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EDIT: Crap, it appears I mislead myself. Northern Brewer includes a temperature range of the particular Wyeast you are using, and I assumed this temperature range factored out off-flavors. I read on this stackexchange that it is a good idea to let the temperatures rise after the initial 3-5 days of fermentation. I assumed this meant to the top of the temperature range specified by NB/Wyeast. My Belgian Ale I allowed to go roughly 78*F during the day times. My Cream Ale I allowed to go specifically 71-72*F nearly round the clock. Regardless, I enjoyed this discussion and learned something about yeast starters and temperature!

I have used a yeast starter for my last 3 batches. Two of these batches are bottle conditioning for carbonation, but I took two of them out to test a few days ago.

They were so full of esters that my neighbor referred to the first one as "Bananna Beer", and the second one as "Strawberry Beer".

...

One of the batches that I am annoyed about in particular was a Belgian Trippel that took about 6 weeks (+2 weeks bottle conditioning) and required a secondary, and was the most expensive extract I've bought so far. The other batch was a creme ale that took 2 weeks (+ 2 weeks bottle conditioning).

I've never had the fruity-beer problem because I've done a fantastic job at controlling temperature with a swamp cooler.

However, I can't use a mini-swamp cooler with my yeast-starters, as my home-made stir-plate can't hang.

Questions:

1) Is fruity flavoring always and everwhere a side effect of high-temperature and ester production, or may sanitation problems also generate fruity flavoring?

2) If fruity flavoring is always and everwhere formed by high-temperatures, is it better to forgo a yeast starter if it is not possible to control the temperature of the yeast starter? I also figured that maybe a 12 hour yeast starter at night time would be better than 72 hours in higher heat.

Thank you.

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This is not an answer to your question, so I'm putting it as a comment. The temperature of your yeast starter should not play a role in the ester formation in the larger batch of beer. If you're not doing this already, cold-crash the starter for 24-48 hours before pitching. This will force the yeast to drop out of suspension. You can then decant and throw away the starter beer, which may be estery, and pitch just the yeast. –  Tobias Patton Aug 7 '13 at 23:24
    
@TobiasPatton Thanks for informing me that it shouldn't effect the larger batch. I am pretty sure that I did not cold-crash and decant the first one. I did however cold-crash the second yeast-starter. They both turned out fruity. Hmm perhaps fruity flavors can come from something other than temperature problems. –  Matthew Moisen Aug 7 '13 at 23:27
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Sounds like they fermented higher than you thought they did. How did you read your temperatures? Were you by chance reading the temperature of the water in the swamp cooler, and not the beer itself? –  Scott Aug 8 '13 at 3:53
    
@Scott the Belgian I didn't measure correctly, as I only measured the swamp, but the particular yeast strain allows up to 78*F. The Creme ale I measured directly, and from that I believe the Belgian was fine. homebrew.stackexchange.com/questions/10337/… –  Matthew Moisen Aug 8 '13 at 14:22
    
Regardless of whether or not the yeast says it can allow for up to 78*F, that is incredibly high for yeast, and you will most certainly get some of the characteristics you described by fermenting even remotely close to that temperature. I recently did a farmhouse ale, fermented exclusively with Brettanomyces, which requires 85*F+ temperatures, and aside from the crazy sulfur aroma it had at first (was able to bleed most out of the keg), the thing literally tastes like I'm drinking liquid pear. If you get into the 70's or higher, expect esters and off flavors. –  Scott Aug 8 '13 at 14:38
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3 Answers

First, unless the starter temp goes over maybe 90F, there is no damage to the yeast itself. second, for a starter of the size that you'll need for a tripel, the best course of action is to decant the spent wort before pitching so it won't have any flavor effect on your beer. remember, with a starter you're growing yeast, not making beer, and a starter generally grows better at warmer temps. Another thing to be aware of is that temp ranges listed by yeast manufacturers are based on yeast performance, not what makes the best beer. You will almost always make better beer by avoiding the higher end of the range. Even if you do use a higher temp, you should start the fermentation at a lower temp for the first few days, when the majority of esters are produced. Now to your specific questions...

1.) Ester production is not always caused by high temperatures. That's just one factor. Another is pitching rate. Contrary to what has been repeated over the years, a too high a picthing rate can lead to increased esters due to the effects of the enzyme acetyl CoA. This has been cited both by Neva Parker of White Labs as welll as Dr. Clayton Cone of Lallemand. her's a link to Dr. Cone's statement. http://www.danstaryeast.com/articles/yeast-growth Ms. Parker talks about it here in her presentation "Yeast Mythbusters", although you have to be an AHA member to access the info..http://www.homebrewersassociation.org/attachments/presentations/pdf/2012/1616-08%20Fermentation%20Mythbusters%20-%20Neva%20Parker.pdf

2.) It is absolutely NOT better to forgo a starter in higher temps. As noted above, you want to let the starter ferment to completion, then decant the spent wort. Even if that wort has a high level of esters, the yeast slurry will carry them into the beer. A 12 hour starter doesn't give you enough time for the starter to ferment out and drop the yeast so you can decant.

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Thanks Denny. Could you check my edit to my post above? Now I am curious: I've read here on SO that it is good to raise the temperature of the fermentation after 3 days, which supposedly reduces byproducts of the yeast (other than alcohol). It was because of this theory that I raised my temperatures to the maximum listed on the Wyeast, thinking that the listed temperature ranges would naturally factor out off flavors. –  Matthew Moisen Aug 9 '13 at 3:56
    
In regards to your response to Q1, this is interesting: for the Creme Ale (1.040 OG), I did a 1L yeast starter and saw no activity in the airlock, so I bought another Wyeast pack and dumped it in straight. It turns out my bucket was leaky and it was already fermenting. I know its pure speculation at this point, but I fermented the Creme Ale at 60*F for the first week, then 71-72*F for the second week, yet it is perhaps just as fruity flavored as the Belgian which I fermented roughly 78*F for 3 weeks-- would a yeast starter + additional packet of yeast be a culprit, or is it the 72*F? –  Matthew Moisen Aug 9 '13 at 3:59
    
I'd say it's both. As I pointed out, overpitching can potentially increase ester production. Together with the temp (a cream ale is kind of a hybrid beer and should be fermented cooler) you could experience increased esters. –  Denny Conn Aug 9 '13 at 15:54
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You can get esters from under-pitching as well as high temperature control, so skipping the yeast starter will be much worse than a starter without temp control, since you will be significantly underpitching.

I'm guessing the Trippel was a fairly big beer, for which you need a proportionally larger yeast starter and then some. A 1.080 beer would need a 4 liter starter (2l if on a stir-plate.) 4l is a significant part of a 5gal (19l) beer and could affect the taste of the beer, particularly a light flavored beer like a Trippel - given that starters should be fermented warm, it could easily have been a fruit-bomb. That's why it's advised not to pitch the starter wort but decant and pitch only the yeast.

While your swamp cooler may have worked well for other beers, the increased rate of fermentation for the big beer could have pushed the temperature up higher than in previous brews. Also, swamp coolers do suffer temperature swings which produce further stresses on the yeast and more esters.

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I use a stir plate, and should have done a 2L like you suggested but only did a 1L. It was also my first yeast-starter, so I imagine I screwed up somewhere (especially by pitching directly). The belgian's yeast had a maximum temp of 78*F. Something I did however was add too many frozen water bottles because I didn't at the time know how large of an effect 5 bottles had. This most likely caused large temperature swings, but I'm sure it was still under the range of 78*F. –  Matthew Moisen Aug 8 '13 at 14:27
    
mdma's last point is key. The higher the gravity, the higher the yeast will push the internal temperature of the wort, therefor the more ice you need to account for with your swamp cooler. –  Scott Aug 8 '13 at 14:41
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(To echo a comment on your post…) the temperature of the starter shouldn't affect the larger batch. Please describe the temperature control of the ferment itself, plus please describe the parameters of the starter. Both fermentation temp issues and/or underpitching (which might still be the case if your starter just isn't big enough). Also, what did you do for wort oxygenation and nutrients on the Tripel?

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homebrew.stackexchange.com/questions/10337/… This and the two links in the first sentence describe the temp control process. The starter was only 1Liter, not 2Liters as MDMA correctly states I should have done. I areate with an areation stone. The nutrients I used came from the Wyeast smack-pack-- I didn't add any. –  Matthew Moisen Aug 8 '13 at 14:25
    
It's a good idea to add nutrients both to the starter and to the wort when making a big beer. I'm not even sure there are any significant quantities of nutrients in a smack-pack, just growth media (wort.) –  mdma Aug 8 '13 at 14:58
    
@mdma thanks I did not know that. –  Matthew Moisen Aug 9 '13 at 4:01
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