Hanging onto yeast starter for a few days, when to decant
Meant to brew yesterday but my kid got sick and I'm deferring my brew day until this coming Wednesday (1/1) or the following Saturday (1/4).
I made 2 yeast starters for an 11 gal batch (1.6L each, same yeast, but my flasks are both 2L capacity). They went on the stirplate Wednesday night (12/25) and came off the plate yesterday morning (12/27).
I replaced the foil on each flask with fresh, Starsan-sprayed foil yesterday when I pulled them off the plate. Then I put a plastic sandwich bag over that with a rubber band. Then put both starters into the fridge for cold crash and preservation until my brew day.
My plan is to decant the liquid and add about 300ml of fresh, canned wort and put them in the ferm chamber on the morning of brew day. I'm sure that will wake them up after being in the fridge a few days.
The age of the starters is not my concern. I figure 7-9 days from the time I put them on the plate should not be an issue. I estimated my pitch rate to be 10 billion or so above the yeastcalc.com recommendation for my starting gravity. So I should still be OK on pitching rate.
My question is about best practices and timing for decanting. They've crashed out pretty well already. If I don't intend to use them for another 4-5 days, I'm trying to decide whether I should:
1. Decant all but about an inch of liquid now. Then re-seal and pop it back in the fridge. Then on brew day, decant as much of the remaining liquid as I can and pitch the "wake up" wort.
2. Leave them as is until the morning of brew day. Then decant as much of the 1600ml as I can and pitch the wake up wort.
I'm leaning toward #2. Every time I open the flask it's another opportunity for contamination. Also, 2 decantings increases the opportunity of losing some yeast that might still be suspended in the starter wort.
FWIW, the yeast is WLP007, which drops like a rock. It's formed a pretty tight bed on the bottom of both flasks. My experience with this yeast is that I can pour quite a bit of clear liquid off the yeast bed in the flask before I disturb the bed. I should be able to get a fair amount of the spent starter wort off the yeast.