How to Switch Your Sourdough to a New Type of Flour
Sourdough comes in many forms. You can make a white-flour sandwich bread, a whole-wheat peasant loaf, a rustic spelt boule, or a dense rye. All of these are delicious and serve their own purposes.
If you want to branch out and try these different grains then you will most likely want to convert some of your sourdough starter to the type of flour you'll be baking with. It is fairly easy convert your starter to whichever gluten-containing flour type you would like: white flour, whole wheat, spelt, or rye.
Switching to a gluten-free flour is a bit more tricky as it tends to require more feedings to become vigorous and maintain its efficacy in baking.
How to Switch to a New Flour
Iif you are interested in branching out into the world of various flours then try these tips:
Troubleshooting a New Flour
Not all flours work alike in sourdough. Because of this your starter may go through an adjustment period in which it is not as vigorous and may not perform as well as your original starter.
Whole grains, especially when freshly milled, tend to contain more organisms for the yeasts and bacteria to feed off of. So if you are switching from a whole grain flour to white flour you might see a decline in the health of your starter.
However, flour that has just been ground can be a little "raw" for the starter to utilize. Letting freshly ground flour age for a week or so can let it develop more of the healthy organisms the sourdough starter can utilize.
Rye, in particular, is very well suited to be food for sourdough. So if you are switching a rye starter to a new flour you might notice a change in the health of the starter.
If, after you have given your starter time to adjust, the sourdough starter appears to not be as vigorous as it was with the old flour, try feeding it a blend of the new flour and the old flour for a while to give it a boost.
Also, remember that you have the backup starter in the refrigerator. If all else fails you can discard a less-than-stellar new sourdough starter and either repeat the flour switch as recommended above or try a different flour. Just make sure you always split your starter to maintain a backup.