If you made a list of the most important skills in history, what would be at the top? Would number one be growing food? If so, your number two should probably be preserving it! Bacteria is everywhere. It gets busy with its spoiling work as soon as food is harvested. Here’s how people have learned to slow bacteria down:

Drying: In some regions, Sun and wind dry food quickly. In other climates, food needs a little help. Experiment with a food dryer made from simple materials.

Freezing and cooling: For some people, preserving food is easy. The world is their refrigerator! But people have found natural refrigeration in warm climates too. Experiment with a small, cheap thermometer. Dig a hole one foot deep. What is the temperature underground? Put the thermometer on a string in a creek or pond. Bacteria slows down below 40 degrees. Freezing stops it cold, you might say. Have you tried to take a drink of ice?

Fermenting: Fermenting is a process that encourages safe bacteria to grow. The safe bacteria adds flavor while the sickness-causing bacteria is slowed down.

Pickling: It’s not just for cucumbers! The right salt and vinegar recipe has enough acid to keep bacteria from growing. It adds great flavor too.

Salting: Salt pulls moisture out of food. It makes food like a desert to bacteria. (So does sugar, by the way.)

Canning: In the late 1700s, Frenchman Nicolas Appert experimented with canning. A few years later, the French Navy began using his food preservation method aboard ships. Canning gives bacteria a one-two punch. First, heat destroys bacteria in food and jars. Then, when lids are placed on top, the cooling process creates a vacuum to seal out other bacteria.