A sourdough uses biological leavening, as opposed to other breads, which rely on cultivated forms of yeast. A variety of naturally occurring lactobacilli and yeasts are present in flour. When wheat flour comes into contact with water, the naturally occurring enzyme amylase breaks down the starch into the sugars glucose, galactose and raffinose, which sourdough’s natural yeast can metabolise. With sufficient time, temperature, and refreshments a new or fresh dough will develop a balanced, symbiotic or stable culture. This culture will cause the dough to rise if the gluten has been developed sufficiently. The bacteria will ferment any maltose that the yeast cannot metabolise, and by products are metabolised by the yeast which produces carbon dioxide gas, leavening the dough. Obtaining a satisfactory rise from the sourdough takes longer than a dough leavened with bakers yeast because the yeast in a sourdough is less vigorous. In the presence of lactic acid bacteria however, some sourdough yeasts have been observed to produce twice the gas of baker’s yeast.
To make sourdough, you need a starter. I advise to find someone who can pass down some of their starter, that you may nurture to become your own. Some starters are incredibly powerful, as often the owner can attest to. I was lucky enough to get mine when I spent a week with the Chefs at River Cottage HQ in Devon. If you cannot inherit a starter, then it is all relatively straight forward, in that you will mix flour and water, and leave for 3 weeks. Click here for a recipe.
After you have your starter, you are ready to go.
I follow Chad Robertson’s Tartine Bakery Method:
- The day before you plan to make the dough – feed your starter. I feed mine 200g water and 200g flour in the morning followed by the same in the evening. If I have the time, I will start ramping up the feeding process 2 days before to ensure I have a really active starter.
- The day you plan to make the dough – test your leavens readiness by dropping a spoonful into water. If it floats it is good. If it sinks, it will need more feeding.
- If your leaven is good – pour 700g warm water into a mixing bowl. Chad recommends 26 – 27 degrees C. Then add 200g leaven. Stir to disperse and then keep your leftover leaven. If you don’t plan to use the leaven in a while then you can place it in the fridge and it will happily sit dormant for up to a year.
- Next, add flours. Basic Recipe is White Bread Flour 900g and Wholemeal Bread Flour 100g. Mix dough with your hands. Obviously, you will play around with this and find what works for you. Rye Flours tend to work nicely, and trying to ensure they are as local as possible is important. [Read Zachary Golper 'Bien Cuit' for more information].
- Let rest in a cool, dark place for 35 minutes. This period is called Autolyse. More information on this also towards the end of the article.
- After 35 minutes, add 15g salt and 50g water.
- Fold dough on top of itself to incorporate.
- Transfer to a medium plastic container or glass bowl and cover with a kitchen towel and let rest for 30 minutes.
- The dough will now begin its first rise (called bulk fermentation) to develop it’s flavour and strength. The rise is temperature sensitive, Chad tries to maintain around 27C to achieve bulk fermentation in 3 to 4 hours. You then develop the dough by folding during the bulk fermentation.
- Fold dough, repeating every half hour for 2.5 hours.
- To fold dough, dip one hand in water to prevent sticking. Grab the underside of the dough, stretch it out, and fold it back over itself. Rotate container one quarter turn and repeat. Do this 2 or 3 times for each fold.
- After 3 hours, the dough should feel aerated and softer, with 20 – 30% increase in volume. If not, continue bulk fermentation.
- Pull dough out of container using a dough scraper. Transfer to a lightly floured surface. Lightly dust dough with flour. Through experimentation, I have discovered that I prefer to use Rice Flour.
- Cut into two pieces and work each piece into a round. Dust the tops with flour and cover with a kitchen towel and rest on the work surface for 20 – 30 minutes.
- Line two baskets with clean kitchen towels and generously dust with flour.
- Slip dough scraper under each dough ball to lift it, being careful to maintain the shape, and flip the rounds floured side down into the baskets. Let rest at room temperature, covered with towels, for 3 to 4 hours before baking.
- Bake the Bread: Preheat Oven to 260C. Place two Dutch ovens / Cast Iron Casserole Dishes into the oven to preheat.
- Turn out rounds into the heated cast iron ‘ovens’, score tops, cover with lid and place in oven. Immediately reduce temperature to 230C, and bake for 20 minutes with the lid on. After 20 minutes, remove the lid and bake for a further 16 – 25 minutes until the crust is a deep golden brown. Chad recommends a baking time of 20 – 25 minutes, but my oven is very powerful and I find 16 minutes is perfect.
- Et Voila. Onto wire racks to cool.
- Salted Butter.
Autolyse is a process developed by Professor Raymond Calvel. of the world of bread. Mix only flour and water together and let sit for 20 minutes. Then add your salt, and if using yeast, then your yeast. Autolyse can last for up to 3 hours. Results vary based on your flour.
Chad Robertson recommends a longer autolyse, 2 – 3 hours, in breads with a higher percentage of whole grain flours. Though for his basic sourdough recipe, it is 35 minutes, as per the recipe above. The length of time allowed for the autolyse will affect the amount of kneading required once the levain, or sourdough starter, and salt are added. Including an autolyse phase in bread making will mean a shorter time spent kneading and mixing. Too much kneading can result in an over oxidised dough, which detracts from the finished breads colour, flavour and texture.
Final notes on sourdough;
Sourdough is considered to have better inherent keeping qualities than other breads, due to the lactic acid produced by the lactobacilli, and is especially important in baking rye based breads, where yeast does not produce comparable results. Some bakers have conducted extensive research into the length of the fermentation and cooking time. Chef Zachary Golper, of Bien Cuit Bakery, has a lot to say on the matter, and in fact it is this book that I plan on reading next, to further understand how to make the perfect loaf.
Thanks to Wikipedia, for the Science.
Best Baking Wishes to All.