bunch of other factors, but they are the big ones.

Into a high quality well aerated Ale wort the standard recommendation is to pitch 0.4-1.0Million cells/mL/oP (1-1.65M cells/mL/oP for Lager)
If we were looking at a "standard" 23L, 1.050 wort we would be looking for (0.4-1*10^6)*23,000*12.5 = 115000000000 (1.15*10^11 to 287500000000 (2.875*10^11) cells.
When you think that a fresh Wyeast/Whitelabs claim to have 100 Billion (1*10^11) cells, its pretty obvious most home brewers will be pitching at the very bottom of the recommended range.

One other point (this is me killing sacred cows again) - it is very bad brewing practice to leave wort in contact with old yeast any longer than necessary. With an appropriately sized pitch and a healthy wort, the ferment will be over less than 5 days, a day or to clear and get it off the yeast.
After 14 days there is measurable harm done to the beer, mostly through yeast autolysis.
Either pitch enough yeast, brew warm enough, aerate better... or rack the beer before dying yeast causes problems.

If you were referring to brulosophy.com, please don't they are to brewing science what Myth Busters are to physics (I think reading too much of it will send you blind).
Mark

 

[peteru]

It depends what you want from the yeast. Changing temperature will change the characteristics and growth rates. There is no simple answer to the flavour question - experimentation will give you the answers.

 

[barls]

mate lagers should be around the 10-12 mark not 18. at 18 with a lager your making a headache maker. a lot of fussel alcohols.
ales at 18-20. as i said in the other thread.
the different yeasts have different preferred bands.
most of the companies will give you a 4-5 degree range as optimum. aim to be in the middle of that the first use of the yeast and adjust the temp as you see fit.

the kit manufacturers put that on there so that you will get it to finish and quickly. its not the best advice from them. my advice and that of most of us in here is throw the piece of paper away.

there is no magic sweet spot for all yeasts they are all different and depends on what it is and in this case refer back to the manufacturer.

 

[Garfield]

If you're saying you'll use the kit yeast then it's probably English ale. It might give a lagerish brew at 18' but you should let it up to 22-24' in the last few days to blow off diacytel (butterscotch flavour ester) which develops low temps.

If you buy a lager yeast then you'll ferment much cooler but should still let temp up near the end

 

[trustyrusty]

Thanks... how many days at 22-24? Would that also work when I put in the keg and it gets to 22?

 

[Garfield]

No. Yeast needs to still be active to metabolise the residual diacytel. A couple of days is usually enough or just let it finish off the fermentation at low to mid 20s. After this you can cold condition in fermenter or keg if you want. All of these numbers depend on yeast strain, of course

 

[trustyrusty]

Thanks - What if the yeast is still active in the keg? I like to naturally carbonate...When the Gravity is 1010 and I am looking for 1005 for example I keg it as a sort of second fermentation, that is a room temp genearally around 21 / 22 in the room. It is pretty insulated. Seems to work well, never have any off flavours. I then cold condition for 2 weeks in the fridge beer drinking, if I can wait that long - btw isnt the yeast always active as in bottling and adding dextrose to carbonate, Thanks

 

[Garfield]

Sounds like a good system. You're pretty much doing what I'm suggesting anyway.

I don't have any keg experience but I like the idea of keg conditioning. Do you have any trouble with yeast sediment in the glass?

 

[trustyrusty]

No, the yeast the is left in drops down below the tube, probably 1/5 inch thick. The yeast gets quite compact.. so not a problem. FYI I filled 2.6 kg gas tank on July 16, still going so I am not using not much gas with carbonation happening. Cheers