Ratio Starter to Biga Ingredient

I've always wondered this also... What I've been doing is weighing out about 4 oz of my starter, then add this to my Soaker or Sponge the day before making my bread.

This has worked for me.   I also use some bread yeast to my loaves to help in the fermenting process during rise.

I will say that my recent SD bread hasn't had that great of SD taste and I'm not happy with my starter, so I think I'll start a new one.

I would also be interested in hearing how others weigh or measure their SD starters in their breads.

Dennis

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This is how I was taught and, in fact, what I do.

First, to be nit picky, a biga is the popular name for a firm pre-ferment using commercial yeast, so technically you will not be making a biga.

To make a pre-ferment with a sourdough culture, which I have been taught to call a firm or liquid levain (depending on the hydration):

1. Know the hydration of your starter.  Yours looks like 100% or more.
2. Then decide how much flour you want to pre-ferment.  This can be as much or as little as you want, but isusually no more than 33%.  I usually pre-ferment 12% which is on the low end of the range.
3. Decide on the hydration of your pre-ferment.  For ease in mathematics you may want to keep this at the same hydration as your starter.
4. Then decide on your innoculation rate.  That is, what percent of the total weight of your pre-ferment will be your starter.  This will depend on the general heath of your starter and the temperature at which your pre-ferment will be maturing.  I use 25% innoculation rate in the winter when my house is quite cool and will reduce the percent to 12.5% in the summer.  So, you must understand how long you will be letting your pre-ferment mature, the temperature, etc.  The first couple of times - you guess.  If you find your pre-ferment over mature you may wish to reduce the innoculation rate.
5. Now we get out the slide rules.  Let's say that your total formula calls for 40 gms of flour and you wish to pre-ferment 25% of the flour.  Your starter is at 100% hydration and you wish to make a pre-ferment at 100% hydration.  Assume, that whatever starter you put in the pre-ferment will be removed from it to keep the starter going (even if it is not, the amount is likely to be small and we are trying to keep the math simple)  You decide on an innoculation rate of 25%.  The total weight of the flour in your pre-ferment will be (.25* 40gms - 10gms) 10 gms. The weight of the water will be (10*1.00 = 10) 10 gms.  The total weight of your preferment will be 20gms.  The weight of the starter to add will be (.25 *20 = 5) 5 gms.  You will make 25 total gms of the pre-ferment and remove 5 gms after it matures to replace the starter you used.

Of course, you can make the math more complex.  I certainly do, but this is a fairly accurate way to calculate how much starter to use. I did the algebra and worked up a spreadsheet that will calculate how much starter to use at any percent of starter vs pre-ferment hydration and does not require the removal of the starter.  So have others and they are posted in the tools section of these pages.  I thought I would explain the rationale, though

Or, you can just use a good, existing recipe...

Hope this helps.

Thanks for that proth5 ..I was puzzling over innoculation percentage, your post cleared that up :)