Slow Fermentation - Wash & Reuse or Throw Out Yeast?

[Kelpdog]

I made a 3 liter starter of PacMan for a brew two weeks back. I used my newly constructed fermentation chamber to control temp for the starter. Unfortunately I botched the settings on the digital thermostat, setting the temp offset by 10c cold instead of setting the delay for the cool cycle at 10minutes. I didn't realize this until pulling the starter out to pitch.

It ended up taking about 36 hours to get krausen and airlock activity. 10 days later I still have airlock activity ( I started the fermentation at 65F and ramped it up to 68F after five days). Since it appears that I had a slow and weak fermentation, I'm wondering if I should bother with trying to wash and reuse the yeast. Will the following generation of yeast show issues related to this challenged fermentation? This was my third generation with this culture.

 

[eastoak]

that yeast will be fine to reuse. it's mostly heat that will affect future yeast generations.

 

[Kelpdog]

Thanks!

 

[05m50dan]

I disagree. The slow fermentation indicates tired yeast. 65*F-68*F is right in the range for that yeast. When using liquid yeast for repitching into multiple batches (like the professionals do) you really need to treat the beer like the pros do too. That means using proper yeast nurtients and airation, only repitching from lower strength beers to stronger strength beers, etc.

There is more information that is needed to really answer the question of reusing or not. Did your beer finish out well (did it reach your expected FG)?, how strong is the beer you are planning on re-using from (if it's a strong beer then your yeast will be exhausted)?

Will your yeast make beer, yes. Will it make good beer, possibly. Will it make great beer? Good healthy yeast will, but unhealthy yeast will struggle to do so.

 

[eastoak]

I disagree. The slow fermentation indicates tired yeast. 65*F-68*F is right in the range for that yeast. When using liquid yeast for repitching into multiple batches (like the professionals do) you really need to treat the beer like the pros do too. That means using proper yeast nurtients and airation, only repitching from lower strength beers to stronger strength beers, etc.

There is more information that is needed to really answer the question of reusing or not. Did your beer finish out well (did it reach your expected FG)?, how strong is the beer you are planning on re-using from (if it's a strong beer then your yeast will be exhausted)?

Will your yeast make beer, yes. Will it make good beer, possibly. Will it make great beer? Good healthy yeast will, but unhealthy yeast will struggle to do so.

In this case he had his thermostat too cold and that was the reason for the slow ferment, not tired yeast.

 

[hautlle]

I don't really see any reason to use temp control on a starter. You're not drinking the results, so just let them do their thing at room temp. With a starter you're making yeast, not beer.

 

[05m50dan]

@eastoak~
There is more to re-using yeast than if they weren't maintained in a cool environment. Yeast need to be healthy to make a good beer. If they were not taken care of in previous batches, ie., not properly aerated, not given nutrients, if they were used to make a strong beer, if the temperature was fluctuating all over the place...all these things stress the yeast, making future generations less healthy.

 

[05m50dan]

I don't really see any reason to use temp control on a starter. You're not drinking the results, so just let them do their thing at room temp. With a starter you're making yeast, not beer.

Agree! Yeast starters should run in the 70-80°F range for best results. The only reason to cool them down is just to get them to pitching temp before you pitch.

 

[eastoak]

@eastoak~
There is more to re-using yeast than if they weren't maintained in a cool environment. Yeast need to be healthy to make a good beer. If they were not taken care of in previous batches, ie., not properly aerated, not given nutrients, if they were used to make a strong beer, if the temperature was fluctuating all over the place...all these things stress the yeast, making future generations less healthy.

i hear what you're saying and don't disagree with those points but like i said this is a case of yeast being too cold. cold is not a stressor of yeast, it makes them go dormant or work slower. as you know yeast is kept in a refrigerator after it's propagated and packaged for sale by the yeast companies. as far as we know there were no temperature fluctuations, lack of nutrients, lack of aeration, or high gravity associated with the original poster's beer.

 

[Kelpdog]

Thanks for the replies - somehow didn't get notification of them so late to the game here. Here are few clarifying points.

Room temperature is relative - I live in a 700 sq ft cabin largely constructed from driftwood with wood heat. This time of year the ambient temperature flucuates, hopefully daily, from the low 40's to the upper 70's. We had one area of the house where I could kind of control temperature, but the fermentation chamber will be a big improvement. Even though I'm only trying to make yeast not beer with the starter, it seems logical that the same rules apply to keep yeast happy healthy and producing optimally. I generally have tried to do my starters between 65-70F and I do use a stir plate.

My aeration setup is not ideal - I use an inflatable mattress pump with an inline filter for 5-10 minutes. Since getting setup to do starters (about nine months ago) my fermentations have been markedly improved, with the exception of Wyeast 1968 which never seems to fully attenuate for me and I end up with over carbed beers. I add yeast nutrient when doing big beers, but have not made a practice of it with all my starters.

This brew was a dark ipa/cda with an o.g. of 1.058. The f.g. should have been 1.010 - 1.013 depending on which software I inputted the recipe into. I measured it yesterday at 1.008 which isn't out of character for the Pacman yeast strain. I'll be bottling towards the end of the week.

My concern about this was not based on the cold impacting the yeast directly, but that the starter was too cold to allow the yeast to propagate resulting in significantly under pitching. I don't fully understand how stressed the yeast cells are when under pitching or if it is more of a quantity and timing thing related the fermentation process.

 

[eastoak]

My aeration setup is not ideal - I use an inflatable mattress pump with an inline filter for 5-10 minutes.

you would get just as much O2 into the wort, maybe more, by just shaking the fermentor. pumps and filters are more complexity for no more performance.

I add yeast nutrient when doing big beers, but have not made a practice of it with all my starters.

wort has all of the nutrient that the yeast need, adding more is not critical.

I don't fully understand how stressed the yeast cells are when under pitching or if it is more of a quantity and timing thing related the fermentation process.

when you under pitch fewer yeast have to do more work so they get tired, produce off flavors, die early and so on. it's more complicated than that but i'm not a yeast scientist and that really is the gist of it.

 

[statseeker]

Why do all of you seem to make things seem so complicated?

Just running the wort from a spigot on the kettle into the fermenter will introduce more than enough oxygen to keep your yeast happy.

Slow bubbling or whatever isnt an indication of poor fermentation. Unusually high final gravity, unusually long lag time, off flavors, etc are indicators of poor fermentation. 36 hours is not unusually long to get a krausen. If the beer tastes good, I think OP had a completely normal fermentation. There should be no problems washing and reusing the yeast in my opinion.

 

[05m50dan]

Just running the wort from a spigot on the kettle into the fermenter will introduce more than enough oxygen to keep your yeast happy.

Not true, especially if you are trying to get multiple generations of beer from a single vile (I believe the OP said this was his 3rd generation for that yeast). According to the Yeast book by Chris White (Whitelabs) the recommended dissolved oxygen in wort prior to pitching is between 8-10 ppm. Shaking the carboy/bucket vigorously for 5 minutes (which is significantly more than just letting it cascade from your BK to your carboy/bucket) only gets about 2.71ppm of dissolved oxygen.

The book goes on further and explains that chronic underoxygenation decreased overall performance in subsequent generations. This test was done at nearly 2x the level of disolved oxygen then that of shaking alone (5ppm). They studied the results out to 5 generations..."By the fifth generation, the fermentation displayed a significan increase in lag time, an increase in the time to complete fermentation, and a higher terminal gravity than the earlier-generation fermentations."

That being said, they didnt break down other non-Pure oxygen methods, but from what I have read elsewhere is that you will get significantly more dissolved oxygen from shaking then simply bubbling atmospheric air through a hose.

On another note, there was an article in the new December 2013 BYO magazine (http://byo.com/stories/issue/item/2891-aeration-mr-wizard) that talks about aeration via a Venturi device which is cheap and easy to do. The author of that article personally used that means without difficulty, and recommends it for those who dont have access to pure oxygen infusion techniques. I also found this article here on homebrewtalk (https://www.homebrewtalk.com/entries/wort-aeration-how-to-build-a-free-pump.html) which explains the Venturi device a little better.

 

[eastoak]

Shaking the carboy/bucket vigorously for 5 minutes (which is significantly more than just letting it cascade from your BK to your carboy/bucket) only gets about 2.71ppm of dissolved oxygen.

are you sure that's what it says?

 

[eastoak]

this is from Wyeast's website the chart did not really survive the cut and paste job but you can sort that out. as you can see just sprying the wort into the fermentor gets you 4ppm right off the bat.

Methods of Aeration / Oxygenation

Homebrewers have several aeration/oxygenation methods available to them: siphon sprays, whipping, splashing, shaking, pumping air through a stone with an aquarium pump, and injecting pure oxygen through a sintered stone. We have tested all of these methods using a dissolved oxygen meter and have found that, when using air, 8 ppm of oxygen in solution is the best that you can achieve. Injecting oxygen through a stone will allow much higher dissolved oxygen levels. The chart below shows methods tested and the results.



Method DO ppm Time
Siphon Spray 4 ppm 0 sec.
Splashing & Shaking 8 ppm 40 sec.
Aquarium Pump w/ stone 8 ppm 5 min
Pure Oxygen w/ stone 0-26ppm 60 sec (12ppm)


this addresses the aquarium pump method.

It was concluded that pumping compressed air through a stone is not an efficient way to provide adequate levels of DO. Traditional splashing and shaking, although laborious, is fairly efficient at dissolving up to 8 ppm oxygen. To increase levels of oxygen, the carboy headspace can be purged with pure oxygen prior to shaking. The easiest and most effective method remains injecting pure oxygen through a scintered stone.


http://www.wyeastlab.com/hb_oxygenation.cfm

 

[05m50dan]

According to the "Yeast: A Practical Guide to Beer Fermentation", by Chris White (Whitelabs) and Jamil Zainasheff (The Brewing Network & Heretic Brewing Co.) on page 79 there is a chart that outlines the measured dissolved oxygen in a batch of 1.077 SG wort at 75*F oxygenated in different ways. The control group was the shaking method, and the reading was 2.71ppm.

If you have studied this (and I'm not saying you havent) you understand that both temperature and density affect the amount of oxygen that will remain dissolved in wort (lower density and lower temps allow greater amounts to dissolve). The Yeast book gives both a gravity and a temperature reading as part of their research, whereas the Wyeast site doesnt even mention that what they are testing is actually wort. It may be wort, it may just be distilled water. The data from the Yeast book eliminates those unknow variables...it is brewers wort at a gravity of 1.077 and a temp at 75*F. Can you get a higher ppm from shaking, I'm sure you can, but you probably need a lower SG.

I'd rather base my practice on data with less unknow variables then random statments. I also dont desire to argue the points anymore either. Was giving advise based on my experience with brewing and the knowledge I've gathered both from reading and listening to The Brewing Network's Sunday Session and Brewstrong episodes where a lot of this information is covered. Do whatever you feel comfortable doing.

 

[eastoak]

According to the "Yeast: A Practical Guide to Beer Fermentation", by Chris White (Whitelabs) and Jamil Zainasheff (The Brewing Network & Heretic Brewing Co.) on page 79 there is a chart that outlines the measured dissolved oxygen in a batch of 1.077 SG wort at 75*F oxygenated in different ways. The control group was the shaking method, and the reading was 2.71ppm.

If you have studied this (and I'm not saying you havent) you understand that both temperature and density affect the amount of oxygen that will remain dissolved in wort (lower density and lower temps allow greater amounts to dissolve). The Yeast book gives both a gravity and a temperature reading as part of their research, whereas the Wyeast site doesnt even mention that what they are testing is actually wort. It may be wort, it may just be distilled water. The data from the Yeast book eliminates those unknow variables...it is brewers wort at a gravity of 1.077 and a temp at 75*F. Can you get a higher ppm from shaking, I'm sure you can, but you probably need a lower SG.

I'd rather base my practice on data with less unknow variables then random statments. I also dont desire to argue the points anymore either. Was giving advise based on my experience with brewing and the knowledge I've gathered both from reading and listening to The Brewing Network's Sunday Session and Brewstrong episodes where a lot of this information is covered. Do whatever you feel comfortable doing.

lol.

 

[05m50dan]

Lol?

 

[eastoak]

most studies that call for 5 min of shaking are talking about worts that are < 1.065. SG higher than that mean, duh, you shake a little longer. shaking is second only to pure O2 (which is what i use unless i'm using dry yeast) in every comparison i've ever seen.

this study used water instead of wort but they explain why it does not matter much. conclusion: shaking (drum roll) rocks.
http://www.brewangels.com/Beerformation/AerationMethods.pdf

 

[05m50dan]

We are not disagreeing in relation to shaking, and your video agrees with my earlier statement that just letting the wort fall from the BK to the Fermentor isnt getting enough oxygen dissolved.

 

[statseeker]

You forget that it takes several continuous minutes to get your wort into the fermentor via a spigot. I can make it take 20 mins if I want to. You can't tell me that 20 mins of continuous splashing in 5 gallons of wort doesn't introduce a satisfactory amount of dissolved oxygen for healthy yeast reproduction and eventually fermentation. I mean...you can and probably will. But I'll continue doing things the way I'm doing them and continue to get normal attenuation. It's all good.

Having the Yeast book in front of me...it says that no home brewer with a normal budget can really afford a device to measure dissolved oxygen. So we pretty much have to go on fermentation signals/characteristics and taste to determine if we did oxygenate well enough. Barring that we need a bottle of O2 and scinter stone. Extra equipment to maybe get a few more degrees of attenuation or possibly overoxygenate.

My original thought stands. We're way overthinking this. Splashing works. It's easy. Most of us aren't taking the same yeast cake out several generations. Just do what's best for you.

 

[05m50dan]

@statseeker~
I agree that "no home brewer with a normal budget can really afford a device to measure dissolved oxygen", but I disagree with you final conclusion. You can make beer without adding any oxygen, or even splashing it around. The point is, we are discussing OPTIMAL oxygenation strategies, based on published research and professional brewing practices. I may not be able to reasonably purchase a dissolved oxygen meter and test every batch of wort before pitching yeast, but I can read the research of people who have one and have researched which practices get closest to the recommended values. When I dedicate my time and effort into making beer, I want to make the best beer I reasonably can. That means finding the best practices that are within reason (and budget) to make my beer. As to yeast and oxygenation, I purchased a 5 micron stone and a Pure Oxygen delivery system. This is the best method for delivering the RECOMMENDED level of oxygen to your wort. I know that not everyone has one, and if you dont that's fine. The point is that you should use the information that is available to you to make the best choices for your system, based on what you have. I dont think that anyone here would say that the best practice is to slowly drip cooled wort into their fermentors for 20 minutes. You'd risk infection less and get more dissolved oxygenation by running the wort into your fermentor as quickly as you can and then shaking it for 5 minutes. You will make beer though.

You also mention the possibility of over-oxygenating, but that is very unlikely if you are oxygenating a full batch of wort (vs just a starter), unless you completely ignore recommended practice (1 liter/min x 1 minute through a diffusion stone).

Over-all do what you like, and do what works for you. The OP was referencing using his yeast for multiple generations, and insufficient dissolved oxygen during the reproductive phase of yeast decreases overall yeast health in future generations, meaning it will affect attenuation, flocclation, and fermentation time in future batches. You may not be worried about using your yeast for future generations/batches, but the OP was.