What's the point of long/complex sourdough feeding techniques?

Question

About a year ago, a friend taught me how she makes her sourdough bread and gave me a portion of her starter. It works great and makes fantastic loaves. I've started to look at other recipes online and in various books (e.g. Flour, Water, Salt) to better understand how different types of sourdough breads are made and I've realized that the splitting/feeding of the starter in my recipe is quite a radical departure from every other Levain/sourdough-starter recipe I've found. Otherwise, it seems to be the standard high-hydration (78%-80%), autolyse (2 hr), bake-in-a-dutch-oven approach that's so common these days.

Specifics:

• I typically only have time to bake once a week, so I store my sourdough culture in a glass jar in the fridge.

• For most of the past year, when preparing my dough I would simply
  take the starter out of the fridge, split it, and dissolve both
  portions directly in warm water (~90 F).

• The starter would then get some flour and be put back in the fridge
  (100g starter, 100g water, 100g flour).

• The portion for the bread would simply have the flour and salt added, autolyzed with occasional folding, divided and allowed to rise
  overnight (~12 hours).

In contrast to this simple approach of dissolving the starter directly in water and then adding the flour for autolysing, every other recipe I've found seems to require a 12 or 24 hour pre-feeding routine that involves feeding the starter first, then discarding most of this newly fed starter before adding this "revived" starter to the water/flour before either a long bulk fermentation or a long rise time. Or some even require multiple feedings...

Why do people spend so much time and energy on long drawn out pre-feeding routines? My approach obviously works - the bread rises just fine, the crumb is fantastic (that's mostly due to autolyse and cooking in a dutch oven), it develops a nice flavor and a little sourness over the 12 hour rise time (especially if it's a cold night).

What am I missing? Better flavor? I can seen an argument for getting the culture more active this way, but I don't see much difference between that and simply allowing my culture to warm up to room temperature. In fact, I've started letting my culture warm up before splitting it this past month, as well as leaving the newly fed cut at room temperature for several hours before sticking it back in the fridge - however, I haven't noticed any difference in flavor nor in how long it takes to rise, etc.

Answer 1

Absent a definitive answer here, I'm going to take a stab at this based on some experience I had with difficult sourdough starters. Note that I make a lot of sourdough items but do not do any kind of multi-stage prefeeding ritual.

Sourdough is a culture of multiple types of bacteria and wild yeast. Sometimes wild yeasts do not reproduce rapidly or produce as much carbon dioxide (for leavening) as commercial yeasts. I've definitely had the problem before with a starter that it wouldn't produce anything other than a superdense bread, no matter how long the dough rise.

Most of us keep our starters in the fridge (unless we run commercial bakeries). Thing is, at fridge temperatures, the bacterial culture will grow, albeit slowly, but the yeast will hardly reproduce at all, and will produce no carbon dioxide. So, when you take it out of the fridge, if you use the culture immediately you may have an imbalance of active bacteria but sleepy yeast (this is some inexpert armchair biology here, so a big pinch of kosher salt with it).

You are solving this via the use of 90F water. I solve it by proofing a sponge for 7-12 hours. However, there are clearly sourdough aficionados who feel that this is not sufficient to restore the yeast to full strength and that it needs more time and feeding. The feed, split, and discard routine I believe comes from commercial bakeries that never refrigerate their starters because they use it every day; it is the advice given in the Berkeley Cheese Board's cookbook, for example. Doing this over 36 hours or so could be assumed to get the sourdough into the same state it would have been for a sourdough kept constantly at room temperature and rotated every 24 hours, allowing you to use the exact same rising times/temps as they would use.

Now, back to my all-natural wild yeast starter that wouldn't rise very well. I did not try feed-and-split for 36 hours; maybe that would have made it rise adequately and is the reason for this technique. Instead, I started the starter-making process over and got a better strain of yeast the second time.

Answer 2

FuzzyChef is correct that one reason for a multistage approach is to ensure the starter is operating "at full strength" before mixing the final dough. (And it's also important to note the imbalance of bacteria and yeast mentioned in that answer.) A lot of people don't bake bread reliably every week, and reviving a starter that's been in the fridge for longer can sometimes take a feeding or two. A recipe that suggests doing this may be just ensuring the starter is in good condition.

It's also somewhat unpredictable how starters will evolve over time with lots of refrigeration -- some will build up acid over time and then become sluggish. Some are fine for a while as long as they are used regularly, but then something gets imbalanced. Most recipes that recommend a multistage approach will do a larger dilution of the initial starter, which helps to avoid acidic build-up and make sure the yeast always have plenty of food.

I cannot understand why a recipe would suggest discarding part of the mixture after a feeding like that, though. That's just wasteful, and I'd question any recipe that suggests that. (Most recipes that suggest discarding starter on a regular basis on based on old practices that didn't realize it's perfectly fine to keep rather small amounts of starter reserved in the fridge -- you don't need a lot. I often keep mine in a tiny mustard jar; a few tablespoons is generally plenty.)

If you need to revive a sluggish starter, you may end up with too much to use by the time you've fed it enough to revive it. But as a matter of course, that shouldn't happen with healthy starters unless they've been stored for a long time.

Anyhow, there is one more important reason to do a multistage technique for baking bread sometimes, and that is because it does affect flavor profile and can affect stability of the final dough (along with rise, oven spring, etc.). Some people use "sourdough" yeast to produce all sorts of bread types. If you have a starter that produces a rather sour sourdough, doing a multistage recipe (without discarding any) can dilute the sourness and allow yeast growth rates to overtake the lactic bacteria that produce the sour flavor. If you want to produce sweet rolls or buns, or some other bread type without much "sour" flavor using natural yeast, a multistage method is the best approach. Heavier doughs (with whole grains, or with lots of added butter, sugar, and other ingredients) may also require a strong starter to ensure a full rise.

And while you've had good results without prefermenting the starter, excess acid build-up in a starter over time can deteriorate final dough quality. Aside from flavor, excess acid can break down gluten, inhibit yeast growth (compounding the problem -- you wait longer for the dough to rise, and it just gets more sour with ever less rise), and even lead to a loaf lacking elasticity to rise properly in the oven, perhaps instead spreading sideways or showing little discernible oven spring.

Diluting refrigerated starter and feeding it before use in a final dough helps to mitigate these problems, if you have them. With a healthy starter used regularly, you may not encounter such problems, so there's no difficulty and no need to do multistage builds unless you want a less sour final product or start seeing inferior rising power.

Answer 3

I have seen little difference between feeding a starter and making the dough for bread, they both require added flour and water. Taking a starter right out of the fridge and making dough, however, may give you the results you want, but letting it warm up and feeding once or twice before baking assures the best condition so the yeast in the dough during the proofing or riseng stages can eat the sugars and starches in the wheat, which releases the nutrients for better digestion. And people who are gluten intollerant can eat sourdough bread because the gluten is alaready predigested, unless it has sleepy yeast in it that isn't doing everything it should. This is only one reason for feeding after refrigerating before baking. Another reason is baking with and maintaining sourdough starters requires time. Things go more slowly than with baker's yeast, which is fast rising but short lived. My information about gluten intolerance is found on several sites, especially at TraditionalCooking and here: https://www.thehealthyhomeeconomist.com/can-celiacs-eat-true-sourdough-bread/