You didn't say how long this baking project took before you put the
bread in the fridge. I'd be astonished if the dough soured in one
day of working and one night in the fridge. Putting dough in the
fridge overnight is on of the best methods for improving the flavor
of breads made with commercial yeast. It retards the yeast but
allows the enzyme action that reduces the starches to sugars to
continue. The bread should be sweeter, not sour. Only after several
days will the dough start to sour. I use the fridge all time for
yeast doughs for bagels, bialys, rye and wheat breads, focaccias,
pizza. They all get sweeter, caramelize to a more golden crumb, and
have deeper brown crust because of the additional sugars developed
while in the fridge. Many of the recipes in Peter Reinhart's Bread
Bakers Apprentice use the fridge as a flavor enhancer. The flavor
that results is a nuttier sweetness, not sour.
Are you sure you are not just picking up flavors from the
fridge? BTW. salt can be used as a yeast inhibitor, but of course,
salt affects the flavor.