How To . . . Rehydrate Yeast

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How To . . . Rehydrate Yeast

Postby Aleman » Sat Apr 05, 2014 16:28

Hardly the most complex of how to's this one It does surprise me the number of methods that people use, and most of them are not correct . . . . for brewing yeast! Bread yeasts are a completely different animal . . . actually they are not . . . and the requirements are different.

Firstly you need to use the correct amount of water, not wort or a sugar solution but normal tap water . . . preferrably water with a medium to high mineral content. The reason for this is simple, when you add a dehydrated yeast cell into a solution it rapidly absorbs liquid, but the yeast membrane is not selective at this stage and allows 'everything' and 'anything' across the membrane, including all those sugars and minerals. This can cause extreme osmotic stress to the poor yeast cell as it tries to wake up, and it will either end up poorly or could even explode and die, not a good result really, so just medium to high mineral content water.

Secondly the right amount of liquid should be used . . . Fermentis suggest using 10 times the weight of water as yeast, so an 11g sachet of yeast needs 110g of water (which is as near as dammit 110ml), 100g of yeast needs 1000ml

Thirdly, the water, after boiling to ensure sterilisation, needs to be at the correct temperature, and this varies for variety to variety. Nottingham for example needs to be at 36C . . . Fermentis Saflager W34/70 needs 21-25C, . . . SO4 needs 25-29C. Lallemand report a 20% loss in viability compared with rehydrating at 30C instead of 36C . . . and if you are close the limit for under pitching this could be an important factor. DO NOT guess the temperature! Use a thermometer! This is one of the easiest things to do, and guessing wrong will almost certainly kill your yeast.

Fourthly, Sprinkle the yeast onto the surface of the cooled water and stir gently to mix it in . . . I know it just says sprinkle it on and leave it . . . but you need to stir it to mix it in, (I actually use my stir plate while pouring the yeast into the sterile conical flask), and then leave it to stand (covered) to rehydrate usually 15-30 minutes depending on variety, (Lallemand say 15, Fermentis 30).

Fifthly, as you are filling the FV with cooled wort, give the yeast another stir, and pour it into the Fermenter.

Result, Happy yeast ready to get cracking to turn your wort into luscious beer.

This recent experiment should give you some rehydration temperatures to play with.

please note:The use of punctuation, bold, underlining, italics, and different sized type, follows the convention used in writing, for many years, to place emphasis on the point being made, and to highlight the importance of that point in the opinion of the author. It is not the intention of the author to shout, if that was the case the author would adopt the, much more recent, convention of using all capital letters.
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Re: How To . . . Rehydrate Yeast

Postby Barney » Sat Apr 05, 2014 19:50

Thanks for that Interesting post and the link. I had not realised the importance of both temperature and rehydration. I had been thinking "oh its only dry yeast just chuck it straight into the fermenter" . I will change my approach a little with that extra insight.
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Re: How To . . . Rehydrate Yeast

Postby Dusty » Sun Apr 06, 2014 16:20

Very informative,thanks :cheers:
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Re: How To . . . Rehydrate Yeast

Postby Mark » Mon Apr 07, 2014 23:09

Thanks Aleman. Could you suggest a brand of bottled water that would be suitable?

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Re: How To . . . Rehydrate Yeast

Postby BarnsleyBrewer » Tue Apr 08, 2014 00:15

A good how to Aleman


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Re: How To . . . Rehydrate Yeast

Postby Sqrson » Tue Apr 08, 2014 08:17

Ths for the info :cheers:
What temp would you recommend for dreaded Wherry yeast :?: I never rehydrated yeasts before, but will do for that one

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Re: How To . . . Rehydrate Yeast

Postby Aleman » Tue Apr 08, 2014 08:54

Mark wrote:Could you suggest a brand of bottled water that would be suitable?

Look for one with a typical composition with a calcium level of 125-175 (slightly higher won't hurt)

Sqrson wrote:What temp would you recommend for dreaded Wherry yeast :?:

No idea, as we don't actually know what yeast is in the packet. (I'd guess at Muntons gold or Nottingham), 30C should give good results.

please note:The use of punctuation, bold, underlining, italics, and different sized type, follows the convention used in writing, for many years, to place emphasis on the point being made, and to highlight the importance of that point in the opinion of the author. It is not the intention of the author to shout, if that was the case the author would adopt the, much more recent, convention of using all capital letters.
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Re: How To . . . Rehydrate Yeast

Postby GaryG » Tue Apr 08, 2014 23:11

Aleman wrote:
Sqrson wrote:What temp would you recommend for dreaded Wherry yeast :?:

No idea, as we don't actually know what yeast is in the packet. (I'd guess at Muntons gold or Nottingham), 30C should give good results.


So you think buy a separate yeast that we know type meaning we know the correct temp.

I have always just poured the yeast on top of the warm wart. What will the benefits be in re hydrating when my kits have always turned out OK.


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Re: How To . . . Rehydrate Yeast

Postby oldjiver » Tue Apr 15, 2014 21:17

Having re hydrated with plain water, is there any advantage (after a certain time) in then adding malt/sugar to make a starter for adding later. Or is it just no advantage with dried yeast?
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Re: How To . . . Rehydrate Yeast

Postby Good Ed » Tue Apr 15, 2014 21:26

oldjiver wrote:Having re hydrated with plain water, is there any advantage (after a certain time) in then adding malt/sugar to make a starter for adding later. Or is it just no advantage with dried yeast?


No, dried yeast are designed to be rehydrated as Aleman's post above, it's then ready to go in your beer. If you start adding stuff to it and leaving it longer the poor things will be exhausted to do anything with your beer.

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Re: How To . . . Rehydrate Yeast

Postby oldjiver » Tue Apr 15, 2014 21:37

:hat: Reason I asked was that much store was made in the past of building up a great foaming starter with no difrentation made between dried and liquid yeasts. Times are changing!
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Re: How To . . . Rehydrate Yeast

Postby Bribie G » Wed Apr 16, 2014 01:19

Good advice above.
The Yeast Book by Chris White (the Whitelabs guy) states that around half the yeast cells can be killed by pitching them into wort or sugar solution.

I'm currently on the third generation of Danstary BRY-97 that started off as a dry yeast, but once it's gone through a brew then it can be treated as a liquid yeast from then on.
Re making a starter, it's tempting to try and breed up a big starter for a Lager from one packet of yeast, but as mentioned by Good Ed that's only going to confuse the yeast. Dried yeast is "bred" with good healthy cell walls packed full of all the lipids etc so it's good to go fairly quickly. If you make a starter it's not really going to breed much, just start fermenting as opposed to increasing cell numbers. If pitching into a cold lager it's best to use two packs.

I was talking to a brewer at a craft brewery last week and picking his brains about Lagers (the guy's German) and he said it's far better to pitch cold then bring the temperature up rather than under-pitch warm and drop the temperature in the hope that the yeast will breed up in the meantime. Can produce two quite different beers apparently.
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Re: How To . . . Rehydrate Yeast

Postby Good Ed » Wed Apr 16, 2014 21:02

Bribie G wrote:I was talking to a brewer at a craft brewery last week and picking his brains about Lagers (the guy's German) and he said it's far better to pitch cold then bring the temperature up rather than under-pitch warm and drop the temperature in the hope that the yeast will breed up in the meantime. Can produce two quite different beers apparently.


you're dead right there Bribie :thumb: , and welcome btw, I remember you from Another Place, for lagers Jamil always recommends pitching at 7C then bring the temperature up over 24-48 hours to 10C

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Re: How To . . . Rehydrate Yeast

Postby CraftyTim » Wed Apr 16, 2014 21:50

Aleman wrote:
Fourthly, Sprinkle the yeast onto the surface of the cooled water and stir gently to mix it in . . . I know it just says sprinkle it on and leave it . . . but you need to stir it to mix it in, (I actually use my stir plate while pouring the yeast into the sterile conical flask)


Do you have a fancy stir plate that allows you to 'gently' stir it in? My stirplate is pretty much on or off and it stirs fast and not too gently!

What are your thoughts about dried yeast storage? Is the freezer OK? What about an opened packet, can any unused yeast be used at a later date?

:cheers:

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Re: How To . . . Rehydrate Yeast

Postby Good Ed » Wed Apr 16, 2014 21:58

CraftyTim wrote:Do you have a fancy stir plate that allows you to 'gently' stir it in? My stirplate is pretty much on or off and it stirs fast and not too gently!

What are your thoughts about dried yeast storage? Is the freezer OK? What about an opened packet, can any unused yeast be used at a later date?

:cheers:


I find a spoon does the job, however it does need an operator :whistle:

Stored in a fridge unopened at typical temperature of 3C, it loses 4% of viability per year, so pretty good. Opened packets, not worth bothering with, and the freezer a no no.

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Re: How To . . . Rehydrate Yeast

Postby BarnsleyBrewer » Wed Apr 16, 2014 22:01

I buy a 500g pack of Nottingham that ferments everything I brew..
As soon as I open the pack I vacuum seal it into individual packs of 40g that ferments me 13 gallons..
I then store it in the freezer ;-)
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Re: How To . . . Rehydrate Yeast

Postby CraftyTim » Fri Apr 18, 2014 01:30

BarnsleyBrewer wrote:I buy a 500g pack of Nottingham that ferments everything I brew..
As soon as I open the pack I vacuum seal it into individual packs of 40g that ferments me 13 gallons..
I then store it in the freezer ;-)
BB


I knew the man from Barnsley would find the cheapest route.

Nice one :cheers:

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Re: How To . . . Rehydrate Yeast

Postby Aleman » Fri Apr 18, 2014 11:59

Good Ed wrote:Stored in a fridge unopened at typical temperature of 3C, it loses 4% of viability per year, so pretty good. Opened packets, not worth bothering with, and the freezer a no no.

Sorry Ed, but the freezer is the correct place to store dried yeast, there is nothing to be affected by the lower temperature.

Admittedly I suspect that the viability drop is not going to be significantly less than in the fridge at 3C . . .but the temperature in a freezer is much more constant.

please note:The use of punctuation, bold, underlining, italics, and different sized type, follows the convention used in writing, for many years, to place emphasis on the point being made, and to highlight the importance of that point in the opinion of the author. It is not the intention of the author to shout, if that was the case the author would adopt the, much more recent, convention of using all capital letters.
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Re: How To . . . Rehydrate Yeast

Postby Crankwood » Sat Apr 19, 2014 22:38

Some great advice, cheers Aleman
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Re: How To . . . Rehydrate Yeast

Postby Bribie G » Tue Apr 22, 2014 04:43

I generally freeze any unopened packs of dried yeast anyway. I once lost a sachet in there for about a year. It was only a kit yeast that I'd been keeping for emergencies, and out of interest I rehydrated it and pitched it into a litre of wort. It was crawling out of the vessel the next morning.
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Re: How To . . . Rehydrate Yeast

Postby rpt » Fri Nov 21, 2014 18:18

It's important to stir gently after sprinkling the yeast onto the surface of the water. This is better than not stirring so that all the yeast gets wet.

Lallemand's beer specialist wrote:You can stir slowly so that all the yeast is in contact with water. Vigorous stirring should be avoided because the cell membranes are fragile at the beginning of the rehydration process.

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Re: How To . . . Rehydrate Yeast

Postby Pjam » Tue Jan 06, 2015 15:29

Aleman wrote: not wort or a sugar solution but normal tap water . . .


I've started doing this instead of the 'Sprinkle' method and I've done it word for word ........ 'normal tap water' ......... it doesn't say normal treated tap water though. It's only 110ml but should I have taken from my campden tablet treated water?
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Re: How To . . . Rehydrate Yeast

Postby Aleman » Tue Jan 06, 2015 15:31

Ideally yes, but at 110ml in what will be a 25L batch (??) it's not going to cause any issues.

please note:The use of punctuation, bold, underlining, italics, and different sized type, follows the convention used in writing, for many years, to place emphasis on the point being made, and to highlight the importance of that point in the opinion of the author. It is not the intention of the author to shout, if that was the case the author would adopt the, much more recent, convention of using all capital letters.
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Re: How To . . . Rehydrate Yeast

Postby Pjam » Tue Jan 06, 2015 17:55

Aleman wrote:Ideally yes, but at 110ml in what will be a 25L batch (??) it's not going to cause any issues.


Phew. Still learning. Thanks Aleman :thumb:
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Re: How To . . . Rehydrate Yeast

Postby Pjam » Thu Jan 22, 2015 17:13

oldjiver wrote:Having re hydrated with plain water, is there any advantage (after a certain time) in then adding malt/sugar to make a starter for adding later.


In the case of NBS West Coast Style Ale Yeast I would say yes. It's a brilliant yeast IMO but very slow to start, 36 hours I've found! So re hydrating and then adding to a starter the day before pitching, would seem to make sense.

Unless you know otherwise?
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