Yeast life, aerobic to anaerobic - when do they transform?

[MalvinaScordaad]

The use of Oxygen as stated above is correct however it does not constitute a separate part or even an absolutely necessary part to be considered a phase of fermentation. Minimizing as much O2 fermenting white wine is normal practice.
Malvina

 

[robie]

Bob, I understand what you are saying.
I am not saying it is up to the wine maker to turn off one phase and turn on the next. I don't think anyone would believe that to happen. I am saying the kit makers simply are guesstimating about when the aerobic phase is ending, so they have you add an air lock. Of course at about the same time fermentation has slowed somewhat and oxidation is now becoming a much bigger factor.

Malvina,
Whether anyone wants to split hairs and call it a phase of fermentation, is not the point. Regardless, for typical alcoholic fermentations, from the yeast's point of reference, there is an aerobic phase and an anaerobic phase within the "single" alcoholic fermentation stage.
.....

I like what Wyeast said about 8 PPM versus 16 PPM of oxygen; 8 PPM being the minimum. I know how important oxidation prevention is for whites, and I know the easy way out is to starve the yeast/fermentation process of oxygen. Some wineries seal up their stainless steel tanks of Chardonnay and leave it that way until alcoholic Fermentation is completed. This has worked for many for years. However, I don't think this approach is necessarily the best, but I do maintain it is the easiest. Reds are my favorites, but whites are my passion. I can make a white without sealing it up and without oxidation. This also has worked for many for years.

It all really comes down to one's own preferences and experiences. It's like arguing over which is prettier, a blond or a redhead... it's all a matter of preference.

 

[MalvinaScordaad]

Well then Robie if Stainless Steel Tanks are sealed making whites preventing any O2 to enter which is the mostly common industry practice, it seems to me then from a "yeast's point of reference" as you put it,there isn't an aerobic phase at all. But more importantly, I don't think we are arguing technique here, I think it is more trying to define the terms and end the confusion that some kit makers seem to think they have to expose a kit to O2 to ferment. A sterile concentrate or juice is no different than fermenting a fresh juice. And the safest way to deal with a ferment which has no cap is to minimize o2 exposure during fermentation.

That being said, I am not sure why you would use the analogy of hair color in this discussion Robie.
Malvina

 

[BobF]

Other than the annoying ambiguity in terms that get thrown around, the only reason I chimed in was because I didn't want the idea that reduced O2 exposure was somehow beneficial to yeast.

I think sealed containers for whites does NOT imply no O2. I *think* there is an assumption about dissolved O2 already being in the juice.

 

[Dugger]

I hesitate to interrupt this intriguing technical discussion, but with regard to confusion about the terms primary and secondary fermentation, I find there is no confusion.
For me and I suspect for most home winemakers these terms pertain to the containers in which the phases of fermentation (alcoholic) are carried out. The initial part of the fermentation is usually done in a primary fermenter - normally a bucket, and the completion of the fermentation is usually carried out in a secondary fermenter - normally a carboy. These simply get referred to as primary and secondary fermentation.

 

[BobF]

Dugger - that's one of the good/bad things about English. Common usage often overrides proper usage.

Secondary vs primary normally doesn't mean much. Until you start doing something that requires a real secondary ferment. That's when conversations have the potential to go sideways.

 

[MalvinaScordaad]

Other than the annoying ambiguity in terms that get thrown around, the only reason I chimed in was because I didn't want the idea that reduced O2 exposure was somehow beneficial to yeast.

I think sealed containers for whites does NOT imply no O2. I *think* there is an assumption about dissolved O2 already being in the juice.

Exactly. Yeast can benefit from o2 but exposure without a cap or layer of C02 is not beneficial to fermenting juice. And you are correct there is enough dissolved O2 for the yeast to be happy.
Malvina

 

[MalvinaScordaad]

I hesitate to interrupt this intriguing technical discussion, but with regard to confusion about the terms primary and secondary fermentation, I find there is no confusion.
For me and I suspect for most home winemakers these terms pertain to the containers in which the phases of fermentation (alcoholic) are carried out. The initial part of the fermentation is usually done in a primary fermenter - normally a bucket, and the completion of the fermentation is usually carried out in a secondary fermenter - normally a carboy. These simply get referred to as primary and secondary fermentation.

I am glad you have no confusion. But my confusion if you will permit me is to wonder why you don't start in a Carboy in the first place. And the reference you speak of Primary and Secondary, while is generally accepted, means exactly what? At what Brix do you transfer? Why do you choose that Brix? Does it matter if you do or don't? If you have terms Primary and Secondary then their must be a reason for the difference. Is it only the container you happen to choose to ferment in? For example if I stay in the bucket until dry can I avoid a secondary fermentation? or if I start in a Carboy did I just skip a Primary Fermentation? What's the point?

 

[Bartman]

Wow, this topic has really gone off the rails - on terminology alone! ShaneK's original question was when to attach an airlock, since the kit-makers tell you to rack from the bucket to a carboy and attach an airlock around 1.020 S.G. while others (like me) will tell you to "ferment to dry" in the bucket. He wasn't worried about delineating the primary vs. secondary fermentation periods - I think he just wanted to know when to attach the airlock so his mead won't oxidize.

I say ferment to dry in the bucket, and rack to a carboy after 6-10 days (my personal experience). I don't differentiate between primary and secondary fermentations, and since I don't do MLF, I couldn't care less. There is no point is identifying those periods of fermentation as 'primary' or 'secondary' other than to break down the process into functional periods by which the beginning home-winemaker can properly complete the different steps, even if their understanding of the steps is somewhat flawed by the terms applied.

 

[BobF]

Bart - IMO, this is the beauty of interactive discuss in contrast to FAQ & book reading. You never know where discussions will and there is always something new to discover and explore.

As long as the original question gets answered, it's ALL good IMO.

 

[Dugger]

I am glad you have no confusion. But my confusion if you will permit me is to wonder why you don't start in a Carboy in the first place. And the reference you speak of Primary and Secondary, while is generally accepted, means exactly what? At what Brix do you transfer? Why do you choose that Brix? Does it matter if you do or don't? If you have terms Primary and Secondary then their must be a reason for the difference. Is it only the container you happen to choose to ferment in? For example if I stay in the bucket until dry can I avoid a secondary fermentation? or if I start in a Carboy did I just skip a Primary Fermentation? What's the point?

I start in a bucket to allow head room for foaming and to allow easy punching down of grapeskin packs and oak bags. I could start in a large carboy if it had enough head space but I wouldn't be able to use bags for the skins or oak and this is messier at racking time; the bucket is much more convenient.
I usually ferment to dry in my bucket, but I do put it under airlock at about SG 1.010 or so; vigorous fermentation has slowed down by this point and I feel comfortable putting it under a tight lid. If I did transfer to a carboy, I would do it at about the same SG; I could probably pick a different SG and it wouldn't make a lot of difference - this happens to be the one I use. Some kit instructions also use a SG around this number to transfer.
As I mentioned in my earlier post, the fermenting container has given rise to the terms Primary and Secondary and these refer only to the stage of fermentation. The terms help us home winemakers easily identify what stage we are at in a discussion or trying to identify a problem.

 

[MalvinaScordaad]

Well if you have a Cap from skins then you can stay in a "Primary Container" open or wide top to the end. But if you don't then you can be in a "Secondary Container" from the beginning. Yes about foaming over you can use 2 "Secondary Containers" ( carboys with air locks) when beginning with head space to allow for foaming and as the foaming subsides you can combine the "Secondary Containers" into one. That is what I have always done making whites when not using a Tank. When I use a tank I leave some head space in the top so as to not foam out of the air lock of the tank. When it subsides I lower the lid onto the wine. As an aside this headspace does provide enough O2 for proper yeast development.
Malvina

 

[Dugger]

Thanks for the suggestion, but I think I'll stick to the way I've been doing it - it's simple and works well for me.

 

[BeerAlchemist]

A brewers perspective...after all, beer and wine yeast (as far as sacc c...not too sure about sacc b) are extremely similar its what they eat that really differentiates things.

I think its pretty well covered; but, fermentation comes in three phases: lag, logarithmic growth, and stationary phase according to Chris White of Whitelabs.

In the first phase taking place in the first hours after inocculation the yeast is uptaking nutrients and oxygen both of which are critical. The latter is critical as oxygen is used by yeast to produce saturated fatty acids and sterols which result in a healthy cell membrane capable of readily moving nutrients in and out of the cell wall as needed. The presence of adequate oxygen is also important as it means that as the yeast begins to multiply its subsequent generations will start off with a permeable cell wall.

The second phase kicks off in around 12-24 hours. This is where the yeast have fully loaded themselves with all the oxygen and nutrients they need and then begin attacking the sugars to provide the energy required for reproduction. The main byproduct at this aerobic fermentation is CO2 and bubbling/foaming becomes apparent. As this phase continues the oxygen is slowly scrubbed from solution by the new yeast cells creating an increasingly anearobic environment. It is at this point that the yeast then switches gears and begins producing alcohol as a byproduct of their activity. At this point in the game the yeast are so busy getting drunk off their alcohol poo they only care about eating more sugar and ignore oxygen so by losing their O2 scrubbing abilities oxidation becomes an issue and we need to be careful about how we proceed.

The last phase is when the yeast scrounge their fermentation byproducts and begin flocculating out of solution.

So, just like in brewing beer, there is no such thing as a secondary fermentation...it is a misnomer. If we rack off the yeast before we hit terminal gravity you do not get a secondary fermentation you get the continuation of the primary fermentation that was not complete, the action of moving the liquid will stir up the yeast some providing some renewed vigor as well as aggravate the solution so that disolved CO2 will come out of solution more rapidly giving the false appearance of a new fermentation; but, if we use the hydrometer as the measure of fermentation instead of bubble activity you quickly realize its all the same ferment.

The last thought, when they change gears from aerobic to anaerobic is really hard to know as the phases overlap to a certain degree and the speed in which the phases transpire will occur differently depending on yeast type, pitch rates, nutrients, oxygen, and temp. Again, from a brewers perspective, when I see a lot of foam on top (krausen in brewing terms) I know I'm producing plenty of CO2 which is protecting my beer/wine from oxidation and the yeast are still scrubbing some oxygen from solution. When that begins to falter I know the yeast are moving towards alcohol production and its time to really consider sealing things up.

 

[MalvinaScordaad]

Never too late to the party with myth killing information. Good for you!
Malvina