It happens all the time: You buy a loaf of sliced bread, set it on your counter or in the cupboard, and after a several days it’s stale and starting to mold. It’s a problem older than the commercial bread-slicing machine itself, whose inventor in 1928, Otto Rohwedder, used hat pins to keep the slices pushed together so they’d stay fresh longer, but probably required a lot of Band-Aids.
These days, some of us try to keep sliced bread fresh by storing it in the refrigerator. Keeping bread cold certainly retards mold growth, but according to Wayne Gisslen, author of Professional Baking, refrigerating sliced bread (or any bread for that matter) makes it go stale faster. Six times faster, in fact, than a loaf kept out at room temp.
Why? The culprit is a process known as retrogradation, where the starch molecules in the bread crystallize at temperatures between 36 and 40 degrees Fahrenheit (basic fridge temperature). Physicists Stephen Reucroft and John Swain say the only way to save stale refrigerator bread is to heat or toast it, which then returns the starches back to their original state. But reheating bread that turned stale via retrogradation speeds up its ability to go stale again, so the bread is only good for two hours or so.
So: If you plan on eating your sliced bread in less than a week, storing it at room temperature (ideally in a dark, cool place) should be fine. But if it’s taking you longer than you thought to eat up those slices, try wrapping the loaf in heavy-duty plastic wrap or a zippered freezer bag and freezing it. Retrogradation slows down considerably below the freezing temperature because the water in the bread freezes, which restrains the starch molecules from forming crystals. Simply defrost and you should be good to go. Of course, breads containing a heavy dose of preservatives like calcium propionate and potassium bromate (banned in some other countries, but not in the U.S.) take much longer to turn moldy. Up to you if these breads have a place in your shopping cart.
I prefer to store freshly baked and sliced bread in my pantry for a few days, which is cool and dark, or in the freezer for later use. The same goes for supermarket sliced bread—no flavor lost through freezing. Bonus: I never have to scramble to find hat pins to keep the slices together.
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