February 8, 2011 - 2:50pm
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?
Share
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.
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:
http://www.thefreshloaf.com/node/10375/lactic-acid-fermentation-sourdough
Also the changing conditions in a new starter. Linkage here:
http://www.thefreshloaf.com/node/10856/pineapple-juice-solution-part-1
http://www.thefreshloaf.com/node/10901/pineapple-juice-solution-part-2
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.
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?