How to Preserve Food: Four Methods and What Goes in Which

Today is the four methods, whole, with the corner running behind me.

Let me start with why food spoils.

Because once you know what's attacking the food, you can see what each method is defending against, and the methods stop being four separate crafts and become four answers to the same question.

There are four drivers of spoilage, and every preserving method that has ever worked attacks one or more of them.

The first is microbes, bacteria, yeasts, molds, which are on every surface of every food and in the air of every kitchen, and which, given warmth and water and time, will eat the food before you do.

The second is the food's own enzymes, the chemistry inside the food that was running while it was alive and keeps running after harvest, ripening the fruit past ripe, softening the vegetable, browning the cut apple, turning the sweet pea starchy in a day.

Enzymes don't need microbes, they're the food digesting itself.

The third is oxygen, which oxidizes fats until they're rancid, dulls color, and feeds the molds in most of the bacteria that would otherwise struggle.

And the fourth is moisture, water, in the food and around it, which is what nearly every microbe needs to grow at all.

Take away the water and most of them simply stop.

Microbes.

Enzymes.

Oxygen.

Moisture.

Hold those four in your mind, because here is what each method does to them.

Canning uses heat, and it attacks three of the four at once.

The heat of processing kills the microbes in the jar and destroys the enzymes, so that nothing living or chemically active is left inside.

And the seal, the vacuum that forms as the jar cools and pulls the lid down, shuts out oxygen and shuts out any new microbe that might want in.

What's in a properly canned jar is food that has been sterilized and sealed, and it will keep, on a shelf, at room temperature, for a year and often longer.

Because nothing in it can act and nothing can get to it.

It's the most complete of the methods and the one with the least margin for error.

For exactly that reason, if the heat wasn't enough, the jar looks the same as one where it was.

Drying attacks moisture.

It removes the water that microbes need, and it does it so thoroughly, a dried vegetable is under a tenth water, that bacteria and molds can't grow on it at all.

It slows the enzymes as well because most enzyme reactions need water to run in.