Post Number: 219
Posted From: 18.104.22.168
|Posted on Monday, August 14, 2006 - 02:47 pm: ||
This might be a good question for Fredrick, but anyone can chime in if you've got a thought.
My step-up procedure is: Slant innoculation to 10 ml wort - 10 ml fermenting wort to 30 ml wort - 30 ml fermenting wort to 500 ml wort on stir plate - 500 ml fermenting wort to 2000 ml wort on stir plate - pitch to 6 gallons wort.
I've gotten to wonder...
Currently, I decant my 500 ml wort and dump the yeast into the 2000 ml wort. I'm wondering if I'd get a better cell count and more yeast volume if I pitch a small portion of the 500 ml fermenting wort into the 2000 ml wort, then combine the results of the two starters together. My thinking is that, with the way I'm doing it now, I'm pitching more than enough yeast to get the 2000 ml going, and not gaining near as much growth benefit as I would if the yeast had to reproduce from a smaller number.
Post Number: 77
Posted From: 22.214.171.124
|Posted on Tuesday, August 15, 2006 - 12:36 am: ||
I am thinking exactly the same thing. I just started a 2 year old 1318 that took 4 days to swell. I poured the contents into 1 pint of aerated wort and let it finish. I then poured the first cup of relatively clear beer divided equally into 2 half gallon jars that each contain 1 quart of wort. The second cup of beer covering the floculated yeast cake was swirled and poured into a sanitary jelly jar for future use. The cup of beer from the first pint was sufficient to start the 2 quarts of starter wort. I think I would have ended up with very very few additional cells had I pitched the entire contents of the pint into the 2 quarts of starter.
What is a good source of supply for the vials for slants?
Post Number: 221
Posted From: 126.96.36.199
|Posted on Tuesday, August 15, 2006 - 12:49 am: ||
You can make your own. I used to, but switched to these guys:
Post Number: 3313
Posted From: 188.8.131.52
|Posted on Wednesday, August 16, 2006 - 12:12 pm: ||
I've been away for a few days...
In the simple treatise, the rule would be that for any amount of fermentable sugar you get an amount of *new* yeast, that is proportional to that amount of sugar.
The ration of new yeast / sugar is the biomass yield. A few factors affect that. Aeration and stirring are probably most important. Additional FAN may help too.
So roughly speaking, I wouldn't expect any major practical differences in yield depending on wether you let the 500ml finish and just take the yeast before adding 2000 ml fresh wort, or if you let the 500ml finish half way and then all all of it to another 2000ml.
I think the difference would depend more on your aeration. If the stepsize is too large, the biomassyield would drop. Given that you only aerate between the steps so to speak, I think keeping the population steps around or below 10 is good.
Lower pitching rates first of all gives a significantly higher *relative growth*. But it's the absolute growth that is relevant to the pitching rates. Extremely high pitching rates, and extremely low pitching rates probably both gives worse absolute growth. I think a few generations is ideal. It prevents relative buildup of older individuals withing the population, and it also prevents excessive stress by oxygen depletion, which in turn may give slightly lower viability.