Peter Reinhart's Whole Grain Question
I've been baking from Peter Reinhart's Whole Grain cookbook for about a month now. I'm not an experienced bread baker, but I've slowly been increasing the hydration of my dough, learning to shape slack doughs, and improving the crumb of my hearth breads.
I'm having a bizarre issue with my pre-doughs (the soaker and the biga in Reinhart's terminology); both the soaker and the biga tend to develop a greyinsh-brown film on top. If I leave the soaker out at room temp, this film becomes pronounced and very hard (I lose a good portion of the dough by trying to pick it off). It's diminished by storage in the fridge, but still noticeable as a darker coloring, only on the top of the dough that is exposed to air. This seems to happen whether I use water, buttermilk, whey or milk as the liquid in the recipe, and it happens both with yeast (biga) and without (soaker). It seems to get worse with time (if I leave the pre-doughs in the fridge for 2 or 3 days it is more pronounced than after 24 hr).
Does anyone have experience with this? It doesn't seem to always happen; I've been using the same batch of flour (25 lb batch of organic, freshly-milled hard red wheat flour from a local farm); I haven't gotten around to buying a different source of flour from the store and checking it out.
Anyone know what this is, or have ideas as to how to prevent it?