PDA

View Full Version : To Stir or Not to Stir



andee5460
05-29-2017, 07:52 AM
I've read to stir the must during first fermentation 3 times a day and others say don't touch. Why different methods?

caduseus
05-29-2017, 08:25 AM
Stir at least 2x/day the first 3 days to aerate the must to get the yeast oxygen. Thereafter you de-gas at least once a day to get the carbon dioxide out.
Whomever told you not to stir does not know what they are talking About or they are beer brewers who have no knowledge of mead. You don't stir beer but beer is not mead

Trenchie
05-29-2017, 08:45 AM
there are two basic "methods"; 'meticulous' and 'pitch and leave'. each then has it's own wide variety of options.

'pitch and leave' is just that, mix the ingredients together, store the batch away and leave it alone, age it until ready. simple yet challenging in it's own regard. no stirring involved. you'll get many opinions against this but not as the option is wrong, but that there is a 'better' option, that being the more attentive meticulous method.

in being more attentive and involved with the fermentation and ageing, the meticulous method employs one of a variety of "plans" (and some hybrid plans). the basic one is the SNA (staggered nutrients addition) where nutrients are periodically added to the batch to assist the yeast and aid in fermentation. here, stirring is a strongly encouraged tool for degassing and raising the lees.

so you have encountered an opinion on stirring, and like all opinions, they are relative and subjective. you will require your own research and learning to understand the basis on which those opinions are derived. and it's a good idea to get both (all) sides of the story. start with the newbie guide on this website, green bar at the top of the forum area, a link on the right side of that bar called "Newbee Guide".

PS: look at plans to understand the need for stirring/degassing, such as JAOM (Joes ancient orange mead) and BOMM (brays one month mead) for other insights into the "meticulous method".

EDIT: I'm also still learning ... and I think I just learned that a JAOM is a 'pitch and leave' recipe/plan. so read the forums too.

jeffvenuti
05-29-2017, 09:58 AM
Andee, where have you heard "don't touch"? Not likely in these forums, unless it's for JAOM which is really a special case.

Stasis
05-29-2017, 12:06 PM
There are some mazers who don't touch the mead. You could find older threads where little is done to aerate or degas. If I remember correctly there is a bomm where nutrients are front-loaded to make it more likely for there to be residual sugars at a lower abv, but I'm not sure what is done with regards to stirring. There has been some "recent" anecdotal success with not touching the mead, but that was probably down to dumb luck more than anything. If you want your average batch to be better in less time you should definitely look into taking better care of your mead and therefore stirring

caduseus
05-29-2017, 12:42 PM
Yes you make a good point. low abv meads (<7%) may be able to get by with a lot less stirring but i dont have experience with any low alcohol beverages.

I would most likely add some hops and acid to help sterilize as there is not enough alcohol below 7% to keep it sterile.

bernardsmith
05-29-2017, 02:04 PM
Stir at least 2x/day the first 3 days to aerate the must to get the yeast oxygen. Thereafter you de-gas at least once a day to get the carbon dioxide out.
Whomever told you not to stir does not know what they are talking About or they are beer brewers who have no knowledge of mead. You don't stir beer but beer is not mead

Let me state that I stir during active fermentation but I do so without a profound understanding of the rationale.

Does any stirring we do introduce enough O2 into a batch of mead that could possibly be called "aeration" with the effect that the amount of O2 we can introduce will have ANY noticeable effect on the yeast? Strikes me that stirring degases and removes CO2, but does it in fact add any significant amount of O2? What is the scientific evidence for the amount of O2 the yeast need and the amount of O2 that stirring incorporates? In other words, what is the basis for the idea that yeast need O2 once fermentation has begun and if they do need O2, how much do they need, and if they need O2 how much O2 does stirring provide?

But let me assume, for the moment, that stirring is an effective method for introducing O2 into the must (or mead), what is the effect of providing the yeast with O2 after they have begun to ferment sugars? Doesn't the availability of O2 allow the yeast to metabolize sugars without producing alcohol (why would that be a good thing?) Doesn't the availability of O2 after the yeast have begun to metabolize sugars allow the yeast to spend more energy budding (and why would that be a good idea?). In short: what benefit does the addition of oxygen provide the mead maker after the yeast has begun to ferment the sugars?
Wine makers stir to ensure that the cap of fruit is constantly being broken up which would prevent CO2 from escaping , and potentially causing pressure to build up leading to "explosions" of wine. Stirring also ensures that the fruit that forms the cap is constantly kept soaking wet so that mold does not grow on it and helps ensure that all the fruit is in contact with the yeast. But what is the rationale for mead makers to stir several times a day during active fermentation?

caduseus
05-29-2017, 02:49 PM
Let me state that I stir during active fermentation but I do so without a profound understanding of the rationale.

Does any stirring we do introduce enough O2 into a batch of mead that could possibly be called "aeration" with the effect that the amount of O2 we can introduce will have ANY noticeable effect on the yeast? Strikes me that stirring degases and removes CO2, but does it in fact add any significant amount of O2? What is the scientific evidence for the amount of O2 the yeast need and the amount of O2 that stirring incorporates? In other words, what is the basis for the idea that yeast need O2 once fermentation has begun and if they do need O2, how much do they need, and if they need O2 how much O2 does stirring provide?

But let me assume, for the moment, that stirring is an effective method for introducing O2 into the must (or mead), what is the effect of providing the yeast with O2 after they have begun to ferment sugars? Doesn't the availability of O2 allow the yeast to metabolize sugars without producing alcohol (why would that be a good thing?) Doesn't the availability of O2 after the yeast have begun to metabolize sugars allow the yeast to spend more energy budding (and why would that be a good idea?). In short: what benefit does the addition of oxygen provide the mead maker after the yeast has begun to ferment the sugars?
Wine makers stir to ensure that the cap of fruit is constantly being broken up which would prevent CO2 from escaping , and potentially causing pressure to build up leading to "explosions" of wine. Stirring also ensures that the fruit that forms the cap is constantly kept soaking wet so that mold does not grow on it and helps ensure that all the fruit is in contact with the yeast. But what is the rationale for mead makers to stir several times a day during active fermentation?

Chris whites yeast book explains much of your questions.

Dadux
05-29-2017, 03:26 PM
Let me state that I stir during active fermentation but I do so without a profound understanding of the rationale.

Does any stirring we do introduce enough O2 into a batch of mead that could possibly be called "aeration" with the effect that the amount of O2 we can introduce will have ANY noticeable effect on the yeast? Strikes me that stirring degases and removes CO2, but does it in fact add any significant amount of O2? What is the scientific evidence for the amount of O2 the yeast need and the amount of O2 that stirring incorporates? In other words, what is the basis for the idea that yeast need O2 once fermentation has begun and if they do need O2, how much do they need, and if they need O2 how much O2 does stirring provide?

But let me assume, for the moment, that stirring is an effective method for introducing O2 into the must (or mead), what is the effect of providing the yeast with O2 after they have begun to ferment sugars? Doesn't the availability of O2 allow the yeast to metabolize sugars without producing alcohol (why would that be a good thing?) Doesn't the availability of O2 after the yeast have begun to metabolize sugars allow the yeast to spend more energy budding (and why would that be a good idea?). In short: what benefit does the addition of oxygen provide the mead maker after the yeast has begun to ferment the sugars?
Wine makers stir to ensure that the cap of fruit is constantly being broken up which would prevent CO2 from escaping , and potentially causing pressure to build up leading to "explosions" of wine. Stirring also ensures that the fruit that forms the cap is constantly kept soaking wet so that mold does not grow on it and helps ensure that all the fruit is in contact with the yeast. But what is the rationale for mead makers to stir several times a day during active fermentation?

I'll make it short because im short on time

1- The topic ahs been heavily discussed in other threads, if you search for them you might get a deeper understading than what i'll post

2- Aereating and degassing are different things. Leaving degassing aside, aereating provides the cells with O2. Many people aereate with an air stone and an aquarius pump or with other methods. When stirring vigorously you will remove the CO2 and then allow more oxigen to be introduced in the must. This is not as effective as the pump or more "advanced" methods, but it still does indroduce the must with a considerable ammount of O2. This ammount has been deemed less than necessary but better than none, but it was discussed extensively in other thread if multiple aereations a day was similar to one aereation with an air stone.

3- Oxigen is a key molecule for yeast cells even if the dont use it to produce respiration, because its usefull to build other products, the most common you'll here about are sterols, which are a family of lipids (fat) that are important for the cell membrane. The product GoFerm actually comes packed with sterols since its important that yeast get a lot of sterols early on. This is why its important aereating at pitch. When the cells reproduce the ammount of sterols per cell is lower (same total ammount, distributed in more cells). Because of this, aereating again helps yeast create more of this lipids. They help in osmotic stress (so when pitching at lower gravities this is not as needed, but there are beer studies that actually say that its still benefitial) and other processes, so you get a cleaner ferment. I remember reading studies conducted that stated that aereating was beneficial to flavour until the 1/3 sugar break. This is why we usually aereate for 2 or 3 days. And actually its been proven that very little of the oxigen introduces is used for respiration (which would mean less alcohol) and most/all is used to make other compounds

4-Flavour compounds are produced by the yeast during the growth phase. As you say, this means they will divide more, and thus make more esters that will "improve" the flavour of the mead (the "" are because different yeasts will give diferent flavours and not everyone likes them, but depends on the strain too, some dont produce this flavours. So its an overall improvment but some people prefer one strain over others because they like the flavour it imparts more or whatever. bottom line, more esters are not ALWAYS desired, but its usually considered a positive effect on alcoholic beverages, specially dry ones)

5- The ammount of O2 needed depends between strains and other things, but for beer i think it was around 15 ppm every 24h (altough im just quoting from my mind, please someone correct me here if im wrong), and actual stirring only introduces around 8 ppm

6- Also degassing is a complicated topic. Some people have argued that its irrelevant since the yeast produce too much CO2 and too fast to make any real difference, but higher CO2 in must is associated in beer with less esters (actually, more preasure in the ferment = less esters, be that from CO2 or other sources). I read that in a post about open-top fermentation, wheather or not degassing actually makes a difference in that, i still do not know. But its worth keeping it in mind.

Hope this helps you understand

bernardsmith
05-29-2017, 05:45 PM
With apologies, Dadux, but your account does not help me understand. I am also quite aware of the difference between aertion and degassing. That was not in fact my question. My question was what is the SCIENTIFIC basis for assuming that a) stirring will incorporate any needed O2 that the yeast may need and b) what is the scientific basis for assuming that FERMENTATION needs more O2 once fermentation is under way. Indeed, your post suggests to me that we may be looking at the skies and parroting that the sun orbits the earth.
You refer to sterols , but don't yeast need the sterols during the lag period? If they need oxygen three days into the fermentation to produce sterols does that not mean that we have a less than viable colony of yeast during the first two days? White and Zainasheff seem to agree that added O2 helps produce more yeast cells (through budding) but we are - I assume - pitching a large enough VIABLE colony of yeast from minute 1 . Why am I looking for the yeast to consume sugar in my must to produce daughter cells? For the additional esters the yeast will produce? But my colony was producing all the esters I need/want... If the colony is too small I simply add another packet of yeast..
You use O2 and air as synonyms, but White and Zainasheff state (see page 83) that what they call "high gravity worts" (ie what we might consider as standard musts with gravities of 1.092 and above ) MUST be aerated with O2 and not air as "air will not provide a high enough level of dissolved air"... so are we to stir to provide "insufficient" O2 or are we stirring because stirring DOES provide enough O2 (and so we dismiss White and Zainasheff!) or are we stirring because brewers say their yeast needs O2 because they use and reuse their yeast multiple times... (see page 82 for a discussion of the problem of insufficient O2 and the use of the FIFTH generation of the same yeast colony.). so I ask again, what is the basis for STIRRING and what is the basis for assuming that yeast need air to produce alcohol. Nothing that White and Zainasheff or that Dadux has written provides me with a convincing case. Of course, I may be misunderstanding what they and Dadux mean... But what W & Z say seems to suggest something very different.
I guess what I am looking for is an expert on yeast who can provide me with published peer reviewed material on the rationale (if there is ) for aeration by stirring once the lag phase has ended and throughout the active phase of fermentation. once

caduseus
05-29-2017, 06:01 PM
With apologies, Dadux, but your account does not help me understand. I am also quite aware of the difference between aertion and degassing. That was not in fact my question. My question was what is the SCIENTIFIC basis for assuming that a) stirring will incorporate any needed O2 that the yeast may need and b) what is the scientific basis for assuming that FERMENTATION needs more O2 once fermentation is under way. Indeed, your post suggests to me that we may be looking at the skies and parroting that the sun orbits the earth.
You refer to sterols , but don't yeast need the sterols during the lag period? If they need oxygen three days into the fermentation to produce sterols does that not mean that we have a less than viable colony of yeast during the first two days? White and Zainasheff seem to agree that added O2 helps produce more yeast cells (through budding) but we are - I assume - pitching a large enough VIABLE colony of yeast from minute 1 . Why am I looking for the yeast to consume sugar in my must to produce daughter cells? For the additional esters the yeast will produce? But my colony was producing all the esters I need/want... If the colony is too small I simply add another packet of yeast..
You use O2 and air as interchangeable, but White and Zainasheff state (see page 83) that what they call "high gravity worts" (ie what we might consider as standard musts with gravities of 1.092 and above ) MUST be aerated with O2 and not air as "air will not provide a high enough level of dissolved air"... so are we to stir to provide "insufficient" O2 or are we stirring because stirring DOES provide enough O2 (and so we dismiss White and Zainasheff!) or are we stirring because brewers say their yeast needs O2 because they use and reuse their yeast multiple times... (see page 82 for a discussion of the problem of insufficient O2 and the use of the FIFTH generation of the same yeast colony... so I ask again, what is the basis for STIRRING and what is the basis for assuming that yeast need air to produce alcohol. Nothing that White and Zainasheff or that Dadux has written provides me with a convincing case. Of course, I may be misunderstanding what they and Dadux mean... But what W & Z say seems to suggest something very different.
I guess what I am looking for is an expert on yeast who can provide me with published peer reviewed material on the rationale (if there is ) for aeration by stirring once the lag phase has ended and throughout the active phase of fermentation. once

Bottom line: are you telling the newbee not to stir? which Is the REAL purpose of this thread after all not a debate over extremely dissecting minutiae.

Dadux
05-29-2017, 06:49 PM
With apologies, Dadux, but your account does not help me understand. I am also quite aware of the difference between aertion and degassing. That was not in fact my question. My question was what is the SCIENTIFIC basis for assuming that a) stirring will incorporate any needed O2 that the yeast may need and b) what is the scientific basis for assuming that FERMENTATION needs more O2 once fermentation is under way. Indeed, your post suggests to me that we may be looking at the skies and parroting that the sun orbits the earth.
You refer to sterols , but don't yeast need the sterols during the lag period? If they need oxygen three days into the fermentation to produce sterols does that not mean that we have a less than viable colony of yeast during the first two days? White and Zainasheff seem to agree that added O2 helps produce more yeast cells (through budding) but we are - I assume - pitching a large enough VIABLE colony of yeast from minute 1 . Why am I looking for the yeast to consume sugar in my must to produce daughter cells? For the additional esters the yeast will produce? But my colony was producing all the esters I need/want... If the colony is too small I simply add another packet of yeast..
You use O2 and air as synonyms, but White and Zainasheff state (see page 83) that what they call "high gravity worts" (ie what we might consider as standard musts with gravities of 1.092 and above ) MUST be aerated with O2 and not air as "air will not provide a high enough level of dissolved air"... so are we to stir to provide "insufficient" O2 or are we stirring because stirring DOES provide enough O2 (and so we dismiss White and Zainasheff!) or are we stirring because brewers say their yeast needs O2 because they use and reuse their yeast multiple times... (see page 82 for a discussion of the problem of insufficient O2 and the use of the FIFTH generation of the same yeast colony.). so I ask again, what is the basis for STIRRING and what is the basis for assuming that yeast need air to produce alcohol. Nothing that White and Zainasheff or that Dadux has written provides me with a convincing case. Of course, I may be misunderstanding what they and Dadux mean... But what W & Z say seems to suggest something very different.
I guess what I am looking for is an expert on yeast who can provide me with published peer reviewed material on the rationale (if there is ) for aeration by stirring once the lag phase has ended and throughout the active phase of fermentation. once

Ok, i'll try again.
Leaving stirring for later, about O2, yeast and fermentations (mid fermentat oxigenation)
If an expert writes a paper and says "we did trials when we produced wine adding O2 and not adding O2 at 1/3 sugar break, and a blind sensory panel determined that the first group was better" would you not do it? plus, after you do it, meads seem to turn out better. I think you already got this far, im writing it because its actually what the thread is about. So yes, we should stir and aereate.
Now, to the "why O2 helps". Dont have time to actually support this with scientific material, maybe tomorrow, if you dont mind, but i'll try to explain it basing it in what i wrote earlier.

-You want the yeast to reproduce. A lot. or else, the ferment will take forever and/or stall. This (budding) happens even if you dont aereate. Can you get away with adding more yeast? probably, if you rehidrate with goferm or is a low gravity must (for mead). In fact, this is what is recommended in sack meads and show meads. Its not a coincidence. In normal ferments you dont exaclty want MORE cells, you want HEALTHIER cells.

-O2 is a nutrient. you decide to add Fermaid or whatever is your nutrient brand pick to your mead and this has many things to your mead. Same way with O2. You can just not add the fermaid and add more eyast (show mead), but why would you when its healthier for the yeast to be fed? its stupid. Cells need nitrogen for many things. They also need O2. Yeast is NOT anaerobic only. There is a reason for it being also aerobic. When deprived of oxigen they can live, just not as well

- Lets do some math. Follow my argument for a second. You pitch your yeast and add oxigen at pitch. Then the yeast use it to form compounds that will improve their lives, and so, the final ferment will be better because they will be less stresed. If you understand that, then imagine yeast reproduce... say 5 times in the ferment (total random number, its probably more). That means that when there were two cells, now you got 2x2x2x2x2 = 32. 16 times more. And so, the sterols are 1/16 what they need. So this cells dont have all they need. When you aereate again, when the yeast is growing, they can build enough sterols, and so, continue a happy life. Anyway, if we disregard the math, there are a series of studies that have been made and many places call for aereation for this exact reasons, and also because it diminishes the concentration of H2S. I also want to point out that its harder to find articles about wine aereating for spoilage reasons, but super easy to find articles and posts about starter aereation on beer. And there is no difference. In a starter, yeast is growing. Same in mead fermentations early on.

About aereating by hand (shaking, stirring and whatnot) it has been published in that book you quote that it does add oxigen. Enough? no. For them. However, as i said, i made some arguments about why it could be enough in another thread, and that is, that if you aereate once with a stone and add 15 ppm of O2, and you aereate one with stirring and add 8 ppm of O2, what prevents you from just stirring 2 times/day? Also, lalvin has in its information sheets, a recommended level of O2 in each yeast (unfortunately, they just state if the O2 need is "normal, low or high", same as with nitrogen, but as you can see it might not be the same in all strains). I will say, however, that this comment about if stirring is enough is complete speculation. Im 99% sure its better toi do it than not to do it. Is it enough? I am not sure.

About how oxigen helps the yeast and how yeast that has been cultivated or grown in oxigen-rich medium ferments better, i do have a couple of papers (Its not exactly what you are looking for because it does not talk about stirring mid ferment exactly, just yeast growing when previously provided with O2 or not, sorry its not more but maybe its a start, as i said maybe tomorrow i'll do an extensive search). If you (or anyone) want them PM me with your email, cause they are not for free and i cant upload PDFs.

You are right taht we do not have all the facts (i think we never do in science-related topics anyway) but i think we do have an understanding about why its good to aereate. I've tried my best to make it understandable and i know its not exactly the answer you want, but its all i got.

Dadux
05-29-2017, 07:58 PM
Also, by what you have posted im not exactly sure you understand a couple of basic concepts. I just want to point them out just in case

Why am I looking for the yeast to consume sugar in my must to produce daughter cells? For the additional esters the yeast will produce? But my colony was producing all the esters I need/want... If the colony is too small I simply add another packet of yeast..
Well alcohol is produced anyway, and this way alcohol is produced faster. Sugar is metabolized to get alcohol, CO2 and energy. If that energy goes to make daughter cells or to just staying alive its irrlevant, you get the alcohol anyway. Because growth is exponential, maybe you are ok with pitching 2 packets, but im sure you would not like to pitch 50 of them right? its easier to have yeast reproduce. And its not like you can really stop it anyway. Growth phase is there wheather you want it or not,

You refer to sterols , but don't yeast need the sterols during the lag period? No, yeast need sterols during their whole life. ITs what protects them. They are FORMED during lag period, usually, but as i said before, when the cell divides they will have half the ammount of initial sterols, and thus need to make more. Once the colony stops growing (after growth phase) aereating is not recommended because if you have done it before, the yeast have all the sterols they need and wont reproduce anymore

we are - I assume - pitching a large enough VIABLE colony of yeast from minute 1 Viable and Optimal are not the same. You pitch enough yeast so they can survive even if the conditions are not ideal or that they can displace any other microbes living in the must (that is, the number is high enough to establish themselves). That does not mean that you pitch enough yeast for the whole ferment. There is lag phase, then growth phase then stationary phase...

...are we stirring because brewers say their yeast needs O2 because they use and reuse their yeast multiple times... No. Yeast, as it comes packaged, does not have enough nutrients of any kind for a full ferment, including oxigen. Wheather or not when you repitch they have more or less i do not know, but in any case, its not enough even when pitching new dry/liquid yeast from a packet.

...what is the basis for assuming that yeast need air to produce alcohol. None. They dont. They do however need to remain healthy for a long period of time. And if they dont even start healthy what do you expect? its not related to alcohol production, but to cell life. When a cell has un-optimal conditions, this produces stress. Too much stress and you get H2S, fusels, or stalled ferments because cells die. This is what you try to avoid.

As i said, this is some things i consider basic. Im not sure if you knew them, but your answer made me think maybe you didnt and if so maybe some of your misunderstanding came from there.

bernardsmith
05-30-2017, 11:34 AM
Without any desire to hijack the original question, I do think that I do understand the basics of what Dadux, you refer to. My arguments is that you assume that as mead makers and wine makers we NEED to provide the conditions that yeast cells need to bud because without reproducing the colony we have pitched is in fact too small to be "optimal". I disagree. I pitch what I think is an optimal sized colony, provide that colony with optimal nutrients and ensure that the O2 it needs to produce the total amount of sterols it needs is sufficient. I am not in the business of growing yeast, cultivating yeast or harvesting yeast. I buy as many packs of yeast as I need for each gallon of must. I need a viable colony to survive about 14 days. That's it. The question is then IF those conditions are met what purpose does providing the yeast with MORE oxygen in day 2 , or 3 or 4 or later during the fermentation?
So, to stir ... or not stir? IF - IF the yeast need MORE oxygen after the lag phase (that is to say during either the growth phase or the stationary phase) then even if stirring is no where near good enough to incorporate the 8 ppm of O2 that the yeast need during the lag phase it is better than nothing, but if all the O2 the yeast need they need before they enter the growth phase then stirring is like waving a magic wand and saying "abracadabra". and so far, despite several PMs very kindly sent to me by Dadux , for which I am very grateful, I am unconvinced that I have seen any solid evidence that suggests we need to provide O2 during active fermentation. Not to say that the evidence does not exist - I am only arguing that so far nothing I have read shows any need for ADDITIONAL O2 30 minutes or so after pitching the yeast.

Dadux
05-30-2017, 11:57 AM
Without any desire to hijack the original question, I do think that I do understand the basics of what Dadux, you refer to. My arguments is that you assume that as mead makers and wine makers we NEED to provide the conditions that yeast cells need to bud because without reproducing the colony we have pitched is in fact too small to be "optimal". I disagree. I pitch what I think is an optimal sized colony, provide that colony with optimal nutrients and ensure that the O2 it needs to produce the total amount of sterols it needs is sufficient. I am not in the business of growing yeast, cultivating yeast or harvesting yeast. I buy as many packs of yeast as I need for each gallon of must. I need a viable colony to survive about 14 days. That's it. The question is then IF those conditions are met what purpose does providing the yeast with MORE oxygen in day 2 , or 3 or 4 or later during the fermentation?
So, to stir ... or not stir? IF - IF the yeast need MORE oxygen after the lag phase (that is to say during either the growth phase or the stationary phase) then even if stirring is no where near good enough to incorporate the 8 ppm of O2 that the yeast need during the lag phase it is better than nothing, but if all the O2 the yeast need they need before they enter the growth phase then stirring is like waving a magic wand and saying "abracadabra".

Well you can go and disagree all you want but do a quick search of how much cells are there during fermentation of a worth.
Yeast is a microbe, and those reproduce fast because its how evolution works. They pass their genes and this way they increase their fitness until the enviroment does not support more cells and they cant grow more.
http://www.homebrewtalk.com/showthread.php?t=226087
For example there is said that around 800 billion cells in 5 gals are found after the ferment is over (and that is in a OG of 1.060 or so, when more sugars are present they can increse their numbers even more). A pack of yeast usually has 5 billions yeast per gram (just read what mine have, mangrove jack M05 dry mead yeast). So if you pitch 1 pack of 10 grams (mine say its enough for 5 gals) that is 50 billion cells. From there to 800 billions... well i'll leave the math to you. You'd need to pitch 16 10 gram-packs to get that ammount (160 grams of yeast).
I might just get a sample and count myself, its quite easy. But rather pointless

You cant just stop yeast from reproducing. Its not like you can just say ENOUGH and they'll stop. What you pitch is a viable colony. Definetly not an optimal one...
Edit: if this still does not convince you that new cells are "born" and those cells need to replenish their cell walls with certain lipids i think i cant explain it any further. That's it. Pitched yeast makes more yeast, and they need to replenish the sterols. Yeast will be growing for around 1-2 days i estimate (depends on duration of lag phase) so you do need to provide oxigen for them to be a peak health. The sterols needed for 10 grams of yeast are not the same than the needed for 160 grams. YOu are not growing yeast, but it will grow nontheless because it is its nature.

caduseus
05-30-2017, 05:05 PM
Without any desire to hijack the original question, I do think that I do understand the basics of what Dadux, you refer to. My arguments is that you assume that as mead makers and wine makers we NEED to provide the conditions that yeast cells need to bud because without reproducing the colony we have pitched is in fact too small to be "optimal". I disagree. I pitch what I think is an optimal sized colony, provide that colony with optimal nutrients and ensure that the O2 it needs to produce the total amount of sterols it needs is sufficient. I am not in the business of growing yeast, cultivating yeast or harvesting yeast. I buy as many packs of yeast as I need for each gallon of must. I need a viable colony to survive about 14 days. That's it. The question is then IF those conditions are met what purpose does providing the yeast with MORE oxygen in day 2 , or 3 or 4 or later during the fermentation?
So, to stir ... or not stir? IF - IF the yeast need MORE oxygen after the lag phase (that is to say during either the growth phase or the stationary phase) then even if stirring is no where near good enough to incorporate the 8 ppm of O2 that the yeast need during the lag phase it is better than nothing, but if all the O2 the yeast need they need before they enter the growth phase then stirring is like waving a magic wand and saying "abracadabra". and so far, despite several PMs very kindly sent to me by Dadux , for which I am very grateful, I am unconvinced that I have seen any solid evidence that suggests we need to provide O2 during active fermentation. Not to say that the evidence does not exist - I am only arguing that so far nothing I have read shows any need for ADDITIONAL O2 30 minutes or so after pitching the yeast.

And where is the evidence you should NOT stir? Especially for a traditional for which there is no fruit.

In tbe movie "Thank you for smoking" the lead character says "I don't need to prove smoking is harmful just that not smoking is not harmful... I just need to cast a shadow of doubt".

You can cast a shadow of doubt on anything- i.e. did we really land on the moon, was Hitler really evil or just misunderstood- but casting doubt is not enough to completely throw out an opposing argument- unless you are talking about the death penalty.

So rather than just cast doubt, please provide evidence that your argument is valid rather than say our argument is not valid.

bernardsmith
05-30-2017, 05:54 PM
Not trying to cast an iota of doubt. I am simply asking whether yeast need O2 after the lag time, what that O2 is used for after the yeast have started to transport sugar through healthy cell walls, and whether IF the yeast need O2, stirring will incorporate anything like enough O2 (given the amounts that White and Zainasheff argue a wort needs (8 ppm ) before pitching the yeast). I prefer data and evidence to "what everyone knows" and I am simply asking for the evidence. That's all. If you have the evidence please provide it. If you don't then you and I are simply doing what everyone else does whether that makes good sense or not

bernardsmith
05-30-2017, 05:55 PM
Sorry, but I am not trying to cast an iota of doubt. I am simply asking whether yeast need O2 after the lag time, what that O2 is used for after the yeast have started to transport sugar through healthy cell walls, and whether IF the yeast need O2, stirring will incorporate anything like enough O2 (given the amounts that White and Zainasheff argue a wort needs (8 ppm ) before pitching the yeast). I prefer data and evidence to "what everyone knows" and I am simply asking for the evidence. That's all. If you have the evidence please provide it. If you don't then you and I are simply doing what everyone else does whether that makes good sense or not

Squatchy
05-30-2017, 06:17 PM
SO back to the OP's question. You would be amiss to not stir your lees all the time. Whether they need O2 or not is a sidebar. When you let the lee's pile up on top of each other for long periods of time they become rotten and produce off flavors. Much/most of what you read on the web is very bad information.

The info here is very modern. And even though this thread has been strung out over very little you will still find the best info on the web right here in our community.

Dadux
05-30-2017, 07:15 PM
SO back to the OP's question. You would be amiss to not stir your lees all the time. Whether they need O2 or not is a sidebar. When you let the lee's pile up on top of each other for long periods of time they become rotten and produce off flavors. Much/most of what you read on the web is very bad information.

The info here is very modern. And even though this thread has been strung out over very little you will still find the best info on the web right here in our community.

Yeah it kiiiinda got sidetracked. Sorry, OP. But at least i think the question has been answered