Tue Jun 01, 2010 10:13 am
The problem is that the smallest size starter that the calculator will recommend is 1L. This minimum size is based on Jamil's supposed experiments that showed anything smaller 'wasn't worth it', although I'd love to see some published data behind this to make that call myself (maybe in the yeast book?). Anyway, if you make a 1L starter with a stir plate and a fresh yeast pack, it will grow 130 billion new cells and you'll have 230 billion to pitch. So if you want to get closer to the actual recommended pitching rate of 750 million/mL/°P, you can pour off a portion of the fermented starter before pitching. I'm betting that most people just pitch the whole thing though.
An alternate method for low gravity beers is to make a small, 1 pint starter the morning of brew day and pitch the yeast into that, being sure to hold it at the same temperature as you intend to pitch. As soon as you see a small krausen (or at the latest 8 hours after chilling) pitch the whole thing into the fermenter. You don't want this small starter to ferment out completely because it's not enough to get significant new cell growth and can actually diminish glycogen reserves, but it does work well in waking the yeast up. This works well when pitching into worts that require near 100 billion cells. You can also use this method for higher gravity worts provided you grow enough yeast for the pitch prior to making the small starter, don't rely on the small starter to grow enough yeast for the batch.
If you have a package that has a little less than 100 billion cells, it's ok to make a starter smaller than 1L, just try to keep the ratio the same (1L per 100 billion cells). The amount grown will be the same per liter of starter wort. For example, if you have a pack that is 80% viable and you make an 800 mL starter, the amount of new growth will be 133 billion/L * 0.8 L = 106 billion, for a total of 186 billion.
