A Guide to Sourdough Sourness (How to Control That Tangy Flavour)

Sourness is one of the most personal aspects of sourdough baking. Some people adore a sharp, tangy loaf, while others prefer something far milder and closer to a standard bread flavour. The good news is that sourness is not fixed. It is something you can genuinely control once you understand what causes it.

What Actually Causes Sourness

Sourdough’s tang comes from organic acids, mainly lactic and acetic acid, produced by the bacteria living alongside the wild yeast in your starter. The longer and slower your fermentation, generally speaking, the more these acids build up, and the sourer your final loaf will taste.

Factors That Increase Sourness

A longer cold proof. This is one of the biggest levers you have. Extending your cold proof, up to around 3 days, allows acids to continue developing slowly, resulting in a noticeably sourer loaf the longer it sits.

A more mature or hungrier starter. A starter that has gone slightly past its peak, or one fed less frequently, tends to produce a more acidic, sour flavour compared to one fed regularly and used right at peak.

Warmer, slower ongoing fermentation. While warmth generally speeds fermentation up overall, certain slower approaches (like an extended room temperature bulk fermentation) can allow more acid development over time.

Rye or wholemeal flour in your feeds. These flours carry more of the bacteria responsible for acid production, so regularly feeding with them can nudge your starter towards a tangier flavour profile.

Factors That Decrease Sourness

A stiffer starter. A lower hydration starter, around 50 to 60 percent, ferments more slowly and tends to produce a milder, sweeter tasting result compared to a regular hydration starter.

Using your levain right at peak. Catching your levain at its peak, rather than letting it go past and start to collapse, generally gives a milder flavour than an over-mature levain.

A shorter cold proof, or skipping it altogether. If you proof in a warm spot and bake the same day rather than cold proofing overnight, you will get a noticeably milder flavour, since the acids have had far less time to develop.

Feeding more frequently with plain white flour. Regular feeds keep your starter’s bacteria population balanced towards a milder profile compared to an infrequently fed, more mature starter.

Finding Your Personal Sweet Spot

There is no universally “correct” amount of sourness, despite what you might read online. If you find traditional sourdough too sharp for your taste, do not be put off the whole idea of naturally fermented bread. A milder approach, using a stiffer starter, a shorter cold proof, and a levain used right at peak, can give you all the benefits of sourdough with a flavour far closer to a standard sandwich loaf.

Related Reading

• Are Cold Proofs Really Necessary for a Great Sourdough?

• A Guide to Sourdough Feed Ratios