“Catching” Wild Microbes from the Air? The Magic of Sourdough Fermentation

Have you ever tried sourdough?

Commercial sourdough typically relies on isolated, high-purity yeast strains. This approach speeds up production and delivers a more consistent loaf, but it comes at the expense of the distinctive flavour, texture and mouthfeel that traditional mixed cultures offer.

In truth, wild yeast is everywhere in our surroundings. By simply creating an environment conducive to their growth, you can ‘capture’ the perfect fermenting microbes for baking your own sourdough.

In this instalment of The Alchemy of Food, we are joined by Yijian Yi, founder of Jane & Lucy, who will demonstrate how to cultivate a sourdough starter and bake sourdough bread. To begin, gather 50g of wholemeal flour and 50g of water.

Thoroughly mix equal parts water and wholemeal flour until smooth, cover the container, and set it aside in a cool, well-ventilated spot.

Each day, discard half of the mixture and replenish with 50g of wholemeal flour and 50g of water. After about three to five days, you should start to see bubbles forming in the jar.

At this stage, you can switch to plain flour for feeding, adjusting the water-to-flour ratio to 1.25:1. Continue this routine for another three days or so. Once the jar is full of abundant bubbles, your starter will be lively enough to bake with.

It is best to feed your starter daily to keep it active. Feeding at a higher ratio dilutes the acidity of the fermentation environment, giving the yeast a competitive advantage.

To do this, leave a small amount of mature starter in the jar, add water and flour at a 1.25:1 ratio, stir until well combined, cover, and leave to ferment overnight (about 12 hours) in a cool, well-ventilated place. Afterward, store it in the refrigerator.

If you plan to go without using it for a while, you can freeze or dry a portion to keep as a seed starter, meaning you won’t have to start from scratch next time.

A natural starter is a complex microbial culture comprising yeast, lactic acid bacteria, and acetic acid bacteria. Both lactic and acetic acid bacteria produce acids, which is why the resulting bread has a pronounced tang, a complex and layered flavour, and is known as sourdough.

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