Carlo, we're stumped; but our sourdough expert, Jeffrey Hamelman, has this to say: "So hard to say without seeing the entire process – I’ll bet there was some kind of a change in either time or temperature. It’s not leuconostoc." I know that's not the definitive answer you would have liked to have heard, but hopefully it'll giv eyou a clue as you continue to try to figure out what's happened. PJH

• Reply