The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

How can a starter actually be "aged" or "old" if we cut it in half everytime we refresh it?

gringogigante's picture

How can a starter actually be "aged" or "old" if we cut it in half everytime we refresh it?

I heard someone somewhere talking about a starter that they had that dated back to the Oregon Trail! I was doing the math and thinking about how if that person fed it, say, every week and presumably dumped half of it, then the original starer would be so weak and cut dow it almost certainly wouldn't exist.

Every week, I'll dump half the starter and add another cup of flour and water....which means that the NEW yeast on the NEW flour is what is growing, so how can there be any "old" yeast in there in any real quantity?  It seems that a starter's taste could only be so old with all the refreshing....or am I missing something in my Newbie-ness?

blaisepascal's picture

Sourdough starter is a symbiosis between bacteria and yeast, and in a well-run starter there is a lot of both, especially compared to the yeast on the wheat being fed.

The yeast in the starter has a couple of advantages over newly introduced yeast:  It is already active and hydrated, and doesn't need to be rehydrated to take advantage of the new food, therefore it grows faster to start with, and it has large quantities to begin with.

So if there are 10 yeast cells per unit of dry flour added to a starter, and 1000 yeast cells per equivalent unit of starter being fed, by the time the 10 yeast cells have doubled once, the 1000 cells may have doubled 1.5 or 2 times.  

G-man's picture

From what I've read here, it seems like starters do undergo change over time, but the change is relatively slow and is kept to a minimum when a certain feeding schedule is adhered to. Debra Wink has posted results from her own experiments and those of others showing these things. Linkage here:

Also the changing conditions in a new starter. Linkage here:


Basically when you adhere to the same feeding schedule and keep the starter in the same conditions, you're creating and maintaining an environment that is very hospitable to certain types of microorganisms. As long as you keep the same basic routines, while individual microorganisms may die and be replaced by others, the environment stays the same and therefore the same microorganisms will stick with it.

So long as you keep that 100 year old starter under the same conditions it has been kept for the past 100 years, it should stay pretty much the same.

kygin's picture

I think I understand where you're coming from.  See if you can think of it this way.  I have a houseplant that is over 40 years old.  When it gets straggly, I cut off the ends, throw the rest of the plant away and root the cuttings.  I feed and water them and they grow.  I've done that time and time again.  It's the same plant even though there is nothing left of the old plant except the genes.  It's the same with the sourdough (if you discount all the new strains of yeast that have been introduced through feedings over the years).  Carl's yeast that exist now are the great-great-great....granchildren of the 1847 yeasts.  Does that make sense?

Davo's picture

Hmmm. Kind of. Except that as you note the mix of bugs might have changed, not only yeasts but lactobacilli. Any culture is just a mix of species. Yes your mix might have some bugs that are direct descendents of those that were in it way way back. But they are still just describable species, not expecially different than  other individual bugs of the same species that (logically) also had antecedents living in 1847 - if they didn't, they wouldn't exist (just like anyone reading this forum)! Frankly I think those ancient cultures are socially important. In terms of being a unique sourdough culture, meh, they are no longer any more unique than great great  granpa's hammer from 1847 that's had a new handle and a new head in the last 10 years.

jdunivan's picture

I have no idea if this is correct but this is the way I see it. The strong survive and thrive in the colony and as years go by you have stronger and stronger traits from all the years before. You are feeding them like pets and giving them plenty of food. So naturally they are going to do their job better and differently then in the past. They are much stronger than the wild counterparts where food, water and temperatures are inconsistent. Starving them once in a while may even be good to knock off the weak. As bad as that may sound. Then again we burn them up in ovens. :o)