How long for starter on a stirplate

[craigevo]

When would a starter start to become oxidised for a 1-2L starter on a stir plate ? ie how many hours before the yeast stop taking up the oxygen - isnt this the best time to take it off the stir plate ? then you can pitch the entire thing surely ?

[brewinhard]

Its not just the fact that your starter wort will become oxidized from contantly being stirred and interacting with oxygen, but rather that the wort itself will most definitely have off-flavors (ie increased esters) associated with running the starter at warmer than normal temperatures for a given strain of yeast when trying to propagate and grow more yeast cell counts. Adding a lot of this starter wort to your beer might end up showing up in your finished product which could be undesirable.

[Metal Tiger]

I make a starter 4-5 days before I brew. The size of the starter is calculated from mrmalty.com.
I run the starter on the stir plate for 48 hours. I then put it in the fridge until brew day.
I run the starter 10 degrees above my target fermentation temperature.

On brew day I collect 500ml after the first fifteen minutes of boil (prior to hopping).
I then chill then to my target fermentation temperature. I decant my starter and pitch the 500 ml to the flask.
I then put that back on the stir plate and pitch the entire thing into the final wort.

I have been getting great attenuation for every yeast I done with this method.

Sounds like a great process.

What I do is to use the Mr. Malty pitch calculator. For a 6 gal batch at 1.060ish beer I will usually make a starter the morning of brewing with 1500ml of DME wort and 2 vials of WLP yeast that is within date for an ale. The 6 to 8 hrs of stir plate action will really get the yeast going. Pitch at fermenting temps and my lag times are usually about 8 hrs or so. For lagers a big pitch is necessary so after making a 4 liter starter I let it ferment out completely and do what dunleav1 does by waking the yeast up the morning of brewing.

The Yeast harvester is coming this month with the Ultimate Conical so I will have plenty of yeast after that. I will have to change the process a bit and will do some experimenting. Possibly with so much yeast all I will have to do is to wake it up the morning of brewing.

[KidHop]

I take the dunleav1 approach with a slight modification.

Rather than take 500ml of wort 15 minutes into the boil, I prefer to keep 500ml of pre-made starter wort (from DME) on hand. Brewday morning, I decant off the beer from the starter and "wake up" the yeast with a fresh 500ml of wort. Simple, easy and does not take much time. Great results and very short lag times.

[craigevo]

Any reason why everyone always mentions the magic number 500ml for this wake-up wort ? We are not trying to grow the yeast count so could it be less than 500ml ?

Can I use 150ml ? I have a pressure canner and CAN do pint jars (380ml of wort) or even one quart jars (850ml wort), but its easier for me to use half pint jars since I just have enough space in my canner on a second shelf to fit half pint jars on top of the quart jars. Long winded reason i'm sorry, but still - will 150ml be enough to coax the sleeping yeast out of their slumber ?

[Ozwald]

Any reason why everyone always mentions the magic number 500ml for this wake-up wort ? We are not trying to grow the yeast count so could it be less than 500ml ?

Can I use 150ml ? I have a pressure canner and CAN do pint jars (380ml of wort) or even one quart jars (850ml wort), but its easier for me to use half pint jars since I just have enough space in my canner on a second shelf to fit half pint jars on top of the quart jars. Long winded reason i'm sorry, but still - will 150ml be enough to coax the sleeping yeast out of their slumber ?

Still a little sleepy to reference precise reasons, but I know the Pope has mentioned them a few times. Also note that coaxing the yeast out of their slumber & getting a healthy propagation are 2 different things. Usually we're using a starter to boost healthy cell counts, not just making them active to reduce shock for fermentation.

[spiderwrangler]

150mL would give them food to get going again. By previously fermenting out the starter and cooling it, the yeast have been put into a fairly dormant state. The idea of giving them a bit more starter after decanting is to try to get the best of both worlds... finished out starter with oxidized wort removed, AND actively fermenting and metabolizing yeast. The yeast probably isn't going to polish off that starter wort by the time you pitch if you are only putting it int here the morning you are brewing.