Oxygenation? Or stir start? Or both?

[aangel]

From what I understand, the purpose of a plate stirrer is twofold: oxygenation of the starter, and physical agitation. Oxygenation puts yeast into propagation mode, and agitation makes sure all the yeast cells are exposed to as much oxygen as possible (no dead spots).

Also,, from what I understand, the point of oxygenating your pre-pitch wort is to provide the oxygen the yeast starter will need to propagate to sufficient cell numbers to adequately ferment the wort. SO...

1: if you have a sufficiently large starter # of live yeast cells, do you need to oxygenate your batch?
2: i'm worried about contamination; should i oxygenate my starter at the outset, or regularly, and otherwise leave a bung/blowoff valve in it?

 

[Brulosopher]

1. I've never used pure O2 in my brewery and I've never had a stalled ferment using a well oxygenated starter, for what it's worth.

2. Foil tightly over the top of the flask ought to work fine. Here's my starter method, it's basically fool-proof

 

[RM-MN]

1. No. If you have sufficient yeast cells you don't need to oxygenate the wort. However, you really do want to grow more cells in the wort because this will change the flavors. Instead of adding a starter with plenty of cells you would make better beer by making a smaller starter and oxygenating.

2. You only want to oxygenate the beer before you pitch the yeast. Adding it after fermentation has started will lead to stale beer.

 

[aangel]

1. No. If you have sufficient yeast cells you don't need to oxygenate the wort. However, you really do want to grow more cells in the wort because this will change the flavors. Instead of adding a starter with plenty of cells you would make better beer by making a smaller starter and oxygenating.

2. You only want to oxygenate the beer before you pitch the yeast. Adding it after fermentation has started will lead to stale beer.

With regards to #2 - I meant "in the starter" not in the wort. As in "what's better, stir oxygenating to 7-8% using air, or a well-oxygenated, shaken flask, with re-oxygenation/reshaking a few times over 24h?

Although I suppose I can get the best of both worlds by filling a 2L erlenmeyer flask with 1L worth of wort and pre-oxygenating before stirring, as well as purging the headspace of the flask with oxygen then sealing.

Also, do you mean I want to slightly underpitch the starter size (using mrmalty for my estimates) and oxygenate the batch before I add the yeast, to enable some propagation before attenuation begins?

 

[RM-MN]

With regards to #2 - I meant "in the starter" not in the wort. As in "what's better, stir oxygenating to 7-8% using air, or a well-oxygenated, shaken flask, with re-oxygenation/reshaking a few times over 24h?

Although I suppose I can get the best of both worlds by filling a 2L erlenmeyer flask with 1L worth of wort and pre-oxygenating before stirring, as well as purging the headspace of the flask with oxygen then sealing.

Also, do you mean I want to slightly underpitch the starter size (using mrmalty for my estimates) and oxygenate the batch before I add the yeast, to enable some propagation before attenuation begins?

This is under debate. Most of the brewers here would say to pitch at the rate that is specified by Mrmalty but I've read that Gordon Strong, a Ninkasi winner, pitches a single vial of yeast in all his beers. To get decent beer from that small of a pitch he must be considered underpitching but I would bet that he oxygenates his wort very well so the yeast propagate to the proper level.

 

[eric19312]

I have been assuming the calculators out there provide a pitch rate for properly oxygenated wort.

My understanding is that pro brewers pitch big and oxygenate. Not just to avoid stuck fermentation but to push for fast-clean-predictable fermentations. We homebrewers can let yeast take their time to clean up our fermentation issues, for pros fermentation time is money.

In my home brewing I oxygenate by splashing/shaking up to OG 1.050 or a bit more and with pure O2 over that. When using pure O2 I oxygenate for 60-120 seconds in 5 gallons with longer times for bigger beers. I mainly use the Brewer's Friend calculator to determine pitching rate and building starters.

 

[Cyclman]

My starter process is to calculate yeast needs for a recipe using BeerSmith, and plan the recommended sized starter (I previously used Mr. Malty). I oxygenate the < 80 degree starter, pitch the yeast, then stir it for 2+ days (use a foam stopper). Decant it after 24 hrs. chilling, pitch into wort slightly below fermentation temperature after 2 min. oxygenation of the wort. I ferment at the low end of the yeast's temp range to start, ramp it to the high end as fermentation subsides.

Maybe I am using suspenders and a belt, but it's not that expensive, not that difficult, and I always get beautiful fermentations. I did this with extract, continued with AG, always hit FG. I am drinking my very clean high gravity Bock right now, it fermented beautifully and it is fantastic.

 

[Tutsbrew]

1. I've never used pure O2 in my brewery and I've never had a stalled ferment using a well oxygenated starter, for what it's worth.

2. Foil tightly over the top of the flask ought to work fine. Here's my starter method, it's basically fool-proof

Thanks "Bru", appreciate the tutorial. ...For what it's worth, it's a small world in that I found and subscribed (signed up to follow) to your "Brulosophy" site just a few days ago.

 

[Aunt_Ester]

but I've read that Gordon Strong, a Ninkasi winner, pitches a single vial of yeast in all his beers. To get decent beer from that small of a pitch he must be considered underpitching but I would bet that he oxygenates his wort very well so the yeast propagate to the proper level.

Do you have a source for this? This sounds like bunk.



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[Black Island Brewer]

In Gordon's book "Brewing Better Beer" he says he does make starters, and goes into great detail.

 

[RM-MN]

Do you have a source for this? This sounds like bunk.



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https://www.homebrewersassociation.org/forum/index.php?topic=17065.45

On Reply #51, direct quote was this.

Hmm, seems like you're doing the right things. In general, acetaldehyde says to me that the fermentation is incomplete. You may wish to use yeast nutrients (I like the Wyeast brand, using the dosage recommendations on the package) to ensure a healthy start. You didn't mention if you are using different yeast strains. It could be that you are using some that produce higher levels of acetaldehyde (Budweiser yeast, anyone?). Maybe you should beechwood-age your beer I don't like high sulfur levels in beer, so I try to avoid strains that produce a lot of that character.

According to Kunze, acetaldehyde is increased by: (1) rapid fermentation, (2) temperature increase during fermentation, (3) increased yeast dosage, (4) pressure application during primary fermentation, (5) too little wort aeration, and (6) infected wort. It is reduced by (1) all measures to promote vigorous secondary fermentation and maturation, (2) a warmer maturation stage, (3) sufficient wort aeration, and (4) increased yeast concentration in the maturation stage.

Assuming your temperature isn't getting too high, I'm guessing you might be overpitching and/or getting too quick a fermentation, based on these.

For a normal strength lager, I typically use a smackpack of Wyeast or make a 1L starter with a vial of White Labs. I don't go crazy on yeast, but I will often repitch from a normal batch if I'm making a stronger lager. I oxygenate and pitch with the yeast and wort at the same temperature. I ferment at about 50F, waiting until it seems pretty well done, then I rack to a keg and lower the temperature slowly until it gets to about 33-34F. Then I let it hang out for a long time. I'm more inclined to use the traditional German method of 1 week for every degree Plato of original extract (even though most German breweries only lager for 2-3 weeks nowadays). Then I fine with gelatin and rack to a serving keg. I almost never do a diacetyl rest, but I don't tend to pick strains that are big diacetyl producers. I do taste my beer before lagering, and only do a d-rest if it needs it. I'm kind of fond of WLP833, Wyeast 2124, and Wyeast 2206 for my lagers. Lagering at a very cold temperature for a long time and fining the keg do give me better results. Most off flavors in lagers I taste usually are from rushed processes, or insufficient yeast separation. Be sure not to crash your temperature too fast, because you want the yeast to continue to work during lagering. Temperature control helps because you can knock it down a couple degrees a day until it's where you want it.

 

[Brulosopher]

Thanks "Bru", appreciate the tutorial. ...For what it's worth, it's a small world in that I found and subscribed (signed up to follow) to your "Brulosophy" site just a few days ago.

Right on. Let me know if there's anything I can do to help. Cheers!