Each summer we attempt to raise a small garden at our house. This past year our green beans did well, and we were able to “put some up” to use later in the year. To our delight, when we opened a jar of the green beans this winter, they tasted almost as fresh as when we had picked them. They were much better than what we had been getting from the grocery store cans.

What does “put some up” mean? It means “to preserve the food for future use.” Many of us probably have a refrigerator in our home. A refrigerator is a device that helps us preserve food. We may take the refrigerator for granted, but when you look back at its history, you’ll see that it’s only been around since the early 1900s. The invention of mechanical refrigeration systems not only improved the quality of life for many people, but it also led to some other inventions, such as air conditioners.

The World Before Mechanical Refrigeration

Preserving food has always presented a challenge to man. In some locations crops can be grown year-round, so there is always a fresh supply, but in most locations the growing seasons are cyclical. You grow the crops part of the year, harvest them when they are ripe, and preserve enough to last until the next crop comes in the following year. A number of things could go wrong. The food could become spoiled, in which case it cannot be eaten. The food could become contaminated with bacteria, fungi, or microorganisms that could be harmful or fatal. Man has invented a number of ways to work around these problems.

Grains are staple foods. They can be eaten in their field state or dried and ground to make breads. People learned very early on that if grain was dried properly, and if it was stored in buildings that kept it dry, it would not spoil very quickly and would last until the next season. A number of fruits can also be dried to lengthen the time they can be stored. Bacteria need water to survive, so if food is sufficiently dry, bacteria cannot thrive in it. Drying is one method of preserving food.

Root and tuber type foods, like potatoes, did not lend themselves well to drying in the early days. Instead, they could be stored for extended periods of time by keeping them in dry, dark, cool environments. This was best accomplished by digging underground cellars or by using the insides of caves. Such foods could still spoil, but the conditions greatly slowed down the decaying process, and they would last a lot longer than if they were just left to sit out.

Meats presented some problems. If they spoiled and became infested with bacteria colonies, they would be health hazards that could poison or kill people who ate them. Drying meat works, but other methods, including smoking, salting, and curing, were also used to preserve it. These methods control bacteria growth by limiting the moisture, like drying, but also through the introduction of chemicals that kill the bacteria.

But what if you want to preserve something, such as milk, that will not keep for a long time and does not lend itself to one of these methods? Or what if you have some food you want to store for a short time, or you don’t have the time or materials to dry it, smoke it, cure it, or salt it? What will you do then? You’ll just put it in the refrigerator!

Early refrigerators were similar to today’s ice chests. People would mine ice and snow in the mountains, transport it to their locations, and place it either in a cave or in an underground chamber. Often, they would line the location with straw before putting the ice and snow in. This would insulate it and make the ice and snow last longer. These storage locations were the first “refrigerators.”

The World of Mechanical Refrigeration

Hauling ice and snow into caves and underground chambers is great if you have the ice and snow to bring in, but that is not the case in all places. People began to look at ways to create “cold.” This area of study falls under the discipline of mechanical engineering and is called “thermodynamics.” The term “thermo” means heat, and the term “dynamics” means motion. Thermodynamics is the study of controlling the motion of heat.