Yeast Propagation question

[Drewed]

I'm trying to build up a stock of yeast by making a starter to increase the volume of yeast, then pitching only half of it and keeping the rest in the fridge for later use in little soda bottle pre-forms. This has worked well, but I let my stock get too low and now I am trying to make a large batch of yeast.

I started with a 1600ml starter of DME and gofirm and let the yeast go for a few days on the stir plate. I then cold crashed to settle, which it didn't really do was well as I hoped. I then decanted off some of the liquid and poured the yeast into a Separatory Funnel, and let it sit. I then transfered about 500ml of yeast off of that into another 1600ml starter mix ( DME and goferm ) and ended up with a volcano.

Where did I go wrong? Too much yeast the second time around? Should I have only used a small portion rather than the full amount? If so I assume that I should cold crash again and decant. Is there a way to figure how much yeast to add to a starter to increase yeast volume with out kicking off fermentation?

 

[xico]

If you are using separatory funnels then it sounds like you are committed to lab glassware. Are you autoclaving this glass? How are you sterilizing?

I use flasks for yeast so i can bake them in the oven for an hour to kill off anything inside. If you are trying to get the best numbers for yeast pitching there are two routes to take.

1 is to get a series of small flasks and begin your starter with 5-10mL of original slurry into 50 or 100 mL of starter. Let that go a day and then bump it 10x into the next (500 or 1000mL) and so on. There is no way to know how much you have but at least you are starting with less volume of an unknown number.

2 is to get yourself a microscope and hemocytometer. This is the pricier option. You get what you pay for with both. The microscope should use at least 40x objectives but 100x will be best (and will need oil with it). Cheap scopes will be blurry but will be sufficient to count cells.

Hemocytometers that are worth anything (don't buy the 20 dollar ones unless you are into taking money and burning it) are either disposable at 2 dollars a piece or reusable at 200-250. These will allow you to zero in on exactly how many cells you want to add to your beer.

Numbers are disputed, but if the targets I aim for range from 350-500k cells/per mL/per degree Plato for hefeweizens and 500-750k/ml/degree plate for other sacch. cerevisiae beers. Calculate your batch gravity and volume and then work backwards from there.

The first option is obviously more affordable, I am throwing out both options though to inform you of your options.

 

[Dr_Jeff]

simple answer, to where you went wrong, use a larger flask next time

 

[DurtyChemist]

I’ll make it easier. 1500ml starter. After krausean settles pull it off the stir plate and add it to a 500ml flask/mason jar with yeast suspended. You’ll have 100 billion cells almost every time. If you want consistency or a method to follow just google “homebrewdad yeast calc” and you’ll be set.