Wordloaf's rules for sourdough discard recipes
And one for discard knockoff Carr's whole-wheat table water crackers
I hate sourdough discard. There, I said it.
But I hate wasting flour more, so I learn to live with it, despite it feeling like a burden. There is almost nothing that sourdough discard can do that freshly-proofed starter or levain cannot do better, so I have no interest in using it in recipes where the latter is going to give a superior product. Instead, I look for recipes where its shortcomings aren’t going to matter (and where its high acidity is actually useful, more on which below).
Over the years, I’ve developed a number of rules for making the most of sourdough discard, which I thought would be useful to share here. But first, a primer on how to substitute discard for the flour and water in a recipe:
Assuming your starter (and discard) are at 100% hydration, then every 100g of it contains 50g of flour and 50g of water. To make a substitution, you just reduce the amount of flour and water in the recipe by these amounts.
If it is at another hydration, sorting out how much of each it contains is easy:
Add the hydration (as a decimal) to 1. For example, with a starter at 75% hydration, you’d get 1.75.
Divide the weight of discard by that number. Continuing our example, 100g discard ÷ 1.75 = 57g flour.
Subtract that number from the weight of discard to determine the amount of water it contains, e.g., 100 - 57 = 43g water.
Rule #1: the recipe must use up as much of the stuff as possible
To my mind, the main point of sourdough discard recipes is to get it the hell out of my fridge, so it better use as much as possible or I’m going to be annoyed. I try to use at least a cup in one go, or around 250g.
For any recipe that is structured by flour (especially the gluten in it) you can’t really have all of the flour in the recipe come from the discard alone, since it’s too digested at that point to glue things together. So you’ll need to add some fresh flour; when developing recipes, I usually start with no more than half of the flour coming from the discard and go down from there if needed. (In the rare recipe that isn’t structured with flour, like my sourdough discard granola, which just uses the discard as a clumping agent, this isn’t a problem.)
And get out of here with recipes that use a “homeopathic” amount of discard, of which there are far too many. You know the ones I mean: those that call for 50g of discard (half of which is water) along with 3 cups of additional flour. You might as well wave the container of discard over the bowl and return it to the fridge for all the difference it makes in the recipe.
Rule #2: the discard-less version of the recipe should already contain water
Sourdough discard is typically around 50% water, which means using it also brings water to any recipe you add it to. Thus any recipe that doesn’t normally have a large amount of water in it is likely going to be degraded by adding any significant amount sourdough discard, since it is going to activate the gluten and starches in the flour when it shouldn’t.
Take shortbread cookies, for example, which are bound together by butter, leaving them a sandy, crumbly texture once baked. Adding sourdough discard to a shortbread—which a whole lot of people do—is only going to unshorten them, making them hard and cracker-like. Don’t do this unless you think this is going to improve them somehow.
Ditto for those pie doughs in which at least some of the flour is coated with fat before the liquid is added. The flour in the discard is already wet, so adding it to a pie dough is bound to make it tougher and less delicate than it would otherwise be. This might be fine, though it definitely won’t be the same.
Recipes that get their moisture primarily or entirely from eggs can work with discard, but it still can present problems. One, the eggs might add structure to the finished product that discard cannot. And two, if you retain the eggs, the discard will be adding more water, resulting in a wetter dough. This might require adding more flour to compensate.
Rule #3: Ideally, the sourdough discard is actually doing something useful
While getting rid of sourdough discard is the primary reason for using it, it’s nice if it also serves a purpose in the recipe too, beyond simply replacing some of the flour and water it would otherwise have. What else does sourdough discard contain beyond flour and water? Acidity, and loads of it. This makes the best sorts of recipes for a sourdough discard sub those that already contain an acidic liquid, especially when that liquid does something crucial for the resulting product.
And what’s an acidic liquid used all the time in baking? Buttermilk! Pancakes, quick breads, biscuits, crackers, and many other floury foods often use buttermilk as a source of milk solids (proteins and sugars, for browning and flavor) and lactic acid, for tang and/or to react with baking soda for leavening. Sourdough discard contains a mixture of lactic and acetic acid; aside from the lack of milk solids, it makes an excellent replacement for buttermilk.
The pH of buttermilk is around 4.5, while the pH of sourdough discard is somewhere around 3.5, making it 10 times more acidic. In theory, this means that you should use about a tenth as much to end up with a similar pH in the recipe, but unless the extra acidity causes problems or leaves it overly sour, I tend to use an equivalent amount (meaning if the recipe calls for 100g of buttermilk, I’ll use 200g of 100%-hydration discard, half of which is water), because Rule #1.
All recipes that rely on buttermilk or another acid for leavening include a base (sodium or ammonium bicarbonate), which neutralizes some of the acidity. This means the product will taste significantly less sour than the discard, which is also a good reason to use it in these sorts of recipes.
You can even make up for the missing milk solids by adding nonfat dry milk powder to the formula. Buttermilk and milk are around 10% milk solids, which means for every 100g of buttermilk called for, add 10g of nonfat dry milk powder. (If you want to be super precise, you’d really use 180g of discard in this case—containing 90g of flour and 90g of water—since the buttermilk really only has 90g of water in it. But in most cases the difference is negligible, so it is up to you.) Butter has milk solids in it too, so if the recipe contains a substantial amount of it, adding milk powder is less important.
Rule #4: Avoid sourness where it isn’t appropriate
I’ve made things like tortillas and pasta dough with sourdough discard, and while they’ve worked okay, I don’t care for the tang the discard adds. For this reason, I tend to avoid using discard where the product is going to be noticeably more sour than its discard-less equivalent.
Rule #5: Acetic acid is volatile
This isn’t really a rule so much as a fact: Acetic acid is volatile, while lactic acid is not. This means that acetic acid can boil off during cooking, at least under certain conditions, while lactic acid cannot. Acetic acid has a punchy, sharp aroma and flavor, while lactic acid is far more mild-mannered. While this has no bearing on the discard’s effect prior to cooking, it does means that some of the acidity can dissipate once the product is baked.
The drier the product, the more acetic acid that will boil away during baking. This makes crackers an ideal use for discard, since they contain very little water; even a super sour discard will yield a relatively mild cracker once crisp. Ditto for my sourdough granola. Thinner things are better too, since it provides more surface area for the acetic acid to escape from. Cookies, crackers, and pancakes are all going to release more of it than a quick bread, for example.
Rule #6: I am lazy
Again, less of a rule than a fact. I have no need for complicated sourdough discard recipes, and I don’t want dozens of them. All I need is a handful of simple, staple formulas that I can turn to whenever the discard container starts to fill up and that use up as much as possible in one go—things like granola, crackers, pancakes, or quick breads.
Aside from granola, which I make about every other week, the two recipes I’ve been turning to most often are my new copycat version of Carr’s-style whole wheat crackers and Boston brown bread, both of which normally contain buttermilk. I’ll be sharing the latter one—which is excellent—here soon.
(I’m still working on a recipe for discard “wacky cake”, which is really good when it has worked. Wacky cake is an egg- and dairy-free chocolate cake that is leavened with baking soda and vinegar, the latter for which discard makes an excellent substitute.)
Rule #7: The type of flour in the discard matters
Ideally, the flour in your discard should be identical to the one in your recipe—if you feed your starter with white flour, you want to use it to replace white flour. Right now I have two starters, one with 100% whole-rye flour, and another that is a 50-50 mixture of whole-rye and whole-wheat flour. I combine the two in my discard tub, which means it is 66% rye flour and 33% whole-wheat; it works great in whole-grain recipes like whole-wheat crackers or brown bread. On the other hand, it is not ideal for replacing a substantial amount of white flour in a recipe, especially when the flour is responsible for supplying structure via gluten. This is one reason I rarely make bready things with my discard.
That said, going the other way—using a white flour discard for a whole-grain recipe—will usually work fine, though it may alter the texture and appearance of the product somewhat.
I combed through my archives for discard recipes, and though these rules have evolved over the years I’ve been writing here, all adhere to them:
But in truth, l only really use two styles of discard recipe with any frequency: granola (which I make every other week or so), and crackers, which are always nice to have around. Both keep indefinitely and get consumed regularly, so there’s always need for more, and both use up substantial amounts of discard.
I make a bunch of different discard crackers, but the ones I’ve been making most often lately are a knockoff version of Carr’s whole wheat crackers (which are really more of an English digestive biscuit than a cracker cracker). I based my recipe on Stella Parks’ one for Serious Eats, which—being from Stella—made life easy. I’ve tweaked the method and ingredient list a little, but it’s still really her recipe, adapted for sourdough discard.
Wordloaf paid subscribers can find the recipe below the fold.
—Andrew