[S. cerevisiae]

So how would this plan be for a generic ale brew? Start the starter 24 hrs before pitching time, at 18 hrs pop it in the fridge, decant and pitch 6 hrs later (24 hrs total)

If you want to decant the supernatant (the clear liquid that lies above the sediment), twenty-four hours should be adequate to clear all, but the most powdery yeast strains. 

[S. cerevisiae]

Interesting...so you're saying that pitching a starter earlier (before fermentation is complete) would reduce the oxygen requirement (i.e. oxygenation of wort)?  So for someone who does not oxygenate, they would be better off pitching earlier rather than later?

It's always better to pitch at the end of the deceleration phase than it is after fermentation is complete.  Nothing is gained by allowing a starter to ferment out.  No net increase in yeast biomass occurs during the stationary phase, ergosterol and unsaturated fatty acid reserves are depleted, and the cells are subjected to increasing amounts of fermentation byproducts, including ethanol.  Allowing a starter ferment out also results in the cells being in the yeast equivalent of hibernation. 

At the end of fermentation, yeast cells go into survival mode where their cell walls thicken and they store carbohydrate as glycogen.  In effect, the cells are preparing for hard times.  It takes longer to exit this state than its does when the yeast cells are still in active growth mode; hence, lag times in addition to oxygen demands are also increased. 

There are only two scenarios that I come to mind where it is okay not to aerate a batch of wort.  The first scenario is when pitching a quantity of yeast that is large enough that the cells do not have to undergo much in the way of multiplication.  The second scenario is when pitching dry yeast. 

Dry yeast is propagated using a continuous process that is very different than that that is used to propagate liquid yeast.  Dry is yeast is propagated aerobically in a device known as a bioreactor (a.k.a. chemostat) where the glucose level is kept below the Crabtree threshold via continuous injection of medium (usually molasses with supplemental nutrients) and removal of yeast.  Aerobic propagation is a significantly more efficient process because no ethanol is produced. Aerobic propagation also leads to yeast cells that have fully charged ergosterol and unsaturated fatty acid reserves due to continuous injection of oxygen. Liquid yeast cultures are usually propagated in batches where the glucose level significantly exceeds the Crabtree threshold (the glucose levels found in beer production exceed the Crabtree threshold by a large margin).

[hopfenundmalz]

What is your recommended starter gravity? ~1.032?

[S. cerevisiae]

Most of the starters that I make are in the range of 5% to 10% DME weight by volume (w/v).  I tend to shoot for a 7.5% w/v solution more often than not, which is roughly equal to 7.5 degrees Plato or a specific gravity of 1.030.  Degrees Plato is a weight by weight (w/w) unit of measurement.  A true 7.5% weight by w/w solution is made by dissolving 75 grams of DME into 925 milliliters or water, which will be the equivalent weight of 1L of water, but will not displace 1L of volume.  A 7.5% w/v 1L solution displaces 1L of volume.   I usually start with slightly more than a liter of water and boil down to 1L. 

As I ferment mostly 3.5 gallons batches, my standard starter volume is 600 milliliters.  I start with at most a 4mm nichrome loop of yeast taken from a slant on Tuesday night, and I have ready to pitch culture on Saturday morning.  We are talking about a huge amount of cell growth compared to pitching a White Labs vial into 1L of wort.

[Henielma]

Here in the Netherlands most starters are 100 gram DME and 1 liter water. This has a SG of almost 1040.

[hopfenundmalz]

I wonder about the 1.040 starter gravity one reads often. Several people that are very knowledgable about yeast have said something in the 1.028 to 1.032 range is very good for growing cells.

[yso191]

This is a great thread.  I thought I knew all I needed to know about starters.  I've even printed a couple of posts for future reference.  Thanks S.C!

[jtoots]

This is a great thread.  I thought I knew all I needed to know about starters.  I've even printed a couple of posts for future reference.  Thanks S.C!

Ditto that!  Starters are where I'm putting a lot of my effort the last few batches, still working on it...  Thanks all!

[denny]

I wonder about the 1.040 starter gravity one reads often. Several people that are very knowledgable about yeast have said something in the 1.028 to 1.032 range is very good for growing cells.

AFAIK, Wyeast and others are around 1.020 for yeast propagation.  I try to keep to the low end, 1.030ish.

[jmitchell3]

Do any of you guys make allowances for yeast age and yeast viability?  Ive been using brewers friend yeast starter calc and/or the mr malty calculator...those usually have me doing at least 1L starters with one vial of white labs yeast for 3.5 gals  (Yeast is usually > 2 months old).  Usually target a starter gravity between 1.030 and 1.040.

[klickitat jim]

So I tried this. 2L of pre canned 1.035 starter on stir plate 18hrs, chilled 6 hrs while I brewed, then pitched at 62 with temp controller set at 65. Pitched at about 8 pm yeserday. Checked it this morning and its rockin and rollin.

[S. cerevisiae]

AFAIK, Wyeast and others are around 1.020 for yeast propagation.  I try to keep to the low end, 1.030ish.

+1

I chose 1.030 as my basic starter gravity because it strikes a balance between optimum cell growth conditions and and preparing the cells for the higher osmotic pressures encountered in fermentation. 

With that said, a 5% w/v solution (1.020 S.G.) is optimum for basic cell propagation because it provides enough nutrient for cell growth while placing low osmotic pressure on yeast cell walls.  It's also easier to dissolve oxygen into 1.020 wort than it is 1.040 wort.   The autoclaved 40ml first-level starters that I inoculate from slant are 1.020. 

[S. cerevisiae]

Here in the Netherlands most starters are 100 gram DME and 1 liter water. This has a SG of almost 1040.

A true 10% w/v volume solution has an specific gravity (S.G.) of 1.040.  Mixing 100 grams of DME into 1L of water should result in a S.G. of approximately 1.036 because it is a 9% w/v solution.   If the solution is boiled for 15 minutes, the resulting S.G. should be between 1.038 and 1.040 after it has been cooled to room temperature depending on the evaporation rate.

[erockrph]

AFAIK, Wyeast and others are around 1.020 for yeast propagation.  I try to keep to the low end, 1.030ish.

+1

I chose 1.030 as a basic starter gravity because it strikes a balance between optimum cell growth conditions and and preparing the cells for the higher osmotic pressures encountered in fermentation. 

With that said, a 5% w/v solution (1.020 S.G.) is optimum for basic cell propagation because it provides enough nutrient for cell growth while placing low osmotic pressure on yeast cell walls.  It's also easier to dissolve oxygen in 1.020 wort than it is 1.040 wort.   The autoclaved 40ml first-level starters that I inoculate from slant are 1.020.

More good info. I've always used 1.020 starter wort for my first step when culturing bottle dregs because I thought it was a good idea. Glad to get some validation of that practice.

[troybinso]

As I ferment mostly 3.5 gallons batches, my standard starter volume is 600 milliliters.  I start with at most a 4mm nichrome loop of yeast taken from a slant on Tuesday night, and I have ready to pitch culture on Saturday morning.  We are talking about a huge amount of cell growth compared to pitching a White Labs vial into 1L of wort.

That sounds like a tiny bit of yeast that you are putting in to your starter. Can you estimate how many cells you are grabbing with your loop, and how many cells you end up with after your starter?