1 Posted: Wednesday, October 11, 2017 10:48 AM

I'm a fan of reusing yeast, as slurry, though ordinarily I don't use more than a few cycles before starting fresh. However on this occasion I ventured out to 5 cycles with Nottingham. And one very observable difference is the flocculation behaviour this time. It seems to have slowed to the point that on bottling day the beer was far far cloudier than usual… significantly so. And, this becomes very evident a few days later when I look at the height of sediment that is now forming in the bottles. I have no doubt that the beer will eventually clear but there does seem to have been a real slowing while the beer was still in the FV.

On a related matter, one thing I noticed repeatedly way back when I used to rack my beer into a secondary FV that it seemed to stimulate flocculation. Within hours a significant sediment would have formed in the secondary FV. I guess this was why the use of a secondary for clearing purposes used to be commonly recommended. It was interesting to have this verified in a couple of articles I read just today i.e. agitation actually promotes flocculation.

Cells must come into contact with each other for flocculation to occur, hence the surprising observation that flocculation and the vigour of mechanical agitation are positively correlated.


Given this, I'm wondering now if a bit of a stir after fermentation is complete would actually be a good idea?

And, with that in mind, it's kind of interesting when you consider agitation is often suggested as a fix for a stalled ferment. It may well be it is in fact having the opposite effect!


2 Posted: Wednesday, October 11, 2017 12:01 PM

I've observed the complete opposite with re-using yeast strains. They're usually crap at flocculating for the first 2-3 generations, and after that they start dropping like a stone. I've taken at least one strain past 10 generations and its flocculation was terrific.

I'm about to keg a beer that was fermented with a 9th generation 1469 culture; I'll grab a pic of a glass of it from the fermenter and post it in the kegging thread. I expect it will be slightly cloudy with yeast but essentially clear.

Cheers

Kelsey

3 Posted: Wednesday, October 11, 2017 1:26 PM

Actually I'll just post it here. It's not as clear as they usually are on kegging day but that's probably due to the commando dry hop I did just before the cold crash. Normally I use the tea strainer things and it stops that happening. Either way by the time it's on tap it should have cleared up nicely.



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4 Posted: Wednesday, October 11, 2017 3:20 PM

Otto Von Blotto:

I've observed the complete opposite with re-using yeast strains.

Curious. I was just trying to read a science paper on the topic - 95% of which goes way over my head I have to say! But I did read the following:

Among many brewing properties, yeast flocculation is generally seen as the most instable property. A flocculent strain can gradually lose its aggregation characteristics and become powdery after successive generations


And…

It was proposed that nonflocculent cells can grow dominantly through successive cultivation. However, genetic instability of brewing yeasts seems to be strain dependent. Although some brewing yeasts are vulnerable to a genetic drift, other strains can remain stable over a serial repitchings.


I wonder if Nottingham is just one of those strains that doesn't cultivate so well?

5 Posted: Wednesday, October 11, 2017 6:11 PM

My experience aligns with Ottos here , must be strain dependant as my 1272 , 1469 and coopers commercial strains just keep getting stronger after a few generations
They attenuate better and drop like a stone.
Not used Notty for a while but have a soft spot for it particularly during winter .
My coopers strain is now an animal but still pours cloudy as it should even after keg has been in fridge for a month
1272 is “topped up ” every 40 l of starters or so ( I supply friends with yeast too )
1469 has been neglected for a while but still went very hard and dropped clear on a ESB we decided to brew up for summer and will be used for my “ forward planning ” stout for next winter

Blacky it may come back to how're you're harvesting as much as what you're harvesting

6 Posted: Wednesday, October 11, 2017 9:12 PM

Agree with Otto and the pirate that in general flocculation tends to get better the more generations. This has happened for me with Lagers (Budvar 2000 especially) and most ales as well. However I used a US-05 to like 8 generations and it got steadily worse IMO. Flavour was unchanged but had a bottle for two months which was still cloudy.

7 Posted: Wednesday, October 11, 2017 11:14 PM

Hey BlackSands, when do you collect your slurry? Do you wait until bottling day? How many days after pitching is that? Do you decant anything off the slurry?

I don't doubt that strain genetics plays a role, but brewer behaviour does too. I have a hunch that the timing of the slurry collection plays a crucial role. Dr Chris White and Jamil Zainasheff say in their book, “Yeast,” that slurry should be collected on day seven. I think if you do that, you will select for the more flocculant cells / examples of the strain, whereas if you wait until bottling day you get more of a mixture of flocculant and less flocculant yeast.

Another brewer behaviour that could be a factor is whether you pour off the clear beer before pitching the slurry. Some yeast may still be in suspension in there, so by pouring it off, a brewer once again selects for more flocculant yeast.

Kelsey collects slurry from starters; I bet that it is less than seven days old when he does that. I think he also pours off the clear liquid at the top before pitching.

I have a theory that all of this is related to cell size: that more flocculant yeast are larger and heavier and that less flocculant yeast are smaller and lighter. The reason I say this is because of gravity; it just makes sense. And there may be some support for my theory in the chart in this yeast calculator link: https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

Cell density per gram of dry yeast varies tremendously by strain; you get a lot more cells in an 11.5gm package with some strains than with others. For example, S-33, a powdery strain, has 16 billion cells per gram, vs S-04, a flocculant strain, which has only 8 billion cells per gram….My guess is that even within a strain, there are larger and smaller cells. In other words, while S-04 cells on the whole will be much larger than S-33 cells, some S-04 cells will be larger than others.

I suppose liquid yeast manufacturers take cell size into account by packing the cells in more or less densely.

I don't agree with you that stirring may be counter productive in a stalled ferment. Stirring will bring the yeast that have already settled on the bottom back into suspension, where they will be more effective. The settling process just starts over again, with the heavier cells falling first.

Cheers,

Christina.

8 Posted: Thursday, October 12, 2017 7 AM

When I collect from my starters, the whole thing is stirred up again for a few hours before I pour into the jar. I figure doing this selects a reasonable variety of cells. When I pitch the yeast into the batch though I do tip the “beer” off first, which no doubt contains some yeast cells. I don't think it contains enough to be only selecting highly flocculant cells though because after a two day crash in the fridge the “beer” is pretty clear of yeast.

Yeast cells do vary in size in the same strain, I've noted this many times when doing my yeast viability testing. This photo is from a 45 day old Budvar sample. You can see the different sizes of cells in it.



Cheers

Kelsey

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9 Posted: Thursday, October 12, 2017 7:36 AM

I just about need a hammer and cold chisel to lift the yeast off the bottom of the FV after several generations. Using fairly high floccing yeasts namely 1469 and 1272.

10 Posted: Thursday, October 12, 2017 8:12 AM









11 Posted: Thursday, October 12, 2017 10:10 AM

ChristinaS1:

I don't agree with you that stirring may be counter productive in a stalled ferment.

I know rousing up the yeast is frequently recommended, it's everywhere, all over the net as common strategy to help wake up a stalled ferment but interestingly I've never actually read anywhere where it has ever worked in practice. The usual responses I see are something like “I tried that but a few days later my SG is still at 1.020”. The ONLY thing I have read about fixing stalled ferments that does seem to get things going again reliably is pitching slurry or racking the beer onto another yeast cake.

12 Posted: Thursday, October 12, 2017 11:23 AM

BlackSands:

ChristinaS1:

I don't agree with you that stirring may be counter productive in a stalled ferment.

I know rousing up the yeast is frequently recommended, it's everywhere, all over the net as common strategy to help wake up a stalled ferment but interestingly I've never actually read anywhere where it has ever worked in practice. The usual responses I see are something like “I tried that but a few days later my SG is still at 1.020”. The ONLY thing I have read about fixing stalled ferments that does seem to get things going again reliably is pitching slurry or racking the beer onto another yeast cake.


I have to agree with you that stirring a stuck ferment often doesn't work, but I don't think it makes the situation worse. I think if some ghost cells are pitched at the same time, it can be effective.

I do some cider and wine brewing, for my vinegar business. I have learned that it is pretty much common practice, and necessary, to stir the must on the front end of fermentation, once a day, until the gravity gets down to ~1.020. Currently I am trying a yeast I haven't used before, to ferment some apple cider, and I am having some issues with it. With my old yeast I could be a bit neglectful with the stirring and it would still attenuate quite rapidly. This new yeast is not so forgiving; I am guessing is must be more flocculant. Both are S. cerevisiae strains.

It is funny how different fermenting communities have different practices. This reminds me of a interview I heard with Shea Comfort, the Yeast Whisperer. He started his career brewing beer, then moved to mead, and now to wine. He says that now, when he does brew beer, he stirs the wort once a day, for the first few days, like a winemakers do. His wine-making experience makes him believe it helps fermentation.

Cheers,

Christina.


13 Posted: Thursday, October 12, 2017 9:16 PM

Otto Von Blotto:

When I collect from my starters, the whole thing is stirred up again for a few hours before I pour into the jar. I figure doing this selects a reasonable variety of cells. When I pitch the yeast into the batch though I do tip the “beer” off first, which no doubt contains some yeast cells. I don't think it contains enough to be only selecting highly flocculant cells though because after a two day crash in the fridge the “beer” is pretty clear of yeast.

Yeast cells do vary in size in the same strain, I've noted this many times when doing my yeast viability testing. This photo is from a 45 day old Budvar sample. You can see the different sizes of cells in it.



Cheers

Kelsey


That is a cool picture Kelsey. Yes, it is just as I thought: the cells are different sizes. Thanks for posting it. We are lucky you have a microscope.

How is your viability study going?

Cheers,

Christina.

14 Posted: Thursday, October 12, 2017 9:29 PM

It's not . I'm not giving up on the whole idea though, just with birthdays and other shit getting in the way lately I haven't been able to do daily testing. So, I'm gonna can the Budvar testing because there's little point making up stats to fill the gaps. I'll start it up again soon though with whatever strain I've been spinning up at the time, and hopefully be able to find more time to do the daily testing for longer.

In any case, that 45 day old sample returned a viability of around 86% I think; the calculator had suggested 68% for the same time period, so that's another small data point suggesting that the calculator is dropping the viability too quickly.

Cheers

Kelsey

15 Posted: Friday, October 13, 2017 1:20 PM

ChristinaS1:

BlackSands:

ChristinaS1:

I don't agree with you that stirring may be counter productive in a stalled ferment.

I know rousing up the yeast is frequently recommended, it's everywhere, all over the net as common strategy to help wake up a stalled ferment but interestingly I've never actually read anywhere where it has ever worked in practice. The usual responses I see are something like “I tried that but a few days later my SG is still at 1.020”. The ONLY thing I have read about fixing stalled ferments that does seem to get things going again reliably is pitching slurry or racking the beer onto another yeast cake.


I have to agree with you that stirring a stuck ferment often doesn't work, but I don't think it makes the situation worse.


I do wonder about that…

Brewing Yeast & Fermentation - Christopher Boulton, David Quain:

“Although seemingly contradictory, flocculation requires agitation! The early fortuitous observations of Stratford & Keenan (1987) have been further developed into a persuasive argument. Initial laboratory studies (Straford & Keenan, 1987) showed that the harder flocculent yeasts were shaken the better they flocculated. Indeed, without agitation, a flocculating culture was unable to flocculate. Further, the rate of flocculation increased in parallel with increasing mechanical agitation”

16 Posted: Tuesday, October 17, 2017 7:18 AM

me:

However, just to appease my own curiosity I have just pitched another 5th cycle of Nottingham into my latest batch and will be monitoring that one with great interest!


I can confirm that the flocculation characteristics of Nottingham has definitely changed. My current batch it's exhibiting the same behaviour as the previous one. Generally the yeast appears to be staying in suspension longer but more particularly, it's forming into semi-buoyant yeast clumps. Each time I take a hydrometer sample I get a sample jar full of yeasty globules!

17 Posted: Tuesday, October 17, 2017 11:41 AM

BlackSands:

me:

However, just to appease my own curiosity I have just pitched another 5th cycle of Nottingham into my latest batch and will be monitoring that one with great interest!


I can confirm that the flocculation characteristics of Nottingham has definitely changed. My current batch it's exhibiting the same behaviour as the previous one. Generally the yeast appears to be staying in suspension longer but more particularly, it's forming into semi-buoyant yeast clumps. Each time I take a hydrometer sample I get a sample jar full of yeasty globules!


Oh no! What are you going to do? Try finning? Cold crash?

How many generations did it drop clear / like a stone (which you mentioned in another thread is the thing that attracted you to Nottingham)?

Cheers,

Christina.

18 Posted: Tuesday, October 17, 2017 11:45 AM

Given I have the opposite experience with flocculation (i.e. improving as the generations go on), maybe it's to do with the harvesting from starter method rather than harvesting from fermenter trub.

That being said, I do cold crash as you know, and also use isinglass which drops out more yeast than it would on its own.

19 Posted: Tuesday, October 17, 2017 8:27 PM

ChristinaS1:

BlackSands:

me:

However, just to appease my own curiosity I have just pitched another 5th cycle of Nottingham into my latest batch and will be monitoring that one with great interest!


I can confirm that the flocculation characteristics of Nottingham has definitely changed. My current batch it's exhibiting the same behaviour as the previous one. Generally the yeast appears to be staying in suspension longer but more particularly, it's forming into semi-buoyant yeast clumps. Each time I take a hydrometer sample I get a sample jar full of yeasty globules!


Oh no! What are you going to do? Try finning? Cold crash?

How many generations did it drop clear / like a stone (which you mentioned in another thread is the thing that attracted you to Nottingham)?

This is the second 5th cycle slurry I've used. The previous four cycles behaved consistently with the first time use… i.e dry yeast from a new packet.
The previous 5th cycle batch is one week in the bottle now, tasted as expected at bottling time and is now looking nice and bright, so I'm not expecting any detrimental effects. It's just interesting that the flocc behaviour has changed while in the FV.

Otto:

Given I have the opposite experience with flocculation (i.e. improving as the generations go on), maybe it's to do with the harvesting from starter method rather than harvesting from fermenter trub.

Certainly within the realms of possibility I guess.

20 Posted: Thursday, October 19, 2017 9:51 AM

Hi BlackSands. I was just reading something in one of the Fermentis Tips & Tricks documents that made me think of this thread. There seem to be many versions of their Tips & Tricks on the web, and now that I am looking for it, I can't find this particular one back, and other versions don't mention it. Anyway, it said that flocculation can be sub par when calcium levels are <100 (whatever the unit was).

BlackSands, you have mentioned your water is quite soft. Maybe this is part of the issue?

Cheers,

Christina.