goatchop41
Well-Known Member
I really don't care.
A pretty standard reply when your poor attempt at interpreting something has been thoroughly torn apart by sound logic and knowledge
New research on dry yeast
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A pretty standard reply when your poor attempt at interpreting something has been thoroughly torn apart by sound logic and knowledge
Jack of all biers
Well-Known Member
Some may not care, but if others do, I post the below. It has all be said in one form or another before.
As always, the right knowledge gives one more options with ones brewing. One can sprinkle yeast, but one should know the consequences that could occur and why. The why is the most important bit, as worts ain't worts and temperature is king when it comes die off of dry yeast upon initial rehydration. When death of yeast occurs, is just as important as when it doesn't occur. Viability is not the only issue, as health (vitality) is another. Does the brewer even want consistency? Is that consistency achieved by sprinkling for every beer brewed. Will the viability results occur for a high OG wort at the same rate as a low OG wort or in other wort variables. Should I do like common Kit&Kilo instructions and pitch (sprinkle) at 25C and then lower the temp to fermentation temp in say 24hrs? Do I not want to be bothered with that and pitch double or quadruple the quantity? All valid points to consider. Not knowing the answer to these can lead to annoyance and frustration in home brewing (financial loss in commercial).
No publication I've read says that all or every pitch of dried yeast direct onto wort will lose 50% of viability. In fact the Yeast book says "Do not attempt to rehydrate yeast in cold water." and then goes on to say
"Too cold a temperature can result in the death of more than 50 percent of the population." It is very unfortunate that they don't state what too cold is, but they do stress to follow the yeast producers instructions! So this 50% figure does come from a study or studies, but it isn't well referenced. Unfortunately the statement has been taken far and wide and misunderstood to a large extent.
Given we are talking about Fermentis, their website currently poses a question of 'Will a pitch temp outside of 25-29C (ie 18C) stun my yeast?' and answers it so. "The recommended rehydrate temperature is an optimal temperature. Outside this optimal range (as long as the temperature is above 10°C), you will not stun the yeast but you could get a longer lag phase at the beginning of the fermentation. Of course, this point is depending of the others factors influencing the fermentation (quality of the wort, fermentation temperature, starting gravity, etc…)." What this statement says is that above or below 25-29C non-optimal results (including viability) occur, but the interesting point is they state 10C is a critical temp (not explained, but put it together with the yeast book statement and I think it is clear).
Fermentis' website also currently states that a loss of 3-6% viability should be expected from rehydrating in wort as opposed to water. That statement is in the context of them being in the optimal temperature range.
So, under certain circumstances one can lose up to 50% viability. Think sprinkle pitching on a high OG wort at a cold temp (Doppel Bock for example). Most yeast sprinkle pitched at 18C probably won't lose 50%, but this would have to be OG dependant as to how much % is lost. So my point is, armed with this knowledge one can make the decision, knowing the consequences for resultant beers in different circumstances. ie one would know that sprinkle pitching 2 packets of dry yeast into a doppel bock at 8C, won't result in 120-200 billion cell viability, so one might pitch 4-5 packets. Pitching an Ale yeast at 15C in the same manner may result in a 25%? or 15%? or 10%? loss, so to counter that one may pitch 2 packets instead of 1. Know what you are doing.
So that deals with the viability (cells that live), but what about the affect on vitality (the health of the yeast)? The vitality is important too, as many cells don't die, but aren't then in the best of health after rehydration in mediums such as wort or at lower temps. This is why Fermentis' current study would be very interesting to see (when they release it), as it appears to show results of the resultant compounds in beer that good health with the affects those yeast had on the wort or the affects of their health (ie are they healthy enough to do a good job, not just are there enough numbers) [the two are sort of linked, but it isn't that simple).
This Youtube video is a brewer, who conducted a test with recorded results that show that 5% extra viability is lost by not hydrating Fermentis US-05 yeast, (sprinkled into 20C wort) compared with hydrating at 26.7C in water (in his one test). He approaches the whole thing with a level and balanced view and comes across as reasonable. I do highlight that his counting results are, well, unheard of, as he states 200 billion cells in a dry yeast pack (he's talking Fermentis 11.5gm packs) and states he calculated from his 3 test results a count of 263 billion from his 11.5gm pack. That's 22.9 billion cells per gram, which when compared to what Fermentis state as supplied 10 billion cells per gram and minimum of 6 billion cells per gram, makes his count a freakish result. So it does lead me to question his cell counting practice somewhat. His methods and results here https://drive.google.com/file/d/0BzNmUGsHZf7dOTZzZF9aQVluZXM/view
So with all that, I acknowledge the more I learn the more I realise I know very little. My question to @MHB or others with the knowledge or reference materials is this. Has that die off of yeast cells due to rehydration temp and media been found in studies happen fairly quickly or over a period of hours (ie longer than the 45min in the above test).
EDIT - and after typing all that, I forgot to say that the dry yeast should be brought up to temp first either way, but this goes for any yeast, so I hope it is obvious. Also dry yeast stored at 3C is expected to lose 3-4% viability over a year, so the above youtube test fits those expectations.
I would also like to say, that my personal view is that if rehydrating a packet of yeast into 110mls of sterilised water at 29C for 30mins (or what ever the producer recommends) is the step I have to take only saves 5-10% of my yeast and ensures they are in the healthy state the producer strove to achieve, then that is what I'd recommend for those to do who can.
I wouldn't leave my liquid yeast in the cupboard instead of storing it in the fridge for the same reason.
As always, the right knowledge gives one more options with ones brewing. One can sprinkle yeast, but one should know the consequences that could occur and why. The why is the most important bit, as worts ain't worts and temperature is king when it comes die off of dry yeast upon initial rehydration. When death of yeast occurs, is just as important as when it doesn't occur. Viability is not the only issue, as health (vitality) is another. Does the brewer even want consistency? Is that consistency achieved by sprinkling for every beer brewed. Will the viability results occur for a high OG wort at the same rate as a low OG wort or in other wort variables. Should I do like common Kit&Kilo instructions and pitch (sprinkle) at 25C and then lower the temp to fermentation temp in say 24hrs? Do I not want to be bothered with that and pitch double or quadruple the quantity? All valid points to consider. Not knowing the answer to these can lead to annoyance and frustration in home brewing (financial loss in commercial).
No publication I've read says that all or every pitch of dried yeast direct onto wort will lose 50% of viability. In fact the Yeast book says "Do not attempt to rehydrate yeast in cold water." and then goes on to say
"Too cold a temperature can result in the death of more than 50 percent of the population." It is very unfortunate that they don't state what too cold is, but they do stress to follow the yeast producers instructions! So this 50% figure does come from a study or studies, but it isn't well referenced. Unfortunately the statement has been taken far and wide and misunderstood to a large extent.
Given we are talking about Fermentis, their website currently poses a question of 'Will a pitch temp outside of 25-29C (ie 18C) stun my yeast?' and answers it so. "The recommended rehydrate temperature is an optimal temperature. Outside this optimal range (as long as the temperature is above 10°C), you will not stun the yeast but you could get a longer lag phase at the beginning of the fermentation. Of course, this point is depending of the others factors influencing the fermentation (quality of the wort, fermentation temperature, starting gravity, etc…)." What this statement says is that above or below 25-29C non-optimal results (including viability) occur, but the interesting point is they state 10C is a critical temp (not explained, but put it together with the yeast book statement and I think it is clear).
Fermentis' website also currently states that a loss of 3-6% viability should be expected from rehydrating in wort as opposed to water. That statement is in the context of them being in the optimal temperature range.
So, under certain circumstances one can lose up to 50% viability. Think sprinkle pitching on a high OG wort at a cold temp (Doppel Bock for example). Most yeast sprinkle pitched at 18C probably won't lose 50%, but this would have to be OG dependant as to how much % is lost. So my point is, armed with this knowledge one can make the decision, knowing the consequences for resultant beers in different circumstances. ie one would know that sprinkle pitching 2 packets of dry yeast into a doppel bock at 8C, won't result in 120-200 billion cell viability, so one might pitch 4-5 packets. Pitching an Ale yeast at 15C in the same manner may result in a 25%? or 15%? or 10%? loss, so to counter that one may pitch 2 packets instead of 1. Know what you are doing.
So that deals with the viability (cells that live), but what about the affect on vitality (the health of the yeast)? The vitality is important too, as many cells don't die, but aren't then in the best of health after rehydration in mediums such as wort or at lower temps. This is why Fermentis' current study would be very interesting to see (when they release it), as it appears to show results of the resultant compounds in beer that good health with the affects those yeast had on the wort or the affects of their health (ie are they healthy enough to do a good job, not just are there enough numbers) [the two are sort of linked, but it isn't that simple).
This Youtube video is a brewer, who conducted a test with recorded results that show that 5% extra viability is lost by not hydrating Fermentis US-05 yeast, (sprinkled into 20C wort) compared with hydrating at 26.7C in water (in his one test). He approaches the whole thing with a level and balanced view and comes across as reasonable. I do highlight that his counting results are, well, unheard of, as he states 200 billion cells in a dry yeast pack (he's talking Fermentis 11.5gm packs) and states he calculated from his 3 test results a count of 263 billion from his 11.5gm pack. That's 22.9 billion cells per gram, which when compared to what Fermentis state as supplied 10 billion cells per gram and minimum of 6 billion cells per gram, makes his count a freakish result. So it does lead me to question his cell counting practice somewhat. His methods and results here https://drive.google.com/file/d/0BzNmUGsHZf7dOTZzZF9aQVluZXM/view
So with all that, I acknowledge the more I learn the more I realise I know very little. My question to @MHB or others with the knowledge or reference materials is this. Has that die off of yeast cells due to rehydration temp and media been found in studies happen fairly quickly or over a period of hours (ie longer than the 45min in the above test).
EDIT - and after typing all that, I forgot to say that the dry yeast should be brought up to temp first either way, but this goes for any yeast, so I hope it is obvious. Also dry yeast stored at 3C is expected to lose 3-4% viability over a year, so the above youtube test fits those expectations.
I would also like to say, that my personal view is that if rehydrating a packet of yeast into 110mls of sterilised water at 29C for 30mins (or what ever the producer recommends) is the step I have to take only saves 5-10% of my yeast and ensures they are in the healthy state the producer strove to achieve, then that is what I'd recommend for those to do who can.
I wouldn't leave my liquid yeast in the cupboard instead of storing it in the fridge for the same reason.
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Cant help you there, I've never seen a report that looks at cell counts at 5-10-15... minutes. Most have given at least half an hour for the yeast to fully hydrate (often up to two hours) and start showing signs of life, mostly taking up Methylene Blue which is a slightly suspect test in its own right.
I'm not even sure how you would design a test that told you when the kill occurred and suspect its pretty moot anyway. it the number that survive and the vitality that really counts.
Mark
I'm not even sure how you would design a test that told you when the kill occurred and suspect its pretty moot anyway. it the number that survive and the vitality that really counts.
Mark
hoppy2B
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********. My point is it doesn't matter how you pitch, direct or re-hydrated, it doesn't make a difference to your beer. I have been proven 100% correct. It's the fanatical idiots who have been proven wrong who are making a fuss, not me.
Black n Tan
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Interested in seeing the full results and methods. Wonder if they used included some lower pitching rates because that is where things could get interesting. May be not such a good story for marketing, so I suspect the answer is no. A noticeable omission is the viable cells counts using the three methods. If we assume viable cells counts are in fact reduced by half when hydrating in wort, then may be all this research really shows is that the pitching rate for yeast hydrated in water can be reduced to 25g/HL under ideal conditions, rather than the recommended 50g/HL. Just a thought?? In the meantime, in the absence of methods and complete data, some may run around saying this just confirms what they always new, oh to be so wise!
Jack of all biers
Well-Known Member
You're right regarding the vitality, but that was got me thinking about the Youtube test I posted, as he left them 45mins, which I would expect would be long enough, but it got me wondering if another hour or so would show up some further weakness in the cells that may cause further death rates (for either method). I expect longer than that and growth may start kicking in effecting the results, so another factor to sway a test. All academic anyway. Thanks for the reply. I have found listings of research papers that I suspect have the answers, but I don't have access to them unfortunately.
There are very good reasons why there are recommended pitching rates, these are based on decades of research and the effects of pitching outside the range (either over or under) are well understood.
That being the case why would the experiment repeat what is already well understood. Because it is known what will happen that the test the way it was preformed validates all three methods, as the measured results are so close we can say with confidence that the three methods produce the same number of viable yeast with very similar vitality - if they didn't the beers/results wouldn't be so similar.
The notion that pitching kills half the yeast is I believe a misunderstanding, better to say half the cells die between cropping and pitching. I strongly suspect that a fair fraction of the yeast doesn't survive drying, another fraction just wont fire back up, the total is about half of the starting count. That doesn't mean they were killed when pitching. We cant improve this but can make it worse by pitching outside the recommendations (either rehydrating or direct) parameters or by using too old/badly stored yeast, will all result in more dead yeast - not just kill more yeast.
I also believe this is allowed for in the recommended pitch rates. Lets stay with US-05, reading the spec sheet
when dry yeast is pitched at 100 g/hl i.e. > 6 x 10^6 viable cells / ml.
Note that in this experiment the pitch was half of that so >3X10^6 cells/mL about what you would get from one fresh packet in a standard 23L brew.
Also, the two recommended ways pitching in the spec sheet are "Alternative" no one is preferred or better. Fermentis has always said that its OK to pitch directly into the wort (at stated conditions) and said so one every sachet they sell, or to rehydrate if you do it properly.
From this some home brewers have reached the conclusion that if you don't rehydrate (their way) the world will end (well no, but your nuts will probably fall off) sorry wrong answer.
Mark
That being the case why would the experiment repeat what is already well understood. Because it is known what will happen that the test the way it was preformed validates all three methods, as the measured results are so close we can say with confidence that the three methods produce the same number of viable yeast with very similar vitality - if they didn't the beers/results wouldn't be so similar.
The notion that pitching kills half the yeast is I believe a misunderstanding, better to say half the cells die between cropping and pitching. I strongly suspect that a fair fraction of the yeast doesn't survive drying, another fraction just wont fire back up, the total is about half of the starting count. That doesn't mean they were killed when pitching. We cant improve this but can make it worse by pitching outside the recommendations (either rehydrating or direct) parameters or by using too old/badly stored yeast, will all result in more dead yeast - not just kill more yeast.
I also believe this is allowed for in the recommended pitch rates. Lets stay with US-05, reading the spec sheet
when dry yeast is pitched at 100 g/hl i.e. > 6 x 10^6 viable cells / ml.
Note that in this experiment the pitch was half of that so >3X10^6 cells/mL about what you would get from one fresh packet in a standard 23L brew.
Also, the two recommended ways pitching in the spec sheet are "Alternative" no one is preferred or better. Fermentis has always said that its OK to pitch directly into the wort (at stated conditions) and said so one every sachet they sell, or to rehydrate if you do it properly.
From this some home brewers have reached the conclusion that if you don't rehydrate (their way) the world will end (well no, but your nuts will probably fall off) sorry wrong answer.
Mark
jackgym
Well-Known Member
!00% agree on that one, mate.
goatchop41
Well-Known Member
This higher cell count is actually something that several sources agree with (including Jamil Z., one of the authors of the book Yeast). I can't be assed finding them right now, so you'll have to trust me, a stranger on the internet, but I have seen multiple sources that have done independent cell counts of well treated/correctly stored dry yeast packages and found that the cell count in them was certainly up around the 20B+ cells/g.
The popular conclusion appears to be that Fermentis state 10B cells/g as a minimum to account for poor storage, old packages, etc., whereas in reality a decently fresh pack that has been kept cold will have around double that.
Jack of all biers
Well-Known Member
Thanks for that, I self Googled and found a few references. That'll teach me to trust the yeast producers websites
Sceptical me should have googled that a long time ago. Though in saying that, it appears most of the references for the 20 bill per gm number, come from the methylene blue counting method, which apart from @MHB, Kai Troster doesn't believe is reliable at all (see 2011 link below). Mr Malty pretty much state that other than agreement from Danstar's Dr Clayton Cone, they rely on reports (don't state from where or link anything, but this must be one of them 2011 experiment*), but seem to say until something better comes along they will go with 20 bill per gm (to be honest I'm not sure about their statement, as it's a bit like, it works for me and others, so will be the case for you too. Sounds similar to other arguments I've heard.....).As far as everything else goes, the best advice I have ever read comes from this Q&A from Dr Clayton Cone [Danstar] and is one I had saved some time ago and forgotten about. It speaks for itself.
* Please note that on that link there is a link to a now removed PDF from Fermentis that he and other forum posts (1, 2) have previously linked citing it for the "up to 50% loss in vitality due to pitch temperature". It's a shame Fermentis removed it from their site altogether, rather than just correcting it if results had changed.
Dr Cone is always worth reading, just worth noting that the blog (long before they were called blogs) was written in 2000.
There has been a lot of work done on yeast since then, be worth reading the full results from Fermentis when they become available.
The point Dr C raises about Lipids is very important to anyone propagating yeast, especially note the second blog entry which addresses the role of O2 and Lipid dilution.
JOAB, If you can find out what the missing document is called, fair chance I have it squirreled away somewhere.
Mark
There has been a lot of work done on yeast since then, be worth reading the full results from Fermentis when they become available.
The point Dr C raises about Lipids is very important to anyone propagating yeast, especially note the second blog entry which addresses the role of O2 and Lipid dilution.
JOAB, If you can find out what the missing document is called, fair chance I have it squirreled away somewhere.
Mark
Jack of all biers
Well-Known Member
Yes I was going to post something about the age of the advice, and I have a research article from 1999 that shows 65% is about the best viability they could get with dry yeast, but thought the same as you, that a lot has progressed in the field of yeast dehydration since then. Probably a lot of this confusion exists because once relevant research has been superseded due to better methods making it meaningless. I hope that makes sense. Anyway I thought better of it, due to irrelevance and the fact my posts do prattle on sometimes.
The article is only referenced as https://fermentis.com/SHARED/Doc_60698.pdf so Doc_60698.pdf perhaps if you have it. If nothing else, it would be good to read, as I understand it was in this research that they discovered that there was little or no difference between rehydration in water or wort (hence their previous/current rehydration instructions)
The article is only referenced as https://fermentis.com/SHARED/Doc_60698.pdf so Doc_60698.pdf perhaps if you have it. If nothing else, it would be good to read, as I understand it was in this research that they discovered that there was little or no difference between rehydration in water or wort (hence their previous/current rehydration instructions)
Rocker1986
Well-Known Member
And what have you based that on? It's most likely true if the same amount of cells survive the pitch, but if the dry pitching kills a big enough portion of them then it could adversely affect the pitch rate, which could then adversely affect the beer. I don't think anyone is saying that this will happen 100% of the time with dry pitching - it's just a potential risk that isn't there with properly re-hydrated yeast. And it's a risk I'm personally not willing to take when I do use dry yeast. If others want to do it, that's up to them. But you're not making many allies with your arrogant complete and utter dismissal of decades of scientific research based on nothing but your own beers and/or what basically amounts to a marketing release at this point.
I'm happy to change my mind on it if the science shows it to be that way but until that happens I see no good reason to. And since you don't have a lab to do the tests properly like you accused everyone else of earlier on, what makes you an authority on anything any more than anyone else? Cut the ******** already. Nobody gives a flying **** if you dry pitch your yeast or not, but some of us like to base our practices on real science, not anecdotes.
Jack of all biers
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Brewno Marz
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Serious question on rehydrating. What effect does chlorine (or chloramine) have? My premise is that free chlorine will kill a number of the yeasties. I have been rehydrating in pre boiled water, which, in my mind, disipates free chlorine. Now QUU is using chloramine in my area. So, my reason for using pre-boiled water is now tenuous...but I do like seeing the yeast cream & foam up on rehydration. Am I wasting my time and should I just direct pitch?
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Jack of all biers
Well-Known Member
If you are worried about chloramine, then you could carbon filter your drinking water or treat the water with Ascorbic acid or Campden tablet (Sodium or Potassium Metabisulphite) then boil it. Before I get hailed down with "that's too much effort" - It is the same for your brew water, so why wouldn't you treat the water you rehydrate your yeast in. No more effort, just 100-200ml more treated water.
Brewno Marz
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QUU levels of chloramine are quite low. Ascorbic acid or K/Na metabisulphite is more more likely to impact the end product than the low ppb of chloramine. The question was meant to be whether tap water disinfectants impact or kill the yeast if rehydrating with tap water.
Rocker1986
Well-Known Member
If you boil it, doesn't it remove all the SO2 if you've treated it with one of the metabisulphites, so that'd reduce its impact? I've re-hydrated yeast in the tap water here for years without any issues that I could notice, but obviously I don't have anything scientific to say one way or the other if the tap water disinfectants impact on the yeast.
