Do I need a yeast starter for a 1.040 gravity wort?

Question

I'm brewing on Sunday (today is Friday), and I neglected to get my yeast (WY1056) until just this afternoon. I could make a starter, but I don't know if it would reach "high krausen" in time for pitching Sunday night. And I certainly wouldn't be able to cold crash it, as I normally do.

Or, I could just pitch the smack pack, which has a manufacture date of 13-Feb-2012. Beer Smith tells me that the yeast is 84% viable, yielding 84 billion cells. It also says that for a beer of 1.040 gravity, I need 160 billion cells. In contrast, the smack pack's instructions state that for beers up to 1.060 I don't need to do a starter.

So, who's right? Beer smith or WYEast?

Answer 1

A missing piece of information is how much you're pitching into. If beersmith is saying you need 160 billion, then you're probably pitiching into about 20 litres (5.7 gallons).

Yes you could make a starter tonight and you'd be perfect for pitching on Sunday. Typically a starter needs 24-36 hours for the yeast to reproduce. According to Jamil's yeast calculator, you only need a 1 litre starter, as long as you give the starter a good swirl 3-4 times a day.

Since it's only a 1 litre starter, you don't really have to chill & decant it. It shouldn't affect the flavor of your beer at all.

Alternatively, you could go buy another yeast pack tomorrow and pitch both into your beer. You'd be overpitching slightly, but not by much.