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Old 03-31-2009, 06:18 PM   #1
malenkylizards
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Default Yeast starter temperature, technique and forensics

Hi again guys,

So my Peppa Ya Mango Mead never came to fruition, because I was ascared for my yeast. Full details in another of my posts on a beer forum, but quick synopsis: I got impatient, due to a post-midnight start and sleep deprivation, with my yeast starter, and pitched the yeast while it was still warm. I wasn't thinking clearly and didn't even take a temperature, foolishly, but the *jar* felt lukewarm, i.e., above skin temperature, i.e., above 92*F, call it 97-100*F, and that's on the wrong side of the glass. I've gotten conflicting messages from folks, some saying that the yeast will die in that temperature, some saying they'll not just survive but thrive and ferment very vigorously. Anyway, after 24 hours, there were scarcely any bubbles, and I decided not to brew. The next morning, however, I wasn't sure what to make of it. There was a thick brown sludge on top. I thought it could be either the result of a very good, vigorous fermentation that was just off to a late start, or something horribly, horribly wrong. I didn't feel comfortable wasting a lot of honey and mango and TLC on this risky looking thing, and none of my advice-toting pals were picking up their phones, and at this point the weekend was shot anyway, so I just tossed the stuff.

<tangent>I plan on restarting this Saturday, and won't let anything get in my way...er, unless my yeast doesn't arrive on time. I decided to stop paying $7 per five gallon batch on wet yeast, when the dry stuff seems to work just fine for everyone else. I also couldn't get to my local homebrew store, so found an online distributor, Homebrew Heaven in Washington State. I'd like a closer supplier so I don't have to spend extra on shipping if I want it here soon, but it'll do for now. I bought ten packets of Red Star Pasteur Champagne Yeast, along with some potassium bisulfite and some sparkalloid.</tangent>

Anyway, back to topic. Assuming the yeast arrives in a timely fashion, I'll be making the yeast starter this Thursday, but even if I don't, and even if I somehow botch this yeast starter as well, I'll make the mead and just pitch the dry yeast. I'll always feel safer with a yeast starter though, so I'd like to get a good detailed, yet easy, technique down, compared to my relative winging it this last time.

Roughly, here's my plan that I'd like to edit for detail and efficiency: I'll start by sanitizing one of my five-pound honey jars. I'll stir up a cup of honey, three cups of water, a handful of raisins and some pieces of the fruit [mango] I'm using, and heat it on low, before pouring it into the jar, and putting it in the fridge for half an hour or until it gets close to 70*F. At this point I'll sanitize a clean, freshly laundered cotton dishtowel, dissolve some potassium bisulfite in warm water, and soak the dishtowel in it before wringing it as bone dry as I can. Aerate like crazy, pitch yeast and stir, then rubberband the dishtowel on top. Then just wait.

Questions:
1. WTF happened to my last starter???

2. Sulfite on the towel was an idea I got from meadmadecomplicated.org, to keep foreign entities from entering/surviving. I don't follow their instructions to the letter because, well, they're anally compulsive, but when something has a reasonable safety-to-difficulty ratio, I might as well. However, I'm nervous about the proximity of my poor little baby yeasts to that toxic stuff. Which concern is right? Does it matter one way or another?

3. Temperature. What temperature should I bring it to to pasteurize, and what range should I strive for when pitching? Any good ideas for how to bring the temperature down more quickly? I've got a copper coil for running hose water through, but that fits in my twelve gallon stock pot, not a half-gallon honey jar. I could add ice but you can't really pasteurize ice, in which case you might as well not pasteurize at all. If this is the only/easiest way to do it, I might mix up the must the night before I pitch, let it stabilize at room temperature overnight and cap it with the original lid, then prepare towel, aerate, pitch yeast and seal.

4. I've only used wet yeast before. Anything I'll need to consider with the dry stuff? Do y'all know if it has a shelf life? Do I need to rehydrate it BEFORE making the yeast starter, or does that count as rehydration?


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Old 03-31-2009, 08:47 PM   #2
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Yeast starters aren't necessary when you pitch properly rehydrated active dry yeast. I know, that seems like heresy to a beer brewer accustomed to working with wet yeasts, but honestly you have more than 10x the number of active cells from a rehydrated 5 g packet of active dry than you do from any commercial wet strain tube or activator pack. Starters aren't necessary unless your must is really high gravity (say over 1.130) and even then, they're used more to acclimate your yeast to the high gravity than to build up a larger colony of cells.

But if you really want to do the starter, then I'd recommend mixing up enough honey, juice and/or fruit in your starter to give you a gravity that is roughly half of the starting gravity of your main must. Then rehydrate the yeast according to the instructions from the manufacturer (I think I remember that Red Star recommends water at 90 to 100F, but my numbers may be off a bit). Add NO nutrients until you see signs of active fermentation in the starter. Also, raisins aren't really necessary, and since many commercial raisins are treated with sulfite powder you might be adding some sulfite to your starter that you didn't intend to. Likewise heating and subsequent cooling of the starter aren't really necessary. For that matter, no fruit is really needed in the starter -- honey and water are fine.

Also, if you want to pre-sanitize your starter with K-metabisulfite (I don't bother), then please let it stand for at least 24 hrs before adding that rehydrated yeast. 48 hrs would be better, to allow enough time for the sulfite to dissipate. As far as sulfite soaking the towel, I also have found this to be no problem for your yeasties as long as you wring out the towel first. Personally I now use Star San to sanitize the towels that I place over my primary fermenters.

Almost forgot - let me address your specific questions:

1) Don't really know, but if that must temp was too hot, that would do in your yeast. Even if it isn't technically at the temp that kills yeast outright (above 110F for 10 minutes or longer), a thermal shock of greater than 10 degrees difference between the starter and the must can do them in.

2) No worries as long as the towel isn't dripping toxin into your fermenter.

3) Do not worry about pasteurization for mead musts. If you're worried about fruit, then instead treat them with enough sulfite to sanitize, then wait as I indicated above before putting the fruit in your must. Full strength (as in not diluted) honey is naturally toxic to all common mead spoilage organisms, so as long as you mix your must with clean water (pasteurize the water by boiling, then cooling in a sealed container if you're worried), you'll be safe. Strive for the temperature differential between your yeast and the must to be less than 15 degrees F if possible. Less than 10 degrees is even better.

4) Dry yeast tends to supply far more cells than you'll need for a strong fermentation as long as you rehydrate first. You can pitch dry directly into your must, but many of the cells will have a hard time properly rehydrating that way, so you're better off in plain water, or in water with ONLY a rehydration nutrient (like Go-Ferm) added. They do have a shelf-life, but generally the larger homebrew suppliers turn them over quick enough that you can consider them good to go if you keep the packets in a fridge, for a year or longer. Some (but not all) yeast packets are date coded.



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Old 04-01-2009, 09:22 PM   #3
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Goddammit, I just replied to your post but the computer I was using froze, so let's try and recap.

First off, thanks for the detailed help, Wayne!

I think I will do the starter, especially given the fact that it seems I can cut a lot more corners than I thought; this is a cinch, and pretty much guarantees a fast start. Last batch, I pitched at maybe 10 pm, and woke up less than 12 hours later to find it fermenting so vigorously that fruit had popped up to clog the airlock >:-(, and later explode all over the ceiling, and my face, when I tried to open it up. Oh well, I learned about the magical value of headspace, and not having five pounds of whole fruit [I'll be liquifying the stuff from now on].

I will just do honey and water per your advice. I *might* add nutrients, but I mean, I'll be starting it 36 hours prior to starting the batch, so I might as well let 'em wait too, I gather.

I don't think I want to pre-sanitize my starter with K-metabisulfite, unless it's an ingredient in One-Step [and despite the fact that it's a non-rinse, I'll ******* [kudos, HBT, on your fine and thorough filtering system! I shall have to come up with a new word for piercing a piece of food with a fork] be rinsing it because it doesn't look or smell like anything I want to drink]. I'm curious about these towels that you use over your fermenters though...is this in addition to, or in lieu of, an airlock?? I'm not sure I understand what the point would be in addition, and it sure seems silly not to have an airlock to me.

Re: temperature, that makes a lot of sense, and is probably what did it. The yeast was in the fridge for week or more, and set on the counter several hours prior to pitching it in the starter...so it was room temperature, but the starter must could've been 30 degrees above that. One thing though, the dried yeast is gonna be room temperature, so wouldn't rehydrating it in 95' water be a 25 degree shock? Why wouldn't that destroy 'em?

Another rehydration question, I'm not sure when that's expected to happen...can it happen immediately before pitching, or does it need minutes/hours? I know it'll need some time to get to the same temperature as the starter, starting at 95' and cooling to, say, 75', but does it need more time for, say, the yeast to strengthen?

I would only pitch it dry if, for whatever reason, the yeast starter fails, which I'm not expecting. If I do have to do that, what are the risks? Will it just take longer to rehydrate, or could it keep them from starting/rehydrating at all?

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Old 04-01-2009, 09:45 PM   #4
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It kind of makes no sense at all to rinse a no-rinse sanitizer. Considering the value of a no rinse is that you don't have to risk rinsing with water that may be unsanitary (if you are using tap water). Get as much of it out as you can and seriously don't worry. The stuff is perfectly safe to drink and if you get as much out as you can, it will have absolutely no effect on taste for your brew.

He is referring to using an open top fermentation for primary. A lot of people do their primary in a bucket with a clean cloth on top. This gives tons of surface area for the co2 to escape in, since its production is so vigorous in the early stages. The cloth's only purpose is to keep flys, bugs, and hairs from falling in, since it is producing so much co2, o2 is a non-issue especially since its not a bad thing in the beginning.

Read the instructions on the yeast package for rehydrating. I believe the magic number is 20 or 30 minutes, you can't let yeast stay in the water for more then that or they start dying from a lack of food.

Dry yeast is basically dormant, its alive but not kicking per say. Rehydrating wakes them back up, but doesn't provide any food for them. That is why the difference in temp isn't a big deal. It is more a big deal when you are introducing active yeast to a temperature differential. Say if you use the starter you plan and put that into a higher temp must.

I pitch dry all the time, but more often just rehydrate and then pitch. Rarely need for a starter as wayne said, only time I have used it has been for two very high OG musts.
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Old 04-01-2009, 10:19 PM   #5
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Hightest's Mead FAQ are loaded with tons of info including a page devoted to rehydrating and pitching yeast. Also check out his new pitching method.
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Old 04-02-2009, 05:49 PM   #6
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Both Tusch and travesty have said much of what I was going to say (especially the part about Hightest's FAQ about rehydration). But I do have a few more thoughts to share with y'all. First, just pureeing or finely chopping up fruit won't keep it from rising to the top, forming a cap, and perhaps blowing out your airlock (and creating a mead volcano in the process). That's why I use the sanitized towel trick. You cover your open bucket fermenter with a sanitized, tight woven cotton towel that is big enough to completely cover the opening, and I secure mine in place with a bungee cord around the outside of the bucket. You don't need an airlock for the first part of primary fermentation. As Tusch already said, so much CO2 is created and released up until you get down to the 1/2 sugar break or so, that the must naturally forms a protective blanket of CO2 above it. The towel keeps any large foreign objects from falling into the bucket, and the venting of CO2 thru the weave in the towel keeps any nasty microbes from getting in. This, coupled with the fact that mead fermentations actually benefit from more exposure to oxygen over the first 1/3 of fermentation or so, makes the towel trick actually more desirable than the traditional lid and airlock approach. I do replace the towel with an airlocked solid lid after the rate of fermentation in the primary slows down -- usually at about the 1/2 sugar break.

Again, rehydration is the process of "waking up" yeast that have been put into a natural state of dormancy. In the real world, yeast cells will naturally dehydrate toward the end of the growing season if they haven't found a nutrient medium (like a piece of rotting fruit) to grow in. They naturally rehydrate better in warm water -- up to a point. During rehydration the warmer water actually helps them to restore cell wall integrity faster. But once they are fully rehydrated, you want to make any subsequent temperature changes pretty gradual, or they can be thermally shocked and die. Also, they need nutrient (sugars at least) within 20 to 30 minutes of the start of rehydration, or they become malnourished and can die. So my approach to rehydration is almost like making a mini-starter. I rehydrate in the warm water as recommended by the manufacturer, but after about 20 minutes I'll add a small amount of my main must (about a cup) to the rehydrated yeast slurry, which both feeds them and helps to adjust their temp down to that of the main batch in a less shocking manner. Then, about a half hour or so after that, I'll pitch.

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Old 04-02-2009, 09:33 PM   #7
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Hmmm...I definitely see your point. But I thought that while aerobic environments were good for yeasts to grow and multiply, they aren't going to do a lot of fermenting in said environment.

The process I understood is, you pitch the yeast right after vigorous aeration, then pop an airlock on top. Their environment is aerobic at first, so they multiply, and as they eat up the O^2 to multiply, the must becomes more and more anaerobic, so they switch their mind back to fizz mode, as the great Warren-to-the-G might say.

But clearly, y'all have been making booze in aerobic environments. What am I misunderstanding? Perhaps the most important thing is when you make the change?
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Old 04-02-2009, 10:07 PM   #8
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That approach is perfect for brewing grain beverages, since you'll be done (in most cases) before the yeast reach their ethanol tolerance. With winemaking and meadmaking, you will want to get your yeast as robustly healthy as possible, and early additions of O2 are actually beneficial. It is an old brewer's tale that yeast do not produce alcohol in an oxygen rich environment. They do (although at lower efficiency than when they're anaerobic) especially early on in their lifecycle, and the O2 present in your must will help them not only to bud, but also to build proper osmotic barriers in their cell walls as the colony develops that allow them to ferment sugar more efficiently once they get to the anaerobic part of fermentation. The only worry is that you don't want to introduce so much O2 late in fermentation that it is not all utilized. In that case, you'll promote oxidation of the mead, and perhaps inadvertently aid the development of undesirable infections, such as acetobacter. However, the yeast are perfectly capable of using all the O2 that you can introduce via an open bucket, even with daily vigorous stirring, until past the 1/3 sugar break. So I typically stir the $#!& out of my musts a couple of times a day, splashing vigorously, until the 1/3 sugar point, and then often keep the towel in place rather than a hard cover until about the 1/2 sugar break. By that time your must isn't producing enough CO2 to keep a semi-open headspace like that fully purged, so a sealed, airlocked lid is necessary.


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