Slow fermentation due to poor harvesting technique???

[Brewer X]

Recently I have been getting fermentations on re-pitch that start out strong but drop off to a crawl after about 3 days. Wondering if this is due to poor yeast harvesting technique on my part (harvesting early flockers).

After terminal is reached, I am dropping tank temp a few degrees (approx 5*F) to promote flock. After a couple more days I am harvesting into 1 gal glass jugs. Dumping the first gallon and using the second 2 gals to re-pitch - then dumping remaining yeast. In those two glass jugs I am getting approximately 1.5 gallons of solid yeast slurry. This is for a 7bbl batch. Original yeast is WL 001.

Does it sound like I am harvesting too low in the cone?

[brewingnewbie]

what generation are you at?
is your slurry nice and fluffy or runnier?

personally i used to pitch my 7bbl batches with at least 5 gallons of nice thick slurry and it would take off strong

[Brewer X]

generation

This is happening at 2nd and 3rd generation.

Sounds like you think I'm under-pitching.

I've been worried about over-pitching.

[Moonlight]

Sounds like oxygen deficiency to me. I would like to see a bit more pitched, but if there is not enough to harvest, there's something restricting growth. This much can easily grow to full population...think of how little you get in a fresh yeast culture.

[Brewer X]

yeast

Is there a general rule of thumb - so much yeast at the end of fermentation per barrel = good population?

[safety man]

My #1 recommendation is to buy a microscope, a pH meter, and a hemocytometer. Look at your yeast under a microscope. Use a simple methyline blue stain. You are probably pitching a large amount of dead yeast. Count the total yeast cells then the live and dead.
A simple calculation can tell you how much yeast to pitch.
Avoid harvesting from high gravity brews. These fermentations generally lead to cell mutation and a significant drop in fermentation ability.
Buy a fresh yeast propagation and start over.
Keep accurate records.
If this is too much for your facility, just go with a pH meter. yeast pH>5.1 are dying or already dead.

[TNbrewer]

You want to pitch from the middle 1/3 of the slurry. That way you're not selecting for early or late floccers (did I just make up a new word?). There are a lot of factors influencing slurry thickness, so there's no rule of thumb. On average we are pitching 7-7.5 gals of slurry in 15.5 bbls of wort, but our yeast is slightly fluffy due to "spunding" our fermentations. If I was pitching that much of another brewer's slurry, who doesn't spund, I would be grossly overpitching, due to the much higher cell count of their slurry.

The rule of thumb you are asking about is measured prior to fermentation, prior to pitching. The old rule of thumb is 1 million cells/mL/deg. Plato. So for a 12 Plato beer, 12 million cells per mL of wort. Ale brewers can go a bit lower than this. We use ~750,000 cells/mL. You use the equipment safety man listed to determine this. It does sound like you are underpitching.

It could also be related to wort aeration. Poor aeration can lead to fermentations that seem to start off OK, but finish slowly, over a day or more. A well aerated, properly pitched ale fermentation can go from strongly fermenting to barely bubbling in less than 12 hrs.

yeast pH>5.1 are dying or already dead.

On the matter of pH I would add that it is more dependent on the pH of the beer the slurry is in, since beer pHs vary from brewery to brewery. The general method would be to measure the slurry pH and the beer pH. In fresh, healthy slurry, they should be the same. As soon as the yeast viability starts to fall, you will see the pH start to rise. So a slurry pH of 4.5 from a beer that is 4.5 is good. If it is from a beer that is 4.0, that's a problem.

Cheers,
Chief Mutha Floccer

[Brewer X]

microscope

I do have a microscope and have been doing cell counts. Have not done any staining.

I have heard the rule "do not re-pitch from high gravity beers" many times. What is considered the threshold? My lowest gravity ales are 1.060 to start - which is what I am pitching from.

Maybe I have too many factors just on the threshold of acceptable (i.e. aeration, yeast health, pitch rate, etc) which is leading to "death by a thousand tiny wounds" if you will.

If I am to pitch fresh yeast each batch, I may have to switch to dry yeast for cost's sake. Any opinions, advice on this?

[kugeman]

In my 7 bbl brewhouse I would dump 2-5 gallons of dead yeast. I did cell counts for every batch and for a 12 P beer I would pitch on average 3.5 gallons of california yeast. For a 15.5 P beer I would pitch an average of 5-6 gallons of yeast. After doing post-pitch cell counts my pitches were consistently on. From what you described it sounds like you are 1)underpitching and 2)pitching some of the dead or early floccing yeast from the bottom of the cone. If you pitch the early floccing stuff for 2 or 3 generations you will basically be "naturally selecting" to have a yeast that floccs too early. So I'd dump more yeast first and then pitch more yeast into the beer.

Just my 2 cents.

[Jephro]

Slowing or Stalling Out?

Are you actually having any problems with your beer, or is it just this observation that is giving you concern? How long is it taking for your beer to reach TG?

I would not necessarily be alarmed by fermentation slowing after 3 days unless they are not finishing out. That said I am currently brewing on a 7BBL (10 BBL @ KO) and usually pitch 3-4 gallons (from a pressurized FV as I use a Spunding Device) depending on the yeast at harvest. I take into consideration the age of the yeast, generation, gravity of brew it's being pitched on, and the taste, smell, color and thickness of the yeast at harvest. If i had to guess i would say you may be underpitching a bit, as mentioned above you may want to dump a bit more off before you harvest. Also make sure when you are dumping you do it slowly, as not to suck a hole in the middle and end up dumping the good stuff from the top of the cone- which would also mean you end up harvesting/pitching the old, dead, and early flockers hanging out in the bottom of the cone.

If you are underpitching and your beers taste fine, you are probably just cutting short the number of generations you can get out of your yeast. I have never used dried yeast on a professional level, but i would be weary of changing your yeast on established beers unless you're having real technical problems.

Just my $0.02 FWIW

[gitchegumee]

I never pull yeast from a fermenter that hasn't been crashed cooled. Perhaps your yeast doesn't flocculate and precipitate well with a mere 5F drop. Is there a reason you don't harvest after you crash cool? That really helps develop the yeast cone into fast, medium, and powdery flocs. Good luck!

[gabewilson50]

I never pull yeast from a fermenter that hasn't been crashed cooled. Perhaps your yeast doesn't flocculate and precipitate well with a mere 5F drop. Is there a reason you don't harvest after you crash cool? That really helps develop the yeast cone into fast, medium, and powdery flocs. Good luck!

I'll second that.

[Moonlight]

I never pull yeast from a fermenter that hasn't been crashed cooled. Perhaps your yeast doesn't flocculate and precipitate well with a mere 5F drop. Is there a reason you don't harvest after you crash cool? That really helps develop the yeast cone into fast, medium, and powdery flocs. Good luck!

Crazy! Never heard of this. What is your separation like without crashing?

[SRB]

I feel like a top cropping outlander.....so different. Wired Gourmet I think you called it a "Black Art". Feels like it today.

Great thread...SRB is now a subscriber.

[Woolsocks]

Fermentis

Or you could circumvent the whole problem by using dry yeast from Fermentis. Their US-05 is the same as WL001 or real close.