Recently, I've stumbled upon a way to do just that!
In order to reduce our impact on climate change, I've started making soy milk at least once a week: I drink it 'as is' in the summer and make it into pudding in the winter. Every batch of soy milk generates a cup or so of 'okara' - the depleted soy beans. It turns out that these ferment really easily. Other people have taken advantage of this to speed up the fermentation of idli or just to make the okara more palatable. I've recently realised I can use it to make a speedy sourdough starter! I haven't found any internet references elsewhere describing how to do it, so here's my method.
- Put a lump of fresh okara into a bowl and cover with a cloth. Leave in a warm place for around 24 hours or at room temperature for around 48 hours. If you pick a little bit off the surface it probably won't taste sour: the sourness seems to be mostly in the middle of the lump, but you should see that the surface of the okara has risen and domed a bit. This is particularly easy to see if the container you put it in is completely full.
- Mix the fermented okara with flour and water. I've been using the following proportions: 1 cup fermented okara (pressed down), 1 1/2 cups white flour, 1 tsp salt, enough water to make a soft dough (around 1 1/2 cups). You should find that this mixture tastes sour, even though the surface of the okara probably didn't.
- Put in a bowl that has lots of head-room, cover with a cloth and leave in a warm place overnight. You should find it rises quite a lot although it may have sunk back again by morning.
I've used this to make delicious pancakes, following a recipe from here:
1 cup milk
2 cups sourdough starter (prepared above)
1 3/4 cups white flour
1 teaspoon baking soda
2 teaspoons baking powder
1 1/2 teaspoons salt
1/4 cup white sugar
1/4 cup butter, melted
- Beat eggs in a medium bowl. Add milk and sourdough starter.
- Sift together flour, baking soda, baking powder, salt, and sugar; add to the egg mixture, mixing well. Stir in melted butter.
- Lightly grease a hot griddle. Drop the batter by 1/4 cup onto the griddle and cook until light brown, turning once.
Great with yoghurt and jam!
If you want to make sourdough bread, you don't even need to bother with making a starter - you can just add the fermented okara directly to your dough. In fact, because okara ferments so easily, if you add it to a bread with a long fermentation time, you may well find you make sourdough bread by accident. That's how I got started on this in the first place ;-)
Every week I make Martin a couple of loaves of no-knead bread. It's a 'slow' recipe: you use a tiny amount of yeast and leave the bread to rise for around 18 hours. One day I decided to put okara into it: lots of people add okara to baked goods and I was trying to figure out good uses for the cup or two I was generating every week. When I checked the dough the next morning, I was most surprised to discover I'd made sourdough! I've since found that, if you leave your soybeans to soak overnight at room temperature or leave the okara in the fridge for 4-5 days after it's made, it will almost certainly sour dough. In fact, if you're adding okara to dough with a long fermentation time, it seems the only way to be sure you're not making sourdough is to soak your soybeans in the fridge and use the okara as soon as it is made :-) There's no need to bother with such precautions if you're using a more normal bread recipe or doing non-yeast baking, though: okara won't sour those.
You can't be sure that random okara that has sat in the fridge for a few days will have fermented sufficiently to make sourdough: make sure you start with okara fermented as described at the top of this post.
I make a simple white sourdough using my no-knead bread recipe, following it as given except for using one cup fermented okara in place of 1/2 a cup of the flour and cutting down on the water a little.
Starting with this recipe and taking what I've learned from the no-knead bread, I've also come up with the following recipe for a wholemeal sourdough bread with lots of seeds.
2 1/2 cups wholemeal flour
1 cup cornmeal
1/2 cup rye meal
1/2 cup rolled oats
1/2 cup seeds (pumpkin, sunflower, millet etc.)
1/2 cup fermented okara
1/4 tsp dried yeast
around 2-3 cups water
- Put everything except the water into a large bowl and mix well.
- Add enough water to give a porridge-like consistency.
- Cover with a paper towel and leave in the hot water cupboard until doubled (12-24 hours).
- Tip the dough into a silicone/non-stick loaf tin*, smooth the top, and place in a cold oven.
- Place a dish of cold water in the oven, turn to 220 deg C and bake approx 1 hour (until it smells cooked, a knife comes out clean, and/or it sounds hollow when you tap the bottom).
- Turn onto a rack to cool.
* If you don't have a silicone/non-stick loaf tin, heat your oven as hot as it goes with the empty loaf tin and the pan of water inside it. Tip the dough into the hot loaf tin - the outside of the dough will sear and it won't stick - then bake around 45 minutes.