The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

How to convert a recipe from "firm" starter to 100% hydration starter?

GregS's picture

How to convert a recipe from "firm" starter to 100% hydration starter?

I'd like to make Susan's Ultimate Sourdough (see her blog here). Her recipe calls for 12g starter and 175 g water, from which I assume she is using a small portion of firm starter. She says "Starter is...1:3:4 (starter, water, flour)".

I have a nice 100% starter that I'd like to substitute in the reicpe. I've found postings about how to turn a liquid starter to a firm starter, but nothing about altering actual reicpes. How can I go about converting the reicpe? In addition, what quantity of liquid starter would be appropriate. I've seen recipes that call for everything from a tablespoon of active starter to two cups!

Any help on the recipe and the concepts involved would be very much appreciated.


pmccool's picture

Susan uses 3 parts of water (by weight) for every 4 parts of flour (also by weight) to feed her starter.  If you permit me the liberty of rounding, the 12g of starter called for by the formula will contain approximately 5g of water and 7g of flour.

If you want to work with a 100% hydration starter, I'd suggest using 14g of starter, which will consist of 7g of water and 7g of flour.  My reasoning is that you want to inoculate the dough with a similar quantity of yeast and bacteria and the easiest way to approximate that is to be sure that you are adding the same quantity of flour with your starter that Susan adds with hers.

If you do that, you would deduct 2g water from the 175g called for by the formula, since you added 2g more water from your starter than Susan added from hers.

Practically speaking, 2g of water is negligible.  You might have to adjust the water content of the dough by that much just to account for changes in humidity and moisture content of the flour.

I hope that helps.


GregS's picture

Thank you PMcCool. I'm one of those for whom books like "Math for Dummies" is written. I appreciate your help.


longhorn's picture

The difference between 12 grams of 75% starter and 12 grams of 100% starter is about one gram of flour and one of water. Your scales probably aren't that accurate. Don't sweat it, just do it. You are well within the tolerances of error!

Bake On!