How much yeast do you estimate you have after your 100mL or 1L process?
Also, I like the media jars... any particular brand/model work well? Also, what slant vials do you use?
I recently wrote the article below thinking of posting it somewhere when I came across this thread. You will notice I am a purest when it come to yeast propagation so my methods are somewhat different from those previously described. That said, I believe those methods are sound.
Adventures in Yeast Propagation
For the past 6 years I have been propagating my own yeast from storage and using guesswork for pitching rates. I have assumed that a yeast culture propagated from a slant would have approximately the same cell density as a starter prepared from a liquid yeast pack. I ferment 10.5 gallon batches so I have wanted to use a 3 - 4 L culture in order to produce about 500 600 billion cells for my Belgian Strong ales but have been limited to a 1.5 L culture in my 2 L flask and cheap stir plate. Actually all was going well and my beers have won a lot of medals at some big shows. However, always wanting to brew better beer and believing I was under pitching, I purchased a 5 L flask, built a monster stir plate and began using a 4 L culture. To my surprise, the beer suffered a loss of aroma and flavor (fruity esters and spicy phenols) as reflected in my score sheets. Recently, I purchased a microscope and equipment to count cells. After much study and practice using a hemocytometer and making precise dilutions, I embarked on producing a 4 L culture from 5 single colonies on a streak plate and counted the cells at initial inoculations and at each increase. I want to share these results for those of you who are culturing yeast and want to have a better idea about yeast development but have not yet made the plunge into the microscopic world.
Five single colonies approximately 2mm in diameter were selected from a streak plate that had been incubated at 77° F for 96 hours and placed into a 50ml flask containing 10ml of 1.040 wort and a stir bar. The cell count after inoculation was 10,075,000/ml which could be calculated as 100,750,000 cells as the initial pitch. After 24 hours incubation on a stir plate at the same ambient temperature setting the cell count had increased to 144,000,000/ml with a total of 1.44 billion cells. The 10ml culture was transferred to 100ml of wort in a 250ml flask resulting in a calculated cell density of 14,400,000/ml. After 24 hours under the same conditions the cell count was 194,000,000/ml and calculated as 19.4 billion cells. This was transferred to 500ml of wort in a 1000ml flask resulting in a calculated cell density of 40,740,000ml. After 24 hours I checked the temperature of the culture and found it at 82°F even though the ambient was still set at 77° F. Apparently the stir plate and/or fermentation activity was increasing the temp by 5° F. The cell count was 287,500,000/ml. So the total number of cells in the 500ml culture was 151 billion cells, 1.5 time the amount in a commercial liquid yeast pack. The 500ml culture was transferred to 3500ml of wort, the calculated cell density was 37,734,375/ml. The temperature of the culture was brought down slowly from 82° F to 70° F over the next 36 hours when the final cell count was taken the total was 306,500,000 cells/ml giving an total culture count of 1,287,300,000,000 or over 2.25 trillion cells. I ended up pitching 1600ml of the culture, back to near where I was before I bought the monster flask and stir plate, the wonderful Belgian yeast flavors and aromas are back.
Note: In order to achieve these cell counts, it is essential preform aerobic fermentation at all stages. So be sure to have good aeration. Do not use an airlock, do not overfill your flasks (75% of the total flask capacity is max and less is better). If possible, allow the whirlpool to reach all the way down to the stir bar.