Besides food, I store all sorts of other things in my refrigerator –medications, seeds, open printer ink cartridges – anything that may deteriorate at room temperature – but never bread. Bread is a special case and, since it is a staple in our household as it is in most, I decided it was worthwhile to look into why it is that bread actually gets stale six times faster when you put it in the refrigerator!
Hot and cold are nothing more than the speed at which molecules are moving – they move faster when they are hot, and more slowly when you cool them down. When things get hot, their molecules often bump into each other so hard that they cause bonds between atoms holding them together to break. That can cause a chemical reaction between molecules to occur.
It so happens that food ‘going bad’ is caused by both chemical reactions and by bacteria from the air that can get on it and start multiplying. When it’s cold the rate at which these things happen slows way down. So that gives us a big clue that bread going stale has nothing to do with chemical reactions or bacteria and that it’s just something physical that’s happening especially when it’s cooled down.
Bread has a lot of starch in it and those big starch molecules have little electrostatic charges all over them. That makes them attract and hold little charged water molecules that are free in the bread and also in the air. Trouble is that as water molecules stick, the starch molecules get more and more rigid. That’s why bread goes stale. At room temperature it takes a while for bread to go stale because all the molecules are moving quite quickly and the attraction between them is not strong enough, so water molecules can often shake loose.
Put stale bread in the toaster for a minute or so and the water wriggles free from the starch and the bread gets nice and soft. Put the bread in the refrigerator and the temperature is just right for everything to slow down and stick together better – the starch molecules all become very stiff and of course that means the bread has gone stale.
So – what to do?
- Keep bread in an airtight container. That at least keeps water from the air getting trapped by the starch and - it has the added advantage of keeping fungi floating around in the air getting on it and causing mold. Plastic bags work well and, if you’re careful closing them up, almost no air or fungi can get at the bread so it lasts!
- Buy commercial bread – they put some agent in it that keeps it from going stale as quickly as homemade bread.
- If you make your own bread, put a little honey or sugar in it. Cakes don’t go stale nearly so fast because the small sugar molecules attract water better than starch does, and the sugar molecules don’t go rigid.
- Freeze bread quickly so water molecules are slowed down fast and they don’t have a chance to move into the ‘attractive’ positions on the starch.
May your bread never be stale!! Rie