Why does bread dry out on the bottom and get wet on the top when kept in a refrigerator for extended periods?

Question

I have noticed that any kind of bread - bagels, buns, rolls, loaves - when kept in a plastic bag, in the refrigerator, dries out on the bottom, while the top gets soggy. What's up with this water migration? It doesn't happen to bread kept in plastic bags at room temperature...

Good answeres with precipitation and distillation. I see that water must be evaporating from the bread and then condensing on the top of the bag and precipitating down on the bread.

My only other question is: why does the water condense on the top of the bag specifically? It can't condense on the bottom, because the bread is sitting there. If it condensed on the sides the water could drip down and re-saturate the bottom of the bread. It seems that the water must be condensing specifically on the top of the bag, which is perplexing since the top is a minority of the available surface area inside the bag.

Answer 1

You are probably observing distillation. Water gradually evaporates from all of the bread, but since the air around it is cold, it condenses again on the inside of the bag. That's where it comes in contact with the top of the bread.

Answer 2

I think it has something to do with precipitation. When you closed the plastic bag, there might have been water vapor in it. The water vapor cooled in the refrigerator, and turned to water. It was on the top because the bread pushed down on the bottom leaving no space for the water vapor. The water vapor rose to the top where it turned to water. It doesn't happen in room temperature because water vapor doesn't turn into water in room temperature. That's my theory. It's never happened to my bread, because I don't eat bread.

Answer 3

The freezer -- particularly if it's good bread and doesn't have preservatives. (Ye Olde Cheap BadForYou White Bread lasts weeks on the counter because of the chemicals in it.) If sliced, at least; then I can toast it to unfreeze. If it's a baguette or something unsliced, then it stays in the baggie on the counter and I try to eat it fast!

Answer 4

I keep mine in the freezer and only take out what we need .