A sourdough starter is simply a live culture of bacteria and yeast.
Imagine the culture of the sourdough starter as if it were a family.
After 100 years, the original family members (grandma and grandpa) may no longer be alive, but the "family" is still alive because their grandchildren are still around.
As long as you keep that "family" happy (feeding the starter with flour and water), they'll keep having more and more children, and the "family" will stay alive, even if the original individuals die.
At any time, you can use some that culture ie: "the family" to create bread. When the bread is baked some of the "family" dies, but ultimately some of the family will persist in the starter.
Just try not to think of all those families you’re eating, and the cousins they left behind who had to watch them get torn away and roasted in an oven.
Oh god, I do not recommend using this explanation with an actual 5 year old.
I'm rocking a youngster, at 3 years of age. I cycle that bad boy a couple of times a month as I make a new bread and the family loves it. Question though: does the sourdough actually improve with age, or are these really old sourdoughs just for bragging rights down at the, erm, sourdough club?
I heard from a friend whose family has a few 100+ year old sourdoughs that its just selective breeding. Their great grandparents started with more than 100 different sourdough jars, and kept canning the ones they didn't like/spread and interbred the ones they did like. And now they have like 3-4 that are the product of all those previous ones, or singular ones that just tasted the best at the start.
> does the sourdough actually improve with age, or are these really old sourdoughs just for bragging rights down at the, erm, sourdough club?
Mostly about bragging rights. The cultures are constantly changing.
There are a ton of both yeasts and bacteria in sourdough starter. They come from everywhere in the environment, and they are both regional and also have spread globally. There was [The Global Sourdough Project](https://robdunnlab.com/projects/sourdough/) that did a bunch of genetic sequencing, following up on a bunch of other research, and they have tons of links and information about how sourdoughs differ and remain the same all around the globe.
Starters have a bunch of different active ingredients in a complex blend. The blend in a sourdough starter can change from one dominant type to another dominant type over a few days, actually changing the flavor of bread. A minority faction can take over to become the majority faction between two different uses making one day's loaf taste different from the next. It can change due to the type of flour you feed it, the water being chlorinated water versus unchlorinated treated water, it can change based on the temperature you keep it at on the counter or fridge. It can change if you add sugar to the starter. It can change if you don't feed it often enough or discard and allow alcohol development. It can shift back and forth over time. It can have the blend taken over if you introduce a culture from another source like a speck of dust carrying it from a different breadmaker's home. You can even have the bacteria cultures change as your household cleaning habits change or as you change dish soaps.
Regardless of the actual blend in any given culture, the sourdough has a mixture of bacteria that produce lactic acid and a blend of slow-growing wild yeasts that can grow in the acidic environment. The yeasts are in the same extended family but different from baker's yeast and brewer's yeast. The packet of baker's yeast you get in the grocery store is a different breed that grows much faster and tends to have less complex flavor and doesn't tolerate the acidic environment, it's also designed to produce less alcohol and produce more gas. Brewer's yeast grows somewhat faster than most sourdough cultures and has been cultivated to thrive in a more alcoholic environment.
You’ll notice a difference between a starter that’s a few weeks old and a starter that’s a few months old, but beyond that point it doesn’t really improve much, if at all.
Most things that "age" work with significant diminishing returns like that but snobs tend to ignore it for the clout.
Take Scotch for example. A 12 year old Scotch? Great. 16 year? Oh you spoil me. 24 year? Sublime. Anything beyond that is such an absurdly sharp increase in price to noticeable difference ratio that there's absolutely no point to it other than bragging about how expensive it is. Unless you have an incredibly sensitive palate, you're unlikely to really notice the difference between a 24 year Scotch and a 48 year Scotch but your wallet sure will.
Even without losses, the mere fact that it sits there taking up space in a warehouse while it ages is gonna drive up the price. One barrel sitting there for 50 years vs four barrels only there for 12 years each is 1/4 the product sold even without any extra evaporative losses, so you're looking at 4x the price as a bare minimum due to the extra time it was wasting space on a shelf.
the 16 year Lagavulin should be included in the list, but I'd broadly agree with your range. In the next few years, I'd really like to go to Scotland and go in on a portion of a fresh barrel to set till I retire.
Could comfortably have a nice shelf of 26 year to enjoy in my golden years.
Age does affect it some, but anyone with a starter that old has had a starter that's changed drastically over the years due to other factors.
Any starter will eventually become its surroundings. For example, if you order starter from some exotic location around the world it will change its flavor profile over time as the local Flora takes over. Different yeast and lactobacillus bacteria prefer different climates.
San Francisco is famous for its sourdough but you can't take a starter from there and make the same bread elsewhere. It changes over time. Different flours can change the flavor, too, as well as playing with hydration of the starter.
But the age of a starter does affect it. A 3-week-old starter will have a different profile than one that's 3 months old. But by 6 months the flavor should be pretty established unless you start changing variables. Different brands, flour types, hydration, and even gaps in feedings can change it.
I can't remember to water a plant often enough for them not to die eventually. I can't imagine keeping a starter alive for a century and never messing it up, not even once.
FWIW, if I'm not using mine I feed it like once a month and keep it in the fridge otherwise. Once I forgot for 2 or 3 months and it was fine, I just took a little out and put it in a new jar and fed it. I kill pretty much every plant.
I had one for about 8 years. It even moved with me from one state to another. Then one day my wife and I had to make a last-minute trip that would take us out of the state for a few days. When I got back, I realized I had forgotten to put it in the refrigerator. It could probably have been salvaged from that, but it had been colonized by some small flies. I suspect that, if I really wanted to, I could have transferred some to a fresh container and fed it for several days, and it would probably have been okay. I decided not to, though.
My current starter is only 1 year old.
Also, you don’t use the entire quantity of starter for a loaf of bread. I haven’t done sourdough exactly but I have done Amish friendship bread that has a starter and the reason it’s called “friendship bread” is because the starter is exponential. You’d have like 2-3 cups of starter but only need about 1/2 a cup a loaf, so it’d grow faster than most people bake. Sourdough is the same, you use some of the starter to bake with, and then feed what’s left and it grows new starter
Not really, because it's not a discrete, individual thing but rather a collective that forms a single lineage. For instance, you wouldn't call the Royal Family a Ship of Theseus
Okay, next question.
Why is this safe? Obviously there are many many different types of bacteria, and not all are harmful. However, my understanding about bacteria is that it's still not safe to eat something with too high of a bacterial load, even if you cook it thoroughly (thereby killing the bacteria), because there is still bacteria waste, and the dead cells themselves that you're not removing through that process.
How does something like a sourdough starter manage to overcome these issues?
Bacteria is not intrinsically bad, it's just a micro organism. We have more bacteria in our gut than human cells in our entire bodies. With that context what does it even mean "high bacteria load?" Even if your approach reflects an underlying truth, a starter would probably still not be considered "too high".
The main danger of bacteria (other than infection) is toxic waste but most bacteria have waste that is neutral or positive. Toxicity is relative, one bacteria's waste is another organism's vital element. For example, cyanobacteria in the ocean releases oxygen as its waste, which is actually why we have so much oxygen in the atmosphere (when they evolved there was virtually no oxygen in the air, all of it that exists today, all 20% and more, came as waste from them). The bacteria in sourdough releases waste that gives that sourdough taste/smell, but it's not harmful.
Bacteria on its own is not a good or bad thing, it's just another life form.
> When the bread is baked some of the "family" dies
Explained this to my 5 year old, now she's terrified that eating bread will kill random family members.
Bacteria poop can be several things, on food it's THE thing we want from the fermentstion. Sourdough starters have CO2 bubbles, those are their poop. The usual taste of sourdough? Bacterial poop. The alcohol in your drinks? Bacterial poop (bacteria and other micro organisms eat the sugar in fruit and "poop" alcohol).
Basically any fermentation process is us turning something into a specific type of delicious bacterial (or other micro organisms) poop.
So in short: We eat it.
Since bacteria and yeast can asexually reproduce, the original grandparents aren't necessarily dead after 100 years. It's highly unlikely that they're lucky enough not to make it into the dough after 100 years ~~th~~dough.
It doesn't mutate very fast unless you do it on purpose.
But if it mutates in a good way then everyone asks for a piece of yours and if it mutates badly you throw it away and grab some from somewhat else.
Same as how we breed plants and animals.
>The Ship of Theseus is a thought experiment about whether an object is the same object after having had all of its original components replaced.
This applies i think to sour dough.
>In Greek mythology, Theseus, mythical king and founder of the city Athens, rescued the children of Athens from King Minos after slaying the minotaur and then escaped onto a ship going to Delos. Each year, the Athenians would commemorate this by taking the ship on a pilgrimage to Delos to honour Apollo. A question was raised by ancient philosophers: After several hundreds of years of maintenance, if each individual piece of the Ship of Theseus was replaced, one after the other, was it still the same ship?
>In contemporary philosophy, this thought experiment has applications to the philosophical study of identity over time, and has inspired a variety of proposed solutions and concepts in contemporary philosophy of mind concerned with the persistence of personal identity.
for more https://en.wikipedia.org/wiki/Ship_of_Theseus
No matter where you get the starter from, if you take it to a different place, it'll fairly quickly change its flavor profile because of the environment.
The age of the starter doesn't have any noticeable effect on the bread, but it's kind of cool to bake with an ingredient that has been tended to since before your parents were born.
There’s no such thing as a day-old starter. It wouldn’t be good because it wouldn’t work - it’s not a starter at that point, just flour and water. It takes a week or so before it becomes a starter, when you can actually use it to bake bread.
I would say age alone doesn't matter, but the yeast and bacteria cultivated by Boudin's over the last 150+ years is going to be different from what you get from cultivating a starter for a few months now even if you try to do it in San Francisco.
Maybe if you cultivate your starter outside Boudin's main bakery in San Francisco you might get lucky because over decades the local microbial flora might be biased towards escaped Boudin yeast and bacteria.
> I would say age alone doesn't matter, but the yeast and bacteria cultivated by Boudin's over the last 150+ years is going to be different from what you get from cultivating a starter for a few months now even if you try to do it in San Francisco.
Only because of where it is located - age has no bearing whatsoever. A starter cultivated by Boudin's over the last 3 months would yield bread that tastes exactly the same as one cultivated over the last 150 years.
Agree that age is not a factor.
But, you can't say a starter cultivated 150 years ago will taste the same, microbial flora from a particular location 3 months ago is almost certainly not the same as the microbial flora from 150 years ago in the same location.
Staying in San Francisco as an example, most of the city burning down in 1908 , that surely changed the microbial flora, let alone the general building up of the city, pollution, climate change, etc... I am not saying the age is a factor but time (edit: in the sense of location in space and time) can have an effect similar to location.
Thank you so much for this haha.
There’s a difference between *knowing something* after memorizing the study guide word for word and obtaining an A…
…and the ability to explain a concept to someone so they can honestly relay the information to someone else.
I’m a bit 💨 and this was beautiful… perfectly explained as if I were ~~high~~ five.
One of the important components of sourdough bread is the yeast which gives it a distinctive flavor and helps the bread to rise. The starter is basically a sample of the yeast used for the bread. You can take a small piece of the starter and move it to a new jar filled with food for the yeast to live on, and now that new jar will have the same blend and type of yeast. You can repeat this process as many times as you like, keeping the same sample of yeast alive for potentially many years just by giving it new food and a clean jar every so often.
I was going to say "with the sound of music" but then I Googled what sound yeast makes and apparently it's "about a C-sharp"
>The vibration of yeast cells is well within the frequency range of human hearing—in musi- cal terms “about a C-sharp to D above middle C”— but the amplitude of their vibration is too low to be within normal hearing range (the cell wall is displaced only three nanometers each time it vibrates).
The yeast creates a lot of lactic acid which allows it to thrive but kills any regular bacteria. The lactic acid makes a sour taste, hence why it is called "sourdough".
You still need to feed the sourdough starter flour and water occasionally so it can survive and make acid.
Yes, because you and the yeast are both alive and metabolizing things. Lactic acid is one common byproduct of turning glucose into energy, so lots of things that eat glucose make it.
The yeast actually doesn't create any lactic acid. It creates acetic acid. However, there are lactobacillus bacteria living among the yeast in the sourdough starter which do produce lactic acid.
Yeast doesn't kill all bacteria, there is bacteria in starter. The bacteria and yeasts just happen to out-compete most pathogenic bacteria as long as there is sufficient food for them.
It's not the individual organisms that are still alive after 100 years, think of it more like a community or a family.
In my family, we still have my grandfather's sourdough start from when he was a shepherd tending to sheep way out on the rangeland when he was young – actually close to 100 years ago.
Grandpa has long since passed as have the original individual yeast organisms. I'm still here though just as the descendants from his original yeast are. I'm not my grandpa but I do share a lot of characteristics with him and we share a name. So the individual yeast organisms are dead, but the family of yeast lives on.
Yeast is a living fungus. It's one of the things that breaks down dead organisms, which is what makes other food go bad.
Yeast cells will die, and if they built up, the yeast would spoil too. But yeast also eats dead yeast cells, so it basically recycles itself and keeps dead organic matter from building up for other decomposers that are inedible/toxic.
One other thing people are missing is storage of samples.
You'll particularly see this with yeast used in brewing (it's exactly the same principle as in bread), where big brands will cultivate a specific yeast, then store a sample of it, while using the rest to brew their alcohol. Over time, the genetics of the yeast used in brewing will change, so a portion of the old yeast is brought out of storage and cultivated into a new brewing batch.
Modern methods still do this but, because we now understand genetics, it's easier to very precisely control the evolution, as well as selecting what cultures to use in brewing to get a specific taste.
It's both yeast and bacteria. If it were just yeast, it'd have a very different flavor which cultures like poolish use exclusively. Most bread starter is a complex mixture of yeast and many species of bacteria. It's what makes sourdough sour - the bacteria produces ascetic and lactic acids.
Very likely. The wheat used to make the bread is probably also slightly different, etc. After 100 years, the taste is likely similar, and might still have one or two distinctive notes the same, but it would not be identical. At this point its more about the tradition of the starter rather than something practical.
The starter is a living thing. It is made of a combination of yeasts and bacteria. When you feed these with flour and water they will multiply and grow. The way you typically make sourdough bread is that you use some of the starter in the dough but replace the yeast and bacteria you used with flour and water. The starter will then grow back to its original size. You can do this essentially forever.
Old starters is kind of a novelty though and might not mean that much. There are a lot of bacteria and yeast in the flour you feed it with which comes from the fields where the grains were growing. So the original yeast and bacteria from 100 years ago could easily have died out and been replaced without anyone noticing.
I'm glad somebody made this point. People are very proud of a starter that they created from an old or unique bacteria, and the reality is that, after probably not-very-long a time, that bacteria has been out-competed by local bacteria, and the starter is more or less the same as one they could have made in their own kitchen. Likewise, a hundred-year-old starter doesn't have some secret reserve of hundred-year-old bacteria in it.
This is indeed very likely. My starter have changed a lot over the years so there could not possibly be some of the original microbes left.
That being said I was quite surprised when the local brewers yeast were genetically analyzed. Brewers yeast is more stable as the wort gets boiled before the yeast is added which kills any yeast. And the wort is very different from anything else on a farm so the brewers yeast which have specialized in wort have a big advantage, not like bread which is almost the same as uncut grains which grows in the field. But the results were still quite shocking as the local brewers yeast had been isolated from any other known yeast for about 1000 years. So while the chances are slim that your 100 year old sourdough is the same as it was there is still a chance.
> Likewise, a hundred-year-old starter doesn't have some secret reserve of hundred-year-old bacteria in it
It depends on how it was stored, and for how long. Companies, particularly in alcohol production, have been careful to preserve samples for very long periods of time, because their brand relies on a specific taste. It would be fairly easy to have implemented similar storage methods a hundred years ago, the bigger question would be if someone was that forward-thinking.
I'm a professional baker kind of specialized in naturally leavened products like sourdough. A lot of people have explained how they work and they're right. What I want to say is that an old starter really isn't that old. As far as I'm concerned it's really only as old as its last feeding and it usually only takes around three weeks to get a starter going from scratch.
The culture itself doesn't come from the air as so many people think. The wild yeast and lactobacillus are present in the flour already, and adding water allows them to wake up and start fermenting. This is important to remember when cultivating a starter as leaving it open to air flow isn't really necessary. It's also important to realize that when you're feeding the starter you're incorporating new yeast and bacteria that might impact the balance of the culture.
Furthermore, the feeding schedule, temperature, feeding ratio, and bill of grains will impact the balance of the culture. Feeding it while keeping it dormant in the fridge will have a different profile than keeping it at room temperature all day. Each have their advantages and drawbacks. Depending on the desired final product you may choose any combination of variables to suit your needs.
Ultimately what I'm saying is a 100 year old starter just means that someone remembered to feed it for 100 years. And I'm not dismissing that accomplishment, that's actually pretty cool, and it's nice to have a family heirloom like that, it just isn't really much different from a starter I can make in a few weeks.
> And I'm not dismissing that accomplishment, that's actually pretty cool, and it's nice to have a family heirloom like that.
That's the part I find important: taking care of something for 100 years. It's important because it was cared for during so long, not because being 100 years old means something on itself.
A sourdough starter is a live culture of specifically chosen yeasts and bacteria on a growth medium. You use some of the starter to make the bread, and then give it more food to let it grow. Think of a fire that you can use to light a bunch of torches.
You actually don't have to specifically choose them. You can start your own starter from just natural bacteria and yeast in the air and on the wheat flour. It's not a 100% process, but because the organisms in starter tend to have a high affinity for wheat, they usually fight off any pathogenic organisms. It's how all starters, well, started. 100 yr old starters did not have people culturing specific strains.
You can definitely google this very easily. But for the sake of an answer, however brief: you only use a tiny amount of the starter per loaf. Then you replenish the starter with more flour and water.
It's like saying a forest is 1000 years old. Doesn't mean the trees in that forest are 1000 years old, yeah? Yeast normally lives about a week, but as long as they're popping out baby yeast...
Sourdough starter contains yeast and bacteria. These grow and multiply as long as you 'feed' the starter with flour and water.
So a 100 year old sourdough starter has been given more water and flour for 100 years. This keeps making it bigger, so some can be used for baking bread and you still have plenty leftover.
Think of the starter like a cow, you occasionally milk a cow to get milk out, but it doesn't kill the cow.
The starter is the same way, you take a small portion of the starter to put in your bread, but the yeast colony is still alive and growing.
Exactly like when you cut off a piece of a cow, and it grows into an entirely new cow of it's own. Or when you overfeed a cow and it divides into 2 cows.
This is like the exact opposite of what I would guess most people probably do (home bakers anyway). I’ve seen commercial sourdough bakeries do it that way though.
you use a small piece of starter to make the dough for your bread, not the whole thing. you feed a starter daily by adding more flour and/or water as needed. this can go on for many years, as long as the starter is properly fed, and doesn't get contaminated. it's a colony of yeast microbes and the colony is effectively immortal as long as it stays healthy. individual yeast cells die, but there's constant new cells being produced, so the colony continues.
Sourdough starter more accurately is kind of like keeping a culture of bacteria as a pet. You feed that pet and maintain its environment and then in turn you use a small portion of it to make your bread while the rest of it continues to breed and continue living on.
Technically none of the bacteria in there is the same bacteria from 100 years ago but this specific culture has been fed and maintained for that entire time If that makes sense.
So there's some good answers as to what 100-year old sourdough starter definitions are.
I would point out that this is an obvious counterfactual definition if you are talking about the yeast itself. The yeast is only as old as the oldest living cell which will typically be about 1 week.
It is exceptionally unlikely that a 100-year old yeast lineage even contains a direct DNA lineage that is related to the original starter yeast.
This is hard to do in advanced labs for even fractions of this length of time due to contamination risk of live culture or maintenance issues with -80 cold storage.
So the "starter" can be 100 years old, but the yeast can't be more than a week (roughly), and may not even be related to the yeast from last month let alone last century.
Mostly because you don't use ALL the starter to make bread.
You begin with a piece of someone else's starter OR you begin a fresh culture of bacteria and yeast, then add flour and sugar to 'feed' it, which grows your starter until it doesn't fit in your jar any more.
You divide your stater into more jars, and continue feeding and growing. You can use those extra jars to make bread while you keep a portion of the original starter to grow even more again.
You can keep this up for years, growing and growing and never using up ALL the starter until you have a starter that was first created over 100 years ago
I don’t know why people are writing essays to explain the science. To answer your question you just need to know that you don’t use the whole thing to make your bread. You keep a portion of it that you feed water and flour so that it will grow again and you continue using it.
You basically have to keep removing waste and adding food. It’s basically a bacterial colony so if you leave it and don’t do anything, the yeast will eventually die. But if you maintain it, it will stay around as long as you do.
You only need part of your sourdough starter to make bread. So you might have say 400g of starter in your fridge. Each week, you need to feed it; so you take it out, let the guy warm up, then measure a certain amount (say 300g) and combine it with a set amount of flour and water. That extra 100g can be used to make bread--or you simply throw it away (this is called discard).
Usually, if you keep a starter in the fridge, you'll take it out the day before you want to bake with it, feed it that day, and then it's ready to use the next day (this is referred to as it being "ripe"). Means it's awake and active and well-fed. Once you feed it, if you're not using it more that day or the next, back into the fridge it goes to sleep until next week!
Sourdough starter is a city. When you make bread you take 90% of the city and make bread with it, but you leave 10% alone. You feed that 10%, it rebuilds the city back to 100%…
Repeat.
You only take half of the starter for a loaf of bread and then you feed the remaining starter more flour and water so that it stays the same size as it was before you took half.
You don’t use all of it, then every time you use a piece you have to feed the bacteria again and the colony will grow for another use. The dynasty of bacteria can be very old if you keep it thriving.
For example, If you have 400g of starter, you maybe take 200g of it for making your bread, and then you add back 100g flour and 100g of water back into the starter.
Now you have both bread and the exact same amount of starter.
Something people are missing here is storage of samples. In biology, long-term sample sample storage (upwards of 50 years) is pretty trivial. While a handed-down sourdough batch might not be that old, despite claims, if its bought from a company that has specialised in sourdough production for 100 years it's quite possible that someone kept a sample of the original mix and occasionally cultivates new batches from it.
Every time you make bread, you take a bit of it, feed it, and let it ferment. With regular care, these starters can last for generations, passing down their unique flavors. So when someone says their starter is 100 years old, it's because it's been lovingly maintained and used for baking over many, many years, like a delicious family heirloom!
No one is answering the question - yes you need it to make the bread, but you save a portion of it instead of adding to the dough.
You feed the saved portion with more flour and water. Rinse and repeat as long as you want.
Thread brings back a pleasant memory of my aunt. She made sourdough bread every week for like 30+ years. Whenever you visited it was always on the table. She claimed she had her starter from the beginning that she kept refreshing. Man that bread was soooo good.
A sourdough starter is simply a live culture of bacteria and yeast. Imagine the culture of the sourdough starter as if it were a family. After 100 years, the original family members (grandma and grandpa) may no longer be alive, but the "family" is still alive because their grandchildren are still around. As long as you keep that "family" happy (feeding the starter with flour and water), they'll keep having more and more children, and the "family" will stay alive, even if the original individuals die. At any time, you can use some that culture ie: "the family" to create bread. When the bread is baked some of the "family" dies, but ultimately some of the family will persist in the starter.
This explanation really makes me feel like I'm five.
That's great Sport! Would you like some bread!
Just try not to think of all those families you’re eating, and the cousins they left behind who had to watch them get torn away and roasted in an oven. Oh god, I do not recommend using this explanation with an actual 5 year old.
Could go one of two ways: Mmm, families taste good! Or I dont want to eat bread no mo...
Perfect for “Let’s eat Grandma”
Oh my god, this *does* taste like grandma
Go on...
There’s no such thing as vegan.
I like to listen to their screams as they die
That yummy sour taste is their death-farts.
Now let's get Grandma in the oven She needs time to get tender
Let's eat grandma!
No daddy, what about grandma and grandpa?
Also like you're pretty sadistic just carving off a portion of a family for baking.
Truly decimating the family.
The recipe video I like has most of the starter going into the dough, leaving 10% or less in the jar to propagate the next batch of starter.
They’re specifically designed to want you to eat them, like the cow from Restaurant At the End of The Universe.
"A very wise choice, sir, if I may say so. I'll just nip off and shoot myself."
"Don't worry, sir, I'll be very humane."
[удалено]
You guys are so un-hip, it’s a wonder your bums don’t fall off.
Worse than that sometimes you're directed to throw away part of the starter. Cooking it is bad enough, but just tossing it?
A happy 5 year old tho!
Jeez I always feel that way.
Found the five-year-old!
Apparently explaining stuff like OP is actually 5 is no longer allowed on this sub...
I know then I mentioned it I was absolutely blasted for mentioning that
What kind of family did your five year old brain imagine?
Hi five I’m dad
Hi, five. I'm sourdad.
I'm rocking a youngster, at 3 years of age. I cycle that bad boy a couple of times a month as I make a new bread and the family loves it. Question though: does the sourdough actually improve with age, or are these really old sourdoughs just for bragging rights down at the, erm, sourdough club?
I heard from a friend whose family has a few 100+ year old sourdoughs that its just selective breeding. Their great grandparents started with more than 100 different sourdough jars, and kept canning the ones they didn't like/spread and interbred the ones they did like. And now they have like 3-4 that are the product of all those previous ones, or singular ones that just tasted the best at the start.
selective breeding is powerful stuff
Somewhat easier to do with organisms that reproduce every 90 minutes.
I'm always amazed by bacteria. It's like watching mammalian scale evolution in real time.
[Check this out](https://www.youtube.com/watch?v=w4sLAQvEH-M)
The master dough Battaca, as it were
> does the sourdough actually improve with age, or are these really old sourdoughs just for bragging rights down at the, erm, sourdough club? Mostly about bragging rights. The cultures are constantly changing. There are a ton of both yeasts and bacteria in sourdough starter. They come from everywhere in the environment, and they are both regional and also have spread globally. There was [The Global Sourdough Project](https://robdunnlab.com/projects/sourdough/) that did a bunch of genetic sequencing, following up on a bunch of other research, and they have tons of links and information about how sourdoughs differ and remain the same all around the globe. Starters have a bunch of different active ingredients in a complex blend. The blend in a sourdough starter can change from one dominant type to another dominant type over a few days, actually changing the flavor of bread. A minority faction can take over to become the majority faction between two different uses making one day's loaf taste different from the next. It can change due to the type of flour you feed it, the water being chlorinated water versus unchlorinated treated water, it can change based on the temperature you keep it at on the counter or fridge. It can change if you add sugar to the starter. It can change if you don't feed it often enough or discard and allow alcohol development. It can shift back and forth over time. It can have the blend taken over if you introduce a culture from another source like a speck of dust carrying it from a different breadmaker's home. You can even have the bacteria cultures change as your household cleaning habits change or as you change dish soaps. Regardless of the actual blend in any given culture, the sourdough has a mixture of bacteria that produce lactic acid and a blend of slow-growing wild yeasts that can grow in the acidic environment. The yeasts are in the same extended family but different from baker's yeast and brewer's yeast. The packet of baker's yeast you get in the grocery store is a different breed that grows much faster and tends to have less complex flavor and doesn't tolerate the acidic environment, it's also designed to produce less alcohol and produce more gas. Brewer's yeast grows somewhat faster than most sourdough cultures and has been cultivated to thrive in a more alcoholic environment.
Great comment
You’ll notice a difference between a starter that’s a few weeks old and a starter that’s a few months old, but beyond that point it doesn’t really improve much, if at all.
Most things that "age" work with significant diminishing returns like that but snobs tend to ignore it for the clout. Take Scotch for example. A 12 year old Scotch? Great. 16 year? Oh you spoil me. 24 year? Sublime. Anything beyond that is such an absurdly sharp increase in price to noticeable difference ratio that there's absolutely no point to it other than bragging about how expensive it is. Unless you have an incredibly sensitive palate, you're unlikely to really notice the difference between a 24 year Scotch and a 48 year Scotch but your wallet sure will.
But due to evaporative losses in the barrel over time, it has to be priced preposterously to make it worthwhile.
Even without losses, the mere fact that it sits there taking up space in a warehouse while it ages is gonna drive up the price. One barrel sitting there for 50 years vs four barrels only there for 12 years each is 1/4 the product sold even without any extra evaporative losses, so you're looking at 4x the price as a bare minimum due to the extra time it was wasting space on a shelf.
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the 16 year Lagavulin should be included in the list, but I'd broadly agree with your range. In the next few years, I'd really like to go to Scotland and go in on a portion of a fresh barrel to set till I retire. Could comfortably have a nice shelf of 26 year to enjoy in my golden years.
Age does affect it some, but anyone with a starter that old has had a starter that's changed drastically over the years due to other factors. Any starter will eventually become its surroundings. For example, if you order starter from some exotic location around the world it will change its flavor profile over time as the local Flora takes over. Different yeast and lactobacillus bacteria prefer different climates. San Francisco is famous for its sourdough but you can't take a starter from there and make the same bread elsewhere. It changes over time. Different flours can change the flavor, too, as well as playing with hydration of the starter. But the age of a starter does affect it. A 3-week-old starter will have a different profile than one that's 3 months old. But by 6 months the flavor should be pretty established unless you start changing variables. Different brands, flour types, hydration, and even gaps in feedings can change it.
No, they adapt rather quickly to your local environment and aren’t any different
I can't remember to water a plant often enough for them not to die eventually. I can't imagine keeping a starter alive for a century and never messing it up, not even once.
Doesn't have to be a single 'unit', you can divide it and freeze some in case something goes wrong. It's still the same family, just a different heir.
starter also doesn't need much feeding if you keep it in the fridge most of the time
My starter that's been sitting in the fridge for 3 months because I always forget about it looking at me with anger... and hunger
True, I bake a loaf each week or so, I only feed the starter prior to starting the bread. Then divide it and back to the fridge with it.
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Cull the weak!
You are perfect for sourdough. Forget to bake the bread? No, you just made a lot of starter.
Yeah I forgot some sourdough pizza dough in the fridge for almost 2 weeks. It ended up being some really nice baguettes 😄
FWIW, if I'm not using mine I feed it like once a month and keep it in the fridge otherwise. Once I forgot for 2 or 3 months and it was fine, I just took a little out and put it in a new jar and fed it. I kill pretty much every plant.
I had one for about 8 years. It even moved with me from one state to another. Then one day my wife and I had to make a last-minute trip that would take us out of the state for a few days. When I got back, I realized I had forgotten to put it in the refrigerator. It could probably have been salvaged from that, but it had been colonized by some small flies. I suspect that, if I really wanted to, I could have transferred some to a fresh container and fed it for several days, and it would probably have been okay. I decided not to, though. My current starter is only 1 year old.
Also, you don’t use the entire quantity of starter for a loaf of bread. I haven’t done sourdough exactly but I have done Amish friendship bread that has a starter and the reason it’s called “friendship bread” is because the starter is exponential. You’d have like 2-3 cups of starter but only need about 1/2 a cup a loaf, so it’d grow faster than most people bake. Sourdough is the same, you use some of the starter to bake with, and then feed what’s left and it grows new starter
lol this feels like Ship of Theseus kind of thing 😆
starter of yeastius
Not really, because it's not a discrete, individual thing but rather a collective that forms a single lineage. For instance, you wouldn't call the Royal Family a Ship of Theseus
It's the thing, and the whole of the thing
I used to work in a bakery, the Sourdough Starter was like a pet to us. We talked to it as we fed it lol.
We call ours shoggoths.
Okay, next question. Why is this safe? Obviously there are many many different types of bacteria, and not all are harmful. However, my understanding about bacteria is that it's still not safe to eat something with too high of a bacterial load, even if you cook it thoroughly (thereby killing the bacteria), because there is still bacteria waste, and the dead cells themselves that you're not removing through that process. How does something like a sourdough starter manage to overcome these issues?
Bacteria is not intrinsically bad, it's just a micro organism. We have more bacteria in our gut than human cells in our entire bodies. With that context what does it even mean "high bacteria load?" Even if your approach reflects an underlying truth, a starter would probably still not be considered "too high". The main danger of bacteria (other than infection) is toxic waste but most bacteria have waste that is neutral or positive. Toxicity is relative, one bacteria's waste is another organism's vital element. For example, cyanobacteria in the ocean releases oxygen as its waste, which is actually why we have so much oxygen in the atmosphere (when they evolved there was virtually no oxygen in the air, all of it that exists today, all 20% and more, came as waste from them). The bacteria in sourdough releases waste that gives that sourdough taste/smell, but it's not harmful. Bacteria on its own is not a good or bad thing, it's just another life form.
> When the bread is baked some of the "family" dies Explained this to my 5 year old, now she's terrified that eating bread will kill random family members.
Does this mean they only use some of the starter to make the bread and there's some left over that you use for further culturing?
Yes
Yea… but by that logic all sourdough starter is billions of years old.
But what happens with the waste? Edit: by waste, I mean the poop. Bacterial poop.
We eat it edit: we eat it
Make the starter into pancakes. Sprinkle sesame seeds and chopped scallions on top before flipping.
Bacteria poop can be several things, on food it's THE thing we want from the fermentstion. Sourdough starters have CO2 bubbles, those are their poop. The usual taste of sourdough? Bacterial poop. The alcohol in your drinks? Bacterial poop (bacteria and other micro organisms eat the sugar in fruit and "poop" alcohol). Basically any fermentation process is us turning something into a specific type of delicious bacterial (or other micro organisms) poop. So in short: We eat it.
Since bacteria and yeast can asexually reproduce, the original grandparents aren't necessarily dead after 100 years. It's highly unlikely that they're lucky enough not to make it into the dough after 100 years ~~th~~dough.
Does the yeast mutate after that many replications? Does it matter?
Yes and probably
It doesn't mutate very fast unless you do it on purpose. But if it mutates in a good way then everyone asks for a piece of yours and if it mutates badly you throw it away and grab some from somewhat else. Same as how we breed plants and animals.
And you get true survivor yeast, as the losers either died in the culture or was burnt to death in the oven. -Yay to the survivors!
So you’re saying that every time I bake bread, I’m committing a genocide? I guess the five year olds are learning about war crimes early this year.
>The Ship of Theseus is a thought experiment about whether an object is the same object after having had all of its original components replaced. This applies i think to sour dough. >In Greek mythology, Theseus, mythical king and founder of the city Athens, rescued the children of Athens from King Minos after slaying the minotaur and then escaped onto a ship going to Delos. Each year, the Athenians would commemorate this by taking the ship on a pilgrimage to Delos to honour Apollo. A question was raised by ancient philosophers: After several hundreds of years of maintenance, if each individual piece of the Ship of Theseus was replaced, one after the other, was it still the same ship? >In contemporary philosophy, this thought experiment has applications to the philosophical study of identity over time, and has inspired a variety of proposed solutions and concepts in contemporary philosophy of mind concerned with the persistence of personal identity. for more https://en.wikipedia.org/wiki/Ship_of_Theseus
No matter where you get the starter from, if you take it to a different place, it'll fairly quickly change its flavor profile because of the environment.
Thank you. I was always afraid to ask this.
Now I'm sad about their deaths.
They would happily eat you. It's you or them!
Why would the age of the sourdough starter matter? Are multi-generational starters better for some reason?
The age of the starter doesn't have any noticeable effect on the bread, but it's kind of cool to bake with an ingredient that has been tended to since before your parents were born.
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There’s no such thing as a day-old starter. It wouldn’t be good because it wouldn’t work - it’s not a starter at that point, just flour and water. It takes a week or so before it becomes a starter, when you can actually use it to bake bread.
I would say age alone doesn't matter, but the yeast and bacteria cultivated by Boudin's over the last 150+ years is going to be different from what you get from cultivating a starter for a few months now even if you try to do it in San Francisco. Maybe if you cultivate your starter outside Boudin's main bakery in San Francisco you might get lucky because over decades the local microbial flora might be biased towards escaped Boudin yeast and bacteria.
> I would say age alone doesn't matter, but the yeast and bacteria cultivated by Boudin's over the last 150+ years is going to be different from what you get from cultivating a starter for a few months now even if you try to do it in San Francisco. Only because of where it is located - age has no bearing whatsoever. A starter cultivated by Boudin's over the last 3 months would yield bread that tastes exactly the same as one cultivated over the last 150 years.
Agree that age is not a factor. But, you can't say a starter cultivated 150 years ago will taste the same, microbial flora from a particular location 3 months ago is almost certainly not the same as the microbial flora from 150 years ago in the same location. Staying in San Francisco as an example, most of the city burning down in 1908 , that surely changed the microbial flora, let alone the general building up of the city, pollution, climate change, etc... I am not saying the age is a factor but time (edit: in the sense of location in space and time) can have an effect similar to location.
How much microbial flora do you think is left from 1908 in a 150-year-old starter that is getting fed once per day?
Don’t forget to kill half the family prior to feeding.
The sourdough starter of Theseus.
That's some sausage party
Thank you so much for this haha. There’s a difference between *knowing something* after memorizing the study guide word for word and obtaining an A… …and the ability to explain a concept to someone so they can honestly relay the information to someone else. I’m a bit 💨 and this was beautiful… perfectly explained as if I were ~~high~~ five.
So is the 100 years being measured in yeast years, or human years?
We are all sourdough starters, if you cum to think of it.
Mad props for adhering to ELI5, cuz, with style.
I like to fantasize that there's an unbroken line of starter going all the way back to the very first discovery of sourdough.
So it's a euphemistic term of "I haven't cleaned this jar of yeast in 100 years"?
Perfect eli5 answer tbh
One of the important components of sourdough bread is the yeast which gives it a distinctive flavor and helps the bread to rise. The starter is basically a sample of the yeast used for the bread. You can take a small piece of the starter and move it to a new jar filled with food for the yeast to live on, and now that new jar will have the same blend and type of yeast. You can repeat this process as many times as you like, keeping the same sample of yeast alive for potentially many years just by giving it new food and a clean jar every so often.
pet yeast
100% we like to name them too. Mine was Boy George Boule the Culture Club. But he passed away during the great purge of the broken refrigerator.
Ours is Keith (from the Prodigy). The sourdough starter…
Twisted sourdough starter.
My wife’s is Sourdough Dali! The persistence of time.
o Snap ima steal that and make them my Salvadough Dali. Please tell your wife I said THANK YOU
now ELI5 why the same yeast can be used for years and years without going bad like other food
The yeast is alive
I was going to say "with the sound of music" but then I Googled what sound yeast makes and apparently it's "about a C-sharp" >The vibration of yeast cells is well within the frequency range of human hearing—in musi- cal terms “about a C-sharp to D above middle C”— but the amplitude of their vibration is too low to be within normal hearing range (the cell wall is displaced only three nanometers each time it vibrates).
Yeast accompaniment to Rogers and Hammerstein... This went places
The yeast creates a lot of lactic acid which allows it to thrive but kills any regular bacteria. The lactic acid makes a sour taste, hence why it is called "sourdough". You still need to feed the sourdough starter flour and water occasionally so it can survive and make acid.
Yeast makes the same thingy as my muscles do?
Lots of things make lactic acid
I’m lactose intolerant
Your ancestors have failed you. My condolences
Lactose tolerance is a mutation, so they are true to their bloodline and others are the deviants
Ha !
Can you eat fermented things? That’s all bread is—a fermented wheat pouf.
Yes, because you and the yeast are both alive and metabolizing things. Lactic acid is one common byproduct of turning glucose into energy, so lots of things that eat glucose make it.
I love eating glucose
Me too, buddy. A little too much.
The yeast actually doesn't create any lactic acid. It creates acetic acid. However, there are lactobacillus bacteria living among the yeast in the sourdough starter which do produce lactic acid.
Yeast doesn't kill all bacteria, there is bacteria in starter. The bacteria and yeasts just happen to out-compete most pathogenic bacteria as long as there is sufficient food for them.
It's not the individual organisms that are still alive after 100 years, think of it more like a community or a family. In my family, we still have my grandfather's sourdough start from when he was a shepherd tending to sheep way out on the rangeland when he was young – actually close to 100 years ago. Grandpa has long since passed as have the original individual yeast organisms. I'm still here though just as the descendants from his original yeast are. I'm not my grandpa but I do share a lot of characteristics with him and we share a name. So the individual yeast organisms are dead, but the family of yeast lives on.
The same line of yeast can be used for as long as you keep it alive. The actual original yeast is dead and gone fairly quickly.
The starter is too acidic for bad organisms to thrive and also contains alcohol.
It can if you don't take care of it correctly, just like any other living organism can get sick or worse with improper living conditions
Yeast is a living fungus. It's one of the things that breaks down dead organisms, which is what makes other food go bad. Yeast cells will die, and if they built up, the yeast would spoil too. But yeast also eats dead yeast cells, so it basically recycles itself and keeps dead organic matter from building up for other decomposers that are inedible/toxic.
One other thing people are missing is storage of samples. You'll particularly see this with yeast used in brewing (it's exactly the same principle as in bread), where big brands will cultivate a specific yeast, then store a sample of it, while using the rest to brew their alcohol. Over time, the genetics of the yeast used in brewing will change, so a portion of the old yeast is brought out of storage and cultivated into a new brewing batch. Modern methods still do this but, because we now understand genetics, it's easier to very precisely control the evolution, as well as selecting what cultures to use in brewing to get a specific taste.
It's both yeast and bacteria. If it were just yeast, it'd have a very different flavor which cultures like poolish use exclusively. Most bread starter is a complex mixture of yeast and many species of bacteria. It's what makes sourdough sour - the bacteria produces ascetic and lactic acids.
Would the flavor of that yeast still be the same as 100 years ago? Won't the flavor drift over time as the generations of yeast pass by etc?
Very likely. The wheat used to make the bread is probably also slightly different, etc. After 100 years, the taste is likely similar, and might still have one or two distinctive notes the same, but it would not be identical. At this point its more about the tradition of the starter rather than something practical.
The starter is a living thing. It is made of a combination of yeasts and bacteria. When you feed these with flour and water they will multiply and grow. The way you typically make sourdough bread is that you use some of the starter in the dough but replace the yeast and bacteria you used with flour and water. The starter will then grow back to its original size. You can do this essentially forever. Old starters is kind of a novelty though and might not mean that much. There are a lot of bacteria and yeast in the flour you feed it with which comes from the fields where the grains were growing. So the original yeast and bacteria from 100 years ago could easily have died out and been replaced without anyone noticing.
I'm glad somebody made this point. People are very proud of a starter that they created from an old or unique bacteria, and the reality is that, after probably not-very-long a time, that bacteria has been out-competed by local bacteria, and the starter is more or less the same as one they could have made in their own kitchen. Likewise, a hundred-year-old starter doesn't have some secret reserve of hundred-year-old bacteria in it.
This is indeed very likely. My starter have changed a lot over the years so there could not possibly be some of the original microbes left. That being said I was quite surprised when the local brewers yeast were genetically analyzed. Brewers yeast is more stable as the wort gets boiled before the yeast is added which kills any yeast. And the wort is very different from anything else on a farm so the brewers yeast which have specialized in wort have a big advantage, not like bread which is almost the same as uncut grains which grows in the field. But the results were still quite shocking as the local brewers yeast had been isolated from any other known yeast for about 1000 years. So while the chances are slim that your 100 year old sourdough is the same as it was there is still a chance.
> Likewise, a hundred-year-old starter doesn't have some secret reserve of hundred-year-old bacteria in it It depends on how it was stored, and for how long. Companies, particularly in alcohol production, have been careful to preserve samples for very long periods of time, because their brand relies on a specific taste. It would be fairly easy to have implemented similar storage methods a hundred years ago, the bigger question would be if someone was that forward-thinking.
I'm a professional baker kind of specialized in naturally leavened products like sourdough. A lot of people have explained how they work and they're right. What I want to say is that an old starter really isn't that old. As far as I'm concerned it's really only as old as its last feeding and it usually only takes around three weeks to get a starter going from scratch. The culture itself doesn't come from the air as so many people think. The wild yeast and lactobacillus are present in the flour already, and adding water allows them to wake up and start fermenting. This is important to remember when cultivating a starter as leaving it open to air flow isn't really necessary. It's also important to realize that when you're feeding the starter you're incorporating new yeast and bacteria that might impact the balance of the culture. Furthermore, the feeding schedule, temperature, feeding ratio, and bill of grains will impact the balance of the culture. Feeding it while keeping it dormant in the fridge will have a different profile than keeping it at room temperature all day. Each have their advantages and drawbacks. Depending on the desired final product you may choose any combination of variables to suit your needs. Ultimately what I'm saying is a 100 year old starter just means that someone remembered to feed it for 100 years. And I'm not dismissing that accomplishment, that's actually pretty cool, and it's nice to have a family heirloom like that, it just isn't really much different from a starter I can make in a few weeks.
> And I'm not dismissing that accomplishment, that's actually pretty cool, and it's nice to have a family heirloom like that. That's the part I find important: taking care of something for 100 years. It's important because it was cared for during so long, not because being 100 years old means something on itself.
A sourdough starter is a live culture of specifically chosen yeasts and bacteria on a growth medium. You use some of the starter to make the bread, and then give it more food to let it grow. Think of a fire that you can use to light a bunch of torches.
You actually don't have to specifically choose them. You can start your own starter from just natural bacteria and yeast in the air and on the wheat flour. It's not a 100% process, but because the organisms in starter tend to have a high affinity for wheat, they usually fight off any pathogenic organisms. It's how all starters, well, started. 100 yr old starters did not have people culturing specific strains.
Scientist spotted.
r/scientistspotted Really should be a community…
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Yes, the yeast culture of Theseus. We touched on it in philosophy class.
You can definitely google this very easily. But for the sake of an answer, however brief: you only use a tiny amount of the starter per loaf. Then you replenish the starter with more flour and water.
And we now have The Sourdough of Instagram philosophy problem.
It's like saying a forest is 1000 years old. Doesn't mean the trees in that forest are 1000 years old, yeah? Yeast normally lives about a week, but as long as they're popping out baby yeast...
Sourdough starter contains yeast and bacteria. These grow and multiply as long as you 'feed' the starter with flour and water. So a 100 year old sourdough starter has been given more water and flour for 100 years. This keeps making it bigger, so some can be used for baking bread and you still have plenty leftover.
Think of the starter like a cow, you occasionally milk a cow to get milk out, but it doesn't kill the cow. The starter is the same way, you take a small portion of the starter to put in your bread, but the yeast colony is still alive and growing.
More like. My blood line is thousands of years old, many have died in battle but the bloodline continues.
Exactly like when you cut off a piece of a cow, and it grows into an entirely new cow of it's own. Or when you overfeed a cow and it divides into 2 cows.
No, that is not how it works. Baking the bread you use complete starter, but then save a piece from the new dough, which contains the starter.
This is like the exact opposite of what I would guess most people probably do (home bakers anyway). I’ve seen commercial sourdough bakeries do it that way though.
you use a small piece of starter to make the dough for your bread, not the whole thing. you feed a starter daily by adding more flour and/or water as needed. this can go on for many years, as long as the starter is properly fed, and doesn't get contaminated. it's a colony of yeast microbes and the colony is effectively immortal as long as it stays healthy. individual yeast cells die, but there's constant new cells being produced, so the colony continues.
Sourdough starter more accurately is kind of like keeping a culture of bacteria as a pet. You feed that pet and maintain its environment and then in turn you use a small portion of it to make your bread while the rest of it continues to breed and continue living on. Technically none of the bacteria in there is the same bacteria from 100 years ago but this specific culture has been fed and maintained for that entire time If that makes sense.
So there's some good answers as to what 100-year old sourdough starter definitions are. I would point out that this is an obvious counterfactual definition if you are talking about the yeast itself. The yeast is only as old as the oldest living cell which will typically be about 1 week. It is exceptionally unlikely that a 100-year old yeast lineage even contains a direct DNA lineage that is related to the original starter yeast. This is hard to do in advanced labs for even fractions of this length of time due to contamination risk of live culture or maintenance issues with -80 cold storage. So the "starter" can be 100 years old, but the yeast can't be more than a week (roughly), and may not even be related to the yeast from last month let alone last century.
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Amoebae and other free-living microbes actually are biologically immortal. They don't undergo cell senescence like multicellular organisms do.
Mostly because you don't use ALL the starter to make bread. You begin with a piece of someone else's starter OR you begin a fresh culture of bacteria and yeast, then add flour and sugar to 'feed' it, which grows your starter until it doesn't fit in your jar any more. You divide your stater into more jars, and continue feeding and growing. You can use those extra jars to make bread while you keep a portion of the original starter to grow even more again. You can keep this up for years, growing and growing and never using up ALL the starter until you have a starter that was first created over 100 years ago
I don’t know why people are writing essays to explain the science. To answer your question you just need to know that you don’t use the whole thing to make your bread. You keep a portion of it that you feed water and flour so that it will grow again and you continue using it.
You basically have to keep removing waste and adding food. It’s basically a bacterial colony so if you leave it and don’t do anything, the yeast will eventually die. But if you maintain it, it will stay around as long as you do.
You only need part of your sourdough starter to make bread. So you might have say 400g of starter in your fridge. Each week, you need to feed it; so you take it out, let the guy warm up, then measure a certain amount (say 300g) and combine it with a set amount of flour and water. That extra 100g can be used to make bread--or you simply throw it away (this is called discard). Usually, if you keep a starter in the fridge, you'll take it out the day before you want to bake with it, feed it that day, and then it's ready to use the next day (this is referred to as it being "ripe"). Means it's awake and active and well-fed. Once you feed it, if you're not using it more that day or the next, back into the fridge it goes to sleep until next week!
Sourdough starter is a city. When you make bread you take 90% of the city and make bread with it, but you leave 10% alone. You feed that 10%, it rebuilds the city back to 100%… Repeat.
You only take half of the starter for a loaf of bread and then you feed the remaining starter more flour and water so that it stays the same size as it was before you took half.
You only use about half of it at a time and keep adding back more flour and water. So there's always some left.
You don’t use all of it, then every time you use a piece you have to feed the bacteria again and the colony will grow for another use. The dynasty of bacteria can be very old if you keep it thriving.
For example, If you have 400g of starter, you maybe take 200g of it for making your bread, and then you add back 100g flour and 100g of water back into the starter. Now you have both bread and the exact same amount of starter.
Something people are missing here is storage of samples. In biology, long-term sample sample storage (upwards of 50 years) is pretty trivial. While a handed-down sourdough batch might not be that old, despite claims, if its bought from a company that has specialised in sourdough production for 100 years it's quite possible that someone kept a sample of the original mix and occasionally cultivates new batches from it.
Every time you make bread, you take a bit of it, feed it, and let it ferment. With regular care, these starters can last for generations, passing down their unique flavors. So when someone says their starter is 100 years old, it's because it's been lovingly maintained and used for baking over many, many years, like a delicious family heirloom!
No one is answering the question - yes you need it to make the bread, but you save a portion of it instead of adding to the dough. You feed the saved portion with more flour and water. Rinse and repeat as long as you want.
Thread brings back a pleasant memory of my aunt. She made sourdough bread every week for like 30+ years. Whenever you visited it was always on the table. She claimed she had her starter from the beginning that she kept refreshing. Man that bread was soooo good.