Recipes call for either fed sourdough starter or unfed sourdough starter, but what’s the difference?
After a lot of Googling, I came across this reddit post with some answers. Since this took me so long to find, I decided to make an easily googlable post about fed vs unfed sourdough starter.
Fed Sourdough Starter
Fed sourdough starter is starter in which you have fed approximately 12 hours ago. You can identify that this is potent by doing a “float test”. Simply take a spoonful and put it in a glass of water. If it floats, it’s ready to use and fits into the “fed” sourdough starter. This is what most sourdough recipes call for, and some don’t require added yeast.
Unfed Sourdough Starter
Unfed sourdough starter is sourdough starter that has gone a couple days between feedings. This shouldn’t pass “the float test” (see “Fed Sourdough Starter” for the float test). Almost all recipes that call for unfed sourdough starter will call for added yeast.