How do I make my sourdough more sour, or less?
Sourness comes from two acids made by two organisms at different temperatures and feeding rates. Which one dominates is something you control — with fridge time, starter ratio, hydration and flour.
- Difficulty
- intermediate
- Time
- 10 min
- Read
- 3 min
Short answer
For more sour: a stiffer starter fed less often, a long cold retard of 24–48 hours, some wholemeal or rye, and a warm bulk. For less sour: feed the starter often and use it at peak, keep the bulk cool and short, retard for less than 12 hours, and use white flour only.
A sourdough culture holds yeasts plus two families of lactic acid bacteria. One produces lactic acid — soft, yoghurty, mild. The other produces acetic acid — sharp, vinegary, the flavour people mean by 'sour'. Cool temperatures, stiff doughs and infrequent feeding favour acetic acid. Warm temperatures, wet doughs and frequent feeding favour lactic. That is the whole control system, and once you know it you can aim at a flavour rather than accepting whatever turns up.
Step by step
- Decide which direction you want first.Most people who say their bread is not sour enough are baking with a young, frequently-fed white starter and no cold retard. Most who find it too sour have a neglected fridge starter and a long warm bulk.
- Use the fridge retard as your main dial.Shaping and then proving in the fridge for 12 to 48 hours is the single biggest lever. Cold favours acetic acid, so a 36-hour retard tastes markedly sharper than a 12-hour one. It also improves handling and scoring.
- Change the starter's feeding schedule.A starter fed twice a day and used at its peak is mild. One fed once a week and used past its peak, when it smells of acetone and has hooch on it, carries far more acid into the dough. See `hooch-on-a-sourdough-starter`.
- Change the starter's consistency.A stiff starter — around 50–60 per cent hydration, more like a dough than a batter — favours acetic acid. A liquid starter at 100 per cent or above stays milder.
- Change the flour.Rye and wholemeal carry more minerals and more of the bacteria's food, and ferment faster and more sourly. Ten to twenty per cent rye in the flour is a noticeable step up in tang without changing the crumb much.
- Adjust the amount of starter used.Less starter means a longer fermentation to reach the same rise, and more time means more acid. A 10 per cent inoculation overnight tastes different from a 25 per cent one over four hours, even though both loaves rise the same amount.
- Change one thing at a time and write it down.There are six variables here and they interact. Changing three at once teaches you nothing about which of them mattered.
Tips
- Sourness and rise are separate. A loaf can be very sour and still under-risen, or beautifully risen and completely mild.
- Adding vinegar or lemon juice to fake sourness does not work — it tastes like the thing you added, not like fermentation, and the acid interferes with the rise.
- The San Francisco style people usually mean by 'proper sourdough' relies on a particular resident culture and a long cold process. You can get close but you will not get identical, and a mild European-style loaf is not a failure.
- A starter kept at room temperature and fed daily makes milder bread and is more predictable. A fridge starter is more convenient and makes sharper bread.
Common mistakes
- Trying to get sourness by extending the bulk fermentation at room temperature — You get acidity and gluten breakdown together, so the loaf is sour and flat. Sourness from a cold retard comes without the structural cost.
- Judging the starter by smell alone — A sharp-smelling starter is not necessarily a strong one. What matters for rise is whether it reliably doubles; what matters for flavour is when in that cycle you use it.
If it doesn't work
Bread tastes like ordinary white bread, no tang at all
Cause: Young starter used at peak, short warm bulk, no retard, white flour only. — Fix: Add a 24-hour cold retard and 10–15 per cent rye. That alone usually settles it.
Unpleasantly sharp and vinegary
Cause: Long cold retard plus a neglected, over-acidified starter. — Fix: Feed the starter twice daily for three days before baking, use it at peak, and cut the retard to 12 hours.
Sour and also gummy, dense and sticky
Cause: Over-fermented rather than well-flavoured. Acidity has broken down the gluten. — Fix: Shorten the bulk fermentation. This is a fermentation fault, not a flavour choice. See `sourdough-loaf-flat-and-spread`.
Flavour changes unpredictably between bakes
Cause: Kitchen temperature. A 4°C difference in room temperature changes fermentation speed substantially. — Fix: Use the volume increase rather than the clock, and note the room temperature with each bake.