A Sourdough Starter

Soughdough bread has become fashionable once more, yet it is one of the oldest techniques for making bread in the world, the Anglo-Saxons called bread (paid in tribute to the local lord) made with a yeast culture from beer ‘clean’ while bread made from a sourdough was called ‘sour’ because of the particular ‘tang’ it is flavoured with. Sourdough bread is made by using a small amount (about 30 percent) of a soughdough starter in the initial bread dough. This starter dough contains the natural airborne wild yeast cultures (cultivated and fed) which have landed on exposed flour and water; this wet dough mixture (often called a ferment or barm) is left specifically uncovered for several days to allow for the airborne yeast to settle on it.

As long as the yeast in the starter dough is ‘fed’ fresh flour and warm water, every 24 to 36 hours if kept at room temperature, and every 5 to 7 days if kept chilled in the fridge, a sourdough starter colony can stay alive indefinitely and remain healthy and usable. It is not uncommon for a Baker’s soughdough starter to have many years and even decades of history, kept sustainable from hundreds of previous batches. Although keeping a 300g sourdough starter at any one time in the fridge (to make one loaf of bread once a week) is perfect for a modern-day family.

Note: To make a traditional and authentic soughdough bread from scratch you will need several days to get the process started: and when using a sourdough starter as your yeast source expect your bread dough to take much longer to rise before baking than if using a packet of dried ‘active’ yeast. It can take up to 12 to 16 hours to reach a comparable ‘rise’.

Summary: Reading through this detailed and thorough masterclass below it may at first seem complicated, but all you have to remember is that we are making a very basic flour and water dough and exposing it to the natural wild airborne yeast found all around us, to feed on and multiply in, before adding it into our main bread dough – which is why it is called a ‘starter dough’, it starts off the yeast production in the main dough: it really is that simple.

Regional Differences In Sourdough:

Traditionally in each Bakery (before mass production) a sourdough bread had a regionally distinct taste – the combinations of different wild yeast cultures, air temperatures, air quality, age of the batch, flour type, water type, humidity and elevation from sea level makes each batch of sourdough starter different. Some artisan Baker’s say the San Francisco soughdough starter (ferment or barm) in the USA is the best in the world, while other baker’s claim a British soughdough from the West Country is the best, (and the French have their own ideas) I guess it just comes down to having clean air and a good strain of wild airborne yeast – and coastal regions tend to have both.

Note: even if you import a sourdough starter from a different region, it will, after use, and being kept alive / being fed, take on the regional characteristics of the area and the flour and water you feed it, so you may as well start from scratch yourself at the beginning.

Yeast is a living microscopic organism, (commonly an ascomycetous fungi-of the genus Saccharomyces: wild yeast is called S. Exiguus, while commercial Baker’s yeast is a different strain, called S. Cervisiae). Yeast feeds on carbohydrates in the flour and converts them into enzymes and then alcohol, (and as a by-product makes the carbon dioxide gas which makes the bread dough rise). And although the process was not fully understood by our ancestors this technique of keeping a portion of older sourdough to help the next batch of bread rise is an ancient bread making technique.

For nearly two thousand years women in Western Europe used a large kneading trough (or kimlin) to mix and knead flour and water into a bread dough before baking. This bread kneading trough, (made of stone or metal) found outside nearly all homes, would also contain an amount of yeast rich (left-over) sourdough starter from the day before; a portion of dough specifically left behind (with added water) in the trough to grow more yeast cultures in the night to help the next batch of bread dough rise.

Keeping The Sourdough Starter Alive

When yeast activity stops in the sourdough (there is no fermentation and the dough rather than rising starts to collapse and sink) it will be because it has exhausted the food supply in the flour. At this stage the yeast will start to die off and will no longer be of use in bread making. Therefore you need to periodically ‘feed’ it with fresh bread flour and warm water (and/or any other sugary carbohydrate-rich ingredients, like honey, used in modern sourdoughs).

Each time you feed the starter or ‘ferment’ it will be refreshed and it will cut back on the sour/sharp taste it will impart to the bread dough. Keeping the sourdough in the fridge with lower temperatures reduces the yeast activity, (this is known as ‘retarding’) and therefore it will need ‘feeding’ less often. See the next pages in this article for instructions on ‘feeding’ the ferment and why it therefore gets ‘refreshed’.

Understanding The Charactistics of a Sour Dough Bread

A well made sourdough bread develops a thick, crunchy, caramel crust, which encourages us to chew it, an open crumb, with a sour, salty note, perfect when eaten with butter and cheese.

To get a very sour/sharp taste in the bread (which some people prize) leave the starter as long as possible before using it in a bread dough – this maximises the yeast content, whilst also increasing the acidic quality of the dough. However, if you leave it too long between feedings the yeast culture will die off, having used up all the available food supply, (and you will start to get a vinegar smell instead of a beer smell as too much acid is produced).

This is because it is not only the wild strain of yeast which makes the sourdough bread taste different from non-sourdough bread, other ‘good’ bacterial organisms are present in the aged dough along with the wild yeast; such as lactobacillus and acetobacillus. These bacterium produce lactic and acetic acids, (as they feed on enzyme-released sugars in the dough made by the yeast) acids which greatly contribute to the ‘sour’ flavour of the bread: and make the dough smell of vinegar when it is left too long without being fed/refreshed.

Note: If you prefer a bread which is clean tasting and less ‘sour’ and ‘yeasty’ use the sourdough starter as soon as it is ready, or a day after refreshing and feeding it, so that it can mature in the fridge for 24 hours.