Those yeastie beasties

[Geronimo]

When first pouring the must into a fermenter, the resulting splashing and foaming oxygenates the mixture. When you inoculate the must with yeast, since there is a presence of O2, the yeast will immediately set to work multiplying and growing until they have consumed all the O2. During this aerobic phase (and continuously until the end of the fermentation) yeast will produce mainly CO2 gas and ethyl alcohol, along with some hydrogen, methane, and various other things. CO2 is heavier than air, therefore right after fermentation starts the must will have a blanket of CO2 over it unless it is purposely disturbed by air movement. Even with air movement, the oxygenation of the must after fermentation starts is very minimal unless the must is vigorously agitated which can harm the yeast and oxidize the fermentation.

Once all the O2 is consumed in the must, anaerobic fermentation continues until all nutrients and sugars are consumed. During this phase, the introduction of O2 is typically harmful and can cause premature spoilage, bacterial infections, etc. It is always best to limit the exposure the wine has to O2 from this point and through the bottling process. Even in the bottle, only a small amount of air is left in the headspace. Also, the fermentation should conclude with all available yeast cells to ensure a clean fermentation that does not stop prematurely, and that keeps competing organisms in check. Removing the yeast cake from the bottom of the vessel, or skimming the yeast foam or krausen from the top in mid-fermentation is not advisable. In fact once fermentation appears to be complete, leaving the wine in contact with all available yeast for 2-4 weeks will produce the cleanest, most completely fermented final product.

So in conclusion, you should aerate the must before inoculating with yeast, pitch a healthy yeast dosage and some nutrient, then leave the yeast to do the rest without intervention. Managing the temperature and sanitation throughout these phases is the best practice that will help you end up with the desired final product.

 

[Flem]

Thank you for the answer, Alex. Are you looking for the question? LOL

 

[Geronimo]

This discussion started in another thread, so I decided to start a new one in an effort to keep from hijacking the other one.

 

[Julie]

This discussion started in another thread, so I decided to start a new one in an effort to keep from hijacking the other one.

You should reference the other thread and you should reference where you got your information as well. This helps in preventing confusion.

 

[WVMountaineerJack]

Are you saying not to stir up the primary fermentation because you think you might get a little air in it? You dont want to forget to keep things stirred up a little during the primary, you would have to work really hard to put enough O2 in there during an active fermentation since you would be driving off CO2 at the time there is not much room for the O2 to sneak in. Crackedcork

When first pouring the must into a fermenter, the resulting splashing and foaming oxygenates the mixture. When you inoculate the must with yeast, since there is a presence of O2, the yeast will immediately set to work multiplying and growing until they have consumed all the O2. During this aerobic phase (and continuously until the end of the fermentation) yeast will produce mainly CO2 gas and ethyl alcohol, along with some hydrogen, methane, and various other things. CO2 is heavier than air, therefore right after fermentation starts the must will have a blanket of CO2 over it unless it is purposely disturbed by air movement. Even with air movement, the oxygenation of the must after fermentation starts is very minimal unless the must is vigorously agitated which can harm the yeast and oxidize the fermentation.

Once all the O2 is consumed in the must, anaerobic fermentation continues until all nutrients and sugars are consumed. During this phase, the introduction of O2 is typically harmful and can cause premature spoilage, bacterial infections, etc. It is always best to limit the exposure the wine has to O2 from this point and through the bottling process. Even in the bottle, only a small amount of air is left in the headspace. Also, the fermentation should conclude with all available yeast cells to ensure a clean fermentation that does not stop prematurely, and that keeps competing organisms in check. Removing the yeast cake from the bottom of the vessel, or skimming the yeast foam or krausen from the top in mid-fermentation is not advisable. In fact once fermentation appears to be complete, leaving the wine in contact with all available yeast for 2-4 weeks will produce the cleanest, most completely fermented final product.

So in conclusion, you should aerate the must before inoculating with yeast, pitch a healthy yeast dosage and some nutrient, then leave the yeast to do the rest without intervention. Managing the temperature and sanitation throughout these phases is the best practice that will help you end up with the desired final product.

 

[Geronimo]

Are you saying not to stir up the primary fermentation because you think you might get a little air in it?

Ok I re-read it twice and don't see where I said not to stir up the primary. I rarely find stirring the primary is necessary, but you can do it a number of ways without introducing O2. I think you're referring to this:

During this phase, the introduction of O2 is typically harmful and can cause premature spoilage, bacterial infections, etc. It is always best to limit the exposure the wine has to O2 from this point and through the bottling process.

 

[North_Ga_Jug-Or-Not]

In fact once fermentation appears to be complete, leaving the wine in contact with all available yeast for 2-4 weeks will produce the cleanest, most completely fermented final product.

Great post, only in my experience most want to get the wine off the dead yeast as quickly as possible as opposed to leaving it there. It affects the flavor of the wine, so of course this is all a matter of personal opinion but I get dead yeast out not leave it in.

 

[Geronimo]

Believe it or not, 2-4 weeks isn't long enough for significant autolysis to occur. In many white wines (especially sparkling whites that mimic Champagnes) a certain amount of autolysis is necessary to complete the flavor profile.

Autolysis is highly controversial in beer brewing, but many of the most respected, experienced brewers will tell you that 4 weeks isn't long enough to get concerned. At 4 weeks you get a slightly cleaner profile instead of an autolysis infusion.

http://en.wikipedia.org/wiki/Autolysis_(biology)

Thanks for the input!!

 

[WVMountaineerJack]

Hi Geronimo, it was inferred from your post. Stirring the primary does more than just move the yeast around, it knocks down the cap and keeps everything mixed up etc. Unless you are some kind of maniac stirring your primary with a frenzy I dont think you are going to introduce much O2. I like to stir mine up and stick my head in the bucket and get a big sniff, sometimes I get a little woozy from it but thats have the fun Crackedcork

Ok I re-read it twice and don't see where I said not to stir up the primary. I rarely find stirring the primary is necessary, but you can do it a number of ways without introducing O2. I think you're referring to this:

 

[North_Ga_Jug-Or-Not]

I like to stir mine up and stick my head in the bucket and get a big sniff, sometimes I get a little woozy from it but thats have the fun Crackedcork

Hahaha I do the same thing, my gf told me I look like a kid sniffing a marker when im kneeled down taking it all in. I just like the aroma of fermenting wine, get over the yeast smell which isnt so bad and over the course of the ferment you can smell day by day the juice becoming wine. Now she does it too, once she realised why I was enjoying it. Now I gotta guard my primary it would seem.::

 

[robie]

Good writeup and thanks. I don't completely agree with every part of it. What was written is more applicable for white wines, than reds.

Autolysis is not what you are after in a red wine or an aromatic white wine. It can cause off flavors in a red and negatively affect the aroma in an aromatic.

When the sugar in the must is mostly gone, the remaining yeast secret an enzyme that causes any dead yeast present to start decomposing more rapidly. The live yeast can then use these remains for food. This can be beneficial for Chardonnays and Sav/Blanc, but not typically for reds. (Yes, there are always exceptions, like with a few Pinot Noir wine makers.) This is why it is stressed to not leave a red on the lees too long.

With a kit, you can stir the red wine during primary and introduce some air (oxygen) without beating the yeast to death. Just raise the spoon in and out of the wine as you stir. Same for a white, just not as necessary; be gentle.

With a fresh red grape fermentation, think of all the oxygen being added continuously when a pump-over is being done. Also, when you do a push-down of the cap... Oxygen is not going to hurt the yeast. If you withhold oxygen during an active primary fermentation, you can easily get H2S or an incomplete fermentation (or both). All kinds of goodies are being produced during primary; stress the yeast and some of those goodies won't make it.

Trying to purposely keep oxygen away during primary is completely against the principles of aerobic fermentation.

 

[Geronimo]

Wow that's interesting. That really goes against what the microbiologists at Wyeast have been publishing. Can you find any links to authors that support what you're saying? I'd like to read more on that.

 

[robie]

Wow that's interesting. That really goes against what the microbiologists at Wyeast have been publishing. Can you find any links to authors that support what you're saying? I'd like to read more on that.

Again, what was said in your post is more applicable for whites than for reds.

Of course I don't know which part(s) goes against those microbiologist.

Why don't you give us a link to where you got your information? Maybe there is just a context issue and nothing more. I am interested.

What I am saying is not new or in any way controversial. There are lots and lots of articles on aerobic and anaerobic fermentation on the internet and in wine making books everywhere. Youtube has many videos showing open vat fermentations with pump-over and cap push-downs. As an example, search for "youtube Crushpad".

Do those microbiologists not believe in pump-overs or cap push-downs? In a pump-over, the yeast are fairly roughly forced through a wine pump and the hoses; massive amounts of air is pulled in as the must splashes down on the top of the fermenting must in the fermenter. I have never read that this will hurt yeast in any way. This is pretty much standard practice in many (likely most) wineries for reds.

 

[Geronimo]

Ok, I've read a few wine fermentation links and I can see what they are talking about. Moving from primary to secondary means screening out all the larger crud (pulp, skins etc) but not the yeast. And punching down the cap is the same for beer brewing (especially ales) by swirling in the Krausen. That foam is really a nursery of top cropping yeast that will just lay up there until you mix it in.

The area of difference (apparently) is when the aerobic phase ends and the anaerobic phase begins. Beer brewers wouldn't move a partially fermented brew, so no one cares on that side of the fence. But here's what the Wyeast and White Labs say... in the first 24-36 hours the yeast consume the O2 and reproduce, already making a lot of alcohol and CO2. The must (or wort for beer) becomes saturated with CO2 and the anaerobic phase begins (that's a lot sooner than wine makers put it, but it's a minor technicality and neither one might be right exactly). Once the CO2 starts to out-gas, a blanket of CO2 forms over the fermenting liquid and O2 is no longer able to get to the yeast "cap" or the liquid. Even if O2 was in contact with the liquid surface, it takes a lot of mechanical action or aerate the liquid, and the CO2 has to be driven off first (because the CO2 has the solution saturated). So it sounds like a very minor difference. In beer brewing you'd never move to secondary until after the primary was at the target gravity (which is never below 1.000).

The mechanical action causing trouble with the yeast was pretty severe too. People were adding their yeast, then using a mix-stir on the drill to aerate. They couldn't understand why the fermentations were so sluggish. Save it to say, most people are NOT whipping their yeast to death like that.

So here's my personal experience (very limited with just 9 batches so far). I've used the same methods that I've always used. The juice goes in, add nutrient, the mixture gets whipped (to aerate) and then the yeast gets pitched and an air lock is attached. I control the temp real accurately and hit final gravity in 4-7 days (0.993-0.997). So far 4 of the kits have produced some of the best wine I know of so I'm happy with the results. 2 of the other batches were crap but both were my fault. One I made from concentrate that I muffed the acid test, turning it sour. The other from frozen concentrate that I accidentally added too much sugar (following a recipe) which produced a wine that my wife loves (17%+ ABV) but it's too sweet for me. The other 3 were OK, but were low end kits that I wasn't totally thrilled with.

 

[WVMountaineerJack]

There is nothing a homewinemaker can do to physically beat the yeast to death, you can stir until you burn the batteries out of your drill and the yeast wont even know you are there. They have cell walls and are very small with very little mass in a liquid, you cant swirl or stir them to death. If you sheared them in a syringe you could hurt them, but nothing in your garage or basement is going to do the least bit of physical harm to them. I have been stirring the heck out of my primaries this week after adding dry sugar or honey, only thing that happened was a little fizzing from the CO2 being driven off, yeasties still very happy.

There is also 100 ways to do anything in winemaking, no such thing as the only one right way, that adds to the art or winemaking.

Crackedcork

 

[hobbyiswine]

Great posts from everyone! I think it is great to read through the discussion and get more info from more than one source. I appreciate the dialogue ya'll have going. Thanks for posting and helping a newbie like myself.

 

[robie]

Ok, I've read a few wine fermentation links and I can see what they are talking about. Moving from primary to secondary means screening out all the larger crud (pulp, skins etc) but not the yeast. And punching down the cap is the same for beer brewing (especially ales) by swirling in the Krausen. That foam is really a nursery of top cropping yeast that will just lay up there until you mix it in.

The area of difference (apparently) is when the aerobic phase ends and the anaerobic phase begins. Beer brewers wouldn't move a partially fermented brew, so no one cares on that side of the fence. But here's what the Wyeast and White Labs say... in the first 24-36 hours the yeast consume the O2 and reproduce, already making a lot of alcohol and CO2. The must (or wort for beer) becomes saturated with CO2 and the anaerobic phase begins (that's a lot sooner than wine makers put it, but it's a minor technicality and neither one might be right exactly). Once the CO2 starts to out-gas, a blanket of CO2 forms over the fermenting liquid and O2 is no longer able to get to the yeast "cap" or the liquid. Even if O2 was in contact with the liquid surface, it takes a lot of mechanical action or aerate the liquid, and the CO2 has to be driven off first (because the CO2 has the solution saturated). So it sounds like a very minor difference. In beer brewing you'd never move to secondary until after the primary was at the target gravity (which is never below 1.000).

The mechanical action causing trouble with the yeast was pretty severe too. People were adding their yeast, then using a mix-stir on the drill to aerate. They couldn't understand why the fermentations were so sluggish. Save it to say, most people are NOT whipping their yeast to death like that.

So here's my personal experience (very limited with just 9 batches so far). I've used the same methods that I've always used. The juice goes in, add nutrient, the mixture gets whipped (to aerate) and then the yeast gets pitched and an air lock is attached. I control the temp real accurately and hit final gravity in 4-7 days (0.993-0.997). So far 4 of the kits have produced some of the best wine I know of so I'm happy with the results. 2 of the other batches were crap but both were my fault. One I made from concentrate that I muffed the acid test, turning it sour. The other from frozen concentrate that I accidentally added too much sugar (following a recipe) which produced a wine that my wife loves (17%+ ABV) but it's too sweet for me. The other 3 were OK, but were low end kits that I wasn't totally thrilled with.

Sorry it has taken my so long to get back, I was not on the forum over the weekend.

When I had asked about the context, it was because I didn't know the context concerning beating the yeast to death. I am glad I asked, because using a drill and whipping rod is not something I would recommend for yeast health. Most kits recommend the yeast be sprinkled on top of the wine and not even stirred in. The exception is when one makes a yeast starter, which can be "gently" stirred into the must. (As a side note and just for fun, the moment the yeast contacts the must, legally, it is considered wine.)

Based on that, I don't think pushing down the cap or pumping over would qualify as beating up the yeast. I am sure you agree.

There really is no advantage in locking down the wine under an air lock during primary. Oh, I guess for whites, it could help insure less possible oxidation, but even a slow fermenting primary still produces massive amounts of CO2 to protect the wine from any oxidation. Of course in secondary the CO2 production drops off considerably, so locking down under air lock is necessary.

The cap to which I was referring is the cap created when large amounts of grape skins are present during fermentation of red wines. The CO2 pushes the skins to the top. When fermenting wine from fresh/frozen grapes (and not just juice-only), the cap in a ten-gallon fermenter can be a solid mass of skins, 8 inches thick and very compact. It only takes a couple of hours for this cap to form, so it should be punched down 2 or 3 times a day.

This cap is pushed down so it won't start rotting and also (primarily), so the skins and pulp will contact the juice so color and other good stuff will be extracted from the skins and pulp into the juice.

Nine batches is a pretty decent amount of experience for a home wine maker. The thing is, keep doing whatever works for you. I know wine makers who always lock down their fermentation in primary and they have never had a single problem. There are commercial wineries that ferment whites in stainless steel tanks and keep the wine locked down during the entire fermentation... it works for them!

What I recommend is to try to do each step the best way possible and by the book. That way, when something marginal does occur, you are more likely to get through it OK if you have done everything correctly.

Where kit wine instructions are concerned, I would think the point at which they say to move from primary to secondary is considered to be the point at which they think aerobic switches to anaerobic fermentation. It also takes into account when they believe the gross lees should be racked off. It is interesting they all seem to use the same yeast (EC-1118) most of the time, but their time to rack is different.