Why Food Goes Bad and How to Stop It

Eggs do not last forever, because tiny microbes slowly get to work inside them. Luckily, an egg gives you clues about how old it is, and you can read those clues at home.

Try the float test. Gently place the egg in a bowl of cold water. Every egg has a small air pocket inside, and the shell lets air pass through slowly. As weeks go by, more air sneaks in and the pocket grows. A fresh egg lies flat on the bottom. An older egg tilts upward. An egg that floats to the top has so much air inside that it is probably too old to eat safely.

The smell test is even simpler. Crack the egg into a separate bowl and sniff. A fresh egg barely smells at all. A spoiled egg smells sharply bad, like sulfur, and you will notice right away. If it smells wrong, throw it out.

Also look at the shell before you crack it. Slimy, powdery, or cracked shells can let microbes inside. And check the date on the carton. A best-before date tells you when the egg is at its tastiest, not the exact day it becomes dangerous, so use your tests alongside the date. Eggs kept cold in the fridge spoil much more slowly, because the cold makes microbes grow in slow motion.

Dates help too, and the two kinds mean different things. A best-before date is about taste and texture. A use-by date is about safety and sits on foods like meat, fish, and ready meals: after that day, harmful microbes may have grown even if the food looks and smells fine, so never eat past it.

A cantaloupe looks clean on the outside, but its rough, netted skin can hide microbes. These melons grow on the ground, so germs from soil and water, including ones like salmonella, can sit right on the rind. You cannot see them, but they are there.

When you push a knife through the skin, the blade carries whatever was on the outside straight into the soft, sweet flesh you are about to eat. That is a kind of cross-contamination: germs moving from a dirty surface onto clean food through a tool or your hands. The inside of the melon was perfectly safe until the knife touched it.

The fix is easy. Before you cut, hold the whole melon under running water and scrub the entire surface with a clean vegetable brush. Plain water and a good scrub remove most of the germs. Do not bother with soap, because the rind can soak it up. Dry the melon with a clean towel, then cut it on a clean board.

Once cut, melon pieces spoil faster because their juicy flesh is full of the water microbes love. Store cut melon in a sealed box in the fridge and eat it within a few days. The cold slows the microbes down, though it never fully stops them.

Drying is one of the oldest ways to stop food from going bad. It works because of one simple fact: microbes need water to grow. Take the water away, and mold and bacteria cannot multiply. That is why dried herbs from the shop last for months while fresh basil wilts in a week.

To dry herbs or leaves at home, you can air-dry them. Spread them in a shallow container, or tie small bunches with string and hang them up. Put them somewhere warm with moving air, and check them every day or two. When a leaf crumbles between your fingers instead of bending, the water is gone and it is done.

Sunlight can speed things up, but watch out. Too much direct sun fades the color and cooks away flavor. A warm, airy spot out of the harshest light usually gives the best result. An oven on its lowest setting with the door slightly open also works if you are in a hurry.

Once everything is fully dry, store it in an airtight jar away from light. The jar matters, because dried herbs can pull moisture back out of the air, and moisture is exactly what the microbes are waiting for. Dry food plus a sealed container is a double defense: no water inside, and no new water getting in.

Blanching means cooking food for a very short time, usually in boiling water or steam, and then cooling it fast in ice water. It is a clever trick cooks use, and it is one way heat fights spoiling.

Here is how to blanch broccoli. First wash it and cut it into florets that are all about the same size, so every piece heats evenly. Boil a big pot of water, drop the florets in, and give them just two or three minutes. Then scoop them straight into a bowl of ice water. The ice bath stops the cooking, so the broccoli stays bright green and a little crisp instead of turning soft and gray.

So what does this have to do with food going bad? Two things. The brief blast of heat kills many of the microbes sitting on the surface. It also switches off natural enzymes in the vegetable. Enzymes are chemicals inside the plant that keep working even after harvest, slowly changing its color, texture, and taste. Left alone, they make frozen vegetables turn dull and mushy over time.

That is why blanching and freezing are a team. Blanching knocks out microbes and enzymes first, and then the freezer keeps everything in slow motion. One method uses heat, the other removes warmth, and together they keep food good for months.