Aerate starter or not? (partially fermented wort used)

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Rahahb

Rahahb

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Referencing this thread:

https://www.homebrewtalk.com/f39/need-opinion-asap-236026/

Still hanging out at 1.020. I went to the lhbs today and the owner suggested repitching yeast and using the partially fermented wort. So I just did but now I don't know if I should aerate it. Seems like I should since I'm trying to get this going again but I'm not sure.

Also, when I pour the starter in, do I still need to minimize splashing to protect from oxidation?
 
Oxygen is necessary for lipid synthesis, which is in turn necessary for yeast reproduction. If your yeast want to grow but find a shortage of oxygen, they'll have limited success and will typically end up with a relatively high ester level.

On the flip side, if the yeast don't want to grow and you've got your beer full of oxygen, you'll run the risk of accelerated oxidation.

So, basically, it comes down to the situation in your wort, and whether or not it will be able to support more fermentation. For starters, why was the OG so low? Unless you can identify something specific that happened, I'll bet dollars to donuts that your low OG was actually just a reflection of mismeasurement and that your actual OG was a lot closer to the target. If that's the case, and your actual OG was more in the 1.054 range, you probably won't get much more fermentation from pitching more yeast.

What were the circumstances of your original yeast pitch? Starter or no? How much, and at what temps? The question of oxygenation ultimately depends on what went wrong in the first place. My hunch is that your beer might actually just be done with active fermentation, and that no amount of repitching will help.
 
MalFet said:
Oxygen is necessary for lipid synthesis, which is in turn necessary for yeast reproduction. If your yeast want to grow but find a shortage of oxygen, they'll have limited success and will typically end up with a relatively high ester level.

On the flip side, if the yeast don't want to grow and you've got your beer full of oxygen, you'll run the risk of accelerated oxidation.

So, basically, it comes down to the situation in your wort, and whether or not it will be able to support more fermentation. For starters, why was the OG so low? Unless you can identify something specific that happened, I'll bet dollars to donuts that your low OG was actually just a reflection of mismeasurement and that your actual OG was a lot closer to the target. If that's the case, and your actual OG was more in the 1.054 range, you probably won't get much more fermentation from pitching more yeast.

What were the circumstances of your original yeast pitch? Starter or no? How much, and at what temps? The question of oxygenation ultimately depends on what went wrong in the first place. My hunch is that your beer might actually just be done with active fermentation, and that no amount of repitching will help.
Click to expand...

No idea why the og was low. The lhbs owner said I probably just measured the wort when it wasn't completely mixed. I suppose this could be a possibility even though I thought I had thorougly mixed it.

No starter. I used a yeast I washed from the previous Kolsch(wlp029). I had 2 pint jars, and 1 quart jar, each with ~1/4-3/8" of yeast on the bottom of each. Pitched at 70F. Looking at my notes, it did get cooler toward the day I transferred to secondary(62F). Very nice fermentation judging by the airlock activity and krausen so I thought everything was going ok.

Is it better to leave it alone at 1.020 or try to get it to drop a little more at the possible expense of the whole batch?? Thanks.
 
Rahahb said:
No idea why the og was low. The lhbs owner said I probably just measured the wort when it wasn't completely mixed. I suppose this could be a possibility even though I thought I had thorougly mixed it.

No starter. I used a yeast I washed from the previous Kolsch(wlp029). I had 2 pint jars, and 1 quart jar, each with ~1/4-3/8" of yeast on the bottom of each. Pitched at 70F. Looking at my notes, it did get cooler toward the day I transferred to secondary(62F). Very nice fermentation judging by the airlock activity and krausen so I thought everything was going ok.

Is it better to leave it alone at 1.020 or try to get it to drop a little more at the possible expense of the whole batch?? Thanks.
Click to expand...

Like I said, I think it's extremely likely that your actual OG was in the range described by the kit. No matter how much you shook the wort, it wasn't enough. It's tough to miss your OG on extract kits unless you forget to add something or use the wrong amount of water.

If that's the case, your attenuation is actually in the low 60% range. I dobut you'll see much more at this point, but you can certainly try. You could always do a forced fermentation test: draw 200mL of beer and get the temp to around 90ºF. Add a significant amount of healthy yeast, and see if the thing kicks up any more fermentation. If it does, there's more sugar in there and you can try to get it fermented. If it doesn't, you know there's nothing left to ferment and there's nothing to blame the yeast for.

In any case, how's it taste? If it tastes good, I'd probably just leave it as is and look into better yeast pitching practices for next time.
 
I pulled some wort and pitched some yeast and will report back in a day or so.

I tasted some last night and from what I can tell, it tastes pretty good.
 
Alright. So I kept an eye on the sample I pulled and pitched more yeast in to. I couldn't visibly see anything but I checked gravity a couple days ago just to see if anything had happened. Now the gravity is 1.012, right where it needs to be. No krausen formed. Didn't even see any bubbles. But, it definitely dropped.

Now the question is: Do I try to fix it? A fellow club member suggested pitching some safbrew 05 into the bucket and trying to get it to ferment out. If I do that, should I aerate like I did the first time?

Thanks in advance.
 
If you're at 1.012 I would bet it is done. I would not add any oxygen to the mix, you only want O2 when your yeast are replicating, not when you are trying to dry out the last remaining fermentables. Adding the safale 05 probably won't hurt if you are still itching to fiddle with it but probably isn't necessary. You have to weigh the cost of yeast plus risk of contaminating the batch against possibly dropping the FG by a few hundredths of a point. Best of luck!
 
Rahahb said:
Alright. So I kept an eye on the sample I pulled and pitched more yeast in to. I couldn't visibly see anything but I checked gravity a couple days ago just to see if anything had happened. Now the gravity is 1.012, right where it needs to be. No krausen formed. Didn't even see any bubbles. But, it definitely dropped.

Now the question is: Do I try to fix it? A fellow club member suggested pitching some safbrew 05 into the bucket and trying to get it to ferment out. If I do that, should I aerate like I did the first time?

Thanks in advance.
Click to expand...

Is your main beer still at 1.020? If so, you can try pitching some clean and resistant yeast like us05, but you might have some difficulty getting yeast to take off. Look into your yeast handling, etc. for next time.
 
MalFet said:
Is your main beer still at 1.020? If so, you can try pitching some clean and resistant yeast like us05, but you might have some difficulty getting yeast to take off. Look into your yeast handling, etc. for next time.
Click to expand...

Yep the main batch is at 1.020 still. The pint I removed to test was what went to 1.012.

If I decide to pitch this yeast, just rehydrate, and gently stir in?
 
Rahahb said:
Yep the main batch is at 1.020 still. The pint I removed to test was what went to 1.012.

If I decide to pitch this yeast, just rehydrate, and gently stir in?
Click to expand...

I'd just sprinkle it on top. It might kick up a few more points worth of fermentation, but I wouldn't get my hopes too high. Good luck! Let us know how it goes.
 
Well. Good and possibly bad.

Sprinkled safale us-05 on 4/25. Everything looked good. Opened bucket yesterday to check gravity and saw this:

IMAG0164.jpg


IMAG0165.jpg


IMAG0166.jpg


But at least the gravity has come down, lol. It's 1.014-1.015 at the moment. I didn't taste any yet but it smells ok I guess.

Should I bottle asap or give it a couple more days?
 
I hope so. I know I've only done 3 batches but I just haven't had the kind of skim this has. It looks powdery and just different than the other bubbles I've seen. Not worried about it but didn't know if I should bottle, or wait it out a few more days to drop a bit more.
 
It hung around 1.014 for a few days so I went ahead and bottled. Definitely a nasty skim that stuck to the sides mostly as the level was going down. Used a nylon bag on the end the tube to transfer to another bucket first. Looks like I got all the stuff/mold/whatever it was. Beer tasted ok I guess. We will see how it tastes in a couple weeks.
 
1 week later. I can see a thin layer of scum on the surface of the beer in the bottles. I pulled several at random and all had it. It sticks to the side of the glass when you tilt it. Unlike yeast which seems to just get stirred up. So I'm thinking it really was infected.

Having said that, would the beer be safe to drink if it somehow managed to taste ok? Could the beer have picked up a mold or something from the air that would make it unsafe?

Thanks.
 

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