WHY? Change in flour fed to starter yeilds dead starter after 10 weeks
I've maintaned a 100% hydration sourdough starter fed with Gold Medal bread flour for 3 yrs. I bake several sourdough loaves once a week and keep about 50 grams in reserve (in a glass jar in the frig) between bakings. The starter has always been reliable and doubles in 7-8 hours after feeding. The starter is used in sourdough breads that typically contain about 30% whole grain flour (where 30% is the percent of the total flour weight). I home-mill all my whole grain flour and mostly use organic hard wheat (either hard red winter wheat or hard white spring wheat) and organic rye grain for the flour.
This summer I decided to transition my starter from white flour only to a white flour and whole grain mix - specifically 50% white bread flour (same brand), 40% home milled organic whole wheat flour (milled from organic hard red winter wheat) and 10% home milled organic rye flour (milled from organic rye). I gradually changed the flour mix over a period of 6 weeks, reducing the amount of white flour slightly each feeding until I reached the new proportions. The "new" starter, once established, seemed stable. It doubled after feeding slightly faster (maybe an hour less - which I attribute to the rye) but worked as usual in the standard sourdough formula I routinely use.
However, after working fine for about 6 weeks, the starter began to fail. It gradually became less active (taking longer to double after feeding), then seemed to thin out, Finally, it refused to rise at all.
I always weigh the water and flour that I feed the starter (100% hydration) and I also weigh the flours that are mixed & used to feed the starter, so the proportions are accurate. The water I use has not changed. The bread formula have not changed (they are tried-n-true recipes I've used many times).
What has happened? I am careful to wash my starter jar well so it is clean when I use it to store my reserve (taken from the mature sourdough after it has been fed and doubled). Except for the change in flour compositon for feeding, nothing has changed (as far as I can tell). Anyone care to speculate?
Thanks in advance to all who reply... SF