[klickitat jim]

Personally, id dump it and start over. If I had to reuse it I would take a 100ml and build a starter.

[denny]

Don't know if it'd make a difference but the yeast used was Dannys favorite by wyeast

Um...that's "Denny"....

[S. cerevisiae]

So I just bottled my milk stout and didn't rinse. Now I have this and I'm not too sure what layers I should transfer to my mason jars. Can you help me figure it out? Thanks!!

I can tell you where you went wrong. Your liquid to solid ratio is too low (it should be at least 1:1), which is why you did not achieve good separation.  You left too little liquid in your fermentation vessel when you racked, resulting in a fairly thick slurry after swirling.  The process works best when one leaves at least 1/4th of gallon of clear liquid behind with the break and yeast when racking.   I would swirl the solids into solution, wait a few minutes for the heaviest particulate matter to settle, and carefully decant the thinnest fraction.  The goal is not to attempt to obtain a squeaky clean crop, but more of a "clean enough" crop.  I would also not attempt to "bank" slurry. There are better ways to bank yeast.  Slurry should be approached as a short term way to hold yeast for one's next batch.

[Jimmy K]

Don't know if it'd make a difference but the yeast used was Dannys favorite by wyeast

Um...that's "Denny"....

A wise man once said we should figure things out for ourselves.

[Joe Sr.]

One habit that all brewers should get into is the habit of wiping all pouring surfaces with a cotton ball soaked with 95% ethanol (or 91% isopropyl alcohol if one is patient enough to allow it to flash off) before decanting any yeast culture (that includes starters and all steps in the starter process).  The pouring surface of a container holding a yeast culture should always be treated like it is contaminated.  Just as a nurse or doctor disinfects one's skin before injecting one with a syringe to ensure that the needle does not drag surface bacteria into the injection site, wiping the pouring surface of a container that contains a yeast culture  prevents the yeast culture from dragging any wild microflora that may be resting on the pouring surface into fresh media or wort.  It's a cheap insurance policy.

I work on the assumption that if the beer I'm cropping from isn't infected, then the sanitation is good and I don't need to bother wiping down the rim of my bucket before I pour.  Hasn't failed in hundreds of times.

Wow.  This thread just keeps going and going.

I do what Denny does, except I don't use buckets.  I use better bottles with the orange caps on them.  The bottle and cap are sanitized before the beer goes in and I assume they stay that way.  I haven't had any contamination issues from pouring directly into a sanitized container.  Been doing this for years.

I sometimes think we over-think things.

[S. cerevisiae]

Wow.  This thread just keeps going and going.

I do what Denny does, except I don't use buckets.  I use better bottles with the orange caps on them.  The bottle and cap are sanitized before the beer goes in and I assume they stay that way.  I haven't had any contamination issues from pouring directly into a sanitized container.  Been doing this for years.

I sometimes think we over-think things.

Wiping the pouring surface with an alcohol saturated cotton ball, cotton swab, or piece of cotton gauze is just a good habit to get into when transferring yeast.  I wipe and flame when transferring from a glass container.  It's a carry over from aseptic transfer technique.  The mouths of the culture tubes in which I prepare my slants have never been exposed to airbone dust since they and the solid media that they hold were sterilized with 250F moist heat at 15 PSI above sea level for 15 minutes, but the standard practice is to flame the mouth after removing the cap and before inoculating the slant.  It's an insurance policy against contamination.

[Joe Sr.]

No doubt. I see no negatives to wiping with alcohol. I'd like to say I'll do it but since I haven't had any issues  I'm  just as likely to slack.

[JT]

Wow.  This thread just keeps going and going.

I do what Denny does, except I don't use buckets.  I use better bottles with the orange caps on them.  The bottle and cap are sanitized before the beer goes in and I assume they stay that way.  I haven't had any contamination issues from pouring directly into a sanitized container.  Been doing this for years.

I sometimes think we over-think things.

Wiping the pouring surface with an alcohol saturated cotton ball, cotton swab, or piece of cotton gauze is just a good habit to get into when transferring yeast.  I wipe and flame when transferring from a glass container.  It's a carry over from aseptic transfer technique.  The mouths of the culture tubes in which I prepare my slants have never been exposed to airbone dust since they and the solid media that they hold were sterilized with 250F moist heat at 15 PSI above sea level for 15 minutes, but the standard practice is to flame the mouth after removing the cap and before inoculating the slant.  It's an insurance policy against contamination.

I could probably bump my game up a bit here.  Everything I use currently has been washed and sanitized, or in the case of the flask holding the yeast, covered with foil during propagation.  If I'm using a funnel to transfer into a carboy, you would wash, sanitize,  wipe with alcohol, then flame? Any OTC rubbing alcohol suffice or is there a percent I should be looking for?

[reverseapachemaster]

Don't know if it'd make a difference but the yeast used was Dannys favorite by wyeast

Um...that's "Denny"....

Don't be such a stickler Danny.

[S. cerevisiae]

I could probably bump my game up a bit here.  Everything I use currently has been washed and sanitized, or in the case of the flask holding the yeast, covered with foil during propagation.  If I'm using a funnel to transfer into a carboy, you would wash, sanitize,  wipe with alcohol, then flame? Any OTC rubbing alcohol suffice or is there a percent I should be looking for?

With aseptic transfer, one not only flames the source and destination culture tubes, one also performs the transfer over a flame because it prevents airbone microflora from contaminating the culture (hot air rises). We are talking about transferring very tiny amounts of yeast that will be propagated into larger amounts of yeast at a later time.

With a normal yeast transfer, all we are attempting to do is to reduce the chance of picking up unwarranted native microflora during the transfer.   Hence, we only need to ensure that the lip of the container over which the culture will be poured has been cleaned of wild microflora before pouring.  Most wild microflora do not travel on their own.  They usually hitch a ride on house dust.  Even if you cannot see it, almost everything in one's house is covered with dust particles.  The lip of a carboy, flask, or any other container in which a rubber stopper has been inserted during propagation, fermentation, or cold storage will usually harbor some dust and wild microflora.  Wiping with an alcohol saturated cotton ball, cotton swab, or a piece of cotton gauze before pouring the yeast culture will reduce, if not completely remove that source of contamination. 

The process makes sense if one thinks about what a nurse or doctor does before he/she gives you an injection.  The alcohol prep is to prevent the needle from dragging microbes on your skin into the injection site.  In the case of a culture, wiping the pouring surface will help to prevent the yeast culture from dragging any microbial contamination that may have been resting on the pouring lip into one's fermentation vessel.  A small amount of bacteria can overtake a much larger amount of yeast because the bacteria cell population increases 8-fold every time the yeast cell population doubles.  If we were to normalize the propagation period between yeast and bacteria (bacteria multiplies three times faster than yeast), the growth equations would be:

yeast_cell_count = initial_cell_count * 2ⁿ, where n = elapsed time in minutes since the end of the lag phase / 90

bacteria_cell_count = initial_cell_count * 8ⁿ, where n = elapsed time in minutes since the end of the lag phase / 90


If we run the numbers, it should become crystal clear why one wants to pitch a large, healthy yeast culture while doing everything possible to minimize the opportunity for bacteria to catch a ride into one's yeast crop, starter, or fermentation vessel.  It should also become clear why the growth phase is called the exponential phase.


Cell counts at 90 minutes

yeast_cell_count = initial_yeast_cell_count * 2¹ =  initial_cell_count * 2
bacteria_cell_count = initial_bacteria_cell_count * 8¹ = initial_cell_count * 8


Cell counts at 180 minutes

yeast_cell_count = initial_yeast_cell_count * 2² =  initial_cell_count * 4
bacteria_cell_count = initial_bacteria_cell_count * 8² = initial_cell_count * 64


Cell counts at 270 minutes

yeast_cell_count = initial_yeast_cell_count * 2³ =  initial_cell_count * 8
bacteria_cell_count = initial_bacteria_cell_count * 8³ = initial_cell_count * 512


Cell counts at 360 minutes

yeast_cell_count = initial_yeast_cell_count * 2⁴ =  initial_cell_count * 16
bacteria_cell_count = initial_bacteria_cell_count * 8⁴ = initial_cell_count * 4096


Cell counts at 450 minutes

yeast_cell_count = initial_yeast_cell_count * 2⁵ =  initial_cell_count * 32
bacteria_cell_count = initial_bacteria_cell_count * 8⁵ = initial_cell_count * 32768


Cell counts at 540 minutes

yeast_cell_count = initial_yeast_cell_count * 2⁶ =  initial_cell_count * 64
bacteria_cell_count = initial_bacteria_cell_count * 8⁶ = initial_cell_count * 262,144


Cell counts at 630 minutes

yeast_cell_count = initial_yeast_cell_count * 2⁷ =  initial_cell_count * 128
bacteria_cell_count = initial_bacteria_cell_count * 8⁷ = initial_cell_count * 2,097,152


Cell counts at 720 minutes

yeast_cell_count = initial_yeast_cell_count * 2⁸ =  initial_cell_count * 256
bacteria_cell_count = initial_bacteria_cell_count * 8⁸ = initial_cell_count * 16,777,216

Pitching a large culture limits the number of replication periods that are necessary to reach maximum cell density in a fermentation.  Reducing the number of yeast replication periods, reduces the number of replication periods for bacteria that can withstand a yeast culture's other defenses.  The bacteria population increases every time we repitch a bottom-cropped culture because each repitch is an opportunity for the existing bacterial load to increase.  One of the reasons why top-cropping is preferred over bottom cropping when repitching is because it naturally purifies the culture.  Top cropping does so because bacteria and wild yeast generally do not floc to the top.  This phenomenon is the basis of Max Emil Julius Delbrück's "Natural Pure Culture" method.  Max was a German agricultural chemist who duked it out with Emil Christian Hansen  for the hearts and minds of brewers at the beginning the industrial brewing era.  The name Emil Christian Hansen should be one that all brewers recognize, as Emil was the first brewing scientist to isolate a pure yeast culture.  That culture is known as Carlsberg Bottom Yeast No. 1.  It's still available today from culture collections.  The CBS-KNAW number is CBS 1513.  The National Collection of Yeast Culture number is NCYC 396.  I am fairly certain that Miller's strain is descended from Carlsberg Bottom Yeast No. 1.  The founder of Carlsberg, Jacob Christian Jacobsen, was generous with Emil's discovery.

[phunhog]

What about using chlorine dioxide tablets to kill/greatly reduce the numbers of bacteria in your yeast starter? I do this anytime I am stepping up an older starter to a pitchable quantity.  I agree that prevention is the best but......most of us are playing with yeast in less than perfect conditions.  Seems like cheap insurance.

[S. cerevisiae]

Like acid washing, chlorine dioxide treatment is a short term fix to a long term problem.  Sooner or later, one is going to have to acquire a new culture or grow a new culture from slant.

[ridesalot]

one thing I really like about reusing yeast, if you are making 3-4 batches of beer that can use same style of yeast, by the 4th pitch your amount of yeast is gigantic. on my 4th batch I really didn't make a starter, per se, I just wanted to wake the buggers up. in a 2litre flask I had almost one liter of solid yeast. big pitch, activity in only 2 hours. great beer, im drinking it now.  it was white labs 13 london ale yeast. 

[morticaixavier]

one thing I really like about reusing yeast, if you are making 3-4 batches of beer that can use same style of yeast, by the 4th pitch your amount of yeast is gigantic. on my 4th batch I really didn't make a starter, per se, I just wanted to wake the buggers up. in a 2litre flask I had almost one liter of solid yeast. big pitch, activity in only 2 hours. great beer, im drinking it now.  it was white labs 13 london ale yeast.

what was the gravity? that's an s-load of yeast. even for a big 1.100+ beer I only use about 12-16 ounces of fairly thin slurry.

[dilluh98]

Not to sidetrack the thread but if I were to use the bottom cropping methods outlined by S. cerevisiae on the first page (paragraph 4, I believe) would the "thin slurry," i.e., 1 billion/mL setting on something like Mrmalty.com give me a decent estimate in terms of starter requirements (if not pitching immediately)?

I've heard that most of the calculators out there give slightly (if not grossly) over-shot number in terms of what needs to be pitched and that the numbers get a bit fuzzy anyway due to a lot of factors that can't be accounted for by a few inputs on an online calculator. In that vein, can there be a point at which you've pitched too much yeast? Ridesalot above stated pitching a full liter of solid yeast - good lord!