We tend to go through life thinking that if something is rotten, it’s a sign that it’s time to throw it out. But in fact, food that’s begun to rot is eaten all around the world, and you most likely eat it as well.

Obviously, it’s not exactly appealing to call food out as being rotten, so there’s a more common term for it: fermented. Fermentation simply means giving bacteria time to do their thing; if it’s bad bacteria you can end up with food poisoning, but if it’s good bacteria you end up with pickles.

The act of cheesemaking, for instance, is largely an exercise in controlled spoilage. Introduce bad bacteria and you end up with rotten, ammoniated garbage. But show it some TLC, and something magical happens.

Allowing food to rot has been used as a preservation technique for thousands of years. Fresh food wasn’t always available, so folks had to use some pretty cunning techniques to extend its life throughout the year. Pickling vegetables, making preserves out of fruit, turning milk into cheese, and drying meat were all devised as ways to make food last longer, but fermentation, while not as common a practice in the United States as it is elsewhere around the world, is also a viable option.

Fermented foods are generally packed with loads and loads of salt and possibly other seasonings, then simply left to their own devices. The result depends on what you’re fermenting: start with cabbage and you end up with kimchi; start with fish and you end up with fish sauce.

So read on to learn about 10 foods that we only eat when they’re rotten, whether through fermentation of good old-fashioned aging. Some taste delicious, others are a bit more of an… acquired taste, but they’re all edible thanks to some industrious folks who figured out how to make it that way.

1. Aged Beef



To dry-age beef, slabs of it are allowed to sit in a temperature- and humidity-controlled room for up to three weeks while it develops a crust, usually complete with mold. All of this is cut away after the dry-aging is complete, however, and you’re left with a steak that’s tender, minerally, and more concentrated in flavor.

2. Miso



This Japanese staple is most commonly found in miso soup in the U.S., but is also used in sauces, spreads, and marinades. In order to make it, soybeans are left to ferment with salt and bacteria called Aspergillus oryzae. Barley, rice, and wheat are also sometimes added, and the resulting paste is a flavor-rich umami-bomb.

3. Kimchi



Kimchi is a hallmark of Korean cuisine, and it’s made by slathering cabbages with a salty, spicy mixture, sealing it airtight in a jar, and letting it sit for a few days.

4. Cheese



Ask any cheesemaker, and they’ll tell you that making cheese is the art of controlling rot. Milk is treated with bacteria and enzymes to curdle it, then the curds are cut, formed, and given some TLC for days, weeks, or months until the cheese is ripe.

5. Sauerkraut



Like kimchi, sauerkraut is also fermented cabbage. It’s super-simple to make: shred cabbage, mix in salt, and let it all hang out for a while. Not only is it the best way to top a hot dog, it’s also great for digestion.

Check out more foods that get better with time.

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