While variations of sourdough bread can be found all over the world, and there is evidence that the ancient Egyptians made sourdough bread, it was during the California Gold Rush that the San Francisco Sourdough was born in the modern age, and sourdough has become synonymous with that city.
So what is sourdough bread anyway, how is it made? And how does it differ from other bread?
We have talked before about the four main ingredients that go into making your loaf of bread – flour, water, yeast and salt. In fermentation, the job of the yeast is to produce carbon dioxide from the flour, which enables the dough to rise. Sourdough bread is made differently, it is naturally leavened in that there is no yeast added. Instead, it uses a ‘starter’, a fermented flour and water mixture that contains wild yeast and bacteria. This produces the unique tangy flavour and slightly chewy texture typical of sourdough.
To make a sourdough starter, flour and water are mixed together and left at room temperature. Yeast and bacteria (mostly Lactobacillus sp.) in the air work on the flour, fermenting the sugars and producing gas. You will see the starter start to bubble up after a couple of days as the gas is produced. The starter has to be fed more flour and water to stay alive (if you don’t, you’ll know all about it as it will start to smell really badly, and the starter will die).
There is no EU definition of or legislation about what is meant by the term “sourdough” or “sourdough bread” either, although some countries such as Germany, France and Australia have their own national guidelines. In 2019, the Food Safety Authority of Ireland Artisan Forum, which is made up of food producers and industry experts, attempted to come up with an agreed definition of what can be called sourdough bread and the method by which it is made. For example, consideration was given to the list of permitted ingredients, the minimum fermentation time etc. However, an agreed a definition of sourdough bread has not yet been established.
Some people ask if sourdough bread is gluten free and the answer is No! Sourdough bread is made with wheat or rye flour usually, and these contain gluten. There is a lot of talk about whether or not sourdough bread can make unique health claims but there are in fact no approved health claims for sourdough bread in the EU.
To read more, check out these resources;
- What is sourdough? https://www.bbcgoodfood.com/howto/guide/what-sourdough
- “Bread Science: the Chemistry and Craft of Making Bread” by Emily Buehler, published by TwoBlueBooks;
- The Science of Making Sourdough Bread – https://www.theguardian.com/science/2020/may/23/the-science-of-making-sourdough-bread
- Scientific American – The Science of Sourdough: How Microbes Enabled a Pandemic Pastime – https://www.scientificamerican.com/article/the-science-of-sourdough-how-microbes-enabled-a-pandemic-pastime/
- Irish Bread Blog – The Chemistry of Bread: https://irishbread.ie/Sectors/IBBA/IBBA.nsf/vPages/News_and_Blog~the-chemistry-of-bread-16-04-2021!OpenDocument
- FSAI Artisan Forum – https://www.fsai.ie/about_us/industry_fora/artisan_forums.html
- Health claim for High-fibre sourdough rye bread rejected – https://www.fsai.ie/uploadedFiles/Reg2016_862.pdf
- Make your own sourdough bread – https://www.riotrye.ie/courses/the-common-loaf/
- BBC Travel – why San Francisco does sourdough best http://www.bbc.com/travel/story/20200402-why-san-francisco-does-sourdough-best
