Musings on Sourdough Starters


The Perfect LoafFor many, many years, I owned and maintained my own, private zoo.* I fed and watered the creatures in it, occasionally neglected them, moved them from place to place, and when their population threatened to explode, I took out a large quantity and killed them. That’s what, in a nutshell, every baker does with their sourdough starter.

A sourdough starter is a SCOBY: a Symbiotic Culture of Bacteria and Yeast; a complex colony of living creatures. It’s also what bakers call a preferment, like (but not entirely the same as) a barm, levain, biga, poolish, sponge, and desem. And if you don’t recognize those words or the differences between these items, you probably aren’t baking bread.**

A sourdough culture is, essentially, a zoo with a vast collection of various species of microbes (bacteria and yeasts) and a baker is its zookeeper. Eric Pallant, the author of the entertaining book, Sourdough Culture, wrote a delightful post for The Perfect Loaf called Welcome to the Zoo about starters in which he noted,

…you are responsible for the lives of billions–no, more likely decillions (that is a thousand quintillion)–of microscopic organisms you cannot see. Treat them well and they will reliably assist you in making some very delicious bread.

Keeping a starter is a commitment akin to keeping a pet, with you being both a zookeeper, cage cleaner, and veterinarian. But, as a baker, you eventually have to kill a lot of your pets, at least when you bake them (baking with yeast requires killing billions or trillions of living creatures… (but not if you bake with a chemical riser like baking soda). So bread is the result of the death of billions of those creatures you rsied and loved.

Pallant wrote a second post about the science of fermentation titled, Dust to Dust, and I recommend you also read it. In it, he includes this image to help explain what happens when sourdough meets dough:


It’s a bit more complex than this. Well, a lot more complex once you dig into the science, and if you want to know more, I highly recommend Emily Buehler’s book, Bread Science, and Sandor Katz’s book, The Art of Fermentation. The yeast ( the familiar Saccharomyces cerevisiae among others) and lactic acid bacteria (LAB; see here for a list) act in somewhat different, but symbiotic, ways to produce the gases, acids, and sometimes alcohol, all of which contribute to the digestibility of the dough, and also to its flavour.

The sourdough microbiome is a fascinating topic, for me at least. It’s not enough for me to know it works: I (and other inquiring minds) want to know how and why.

As The Sourdough Project says on its website:

If you mix flour and water, the community of organisms that colonize the resulting concoction is almost always composed of a small handful of organisms that are able to leaven bread, yielding a sourdough starter. Yet, how this happens is one of civilization’s great mysteries, a mystery at the heart of bread making (and, for that matter, traditional beer brewing). While bakers generally understand how to make starters, the underlying biology of the species in these starters remains mysterious.

Non-bakers may not understand why this type of bread is not the same as the commercial bread bought in grocery stores, nor why it is entirely different from the fake sourdough (aka sourfaux) commonly sold there (and even in farmers’ markets, as I discovered recently in Collingwood…) despite the label as “sourdough.” As noted in The Guardian:

…most supermarket sourdoughs are adulterated with anything from yoghurt and vinegar to – and this is the real killer – commercial yeast. Those ingredients aren’t bad for you, unless you have a specific intolerance – but to describe bread made with commercial yeast as sourdough is, not to put too fine a point on it, complete and utter bollocks.

Bakers in the UK launched the Campaign for Real Bread to combat the supermarket labeling of sourfaux as “sourdough,” and to educate consumers about real sourdough. Canada needs the same sort of campaign to combat misleading advertising and labels. But I’m getting sidetracked.

Although I had maintained it for years, my long-time zoo died, or, more properly, was killed by me when I went into the hospital for surgery and cancer treatment back in 2020. And even after I recovered, I instead went back to baking bread by machine and by hand, without using a starter. Now I’m preparing to get another such zoo going. Of course, my first thought was to peruse my large library of bread books (approx. 60 books to date***) to read various ideas about building my starter, and see if anything new or unusual had been written about the process (aside from the joy I get from reading and re-reading books on bread…).

(Yes, I know: I could have frozen it, could have dehydrated it, or simply left it to hibernate in the fridge… but at the time I didn’t want to leave it to chance or take the time. Nor did I want to pressure Susan to maintain it.)

Earlier this year, I decided to experiment. I purchased some pre-made (dehydrated) starter from Kensington Sourdough, advertised as “50 years old, super active, and simply makes great bread. Dry active starter from the heart of Kensington Market to your home!” Sounded great! Well, it didn’t work for me.

I followed the instructions carefully (I’m not new to sourdough, to directions, or recipes) but it didn’t thrive. It failed, it started apparently well, but died shortly after. It ended up in the green bin a week or 10 days later. I tried corresponding with the company about it but they were less than helpful or communicative. I can’t recommend their product. So I decided to return to my previously-successful, homemade starter. that decision inspired me to read in my books.

UPDATE: Kensington Sourdough sent me a new package of dehydrated starter to try again, which I plan to do this weekend… I appreciate their response to my concerns.

A small segue: real sourdough offers many health benefits to its eaters, including improved digestibility. But not being a doctor or a nutritionist, I’ll leave the claims to the experts (or the credible media sites). For me, more simply, sourdough is a delight to bake and eat.

Creating a starter isn’t difficult by any means, and I’ve done it several times, sometimes unsuccessfully, but it does require some attention (not least to defend it against mold and unwelcome bacteria). At its most basic it’s begun with only flour and water. However, some writers recommend using juice instead of water, because fruit juice brings both some sugars to help the ambient yeast get started and acidity because yeast and the helpful bacteria prefer a slightly acidic environment (to about pH 6). Acidity also helps deter some unfavourable bacteria and mold from growing.

Some writers, however, add fruit, honey, and even plain yogurt or kefir to their starters. The fruit brings yeast and bacteria on their skins, and the yogurt/kefir already have a thriving population of friendly bacteria in them. Others use a sprinkle of commercial yeast to get it going (which to me would make it a poolish, but let’s not get sidetracked, again…). And online there are debates about using these additional ingredients. Great, raging, vehement, accusatory debates. In his book, The Art of Fermentation (P.235), Sandor Katz wrote,

With experimentation and quasi-obsession — and the internet — also come fierce debates or, at least, macro levels of minutiae. Sourdough folks divide the world into two kinds of people, those who cultivate “sour” and those who dump it, but they do not stop there…

In his book, In Search of the Perfect Loaf, Samuel Fromartz relates an anecdote about Julia Child’s TV show in which baker Nancy Silverton explained she used a “pound” of purple grapes, smashed in cheesecloth, to help establish her starter. That may seem a bit extreme, but the grapes provide sugar and acidity, while their skins are host to yeasts and bacteria that can accelerate the starter. Similar recipes use apples with hazy skins (the sign of yeast colonies). I am not sure, however, how to cleanse such fruit of residual pesticides without killing off the yeast. I don’t imagine that not cleaning them would be helpful to the starter.

Which flour should I use? For my loaves, I generally use Canadian bread flour or unbleached all-purpose flour, with a little whole wheat thrown (I recently found some unbleached bread flour that I’m testing now for loaves). Bread flour is usually made from 100% hard wheat and has about 13-14% protein. AP is often a mix of 80% hard and 20% soft wheat, and may be a little lower in protein (12-13% in Canada but as low as 9-10% in the USA). However, several of my books suggest using rye or wholegrain flour to begin a starter (the former only available to me at the local Bulk Barn; the latter not available at all as far as I can discover), or organic flour (none available locally but can be ordered online). Or, perhaps, a mix of flours. Eric Pallant, author of Sourdough Culture, recommends a 50/50 blend of bread and whole wheat flour.

(FYI, protein content in Canadian flour is standardized, at 12-14% for all-purpose, whole wheat, and bread flour while in the USA it depends on region, brand, and type).

I’m not sure what, if any, differences in microorganisms are to be found in different types of wheat. All seem to have beneficial types of flora, but what else do they harbour? And how much ambient flora gets included? In the past, I’ve begun a starter with an open container so that ambient yeast and bacteria landed into the starter. That sometimes led to mold and unfriendly bacteria thriving. Sometimes the starter developer beautifully. But perhaps this time I’ll use a lid or cheesecloth cover.

And then, how much flour should I use at the beginning? Some books recommend small amounts to begin with: 50g of flour, while others recommend larger quantities, 100g up to 400g. Pallant (in Sourdough Culture) starts with 100g.

And how much liquid? Some have equal or slightly larger volumes (or weights) of water than flour (e.g. 110g of water to 100g flour), while others have higher volumes of liquid. Jeffrey Hamelin in his book, Bread, recommends 125% hydration, while Mason in All You Knead is Bread suggests 200% (50g water to 25g rye flour). Kimbell in her Sourdough School says 100%. but in her Sourdough School Sweet Baking has 110%. I lean toward Hamelin’s 125%. The point, as I see it, is not to make a thick, dough-like batter, at last initially, but a somewhat runny slurry akin to pancake batter (the liquid allows the flora to move about and feast more easily).

In general, I prefer starting with a small amount of flour: 50-60g. Once the colony is flourishing (usually day three onward), you’ll be discarding 50-80% every feeding, while adding new flour and water. With large starters, and fast growth, this discard (usually composted) can quickly add up to a lot of flour wasted. Once the colony is firmly established (10-14 days) and refrigerated, the loss is less because it’s not as active. But before then, I may end up tossing away a lot of flour. While the discard from an established starter can be used in various forms, such as biscuits, pancakes, or an additive for bread machine loaves, the early stuff isn’t really very good for baking.

So… my next starter — planned for later this week — will be a mix of dark rye, whole wheat, and unbleached bread flour; about 60g total, probably equal amounts, plus water and maybe a splash of something acidic like vinegar or citrus juice. But I may also add a dash of spelt flour, just to see what happens. Part of the fun in this is in the experimentation: baking — indeed all cooking — is for me a science playground: biology, chemistry, and physics come together in the kitchen.

I’ll let you know how well it does. And maybe post some pictures of my new zoon on social media…

(UPDATE: I tried making a poolish using 12-grain, dark rye, and spelt flour but the bread I used it in was undercooked… have to experiment further to see what works…)

A little digression about measurements

I try to avoid bread recipes or directions that use imperial measurements — i.e. those using cups to measure flour — especially when making bread in the machine. Doesn’t matter what your grandmother used, doesn’t matter that it feels homey and quaint: measuring flour by cups is amateurish, and can lead to loaf failure in a bread machine. That’s because a single cup of flour can weigh between 110 and 170g, depending on the brand, type, age, humidity, packing, storage, sifting, and handling. Emily Buehler uses 110g/cup in her book, Bread Science. King Arthur flour uses 120g, Bob’s Red Mill 136g, and some websites use 140 or 150g. Robin Hood bread flour says 16 cups for a 2.5kg bag, or 156g/cup. You can easily find this range of proposed weights online.

Bread machines work best at a hydration level of 60-65%. With such a large range of potential weight, it becomes almost impossible to accurately add the correct amount of liquid using cups (unlike baking by hand, you cannot feel the dough to make sure it’s right). Cups are simply too imprecise. It’s like measuring your drive to work in cubits or rods.

I even measure liquids by weight because it’s difficult to see the surface exactly (the meniscus obscures it). Besides, 1 mL water = 1g. That’s the beauty of metric. You have no simple, elegant relationships like that with imperial measurements. And then you have digital scales with decimal places in imperial values, like 3.3 oz… when the recipe calls for 1½ teaspoons… awkward and amateurish. Metric is the precise and professional way to measure. (Milk is close enough to water that I can weigh it, too)

Yes, some small amounts can be measured in teaspoons or tablespoons when baking because the small inaccuracies don’t make a big difference. A teaspoon of salt weighing 6g or 8g won’t significantly alter a loaf of bread that has 400-500g of flour. But with major ingredients like flour, the discrepancy in cups has a big effect.

That said, if you’re making a starter with a small amount of flour and water, such accuracy isn’t critical; what matters more is the consistency of the mix you’re looking for. You will be adding fresh flour and water and removing excess starter every day for a week or more, making it difficult to impossible to maintain any strict accuracy. However, if you make a large starter (beginning with 100g or more of flour), I recommend using metric measurements (and 125% hydration as Hamelin recommends) to get a more accurate hydration level from the first. End of digression.

Another little digression about bread machine sourdough

No matter what the advertising may suggest, you cannot make real sourdough in a bread machine. The menu cycles are too short to allow the starter’s flora to populate the dough. Plus the heat in the machine is not high enough to create the sort of crusty loaf one likes from an oven-baked loaf. Every bread machine recipe for a “sourdough” loaf I’ve seen uses commercial yeast to get the necessary rise. Any sourdough starter added to the dough is merely to provide a little extra taste and texture, but never enough to make the bread noticeably sour.

Some bread machines (i.e. the Kitchenarm I recently purchased) have a menu option to create a “sourdough” starter using water, flour, commercial yeast, and a lengthy cycle of warming (min. two hours) to encourage yeast growth. This is not sourdough, since it lacks the symbiotic lacto-bacteria and uses commercial yeast (basic rule of thumb: if it uses commercial yeast, it isn’t sourdough). It is really a poolish or preferment. It can make your bread taste better (as preferments generally do), but it won’t give you real sourdough. Commercial yeast is more efficient at populating the dough and will outgrow any native yeast and bacteria quickly.

These bread-machine preferments are not bad, and can improve a loaf, but don’t mistake them for sourdough. And that ends this subsequent digression: you can’t make real sourdough in a bread machine.


* It wasn’t my first micro-zoo. I recall buying “sea monkeys” from a comic-book ad in the early 1960s (a dismal failure if my memory serves), and then having terrariums and aquariums full of local wildlife (most from local ponds and woodlots; insects and arthropods, sticklebacks, salamanders…) during my early teens.

** To be honest, I was unfamiliar with desem and its technique until I began reading Tara Jesen’s book, Flour Power, this June. Each of these is a form of preferment, but somewhat different in creation and use. Some are naturally populated with flora, others use commercial yeast. Baking is full of such terminology that may seem odd to the neophyte or non-baker (like yudane and tangzhou… I’ll save those for another post, but b).

*** Plus about 10-12 issues of baking magazines with a bread focus. My personal cooking library also includes several books on pizza, food science, tea, and roughly 30 on pasta. And I have a few on tea, curries, hot sauces, fermentation, pickling, jams and jellies, spices, and more. Regardless of my skills or lack thereof at cooking and preparing food, I quite enjoy reading many cooking and recipe books.

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Ian Chadwick
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One comment


    Organic and conventional flours produce different sourdough fermentations…
    Before the dough was fermented, there were clear differences in the composition of microbes across the four farming system treatments. For example, conventional flour had a higher amount of lactic acid bacteria from the genus Leuconostoc (19%) compared to other farming systems and the two organic treatments had high amounts of Pseudomonas. After fermentation, there were still differences among the four farming systems. The green manure organic system had the highest amount of Lactobacillus and the no inputs treatment had the greatest amount of Leuconostoc. The yeasts were not impacted by the farming treatment, and several species of yeast (Saccharomyces cerevisiae, Candida humilis/Kazachstania barnettii, Saccharomyces bayanus/Kazachstania sp.) were found across all treatments.

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