## Determining the Hydration of an Existing Levain

Does anyone know how I can determine the hydration level of my levain?

I was given a starter by a friend some years ago, along with instructions on how to refresh it. As I've gotten more serious about my baking, I've wanted to figure out the actual hydration level so that I can make adjustments for various formulae, etc.

It occurs to me that maybe I can just use my friend's ratio of H2O/Flour used in refreshment as the basis of the hydration level. Do I assume that the existing starter has the same ratio, or will the combination of existing starter + new flour & water have a different hydration level than the new stuff added.

In other words: Say I add 100g flour & 130 g water each time I get the starter ready to bake. Can I assume I've got 130% hydration?

Thanks,

steve

You could easily do the math and see that, in the long run, it works out that way.

As an extreme example, let's say you started with 230g of 0% hydration starter (basically flour which we are calling a starter for sake of the example). If you feed it with 100g of flour and 130g of water, you'll have a starter with 330g flour, 130g water, or 40% hydration. Splitting it in two, half to bake with, half to grow, and adding another 100g flour and 130g water, you'll have 265g flour, 195g water, or 74%. The next feeding will yield 232.5g flour, 227.5g water, and 98% hydration (and this is after 3 feedings!). After the 4th feeding like this, the starter is at 113% hydration. After the 5th, it'll be 121%, after the 6th, it'll be 125%, after 10 feedings it's at 130% (well, assuming impossibly-accurate weighings, 129.7%). There'll be 100g flour and 130g water, and subsequent feedings won't change that.

Thanks for confirming what for me seemed the most likely answer... although I didn't think about the fact that even starting with no water, the levain would converge to the level of hydration of the feedings.

Considering this starter has been fed at a 130% ratio for almost 15 yrs, I'm assuming I'm at 130%, and won't bother with the drying out method suggested below!

Thanks again,

steve

You can probably assume that your friend's feeding ratio fairly well matches the intended hydration ratio for the starter in toto. If you want to adjust the hydration level, you might try using the feeding hydration ratio as a base number and work from that foundation.

You could also take a known sample of the current starter, weight it, then dehydrate it in the oven and weight it again. The missing weight should be pretty close to the amount of water that was in it initially.

http://www.thefreshloaf.com/node/15217/bread-dough-formula-math-dilemma-some-help-i-hope

If you feed it several times at the hydration you want, it will be close enough. If you have a feel for how different hydrations look and feel then you can just assume you know what it is and adjust accordingly.

After a few rounds of bread making your starter should for all practical purposes be the hydration you want.

For example, if you start with starter that is 100% hydration and want to have starter that is 50% hydration and if you feed your starter each time with [50% starter, 100% flour, and 50% water] after only 2 feedings the hydration will be down to about 52%. After one more feeding it will be about 50.5%. This ought to be close enough.