[S. cerevisiae]

If you are not seeing a krausen start to form within 12 hours after inoculation with a Saccharomyces strain, then you doing something wrong.  Failure to see at least the start of a krausen within 12 hours after inoculation is usually a sign of a low viability culture, low dissolved O₂, not enough carbon or too much carbon (sugar is carbon bound to water), and/or the incubation temperature is too low.  Most of the time, long periods of time between inoculation and the onset of high krausen with a Saccharomyces strain is the result of low culture viability, which can be a problem during the summer months on the East Coast.  Liquid yeast cultures do not like being shipped in the summer heat. 

Are you making your 1L starters using 100 grams of DME?  Are you incubating your starters at between 22C (70F) and 25C (77F)?  How are you obtaining your cultures?  Are they stored in a refrigerator until use?  How are you aerating your starters?  If using a Wyeast smack pack, are you waiting until the package swells completely before inoculating your starter?

Finally, you do not need to crash a starter.  The wort from a non-stressed starter does not taste or smell foul.  All you need to do is to compensate for the dilution by boiling the wort down approximately 0.002 below your target gravity when pitching a 1L starter into a 19L (5-gallon) batch.

[Phil_M]

If a pack of yeast is suspected of having low viability, what's the best approach? Make a smaller starter and step it up once or twice?

[S. cerevisiae]

If a pack of yeast is suspected of having low viability, what's the best approach? Make a smaller starter and step it up once or twice?

Yes

[johnnyb]

If you are not seeing a krausen start to form within 12 hours after inoculation with a Saccharomyces strain, then you doing something wrong.  Failure to see at least the start of a krausen within 12 hours after inoculation is a usually a sign of a low viability culture, low dissolved O₂, not enough carbon or too much carbon (sugar is carbon bound to water), and/or the incubation temperature is too low.  Most of the time, long periods of time between inoculation and the onset of high krausen with a Saccharomyces strain is the result of low culture viability, which can be a problem during the summer months on the East Coast.  Liquid yeast cultures do not like being shipped in the summer heat. 

Are you making your 1L starters using 100 grams of DME?  Are you incubating your starters at between 22C (70F) and 25C (77F)?  How are you obtaining your cultures?  Are they stored in a refrigerator until use?  How are you adequately aerating your starters?  If using a Wyeast smack pack, are you waiting until the package swells completely before inoculating your starter?

Finally, you do not need to crash a starter.  The wort from a non-stressed starter does not taste or smell foul.  All you need to do is to compensate for the dilution by boiling the wort down approximately 0.002 below your target gravity when pitching a 1L starter into a 19L (5-gallon) batch.

I used a brand new (iirc, 2 to 3 weeks old by manufacturing date) Wyeast smack pack obtained at my LHBS the same day I made the starter. I smacked it as soon as I got home and it started to swell within the hour. It was fully swollen by the time I pitched it into the starter about 3 hours later.

My starter was 100 grams light pilsen DME brought to 1100 ml in distilled water, then boiled back down to 1000 ml and cooled to 70^o F and oxygenated with pure O₂ for 10 seconds before pitching. I used a 3 piece airlock on the flask. (2-liter flask as marked but it holds more like 3.5 liters and has a fairly large surface are when the volume inside is only 1 liter.) The room temp was 71^o maintained by air conditioning.

It had signs of activity within a few hours. I could see the white-ish layer of yeast near the top of the liquid, started getting airlock activity, etc. Within 5 hours it had a very active airlock, a thin layer of yeast on the surface but only covering about 50%, and it smelled great. I was expecting a krausen to form in the near future.

It continued to actively ferment for several more hours but no real krausen ever formed. At hour 10 I noticed a nice white layer of yeast start to form at the bottom of the flask. At hour 11 I decided to crash assuming it had progressed beyond the height of activity. Funny thing is the next morning in the fridge there was a "krausen like" formation on top of about an 1/8" covering 100% of the surface. When I put it in the fridge the top just had a wispy yeast layer on it.

It ended up forming a layer of yeast between 1/8" to 1/4" on the bottom of the flask. I decanted, warmed, and pitched a couple of days later and had one of the quickest blast offs that I've experienced. (Only have about 50 batches of experience so far, but still...) Everything about the fermentation seems to be very healthy so far.

From all the clues, I collected a good quantity of very healthy yeast. Just for some reason it didn't form a krausen. I watched it fairly closely, at least every 30 minutes putting an eyeball on it.

The only reason I want to maintain the practice of crashing is due to being nervous about timing it to be able to pitch into wort at high krausen. Since the timing of when it might be ready can vary, unless it makes a huge difference in performance, I would rather have it ready a few days ahead of time. Is that bad?

[BrodyR]

How long does everyone typically let a starter go for before pitching? I've usually waited a day and try to pitch than the krausen is up but was thinking about pitching one around hour 14 tonight.

Fourteen hours of incubation time is more than long enough for a 1L starter that was inoculated with a vial of White Labs yeast that is less than 4 months old.   Most strains take less than 6 hours to exit the lag phase (many will exit the lag phase in less than 3 hours). The average White Labs vial contains 50 billion viable yeast cells when pitched (100 billion at time of packaging).  Yeast cells divide approximately every 90 minutes after the lag phase has been exited, which means that the culture will contain approximately 100 billion cells 90 minutes after exiting the lag phase.  A 1L starter that was pitched with 50 billion viable cells will reach maximum cell density approximately 3 hours after exiting the lag phase, or roughly 9 hours total for most yeast strains.  Given enough O₂, carbon, physical room to grow, the time to reach 400 billion cells is approximately 10.5 hours, and the time to reach 800 billion cells is approximately 12 hours.

A key point to remember is that the yeast biomass grows exponentially, not linearly.  The growth rate is 2ⁿ, where n equals the number of minutes that have elapsed since exiting the lag phase divided by 90.  The equation for calculating the approximate number of cells at any point during incubation given an initial cell count is:

cell_count_at_time_n = initial_cell_count * 2^{(elapsed_time_since_exiting_the_lag_period_in_minutes / 90)}

The equation shown above is bounded by O₂, carbon, and media volume. 

One last thing, starters should be incubated at room temperature.

This is great info, thanks Mark.

[johnnyb]

I've just done the same process again today as described in my last post except the yeast was dated late March and it is WY1007 instead of WY1450. I pitched at 3:30 EST and it seems to be at high krausen already at 9:30.

[S. cerevisiae]

It continued to actively ferment for several more hours but no real krausen ever formed. At hour 10 I noticed a nice white layer of yeast start to form at the bottom of the flask. At hour 11 I decided to crash assuming it had progressed beyond the height of activity. Funny thing is the next morning in the fridge there was a "krausen like" formation on top of about an 1/8" covering 100% of the surface. When I put it in the fridge the top just had a wispy yeast layer on it.

It ended up forming a layer of yeast between 1/8" to 1/4" on the bottom of the flask. I decanted, warmed, and pitched a couple of days later and had one of the quickest blast offs that I've experienced. (Only have about 50 batches of experience so far, but still...) Everything about the fermentation seems to be very healthy so far.

From all the clues, I collected a good quantity of very healthy yeast. Just for some reason it didn't form a krausen. I watched it fairly closely, at least every 30 minutes putting an eyeball on it.

The only reason I want to maintain the practice of crashing is due to being nervous about timing it to be able to pitch into wort at high krausen. Since the timing of when it might be ready can vary, unless it makes a huge difference in performance, I would rather have it ready a few days ahead of time. Is that bad?

What strain did you pitch?

[johnnyb]

WY1450

[S. cerevisiae]

I have not used that strain since it was called Brewtek CL-50.  From what I can ascertain, CL-50 was acquired from North Coast Brewing (Red Seal Ale).  Mark Reudrich acquired it from U.C. Davis.  It's apparently one of the older U.C. Davis cultures, but I have yet to encounter in my journey through the U.C. Davis culture collections.  I have a British culture that I acquired from U.C. Davis that I need to revisit in the fall.  I used it to make a nice all-Cluster IPA.

[Vitaly]

Hi everybody! I usually use dry Fermentis yeast. Recently I began to make starter. I put 10 gr per 2 L, wait for 24 hours but can't get high krausen. Can you help me what I did wrong?

[klickitat jim]

Hi everybody! I usually use dry Fermentis yeast. Recently I began to make starter. I put 10 gr per 2 L, wait for 24 hours but can't get high krausen. Can you help me what I did wrong?

What size batches do you brew? For 20L of wort, a packet of rehydrated dry yeast ought to be enough. I would skip the starter.

[johnnyb]

I'm really starting to believe in the no stir plate pure oxygen starter method. Even though I'm still crashing at high krausen (rather than pitching at high krausen as recommended) and decanting before pitching, this is my second attempt using the method and both took off faster than my stir-plate starters. Both smelled good too.

4.5 hours since pitching for this one (WY1007) and I already have the first signs of take off.