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paulh
10-02-2008, 06:31 PM
I've never read anything about acclimating the rehydrated yeast to the temperature of the must. I have always just dumped the yeast right into the must after 10 or 15 minutes.

If the yeast is rehydrated in ~105 water and sits for the recommended time, I doubt it's dropped a whole lot (but have never checked it). Maybe down to 90? That's a big difference from 65-70 and can't be doing the yeast any good.

I've never had problems, just wondering if anyone takes the time to acclimate the yeast to the must temperature.

Medsen Fey
10-02-2008, 06:52 PM
I've never had problems, just wondering if anyone takes the time to acclimate the yeast to the must temperature.


Yes, particularly if I am starting with a high gravity must or something I think might be a difficult fermentation.

liff
10-02-2008, 07:20 PM
As for acclimating the yeast rehydration to the must: Every ferment, every time. It seems to work best for me. I have never run two batches at the same time, but I think I notice a difference, so I do it every time.

paulh
10-02-2008, 09:14 PM
Wow, two quick responses saying that both do. I've never found anything before saying this should be done. It was just something that recently came to mind.

So, what's your method?

wayneb
10-03-2008, 12:56 PM
My method's about as simple as it gets. I rehydrate in the warm water with go-ferm, then after about 15 minutes I'll pour in a half-cup of my must at its ambient temperature to the yeast slurry. That small of an addition won't thermal shock the yeast too much, and it provides enough nourishment for the rehydrated yeast to keep them going for up to another 30 minutes or so. That's usually more than enough time to get the yeast temperature within about 10 degrees of the must temperature, and it provides an added advantage of "proofing" the yeast... you'll get obvious signs of fermentation with most yeast strains within 30 minutes of adding a must sample.

liff
10-03-2008, 01:16 PM
My method is the exact rehydration proceedure from GoFerm, then my own take on things.  Original link. (http://www.scottlaboratories.com/info-center/faq-fermentation.asp#nutrients)

Q: When should I add GoFerm? How much should I use?
Go-Ferm should be added in the rehydration water of the active dried yeast prior to the yeast addition itself. The recommended dose is to add 2.5 lb Goferm/1000 gal (of total juice/wine) into 20 times its weight of clean 43°C(110°F) water. Stir the GoFerm to dissolve. For optimal performance, maintain a ratio of 1 part yeast to 1.25 part GoFerm.


So...  8 grams of yeast, 10 grams of Goferm, and about 200 ml  of water (6 ounces is about 180ml).  Wait 15 minutes.  I use bottled water at room temp, so that is about the temp of the must, so from here, 3 ounces of water and 3 ounces of must (same temp) and add it to the rehydration nutrients.  12 ounces total at this point.  I wait anywhere from 30 minutes to an hour, with the rehydration container covered, but not sealed in any way.

After 30 to 60 minutes, I put in 6 ounces of must for a total volume of 18 ml.  About 30 minutes later, 6 more ounces, to 24 ounces.  30 minutes after that, 6 more ounces.  Now I have a quart sized solution of very happy yeast.  Yes, this takes 2 to 3 hours, but I like it.  There is no scientific proof that it works, but I like it, so I do it.

Clearly the pitching temperature was equal a long time before I actually pitched, so why do I go through all of that trouble?  2 reasons.

First, If the yeast are acclimated this way, there will be little to no osmotic shock.  Osmotic shock (http://en.wikipedia.org/wiki/Osmotic_shock) is the real reason that I do this, the temperature differential is a secondary concern for me.  I am not making a starter, rather, I am acclimitizing the yeast to the osmotic pressure of the must so that I do not stress them at the pitch, which is when I want them going strong.

The second reason is I want the yeast going strong.  The more healthy, acclimatized yeast I pitch, the less chance of a different wild/unwanted yeast getting a head start in my must.

Two final thoughts I didn't fit in well:
1)  Pure, undiluted Honey will stop bacterial/fungal growth because of the osmotic pressure differential (dehydrates the cell).  So when making mead, excess or sudden changes of osmotic pressure due to honey is not your friend.  High gravity musts are harder because of the higher osmotic pressure on the yeast, but yeast can handle this if they get to break into the new pressure slowly.

2) 

As for acclimating the yeast rehydration to the must:  Every ferment, every time.  It seems to work best for me.  I have never run two batches at the same time, but I think I notice a difference, so I do it every time.
  If you acclimatize the yeast for osmotic pressure, the temperature thing is a non-issue. 

Liff

paulh
10-03-2008, 01:44 PM
My method's about as simple as it gets. I rehydrate in the warm water with go-ferm, then after about 15 minutes I'll pour in a half-cup of my must at its ambient temperature to the yeast slurry. That small of an addition won't thermal shock the yeast too much, and it provides enough nourishment for the rehydrated yeast to keep them going for up to another 30 minutes or so. That's usually more than enough time to get the yeast temperature within about 10 degrees of the must temperature, and it provides an added advantage of "proofing" the yeast... you'll get obvious signs of fermentation with most yeast strains within 30 minutes of adding a must sample.


Sounds easy enough: just give them a little snack to hold them over while they cool down a bit more.

wayneb
10-03-2008, 02:27 PM
Yup - and although I'm not as fastidious as Liff, the addition of must to a nearly equal amount of rehydrated slurry steps the yeast from zero sugar to half of what they'll see in the main batch of must, so they get temperature and osmotic acclimatization at the same time.