Sourdough#
Week 6. The packet of yeast goes back in the drawer.
What is in the jar#
Bacteria outnumber yeasts about 100 to 1.
- yeasts make carbon dioxide — the lift
- lactic acid bacteria make acid — the flavour
- pH 3.5 to 4.2 keeps everything else out
Two acids, two breads#
| Acid | Lactic | Acetic |
|---|---|---|
| Tastes like | yoghurt, milk | vinegar |
| Made when | 28 to 30 °C, slack, fed often | 18 to 22 °C, stiff, long intervals |
Sourness is a setting.
Feed by ratio#
1:1:1 doubles in 4 to 6 hours at 24 °C and peaks an hour or two later. 1:5:5 takes two to three times as long.
Watch the curve: climb, dome, peak, collapse. Feed at the peak.
A once-a-day jar at 19 °C spends most of its day starving in acid.
The clock does not know your kitchen is 18 °C#
Reading the end of bulk#
- 30 to 50% rise off the mark — not double
- domed, smooth, wobbles like set custard
- bubbles where the dough meets the tub wall
Two ways to get it wrong#
Too early: it finishes in the oven — a cavern under the crust, a blowout down the side.
Too late: proteases win — slack, flat, tears instead of opening.
Cold, then very hot#
Fridge at 4 °C overnight — flavour keeps developing, and cold dough scores clean.
Lidded pot at 250 °C — the loaf’s own steam, trapped. Lid off to colour.