Why does my bread ferment in the middle? I had been making bread reliably for a few years until we moved (from Sweden to Austria) six months ago. Suddenly, any loaf I make rots within a few days in the bread bin. Specifically, it goes soft and moist in the centre (the crust stays fine) and it starts to smell like rotting grapes.

I have tried:


Swapping the flour. I have tried various kinds and qualities.
Swapping the yeast (I use instant yeast)
Baking longer (at 230°C)
Changing the bread bin for a large tupperware with the lid very loose. In Sweden I did not have a bread bin, so I kept bread in a plastic bag, but we never had rotten bread.
Making sure the bread is completely cool before placing in the bread bin.


Can anyone suggest where I might be going wrong?
I have marked George M's answer as the accepted answer, but I thought I would post a slightly expanded answer.

I can confirm that the following ideas that  were raised in the comments did not work:


Hotter oven
Cooking longer
Cooling completely


What has worked is to wrap the bread completely in a tea towel or two until completely cool. Then, the bread stays really fresh for at least a day.

I also found that bread thus cooled can be placed in the bread bin still wrapped in the tea towel, and it doesn't rot.