“Capturing” Cultures from the Air? The Magic of Sourdough Fermentation

Have you ever tried sourdough bread?

Commercially available sourdough bread typically uses isolated, high-purity yeast, which speeds up the bread-making process and yields a more consistent final product. Yet these advantages come at the cost of the distinctive flavour, texture, and mouthfeel that traditional mixed cultures offer.

In fact, yeast is everywhere in our environment. All you need to do is create conditions conducive to their survival, and you can “capture” the right microorganisms for fermentation to make sourdough bread.

In this episode of The Alchemy of Food, we’ve invited Yi Jian, who runs Jane&Lucy, to demonstrate how to make a sourdough starter and sourdough bread. To begin, you’ll need 50 g each of wholemeal flour and water.

Stir together the water and wholemeal flour at a 1:1 ratio until well combined, then cover and place in a cool, well-ventilated spot.

Each day, discard half of the mixture and top up with 50 g each of wholemeal flour and water. After roughly 3–5 days, you should begin to see bubbles forming in the jar.

From here, you can continue the culture using ordinary flour, switching the water-to-flour ratio to 1.25:1. After about another 3 days, once the jar is producing a great many bubbles, the starter will be sufficiently active for baking bread.

The starter is best fed daily to maintain its vitality. A high feeding ratio reduces the acidity of the sourdough environment, giving the yeast a competitive edge.

In practice, leave just a small amount of mature starter in the jar, add water and flour at a 1.25:1 ratio, stir well, cover, and leave in a cool, well-ventilated spot to ferment overnight (12 hours). Then refrigerate for storage.

If you won’t be using it for a while, you can freeze or dry a portion of the starter as a starter for next time, so you won’t have to begin from scratch.

A natural sourdough starter is a mixed culture containing yeast, lactic acid bacteria, and acetic acid bacteria. Both acetic acid bacteria and lactic acid bacteria produce acidic compounds, so the bread that results is tangy, rich, and layered in flavour — hence the name “sourdough”.

To make sourdough bread using your homemade starter, you’ll need: