Pitching a yeast starter into already fermenting beer?

[scottbrews]

Hi all! Beginning brewer here.

I brewed this Imperial Red Ale last Wednesday:

http://www.midwestsupplies.com/fulton-s-libertine-imperial-red-ale.html

The OG was 1.070 and the recipe calls for 8% ABV.

Friday, I had seen no visible signs of fermentation (no bubbles in the airlock). The Wyeast that came with the kit sat in my fridge for 4 months before using it, AND I think I didn't give it enough time to come back to life... or something. So I assumed there was something wrong with the yeast.

So I went to the homebrew store, picked up some new yeast (a White Labs California Ale this time) and at the recommendation of the storekeeper, got a yeast starter kit, which he recommended for such a high gravity beer.

I wake up Saturday and, lo and behold, bubbles are happening in the airlock. So apparently the yeast just took a couple days to get movin' and shakin'.

My question: Should I still make a yeast starter for this batch? If I do, should I only pitch some of it? Is there danger in adding too much yeast to this recipe, especially because now they'd be two different types of yeast?

Thanks all for your input!

 

[thadius856]

Don't bother making a starter for this batch and adding it.

If you're seeing airlock activity now, you either have huge temperature swings (doubtful) or the yeast are already multiplying. Any off-flavors you are going to get from this big of an underpitch (yes, you will get off flavors) are already a done deal. You won't be able to create a big enough starter fast enough to combat it.

Sit back and RDWHAHB.

Edit: For reference, you pitched 25-50 billion cells. For 5 gallons of 1.070, your target pitch was 242 billion cells.

 

[stpug]

What thadius said. Save your yeast for your next batch, this one's already underway. I've underpitched a couple times (not on purpose) and have not been overwhelmed with any off flavors/smells, so YMMV.

 

[scottbrews]

ok, thanks for the advice. Will the ABV end up lower because of the underpitching?

 

[thadius856]

No, the underpitch just means they need to multiply extra generations before they get to work. You'll probably get the same ABV as long as they're not too strained. You'll just get the ester profile from all that multiplication. Usually we decant some of those esters off In the spent starter wort before pitching.

If youve never made this recipe before, arent very familiar with a clone, or have a well trained palette, you probably wont be able to tell the difference.

 

[scottbrews]

Awesome, thanks for the info!

 

[atreid]

Well... technically if you underpitch the yeast has to reproduce to reach that needed critical mass. They need resources to reproduce and the only resource around is your precious sugary wort.

So yes, they consume sugars to reproduce and there's going to be less of it for fermentation. You do the math...

To which extent, I don't know...

 

[atreid]

Actually, if I wanted to guess, I'd calculate how much less abv you'll have by those simple steps:

-Use MrMalty to calculate how much DME you would have needed for a proper starter considering how old was your yeast. This is in theory how much fermentables your yeast would consume to reproduce in your wort.
-Let's say you are using Beersmith, add as much DME into your beer recipe. Your OG will go higher than your true OG was.
-Bring your OG back down to your real OG by removing just enough of your real fermentables (2row, other DME, whatever).
-Now that you're back to your original OG, check the estimated ABV which should be the same as before or very very close. Remove the DME you added relating to propagation. Note the new ABV.

I'm guessing that last ABV is going to be closer to the one you'll actually end up with. Now I just imagined that so I don't even know how it will end up. Might not even be a lot less, but it's still interesting... ;-)

 

[atreid]

For fun, if anybody cares:

Made a 19 liters batch (5 gals) in BeerSmith.

6kg 2row up to 1.070 OG and 8% estimated ABV.

With yeastcalc.com, it says I need to do a 9.4 liters starter using 949g DME (33.4gal).

Added this amount of DME into BeerSmith (upped ABV to 10.1%).

To get it back down to 1.070/8%, I had to scale down the 2row from 6 kg to 4.45kg.

Assuming the yeast will grow to the same amount of yeast compared to a healthy starter and then start the fermentation, I remove all the DME from the recipe. That might not be right. It's a definite possibility that the yeast will grow to a lower mass before starting the fermentation.

So let's say I remove:

100% of the DME (yeast mass=yeast mass from a healthy starter):
1.052 of OG left for fermentation, ABV=5.8%

75% of the DME (yeast mass=75% of yeast mass from a healthy starter):
1.056 of OG left for fermentation, ABV=6.4%

50% of the DME (yeast mass=50% of yeast mass from a healthy starter):
1.061 of OG left for fermentation, ABV=6.9%

25% of the DME (yeast mass=25% of yeast mass from a healthy starter):
1.066 of OG left for fermentation, ABV=7.4%

I'd be surprised if the yeast was propagating as much as in a healthy starter, but I'm thinking 50% isn't unrealistic. In this case, you'd lose a big 1% ABV, which isn't negligeable at all...

Any thoughts?

 

[thadius856]

Okay, there's some math errors in here that are really throwing you off. Let's go line by line.

For starters (pun intended), you would want to cold crash for 24-36 hours to preserve the less flocculant, more attenuative yeast from being decanted off. Then, you pour off the liquid, leaving only the yeast to pitch to the beer. Thus, the DME or AG used in the starter does not add appreciably to ABV because almost all of the alcohol went down the sink drain.

For fun, if anybody cares:

Made a 19 liters batch (5 gals) in BeerSmith.

6kg 2row up to 1.070 OG and 8% estimated ABV.

With yeastcalc.com, it says I need to do a 9.4 liters starter using 949g DME (33.4gal).

We already have some odd errors going on here. For 5 gallons of 1.070, you want to pitch 242 billion cells. This can be done on a stir plate using Brau Kaiser's (K. Troester's) growth model, which gives a starter of 1.1 liters (assuming 1.040 starter wort). That's about 110g of DME in 1.1 liters of water, for reference, using the off-the-cuff magical 10:1 ratio. YeastCalc gives a more precise 4.22 oz, which is 119g of DME.

Added this amount of DME into BeerSmith (upped ABV to 10.1%).

As said above, you don't get any appreciable addition to ABV from a starter. The point is to grow yeast cells fast, not make beer, so the spent starter wort will negatively affect your beer if pitched.

To get it back down to 1.070/8%, I had to scale down the 2row from 6 kg to 4.45kg.

Assuming the yeast will grow to the same amount of yeast compared to a healthy starter and then start the fermentation, I remove all the DME from the recipe. That might not be right. It's a definite possibility that the yeast will grow to a lower mass before starting the fermentation.

So let's say I remove:

100% of the DME (yeast mass=yeast mass from a healthy starter):
1.052 of OG left for fermentation, ABV=5.8%

75% of the DME (yeast mass=75% of yeast mass from a healthy starter):
1.056 of OG left for fermentation, ABV=6.4%

50% of the DME (yeast mass=50% of yeast mass from a healthy starter):
1.061 of OG left for fermentation, ABV=6.9%

25% of the DME (yeast mass=25% of yeast mass from a healthy starter):
1.066 of OG left for fermentation, ABV=7.4%

I'd be surprised if the yeast was propagating as much as in a healthy starter, but I'm thinking 50% isn't unrealistic. In this case, you'd lose a big 1% ABV, which isn't negligeable at all...

Any thoughts?

This whole section no longer applies.

 

[atreid]

and your mistakes are more about what my intent was doing all this.

For starters (pun intended), you would want to cold crash for 24-36 hours to preserve the less flocculant, more attenuative yeast from being decanted off. Then, you pour off the liquid, leaving only the yeast to pitch to the beer.

First, this is 100% wrong. Starters are not washed yeasts and the trub isn't as important. If you were to do that with starters, you'd probably end up with less yeast than in your original liquid vial. The proper procedure is to just grow, decant, THROW AWAY the awful pseudo-beer that is full of propagation off-flavor, and pitch only the yeast cake. You do NOT want that beer in there.

Thus, the DME or AG used in the starter does not add appreciably to ABV because almost all of the alcohol went down the sink drain.

I never implied as such. My only goal was to mimic the effect of underpitching which implies that propagation will occur directly in your wort instead of a proper starter therefore consuming your fermentables for propagation instead of fermentation (wasting it). That is why I determined how much sugar was needed for enough yeast propagation first using yeastcalc.com then I replace some grain with that DME to keep the same OG. At this point, you can evaluate what would happen if that DME was to "go to waste". That is when I remove it from the recipe, which lowers the ABV since that sugar should have been used for fermentation.

We already have some odd errors going on here. For 5 gallons of 1.070, you want to pitch 242 billion cells. This can be done on a stir plate using Brau Kaiser's (K. Troester's) growth model, which gives a starter of 1.1 liters (assuming 1.040 starter wort). That's about 110g of DME in 1.1 liters of water, for reference, using the off-the-cuff magical 10:1 ratio. YeastCalc gives a more precise 4.22 oz, which is 119g of DME.

Still using my same logic, I wanted to estimate how much sugar would have been wasted when underpitching. When yeast propagates within your wort, there are no stir bar effects because you do not agitate your fermenter nor do you expose it to oxygen. This is therefore the worst possible way to make a starter, and you need more sugar. You are right about the 242 billion cells needed for 5 gals at 1.070, but don't forget that he was using 4 months old yeast. If you consider that 36% viability (according to yeastcalc.com because MrMalty said 10% so I'm still using the most favorable estimation here) from 4 months old yeast, it's 9.4 liters of 1.037 starter to reach the proper 242 magic number using the "None, C.White" method.

Actually, answering you did uncover a small mistake in my own logic. Now that I think about it, that crappy starter method with no agitation and not much O2 WILL produce some alcohol (Of course, O2 was present at first when the wort was aerated but it's consumed pretty fast and then you're anaerobic only). So the ABV reduction as calculated won't probably be as much, but the 1% lowering I evaluated was only considering that 50% of the sugar was to be used for propagation while the rest stayed for fermentation, so my estimation still stands (to a point really... it's still very much an approximation).

It was just a geeky way to try to estimate how much ABV you lose by underpitching old yeast. I hope it's clearer now.

Good night!

 

[thadius856]

and your mistakes are more about what my intent was doing all this.



First, this is 100% wrong. Starters are not washed yeasts and the trub isn't as important. If you were to do that with starters, you'd probably end up with less yeast than in your original liquid vial. The proper procedure is to just grow, decant, THROW AWAY the awful pseudo-beer that is full of propagation off-flavor, and pitch only the yeast cake. You do NOT want that beer in there.



I never implied as such. My only goal was to mimic the effect of underpitching which implies that propagation will occur directly in your wort instead of a proper starter therefore consuming your fermentables for propagation instead of fermentation (wasting it). That is why I determined how much sugar was needed for enough yeast propagation first using yeastcalc.com then I replace some grain with that DME to keep the same OG. At this point, you can evaluate what would happen if that DME was to "go to waste". That is when I remove it from the recipe, which lowers the ABV since that sugar should have been used for fermentation.



Still using my same logic, I wanted to estimate how much sugar would have been wasted when underpitching. When yeast propagates within your wort, there are no stir bar effects because you do not agitate your fermenter nor do you expose it to oxygen. This is therefore the worst possible way to make a starter, and you need more sugar. You are right about the 242 billion cells needed for 5 gals at 1.070, but don't forget that he was using 4 months old yeast. If you consider that 36% viability (according to yeastcalc.com because MrMalty said 10% so I'm still using the most favorable estimation here) from 4 months old yeast, it's 9.4 liters of 1.037 starter to reach the proper 242 magic number using the "None, C.White" method.

Actually, answering you did uncover a small mistake in my own logic. Now that I think about it, that crappy starter method with no agitation and not much O2 WILL produce some alcohol. So the ABV reduction as calculated won't probably be as much, but the 1% lowering I evaluated was only considering that 50% of the sugar was to be used for propagation while the rest stayed for fermentation, so my estimation still stands (to a point really... it's still very much an approximation).

It was just a geeky way to try to estimate how much ABV you lose by underpitching old yeast. I hope it's clearer now.

Good night!

All of this makes about zero sense in my current state.

I tried to help by replying to a thread with zero other posts in the Beginner's Beer Brewing Forum of all places. I still don't understand where I'm wrong, and for that, I'm sorry.

Clearly there needs to be an Ultra Newbie's Beer Brewing Forum so I can at least answer questions that I can wrap my freakin' brain around.

G'nite. And best of luck. </unsubscribed>

 

[atreid]

Drugs are bad mmkaaay... don't like academic debate I see... ok.

 

[stpug]

For starters (pun intended), you would want to cold crash for 24-36 hours to preserve the less flocculant, more attenuative yeast from being decanted off. Then, you pour off the liquid, leaving only the yeast to pitch to the beer. Thus, the DME or AG used in the starter does not add appreciably to ABV because almost all of the alcohol went down the sink drain.

The steps outlined here are accurate, as is the reasoning.

First, this is 100% wrong. Starters are not washed yeasts and the trub isn't as important. If you were to do that with starters, you'd probably end up with less yeast than in your original liquid vial. The proper procedure is to just grow, decant, THROW AWAY the awful pseudo-beer that is full of propagation off-flavor, and pitch only the yeast cake. You do NOT want that beer in there.

If you begin a starter with washed yeast then your starter is partially composed of washed yeast, and you would end up with MORE yeast cells than before you began (not less). Your method in bold above is accurate and is nearly the same thing Thadius said.

Drugs are bad mmkaaay... don't like academic debate I see... ok.

Does this kind of jab make you feel bigger and smarter? I hardly consider "You are 100% wrong" academic debate.

 

[bjkgnsnhs]

Don't bother making a starter for this batch and adding it.

 

[atreid]

Maybe I misunderstood what Thadius said then. I thought he said you should cold crash 24-36 to preserve the least flocculant yeast by pitching the actual propagation-beer, which would have left out the flocculant yeast at the bottom. After 24-36 hours of a finished starter, pretty much all the yeast has floculated and pitching the liquid part is a 100% wrong approach. I guess I misread and my understanding of his meaning might have been 100% wrong. I should say sorry but he already /unsub in such a theatrical manner... ...

Does this kind of jab make you feel bigger and smarter?

Give me a break... :smack: A little "southparky" Mr.Macky's "Drugs are bad" big deal.

Did you actually read his reply? "All of this makes about zero sense in my current state." and then blablabla and then /unsub... "...in my current state" vs "Drugs are bad", I think it was pretty on topic.

Anyway that was a very small part of my reply, I only wanted to estimate the ABV reduction from underpitching due to the waste of fermentables going through propagation...

Have a nice day...

 

[stpug]

I agree that you misunderstood what he said. Giving the 24-36 hours of cold crashing allows the least flocculant yeast to flocculate which means that when you decant (throw out) the liquid portion you're not losing those highly attenuative yeast. They're being retained in the yeastcake.

Yes, I read his reply. He threw in the towel - so to speak - on this thread. I guess he didn't want to further debate the differences. That's fine - could have been left at that, or you could have explained your position more clearly. Obviously there was a misunderstanding or interpretation error on both sides and the thread would have been better served by further explanation.

I am intrigued by the notion that underpitching yeast in a batch of beer leads to an appreciable loss of alcohol in the final product as compared to a properly pitched batch; assuming similar attenuation from both batches. I had never really considered this possibility. Taking estimation out of the equation, I assume the best way to determine this would be brew the two batches and send samples for ABV testing to a service like this (http://coastalsciencelabs.com/xcart/home.php?cat=254). This makes me want to know more because, again, I had never considered this or would have even guessed this to be the case.

 

[scottbrews]

Ok -- thanks for the hearty debate, y'all, although I'll admit I don't understand everything just yet.

It sounds like the consensus is, don't do a starter for this batch, just wait until I brew the next one.

It sounds like the yeast will eat up some of the sugars as it's reproducing, which will reduce the overall ABV, possibly knocking it down as much as 1%. But, it won't produce any off colors that would otherwise ruin the beer (at least none that my beginner palette will notice).

I think that's a general consensus, yes?

The recipe calls to move the beer to secondary after 7-10 days. Should I delay siphoning given the delayed time the yeast took to get it started?

Again, thanks for all the advice guys, very helpful for a beginner getting his hands wet. For more advanced brewers is it common practice to always make a yeast starter?

 

[stpug]

It sounds like the yeast will eat up some of the sugars as it's reproducing, which will reduce the overall ABV, possibly knocking it down as much as 1%. But, it won't produce any off colors that would otherwise ruin the beer (at least none that my beginner palette will notice).

I think that's a general consensus, yes?

The recipe calls to move the beer to secondary after 7-10 days. Should I delay siphoning given the delayed time the yeast took to get it started?

Again, thanks for all the advice guys, very helpful for a beginner getting his hands wet. For more advanced brewers is it common practice to always make a yeast starter?

I don't agree that you'll have any loss of ABV but I'm also just a lay person . I wouldn't expect color to change much from wort to beer; maybe a slight bit but nothing too great. Off flavors are always a possibility for a variety of factors; one of which is underpitching.

I'd give it 10 days before a secondary from the time fermentation got going (I almost always skip the secondary actually; go straight to bottling bucket or keg).

Yeast starters are very common these days with most brews using liquid yeast, especially high gravity brews. Dry packets have about 2x the yeast population of liquid yeasts and can handle beer up to about 1.05x without needing more; above 1.060 and you're better off with a couple dry packets.

 

[atreid]

I don't see how underpitching would not result in ABV reduction to some extent (how much would need to be evaluated using a true lab test as suggested by stpug earlier).

For most lifeforms reproduction is one of the most demanding activity (not talking about the act itself lol) so the energy required is everything but negligible. For yeast this energy comes from sugars in the wort only therefore quite a lot of it is wasted in propagation. The off-flavors themselves are produced not from underpitching but from the propagation itself, basically from the shift of metabolic pathway. They are byproducts of propagation and in order to produce them, sugar must be used (as ethanol is produced with fermentation but from a different pathway).

As for the rest of stplug's last reply (10 days primary & thoughts about liquid/dry yeast), he's 100% right! (hehe :fro: )

 

[scottbrews]

Ok, fantastic, well I'll keep rolling with the recipe instructions and keep my fingers crossed!

Thanks,
Kevin