Real Bread Campaign


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Sourdough

The original method of producing leavened bread, and some people would argue still the best.

Although sourdough isn't a criterion of the Campaign's basic definition of Real Bread, we do believe that there are benefits to making bread using sourdough, rather than commercially produced yeast.  These are the result of a combination of the culture itself and the longer fermentation time it requires to generate sufficient gas to leaven (raise) the bread.

You can read some of these benefits of genuine sourdough on our FAQs page.

Sourdough around our site

What is sourdough?

Sourdough is a name for a mixture (dough or batter) of water and cereal flour containing a culture of naturally occurring yeasts and lactic acid bacteria. It is often also used to name breads and pancakes made using such a culture.

Yeasts and bacteria are present all around us – for example in the air, soil and water. Those well suited to bread production are found in relatively high populations on the surface of cereal grains, such as wheat. By grinding the grains into flour and providing a suitable environment for these microorganisms to thrive (basically by adding water, maintaining an appropriate temperature, and providing food in the form of more flour) these populations can be increased in size and concentration, where they co-exist in a symbiotic relationship.

Eventually there will be enough yeast cells giving off carbon dioxide as a byproduct of their respiration to make bread rise. The interaction of the yeast and the natural enzymes they secrete will have a beneficial effect on the flavour, texture and aroma of the baked bread.

At the same time, the populations of bacteria will increase. The interaction of these bacteria and the products of their respiration (including lactic and acetic acids) also contribute to the flavour, texture and aroma of the bread. Additional benefits in a genuine sourdough include slowing the staling of the loaf.

What sourdough isn't

The Real Bread Campaign believes that to be named or marketed using the word sourdough, a bread can only be made:

  • using a live sourdough culture, not inactive dried sourdough powder added purely for taste and acidity
  • without the addition of commercial yeast or other leavening agents (e.g. baking powder)
  • without any artificial additives
  • without using other ingredients/addtives as souring agents (e.g. vinegar or yoghurt)

As the yeast(s) found in a live starter typically produce carbon dioxide at a slower rate than commercial baker's yeast, the rising time is longer. This longer fermentation period allows other changes to occur in the dough that could have benefits other than flavour alone. You can find examples of these potential benefits on our FAQs page.

This is a key reason the Real Bread Campaign's call for an Honest Crust Act includes legal protection of the term sourdough, to allow us all to make better-informed choices about the food we eat.

Baking technologists' sourdough classification

Some baking technologists and commercial bakers have a much wider definition of sourdough than us, which they split into three categories:

Type I - this is the traditional method of making sourdough (though can be in an industrial bakery setting) using a starter cultured from just flour and water, which typically contain a diverse range of yeasts and lactic acid bacteria. A portion is kept back and built up / refreshed for the next bake.

Type II - a more controlled version of the above, cultured from scratch for each bake using selected bacteria (but not always yeasts), for several days often at a relatively high temperature (up to 50C) to generate high acidity. It is mainly as an acidifier/flavouring and usually requires commercial yeast to be added as leavening.

Type III - this merely uses dried sourdough powder as an acidifier and flavouring for a short-process, commercially-yeasted dough.

Loaves produced by the type III process, and type II made using added commercial yeast, are not what the Real Bread Campaign would call sourdough.

What do I need to start a sourdough starter?

Nothing more than flour and water.

The surface of grains, such as wheat and rye, are usually home to thriving colonies of one or more species each of yeast and bacteria. These live in symbiotic relationship with the grain and so are, arguably, the most suitable to start a sourdough culture.  Other ingredients are therefore unnecessary but here are some that might be suggested, along with some theories behind their inclusion:

  • Rhubarb. Acids can help deter pathogenic (bad) micro organisms and create an environment favoured by lactic acid bacteria.
  • Hops also have anti-bacterial properties.
  • Live yoghurt is also acidic and contains lactic acid bacteria, though not necessarily the types most suitable for producing bread.
  • Mashed potato provides an extra source of food for yeast and bacteria.
  • Grapes, raisins, sultanas and so on have yeasts and bacteria on their skins but again, not necessarily the types most suited to making bread.
  • Honey is high in sugars, on which the yeast can feed. Unpasteurised honey might also contain yeasts and bacteria.

Click here for a simple sourdough starter.

But I thought sourdough was yeast free

Nope. Sourdough culture will always contain one or more species of yeast. In some cases these yeasts might even include the same species (Saccharomyces cerevisiae) that is sold as bakers' and brewers' yeast.

That said, the strains of S. cerevisiae found in bakers' and brewers' yeast have been modified of years of selective breeding (for example to produce large volumes of carbon dioxide/alcohol, respectively, and to generate different flavour profiles in the finished product), perhaps even by genetic modification in some cases. It is unlikely that even if S. cerevisiae is present in a sourdough culture that it will be genetically identical to a commercial strain.

Concentrations of yeast in a genuine sourdough may well be lower than in a bread made with commercial yeast. Rather than using a relatively large amount of yeast cells to produce the amount of carbon dioxide needed over a relatively short period of time, sourdough relies upon its smaller number of yeast cells being left for a longer fermentation period to generate the same amount of gas.

A note to sourdough bakers

If you’re marketing sourdough bread as ‘yeast free’, stop it!

Apart from the fact that this could land you in trouble with Trading Standards, it’s not in keeping with Real Bread Campaign values of openness and honesty. Possible alternatives include ‘made without baker’s [or industrial] yeast’, and ‘made using naturally-occurring yeasts’.

One further thought on yeasts in bread – yeasts die at around 60°C. As the internal temperature of bread should reach at least 90°C during baking, by the time a properly made loaf of any type of bread is ready to eat, it will contain no live yeast, only dead cells and byproducts.

So if I have a yeast allergy/intolerance can or can’t I eat sourdough?

Your personal experience may have already given you the answer to this, but the advice we must give you is to get tested by an expert in food allergy/intolerance. This will isolate the cause of your difficulty from all other possible factors. Your GP will be able to help.

Sourdough and coeliac disease, food allergy and food intolerance

See our FAQs page for a brief outline of, and differences between, these conditions.

The FAQs page also contains a growing list of studies, including at least one that has concluded that some people who encounter problems when eating bread made with commercial yeast might be able to eat genuine, long-fermented sourdough. The comments section of the Campaign’s own small sourdough study (to be published later in summer 2011) adds to the growing body of anecdotal evidence that supports this.

The Real Bread Campaign calls for funding for large-scale research to determine the impact of sourdough fermentation of wheat bread in relation to these conditions.

Not sure I like the sound of bacteria in my food

Bacteria are all around, on and inside everything in the world - including you.

With apologies for using the reductive language of certain TV adverts – there are ‘good’ bacteria and ‘bad’ bacteria. Those in sourdough are some of the ‘good’ ones, related to the bacteria used to make cheese, yoghurt, sauerkraut, and some types of salami.

I don’t like the sound of bread that’s sour

Though some bakers take pride in the extremity of their sourdough bread’s tang, a skilled baker controls his or her starter culture in order to get not only depth and complexity of flavour but also a level of acidity that is to his or her taste.

If you've had a less than amazing experience of sourdough from one baker, try a loaf from another - you might find you love it! 

I don't like sourdough

Saying 'I don't like sourdough' is like saying 'I don't like bread' or 'I don't like cheese.' There are probably as many different variations of sourdough bread as there are bakers in the world.

So again, before you deprive yourself of some of the best Real Breads in the world based on one less than world class experience, try a loaf from one or two other bakers.

Controlling acidity

This item is taken from the section on sourdough in Knead to Know: the Real Bread starter:

As well as one or more types of yeast, sourdough cultures contain Lactobacilli (lactic acid bacteria) that produce both lactic and acetic acids. A key part of mastering sourdough is keeping the concentration and ratio of these acids in balance.  Too much acetic acid and the bread will taste very sharp and perhaps vinegary (it is the same acid that is found in vinegar), whereas bread with too little acetic acid and a higher level of lactic acid might not have any discernible sourdough characteristics.

Different yeasts and bacteria are adapted to different conditions.  Lactobacilli that produce higher levels of lactic acid tend to prefer wetter batters kept at around 1-5°C, whilst those producing both lactic and acetic acid thrive better in stiffer batters kept at around 20°C.  Acetic acid is produced in lower quantities than lactic and so takes longer to build up in a dough.

Therefore, to achieve a more pronounced flavour and sourness, you can try keeping your starter at a lower hydration (i.e. dough-like) and retard dough fermentation by proving overnight in the fridge.  For a milder flavour and acidity, try keeping your starter as a batter and prove at room temperature.

Is my '100 year old starter' really the same as it was a century ago?

Maybe...but maybe not.

Studies of sourdough culture have found that the populations of yeast and bacteria evolve over time.

It's a bit like the old gag: 'This is the axe used to behead Queen Mary. Of course the wooden handle rotted, so that was replaced. And then the head rusted, so we put on a new one. But otherwise, it's the same axe'

Then again:  It is believed that some sourdoughs are maintained over several centuries, e.g. the continuous use of Bocker–Reinzucht–Sauerteig (BRS) sourdough over seven decades has been documented ...' The sourdough microflora: biodiversity and metabolic interactions

Either way, the story of your sourdough starter is a good tale to tell as its heritage involves human relationships.

How, where and when you came to become a starter's guardian; from whom you obtained it; that person's tale of how she/he became a custodian; and so on back through time help to make you and the people who eat your loaves members of a cultural network, a community.

Even if you began your starter yourself, the story you have to tell are that your loaves are unique.

Sourdough mapping

The following websites allow people to map their sourdough starters and 'cultural networks.'