How to Make Sourdough Starter

Out of everything that pertains to bread baking, making and maintaining a healthy sourdough starter was my biggest challenge and my largest initial failure. Even my very first sad-looking loaf of no-knead bread was a huge success in comparison. It took me a while, through many trials and errors, to overcome those challenges and finally have what I consider a well-performing sourdough starter.

In hindsight, a lot of those challenges came from false or insufficient information and overthinking. In reality, making a strong sourdough starter is quite easy as long as you don't do it blindly and understand a little bit of science behind it. And open up your mind a little.

What is a sourdough starter?

In so many words, sourdough starter, also known as a pre-ferment, starter, levaine, chief, chef, head, mother or sponge, is a sticky mass with active, naturally occurring wild yeast in it. This mass is composed of a mix of water and flour that is fermented by wild yeast lactic acid bacteria (LAB). While many think that starter cultures are dominated by wild yeast, that's not the case. According to Trends in Food Science and Technology's Sourdough Microflora piece, lactic acid bacteria far outnumber wild yeast in starters, at about 100:1 ratio. Both are required for a healthy starter fermentation and must be in balance.

On their own, all ingredients and microorganisms in a starter culture are flavorless, only the byproduct of their activity produces those complex sweet-and-sour flavors that we love in sourdough breads. Sourdough starter lends breads a greater depth of flavor and is more forgiving thanks to the longer fermentation time.

Wild yeast composition in starter cultures

Unlike commercial baker’s yeast, which are strains of yeast within the species Saccharomyces cerevisiae, the yeasts in levain are of various specifies. They include not only S. cerevisiae but also a mix of other wild yeast species, such as S. exiguus, Hanensula anomala, and Candida tropicalis, Candida Beechii, Dekkera, Kloekera, Hansenula and other. Each sourdough starter will have a unique composition of wild yeasts, with different ratios of yeasts. It is this mix and the ratio of wild yeasts that make each levain unique flavor-wise.

Peter Reiheart in his Artisan Breads Every Day book said the following about making San Francisco sourdough bread at home: "if you don’t live in San Francisco, this won’t be true San Francisco sourdough bread because it won’t contain a large concentration of the microorganisms associated with the Bay Area, especially the famous Lactobacillus sanfranciscensis (these organisms do exist in sourdoughs everywhere, but not to the same extent as they do in and around San Francisco)." So, there you have it. From the get-go, your starter will be different from the starter made by some in another location.

Additionally, not every yeast strain is good for bread fermentation.  According to Yeast Technology, such species as Candida, Dekkera, Hansenula for example, have adverse effect on taste and flavor.

All these wild yeasts in your sourdough starter will compete with each other for food. Stronger, more numerous ones will prevail, and determine the quality of your sourdough starter, and ultimately, the bread.

It's important to realize that, when you grow your sourdough starter from just flour and water, there is a chance that bad yeasts will take over. It will be different from someone else's starter, and it may not be as good. There is always that possibility.

How sourdough starter works

Flour in sourdough starter provides food to yeast and lactic acid bacteria. As soon as food becomes present, a feast begins.

Yeast works by consuming sugar and excreting carbon dioxide and alcohol as byproducts. During this feeding process, yeast cells divide over a dozen times each, increasing the size of the colony, to billions of cells. Each cell produces the gas that leavens and flavors the dough.

The byproduct of lactic acid bacteria activity, on the other hand, is lactic acid.

To summarize, the yeast produces gas which leavens and flavors the dough, while lactic acid bacteria produce lactic acid, which contributes sourness and additional flavor.

Factors affecting levain

Not all sourdough starters are created equal, even if they have the same yeast strain and lactic acid bacteria composition. Ken Forkish, in his famous Flour Water Salt Yeast book points the following factors that significantly impact the flavor and how it behaves.

Factor	Impact
Hydration	More liquid in starter leads to greater production of lactic acid. This promotes smoother, yogurt-like taste. Stiffer starters lead to more acetic acid, resulting in sharper, more tangy taste.
Temperature	Warmer temperatures - 78F - 90F (26C - 32C), favor lactic acid production, faster development Cooler temperatures - 55F to 65F (13C to 18C) - favor acetic acid production, slower development.
Flour	Every flour has own personality and affects starter development and flavor. High-extraction flours, whole grain wheat or rye flours, and high-ash flours result in a more vigorous fermentation. This requires more frequent feeding.
Salt	Salt is used by some bakers, though most don't. Salt slows down fermentation, which may be a desirable effect in some cases.
Commercial yeast	Commercial yeast contains a concentrated amount of S. cerevisiae culture, which causes vigorous fermentation. This leads to commercial yeast dominating and eventually starving out the wild yeasts. It's fine to add a small amount of it to final bread formulations, but is not advisable to use in starters.

Naturally, the ratio of seed starter to flour and water matters too. The more seed starter you add to the mix, the faster it will ferment.

Making sourdough starter

Making sourdough starter was my biggest challenge when it comes to bread baking. I tried every single recipe I could find, but I could not get a strong starter. My starters would rise on their own, but the bread made with them would have a poor oven spring, mediocre taste and dense texture. On top, my starters would turn vinegary after a couple of weeks, no matter how diligent I was with the feeding regimen. I tried every single trick I could find but nothing really worked well enough.

It's only later that I realized that naturally occurring wild yeasts in my area were just not good for leavening bread. But back then I gave up and made the best decision - I bought a packet of dried San Francisco sourdough starter on eBay. That proved to be a game-changer for me.

You will get many different opinions on how to make a sourdough starter. But here is my advice to you: if you want to get up and running with your sourdough bread baking quickly and painlessly, buy yourself a packet of a known good San Francisco sourdough starter and grow your starter from that. You will ensure that you get the right composition of wild yeasts, and that those yeasts will dominate other, less favorable, yeasts.

Making sourdough starter from scratch

If you feel adventurous, and you just want to experience the process of making your own levain from scratch, do it. Chances are, it will work as it did for many home bakers. King Arthur's starter recipe is a good one that many like. If it doesn't, do what I did and buy some known good seed starter. I think it's the best approach for a novice baker. At least when your bread comes out not as good as you'd hoped, you'll know it's not your starter that caused that.

Activating the starter

Once you have your dry sourdough starter, simply mix one tablespoon of it with 100 grams of water and 100 grams of 50/50 mix of white and whole wheat or rye flour. Cover and let sit at room temperature for approximately 2 days, until you see the signs of fermentation and the volume about double.

After that, keep feeding the starter every 12 - 24 hours for 3 days. Once you've confirmed that your starter predictably at least doubles in volume after each feeding, you can start using it to make bread.

When exactly to feed your starter?

Sourdough starter volume increases after feeding, up to 4 times the original size. Once the food source (flour) for yeast is depleted, the starter begins to fall back down.  The ideal time to feed your starter is right after it starts to recede. But don't get hung up on that, the starter will be fine if you are late by a few hours.

If you wait too long after the starter begins to fall, the yeast population will begin to decrease dramatically, while acidity will begin to increase. The longer you wait the more vinegary the sourdough will smell and taste due to the accumulation of acetic acid. Such starters can be revived by feeding them, though sometimes their yeast and LAB compositions may change, resulting in flavor changes and performance. In those cases, I would start a new starter from a frozen dry culture.

That said, you can adjust the parameters (amount of seed starter, water temperature, amount of whole wheat flour) such that your starter is ready for feeding, say, every 12 or every 24 hours. In other words, you should dictate when the starter should be ready for feeding, and not the other way around.

Feeding the starter

There is no one formula or rule for feeding. Some bakers feed starter several times a day, others do it once a day. Remember, even if you are on a specific schedule, you will have to make adjustments as you go, depending on your needs, ambient temperature fluctuations, and other factors.

There is also no single recipe for a sourdough starter either. They vary by the flours they use, the amount of levain, and the water/flour ratio. It all depends on the types of breads that will be baked with that starter and other factors.

When I bake frequently, I follow a daily feeding schedule. I try to keep the amount of the starter as small as possible, enough for two loaves or so.

Below is my basic sourdough starter formulation that works very well for me and that I use most of the time. It's suitable for both white and whole wheat breads and I change it only in special situations.

Ingredient	Amount
Levain	20 g (about one heaping Tbsp)
All purpose flour	100 g
Whole wheat flour	20 g
Water (filtered, about 65F - 68F)	100 g

This formula can be scaled up or down, or modified, to suit your specific bread baking needs, or seasonal ambient temperature changes.

My (updated) current formula uses 83.3% hydration. I used to use equal amounts of flour and water by weight but later increased the flour content as that starter had a better stability and overall health in the long term. Acceptable hydration percentages are 60 to 100. Lower hydration starters promote sharper, more acidic taste. Higher hydration levain promotes a more mellow, yogurt-like tang in bread.

All ingredients are placed in a bowl, or a glass jar, and mixed together with a spoon. The container is then loosely covered and stored at room temperature, about 68F-70F.

When making pure sourdough breads especially, I get better results (quicker and much more predictable rise) when I feed the starter twice every 12 hours before mixing the final dough. To put the starter on a 12-hour feeding schedule I increase the water temperature to 90F-95F without changing other parameters.

Here is how sourdough starters fed with warmer water (left) and colder water (right) look like after 12 hours.

Making sourdough backups

I find this part extremely important. We, home bread bakers, will never have the same diligence and consistency for feeding our sourdough starters as professional bakeries do. We get busy, we forget, we go away on vacation. When that happens, your starter may go bad. You may be able to revive it, maybe not. For those cases you need to have a backup.

Making sourdough starter backups is very simple. Line a large baking sheet or two with parchment paper. Using a pastry brush, smear some healthy, active starter on the paper in a thin layer. For better spreadability, you may want to increase the hydration of your starter.

Leave the sheets in a warm room for the starter to dry. It takes a day or two. Once dry, hold the paper over a large bowl and bend it, letting the dry starter come off and fall in the bowl. Next, using a spoon, break the dried starter into small pieces. Then package and freeze. That's all there is to it.

What to do with 'discard' sourdough starter?

It's wasteful to throw away starter left after feedings. There are ways to deal with this problem. One way is to make your batches smaller and only increase them when you intend to bake bread. Another way is to keep your starter in the fridge to limit the frequency of feedings. Finally, there are many wonderful quick recipes that utilize leftover sourdough starter. Such as:

Quick sourdough rye bread

Sourdough English muffins

Sourdough Biscuits

Sourdough Cinnamon Rolls