Fermentation Temps

[GolfBum]

So I have read about people fermenting some of their saisons and belgian ales at a steady temp and then I have read about people letting their fermentation temps flucuate and rise. Anyone know why people do that, let the fermentation temp rise and flucuate? I have always been told to keep a steady fermentation temp to reduce off flavors and such.

[erockrph]

I don't think they're talking about temps freely fluctuating. Many brewers will bring the temp up a few degrees after the majority of fermentation is completed. This helps the yeast finish those last few points of fermentation and also helps the yeast clean up some of the less desirable byproducts of fermentation.

[Joe Sr.]

The Belgian Saison yeast, in particular, seems to like higher temps to finish.  It likes to stall out and letting it start cool and then warm up during the fermentation apparently helps prevent this.

IME, once it stalls it's very hard to get it to finish. 

[euge]

http://www.wyeastlab.com/rw_yeaststrain_detail.cfm?ID=60

YEAST STRAIN: 3724  |  Belgian Saison™

This strain is the classic farmhouse ale yeast. A traditional yeast that is spicy with complex aromatics, including bubble gum. It is very tart and dry on the palate with a mild fruitiness. Expect a crisp, mildly acidic finish that will benefit from elevated fermentation temperatures. This strain is notorious for a rapid and vigorous start to fermentation, only to stick around 1.035 S.G. Fermentation will finish, given time and warm temperatures. Warm fermentation temperatures at least 90°F (32°C) or the use of a secondary strain can accelerate attenuation.

Origin:
Flocculation: Low
Attenuation: 76-80%
Temperature Range: 70-95F, 21-35C
Alcohol Tolerance: 12% ABV

Thus has absolutely been my experience every time I used it.

[kylekohlmorgen]

There's definitely a difference in controlling at higher than normal temps and letting the fermentation temp freely rise (and consequently fall) without temp. control.

You can use the heat from fermentation to slowly raise the temp over the course of a few days. I usually do a degree or two per day as the fermentation hits high krausen.

Letting the temp swing up and then down by several degrees (5F or more) can shock the yeast, causing them to give off phenols/higher alcohols and then stop fermentation early.

[GolfBum]

Thanks for the responses. When reading some recipes from people it seemed like they raised the temp to get a more flavorful beer. I guess they did it to get the yeast to finish.

[morticaixavier]

Thanks for the responses. When reading some recipes from people it seemed like they raised the temp to get a more flavorful beer. I guess they did it to get the yeast to finish.

It is largely to make sure the yeast finish and clean up any off flavours, however there is still some flavour development, just compared to the early flavour development it is pretty negligible. I like to chill the wort down to about 62-64 (which I pretty much always do anyway) pitch yeast and then turn the temp control up to 72 either when I pitch or the next day. Or, if there is no room in the ferment fridge, chill over night and then put it in the spare bathroom and let it ride. Nice thing about saisons is that if you can't control your temps super well all you need to do is keep it warm.

[redbeerman]

I don't know whether WLP565 is the same strain, but it is notoriously slow getting to a high level of attenuation.  The last saison I made (super saison actually) started at 1.065 and finished at 1.004.  I let it ferment for about 10 days at 65F, it was at 1.012, then put it in my garage around 75-80F and gave it a gentle stir (being careful just to rouse the yeast, of course) for a few days and it went down to 1.004.  I have it on oak right now aging. Tasting I have done shows a very good result.  I prefer this yeast over others I have tried (so far).  Ron and I are going to do an experiment with various saison yeasts and spice/ fruit mixtures in the near future, we will see what happens.

[gordonstrong]

I think I heard at the NHC this year (or someplace else around the same time) that the Saison yeast has a higher oxygen requirement than other yeasts.  Perhaps that could be one constraining factor in reaching the highest attenuation.

I was likely drinking at the time, so it would be great if someone had a real reference to cite.  But it's something I think I'll try next time.  Maybe hit the wort with pure O2 for 2 min and see how the yeast like that.  Or just make it now when the ambient temps are favorable...

[nateo]

PH can drop dramatically during fermentation. Some yeast make pH drop more than others. I haven't done enough experiments to confirm this, but my WAG is that some Saison strains stall out because they drop the pH too low before they can finish fermenting. This phenomena is something I've noticed when making mead with different wine yeasts. Since some Saison strains may be directly descended from wine strains, this may be an issue.

Has anyone using those strains kept notes about pH during ferment?

[euge]

So maybe a tiny bit of bicarbonate at a key time (before it actually stalls) might help avoid this problem?

[nateo]

So maybe a tiny bit of bicarbonate at a key time (before it actually stalls) might help avoid this problem?

The easiest thing to do would be to rouse and degas once it's been fermenting for a few days. I've read stirring in a low-gravity wort decreases ester formation. CO2 in solution = carbonic acid. But CO2 in solution doesn't explain all the pH variation I've noticed in mead fermentation.

I use a 2N caustic potash solution when making mead. I've definitely noticed a correlation between the worst stallers and the biggest acidifiers. I would worry about using bicarbonate because it's such a weak base you might get some off-flavors with too much of it. A little bit of slaked lime would be a better way to go if you don't have food-grade KOH. But that's assuming you've been monitoring pH and can dose it with the proper amount. You also need a plan for when you over-do the base addition and need to add some acid to brighten it up once fermentation is done.

[denny]

PH can drop dramatically during fermentation. Some yeast make pH drop more than others. I haven't done enough experiments to confirm this, but my WAG is that some Saison strains stall out because they drop the pH too low before they can finish fermenting. This phenomena is something I've noticed when making mead with different wine yeasts. Since some Saison strains may be directly descended from wine strains, this may be an issue.

Has anyone using those strains kept notes about pH during ferment?

If that's the case, why would raising the temp (the recommendation for finishing most saison fermentations) work?

[nateo]

If that's the case, why would raising the temp (the recommendation for finishing most saison fermentations) work?

I think there's an obvious correlation between high ferment temps and high yeast activity. Bamforth talked about any 10*C rise in temp doubles the activity of bacteria. We know low pH inhibits yeast activity. We know increasing temp increases yeast activity. I'm just saying raising the temp might achieve our attenuation goals without addressing the cause of the inhibited activity, but without detailed notes of fermentation pH it's just a WAG.

Even if I'm right, you'd still need to weigh the pros and cons of each method to achieve your goals. Higher temp means faster oxidation and increased fusel production. A heavy hand when adding bases can result in unpleasant mineral flavors.

Wine yeasts can also have dramatically different nitrogen needs. Wort contains a lot of FAN so brewers don't really care about this, although wine yeast generally does better with staggered nitrogen additions, instead of a lot upfront. Maybe Saison yeasts are crapping out early because of FAN deficiency?

[redbeerman]

Not all Saison strains have relatively low attenuation.  WLP566 and WY3711 have attenuations well into the 80s.  It seems the classic Belgian saison strains WLP565 (65%-75%) and WY3724 (76%-80%) are the lower attenuating strains.