Sourdough

The original method of raising dough and, some people would argue, still the best.

Photo by Chris Young / realbreadcampaign.org CC-BY-SA 4.0

Photo by Chris Young / realbreadcampaign.org CC-BY-SA 4.0

Although using a sourdough starter isn't a criterion of the Campaign's basic definition of 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.

See also: Create your own sourdough starter


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. Genuine sourdough may stale more slowly, and might have health benefits.

Sourfaux

In 2015, Real Bread Campaign co-ordinator Chris Young coined the word sourfaux for products that are named or marketed using the word sourdough but that were in fact made using baker's yeast and/or one or more additives.

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.

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

  • Made without any additives - ie the main criterion in our basic defintion of bread
  • Leavened only using a live sourdough culture, without the addition of commercial yeast or other leavening agents, e.g. baking powder
  • Made without using other ingredients/additives as souring agents or as sourdough flavouring, e.g. vinegar, yoghurt, or dried sourdough powder

Baked products made using such things are what Real Bread Campaign cofounder Andrew Whitley calls pseudough.

NB We have nothing at all against Real Bread made using baker's yeast. Our issue is with baker's yeast leavened bread (or industrial loaf products) being named or marketed using the word sourdough.

Is sourdough better than ‘normal’ yeast?

Unless you have an allergy or intolerance to baker's yeast, there is nothing wrong with it. You can make great Real Bread with baker's yeast.

A growing number of studies, however, collectively suggest that making bread using a genuine sourdough method might have greater nutritional, and other health benefits, than making loaves without a live starter culture, and/or by a shorter process, such as one accelerated by baker’s yeast.

NB None of this has been proven beyond doubt and the Real Bread Campaign calls for more research to be done on the potentially beneficial effects of sourdough fermentation.

Additionally, some people report that they can enjoy eating genuine sourdough, while they find other types of bread and/or industrial loaf products hard to stomach. These individual experiences are not a license for blanket statements such as 'sourdough bread is more digestible'.

See also this section

Is sourdough the same as soda bread?

No. It would be hard to find two types of loaf making that are more different. Genuine sourdough undergoes long fermentation over many hours in the presence of lactic acid bacteria, as outlined above. Soda loaves are leavened (made to rise) in minutes using chemical raising agents, such as baking powder. Any known, or potential benefits of fermentation simply cannot happen in a chemically-leavened loaf.

Where can I buy genuine sourdough?

You can find all of the bakeries that have told us they bake wihout artificial additives on our Real Bread Map. Once you have found a bakery, you can look for The Sourdough Loaf Mark or ask a staff member if they make genuine sourdough.

How do I know if a loaf is genuine sourdough?

The Real Bread Campaign is fighting for a legal definition for the word sourdough so shoppers know what they’re buying and what benefits they might be getting.

In the meantime, appearance, price, aroma, taste and even the word sourdough offer you NO GUARANTEE.

Tips:

  • Look for The Sourdough Loaf Mark. This is a visual assurance from baker to buy that a loaf is genuine sourdough.
  • Always read the label. Genuine sourdough is made with just flour, water, salt and perhaps other natural ingredients. If it contains additives, baker’s yeast (listed simply as yeast) or chemical leave ing (eg baking powder) then it is not sourdough bread. If there isn't a label (or you just fancy a chat) then...
  • Talk to the baker / salesperson. If s/he cannot confirm that the loaf is made just those natural ingredients, then chances are it isn’t genuine sourdough

We also suggest that you..

...stay away from loaf tanning salons. Even if a loaf is technically sourdough, if it was part-baked elsewhere and then merely re-baked in store (or by a vendor who buys in such products for a market stall), you might want to shop elsewhere for one that is genuinely fresh by a Real Bread baker who helps support skilled jobs in your local community and keep your high street alive.

NB Using taste, texture and aroma to establish whether or not a loaf is genuine sourdough is pure guesswork. A skiled Real Bread baker can use baker's yeast to craft a loaf that has characteristics often associated with sourdough, such as a glossy, open crumb structure (ie big holes); crackling (and, later, chewy) crust; and complex, delicious taste and aroma. Meanwhile, a close-textured, soft-crusted white sandwich loaf can be made in a tin using a sourdough starter.

As for sourness, this is down to both the skill and preference of the baker – it can range from a robust tang to barely perceptible. Conversely, and industrial loaf fabricator can add anything from dried sourdough powder to industrial acetic acid to give sourfaux a bit of bite.

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.

Is sourdough yeast free?

Nope.

A 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 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 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.

Can I eat sourdough if I have a yeast allergy/intolerance ?

Genuine sourdough is made using one or more yeasts but your personal experience may be that you can eat some loaves marketed as sourdough but not others. See the section on sourfaux above.

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 (it might not be yeast at all) 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 published 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, kimchi 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

Sourdough isn't a type of loaf, it's simply a way of leavening dough. Saying 'I don't like sourdough' is like saying 'I don't like bread' or 'I don't like cheese.'

If you do like bread, then there are probably more variations of sourdough-leavened bread than there are bakers on the planet. 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.


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