Underestimated yeast growth for lager starters.

So, I'm brewing a lager on Saturday (American Amber, but with lager yeast). I haven't completely decided on the OG I'll shoot for, but let's say 1.055. I plan to have 5.5 gallons in to the fermenter.

Anyways, Mr. Malty and Yeastcalc.com (I think yeastcalc.com uses the same formulas as Mr. Malty.) say I'll need about 423 billion cells. I did a 2 liter stir-plate starter last night, with the intention of chilling the starter overnight tonight and then decanting in the morning and topping up with another 2 liters and stir that until Saturday morning, at which time I'll start chilling the starter to decant and pitch on Saturday evening.

My only concern is that yeastcalc.com and the wyeast step up calculator predict I'll have around 580 billion cells. I know I could just swirl up all the yeast in the flask and decent about 500ml in to a sanitized jar (maybe use that yeast for bread?) and then go as normal with the 2 liter starter tomorrow morning. According to yeastcalc.com this should get me right around the 1.5 million cells/ml per degree plato pitching rate.

So, finally, my question is for you folks that brew lagers. Have you folks ever over-pitched by 160 billion cells? If so, how'd it turn out compared to one of your lagers pitched at a more normal rate (say 1.5 mil cells/ml/degree plato)?

EDIT: I realize that these are only estimates. Ideally I'd have a hemocytometer.

It's not impossible to overpitch, but it's a lot harder than underpitching. I'd just pitch the whole thing and be done with it.

I certainly wouldn't worry about overpitching by that number of cells for a lager. Depending on the yeast strain, you could crank the temp down a few degrees. For example, Fermentis recommends pitching rates of 80-120 g/hl for their dry yeasts pitched at 12 degrees C (53.6F), but 200-300 g/hl for pitching at 9 degrees C (48.2F).

Don't forget to aerate your wort as thoroughly as possible.

osagedr said:

I certainly wouldn't worry about overpitching by that number of cells for a lager. Depending on the yeast strain, you could crank the temp down a few degrees. For example, Fermentis recommends pitching rates of 80-120 g/hl for their dry yeasts pitched at 12 degrees C (53.6F), but 200-300 g/hl for pitching at 9 degrees C (48.2F).

Don't forget to aerate your wort as thoroughly as possible.

Click to expand...

Cool, thanks for the Fermentis info. I'm using WLP840 (American Lager), so I'll probably want to pitch at about 48 anyways.