A yeast starter without a stir plate
Liquid yeast packs often contain fewer healthy cells than a 20-litre batch of anything above average strength wants. A starter fixes that, and for years I thought it needed a stir plate. It does not. Shaking the starter well once and pitching it at its most active point works just as well for ales.
The routine
- Boil one litre of water with 100 grams of dry malt extract for ten minutes. That gives a gravity of roughly 1.036–1.040, which is gentle on the yeast.
- Cool the flask in a sink of cold water to about 20 °C. Cover it with sanitised foil.
- Pitch the yeast pack, then shake the flask hard for a full minute. This is the only aeration the starter gets, so do not be shy.
- Leave it at room temperature. After four to twelve hours it will have a thick foam on top.
- Pitch the whole starter into the wort while that foam is still high.
Why it works
The yeast in an active starter is at its healthiest: plenty of cells, full of reserves, already fermenting. Pitching it at that point gives a short lag phase, often under six hours in my batches, which matters more to me than the absolute cell count.
Pitching the whole litre of starter wort sounds wrong, but at this size it disappears in a 20-litre batch. For a delicate lager I would still decant.
Things I learned the hard way
- Extract foams up when it boils. Use a flask at least twice the starter volume, or a pot.
- Sanitise the scissors you use to open the yeast pack. Every time.
- Brew day and starter timing need a plan: I make the starter in the morning and pitch in the evening.