Anyone who has pets,” explains baker Francisco Migoya, “knows that they get a bit antsy around mealtimes: well, yeast is just the same.” He is talking (in a characteristically lucid, down-to-earth way) about sourdough. More specifically, about the levain, or starter, that acts as the leavening agent.
“Actually, it isn’t just yeast that helps sourdough rise and gives it flavour,” he says. “For every yeast cell, there are 100 lactobacilli – lactic acid bacteria – that coexist with the yeasts, and act together to poison their environment with alcohol and acids so no other microbes can survive there. Like wolverines, these microbes essentially pee on their food to stop others from eating it.”
Migoya is head chef of the Cooking Lab, the team behind Modernist Bread, a new sister publication to Nathan Myhrvold’s Modernist Cuisine. The word “encyclopaedic” barely does it justice. At 2,196 pages, spread over five volumes, it is exhaustive in its analysis of the ‘staff of life’, with more than 1,500 traditional and avant garde recipes, as well as the science underpinning bread, a host of new techniques and some phenomenal photography.
Sourdough is the most ancient form of leavened bread, and it has a complexity of flavour and texture that breads made with commercial cultivated yeast cannot hope to match, which is why artisanal bakers all over the world have re-adopted it.
How, then, do you go about making your own sourdough? “First you need to get your head around bakers’ percentages,” advises Migoya. “It’s the easiest way to talk about recipes. The flour, or mixture of flours, is always 100%, then whatever else is added – water, starter, fat, salt – is expressed as a percentage of that. The other vital thing is to weigh everything. Measuring by volume is hopelessly inaccurate.”
Migoya advises starting with a simple mix of equal parts flour and water, leaving it for four or five days, feeding it once or twice a day. But many factors determine how quickly it matures: temperature, and how often you feed it, for instance.
Culture hero: Francisco Migoya is an expert on sourdough
“By the time it’s mature, it will be very lively, much increased in volume, and more acidic. You can test it by pulling off a small piece and dropping it in a glass of water: if it floats, it’s mature. That won’t tell you the acidity, though. It’s worth investing in a pH meter to be sure it’s mature. It should be between 4.2, mildly acidic, and 3.8, very acidic.”
Many aspiring sourdough bakers balk at the commitment needed to keep a starter in perfect condition, but Migoya outlines various strategies to combat this. Salting the starter slows down its development, as does refrigeration and making it stiffer by feeding it with more flour than water, while freezing or dehydrating it will stop development completely, which can then be restarted.
Sourdough requires much patience and practice, from knowing when your starter is mature to the techniques of folding and shaping, the deft flick needed to tip dough onto a peel – “don’t give it time to think it might be a liquid,” advises Migoya – and the scoring of the crust.
Much help is available both in Myhrvold and Migoya’s remarkable books and in online videos from professional bakers. That said, those who want to get good are going to need to make a few loaves first. The good news is that the “most expensive ingredient is your time”.
Sourdough bread
For the starter
500g bread flour
(not high-gluten)
500ml water at 24˚C
For the bread
Make a 1kg sourdough boule
480g bread flour
315ml water
195g starter
10g wheat bran
1g diastatic malt powder (optional)
12g fine salt
1. To make the starter, combine the flour and water in a glass jar or plastic tub. Mix until homogeneous, cover with an airtight lid and keep in a place as close as possible to a constant 21˚C.
2. Leave it for 48 hours: you should start to see bubbles of carbon dioxide on the surface. Remove 75% of the mixture, replacing with 375 ml of water (at 24˚C) and 375g flour. Mix it until homogeneous again.
3. Repeat this last step within 24 hours, then daily. By the fifth day, your starter should be ready to use.
4. To make the bread, mix all the ingredients except the salt together until you have a shaggy mass of dough. Put in a lightly-oiled square tub, cover, let it stand for 30 minutes, then add the salt, mix thoroughly and return it to the tub.
5. Ferment the dough for four hours, performing six four-edge folds,
one every 30 minutes after the first hour: using a wide plastic spatula, lift the underneath of each side of the dough, pulling and stretching it to develop
the glutens.
6. Turn the tub gently onto a well-floured surface and pre-shape for baking: the aim is to tuck and stretch the bread until it has an even, taut ‘skin’. A boule should be like a slightly flattened sphere.
7. Transfer, seam side up, to a proofing basket lined with a couche cloth, or a plastic tub. Leave it in the fridge at 4˚C, covered, for 16 hours to prove.
8. Heat a cast iron baking sheet
in a combi oven at 245˚C on its lowest fan speed.
9. Quickly but carefully tip the dough onto a peel. Slash the top of the bread several times in a quick, decisive motion with a razor blade, aiming for a depth of 2mm to 3mm, aiming straight down.
10. Give the oven a burst of steam, then load the loaf onto the baking sheet, close the door and give it another burst, then another two bursts at intervals of one minute. Bake for 20 to 25 minutes in total until crusty and brown, then leave the oven door ajar and leave it for a further 10 minutes.
11. Using a peel, remove the loaf from the oven and let it cool completely on a wire rack. Use within three days.