Sourdough bread

What is sourdough starter?

It's a mixture of flour and water (1:1 ratio, by weight) that has the right kind of lactic acid bacteria and wild yeasts living in it. 

How do I keep it alive and maintain it?

It needs to be fed with more flour and water (always 1:1 ratio, by weight.) Activity of the microbes increases with temperature. In the fridge, they work very slowly, and can remain alive without being fed for several weeks. At room temperature, they need to be fed once a day. 

If you bake every day, you can keep the starter at room temperature, and feed it once a day and bake once a day. If you don't bake every day, you'd be wasting a lot of flour feeding the starter every day. So it makes more sense to keep it in the fridge, and only feed it 12-16 hours before you want to use it.

Recommended procedure if you bake less than daily:

Keep a small amount (about 50g) in a contained with a lid in the fridge.

12-16 hours before you want to bake, take it out of the fridge, and add the same amount that you're going to use for your bread recipe. Half of that is flour and half is water.

For example, one of my recipes uses 250g of starter. I have 50g in the fridge. I take it out, and add 125g of water and 125g of flour. Stir it to mix well. Leave it at room temperature for 12-16 hours. When you start mixing your dough, take 250g from the starter container and add it to the rest of your ingredients. That leaves 50g in the starter container, which can go back in the fridge until next time.

When the starter has been in the fridge, it's cold and not very active. When you take it out of the fridge, and feed it, it gradually comes up to room temperature, and then it takes a while for it to multiply and become more active, using the extra flour you added. After about 12-16 hours, it's very active, and that's the best time to use it for bread dough. You can tell that it's active because it's formed a lot of bubbles and has doubled in volume.

Sourdough starter behavior

When you add more flour and water to starter, you should mix it thoroughly. The existing microbes start multiplying and fermenting the starter. After a while, they produce visible gas bubbles. That's what makes your bread dough rise.

At fridge temperature (40F), they work very slowly, so they don't exhaust their food supply for several weeks.

At room temperature, they work at moderate speed, and it takes 12-16 hours for the starter to be sufficiently active to make bread dough rise in a reasonable amount of time.

The temperature of the water that you add along with flour influences the activity level of the starter. If you're in a hurry, warm water (up to 100F) helps speed things up. If the water is too hot, it kills the starter. Keep it at 100F or below to be safe.

Baking bread

Baking bread is a bit of a science. You have to do things the right way for it to work out, otherwise you get something that doesn't rise and ends up inedible. You have to be fairly accurate with the ratio of the ingredients. And you should measure by weight, since the density of flour can vary a lot. A small digital kitchen scale saves a lot of trouble compared to measuring ingredients in cups and tablespoons.

The kind of flour you use matters: all-purpose flour and cake flour don't have enough gluten and don't rise well. Bread flour has more gluten (12% to 14%) and rises better. Whole wheat flour doesn't rise very well, so it's more difficult to use, but worthwhile for better flavor and nutrition. Rye flour is even more difficult to use.

Ratios of ingredients

Bread recipes are often specified as ratios of ingredients in relation to the weight of the flour. That means you can scale them up or down to make whatever size of bread loaf you want.

Water / flour is the hydration ratio. It's typically in the range from 60% to 70%. Below 60% is a very stiff dough; bagels for example use between 50% and 55%. Above 70% the dough gets very soft and stick, and can be difficult to work with.

Salt / flour - Should be 2%. Too little flour produces bread that tastes very bland, and too much flour becomes inedible.

The amount of sourdough starter to use is pretty flexible. More starter means the dough rises faster. If you're in a hurry, that can be useful. Less starter means it takes longer to rise. Temperature also affects the speed with which the bread rises, so you have 2 ways of adjusting this. Temperature can be adjusted by the temperature of the water you're adding. Room temperature water is fine; if you're in a hurry, you can use water up to 100F.

Mixing

All the ingredients need to be mixed thoroughly and evenly. This takes a few minutes in a stand mixer.

Kneading

Beyond mixing the ingredients together, the dough needs to be kneaded for 10-15 minutes to develop the gluten structure. This is an elastic network of protein, which is formed from the protein in the flour together with water. Kneading strengthens this network. This is what gives bread dough its elasticity, which in turn enables to to rise: The microbes in the sourdough starter metabolize starch into CO2, which produces gas bubbles. The gluten captures these bubbles and keeps them in the dough.

Rise / fermentation

After kneading, the dough needs some time to ferment and form CO2 bubbles. Depending on the dough temperature, this can take between 1 hour (very warm) and 24 hours (fridge temperature.)

After the first rise, most recipes involve kneading the dough briefly, and then letting it rise again. The purpose is to bring more oxygen into the dough, and it also strengthens the gluten further.

The second rise is the most important; when it's done, the bread is put in the oven to bake, and whatever shape it's in at that point is the shape of the finished bread. The dough is usually put in a basket (banneton) for the second rise, which helps it keep its shape. The basket is usually dusted in flour so the dough doesn't stick to it, so that it can be easily dumped from the basket onto a baking sheet or baking stone.

Because the rise depends on the starter activity level, the dough temperature, and the ambient temperature, it's pretty difficult to state a fixed amount of time. You should look at how much the dough has expanded, and the finger poke test (explained below) to determine whether it's done rising.

While the dough is rising, it will dry out on the outside unless it's covered, or unless it's in a humid place. You can cover the bowl with a plate or plastic wrap. For the final rise, where the dough rises above the edge of the basket, I put it in the oven and spray a lot of water on the oven walls and door, to create a humid environment where the dough doesn't dry out.

Baking

The temperature should be around 425F. The baking time depends on the size of the loaf, but 45 minutes is a good starting point. If the temperature is too low or the time is too short, you end up with pale bread without much of a crust. A proper crust should be medium to dark brown.

After baking

Let it cool off for at least 10 minutes (20 minutes is better) before cutting into it, otherwise it sticks to the knife and it's still a bit sticky.

Bread vents a lot of steam after it's done baking. If the steam can't escape easily, the crust gets soggy. Bread needs to cool off on a cooling rack for at least an hour, better 2 hours, before being wrapped up. On the same day it's baked, it can stay unwrapped on the counter. I recommend wrapping it up (plastic bag, fabric bag, paper bag) overnight so it doesn't dry out too much.

Sourdough bread keeps at room temperature for about a week. It starts getting stale after about 5 days, so it's best to eat it before it gets too stale. If you can't eat it in 5 days, it's better to slice it and freeze half of it.

Basic recipe

500g bread flour (this has a higher protein content than all-purpose flour)
250g sourdough starter
280g water
12g salt

Mix ingredients and knead for 10-15 minutes on the "2" setting in the KitchenAid.

Remove the dough hook, cover the bowl, and let it rise for about 2 hours at room temperature. Or put the bowl in the oven and turn on the oven light; this raises the temperature to around 85F which is ideal for bread dough.

Briefly knead the dough and turn it into a round ball.

Put the dough in a floured proofing basket, or a bowl with a kitchen towel covered in flour.

Cover the dough and let it rise for 1-2 hours, until it's expanded significantly. To check, you can poke it with a finger (rinsed with water so it doesn't stick to the dough.) When it rebounds quickly and doesn't leave a mark, it needs more time. When it rebounds slowly and leaves an impression, it's ready to bake.

Preheat the oven to 425F. Put a roasting pan on a lower rack in the oven. Later, we'll put water in the roasting pan to create steam in the oven.

Invert the basket to dump the dough on a cookie sheet (or baking stone) covered in parchment paper.

Wet a knife to prevent sticking, and make a long cut on the top of the loaf, about 1/2" deep. This helps the bread expand in the oven.

Put the loaf in the oven, on a rack above the roasting pan. Pour 1/2 cup of water in the roasting pan and quickly close the oven door.

Bake for 45 minutes.

Remove from the oven and let it cool off on a cooling rack for 1-2 hours.