Sourdough Discard, Math, and Crackers

Sourdough is trending in a big way:

Here are some thoughts that helped me get my head around the life cycle of sourdough starters.


Typical sourdough instructions tell you to discard half your starter before feeding it.

A lot of people have a hard time with this. I myself hate the idea of wasting food.

But what happens if you don't discard any starter?

The amount you need to feed it is proportional to the amount of starter you have.

So if you have 4 ounces of starter, it will be really happy if you feed it another 4 ounces or so of food. Now you have 8 ounces. The next day, it will be really happy if you feed it 8 ounces. Now you have 16 ounces.

And so on.

Do the words "exponential" and "growth" mean anything to you?

Photo: Michelle Orr

How do you avoid being driven out of house and home by your starter?

Here's a crucial insight: a small amount of starter that's fed a lot will be more powerful than a large amount of starter that's fed a little.

So "hoarding" your starter is not helpful, unless you're gearing up for a massive project and really need a lot of starter.

What do do? Here are some options:

1. Feed it less, and have a less happy starter.
2. Keep it in the fridge. Take it out only before you need it, and feed it a few times in preparation for showtime. And make sure to feed it once a week or so regardless.
3. Say you have 4 ozs of starter Before you feed it, "discard" half of it. Then feed it the amount you discarded. Now you have 4 ozs of starter again.

Clearly 1 is not a great plan. And in my experience 2 is more trouble than it's worth.

That leaves us with 3.

The next key insight is that you can do good things with the "discarded" starter:

The easiest thing to do is to mix it with water, boil it, and have it as a porridge. You can also make it into delicious crackers. Or you can make sweet or savory sourdough pancakes. (And you don't have to do these things every day. You can save up your discard in the fridge, especially if you don't need it to be particularly active.)

I imagine you could add some fresh flour, ferment it, and make Øllebrød or kвас from it, bypassing the bread stage. I haven't tried. Maybe I will.

Here's a cracker recipe that works for me. This should work more or less the same regardless of what kind of flour is in your sourdough (wheat, spelt, sorghum, brown rice…).

Sourdough Herb Crackers

400g mature fully-hydrated sourdough starter "discard"
60g extra-virgin olive oil
herbs (rosemary, fennel seeds, ground cumin, curry powder, or as you like)
salt

Mix the starter, the olive oil, the herbs, and some salt in a mixing bowl. If necessary, add small amounts of water or other water-based liquid until the batter is just barely pourable. This will make it much easier to get it to a uniform thickness in the next step.

Turn the mixture out onto a half-sheet pan lined with parchment or a silpat. Spread it out to the edges of the lining and try to achieve as uniform a thickness as possible. Sprinkle a bit more salt on top (use salt with nice texture if you have it). Add more herbs on top too if you like.

Bake it at 300°F or lower for 20 minutes. Take it out and drag a blunt knife gently through it to score it. (This will this help you break it up later. It will also help the middle parts dry more quickly.)

Bake it for another 20 minutes. Keep baking it and checking it every 10 minutes until it is dry and crisp but not burned. If it burned, then use a lower temperature next time. If the edges dry out faster than the middle, then take the edges pieces out and bake the middle pieces for a bit.