Refrigeration systems have come a long way since people used to pack food in warehouses and freight cars filled with slabs of real ice. Over the past century, the advent of mechanical refrigeration systems that lend themselves more easily to mobile refrigeration has been the catalyst for a drastic sea change in human nutrition and health. Due to the rise of mobile refrigeration units in freight cars and trucks, it became possible to transport perishable goods such as meat, dairy products and fruit over long distances. This revolutionised the way people ate, because they no longer had to rely on foods that were in season. Exotic fruits were suddenly being grown in California and shipped to Canada, or grown in the Mediterranean and shipped to Scandinavia. The greater variety of foods available made a more balanced diet possible, and in this way mobile refrigeration
was directly responsible for an increase in life expectancy and even an increase in average human height due to better nutrition.
Not only the variety of foods, but the kind of foods people ate began to change. A smaller amount of meat and dairy products were lost to spoilage, and this drove the prices of these products down. People began eating much more meat and dairy, which has been linked to both positive and negative health effects in various populations. An increase in leisure time was even driven by the more ready availability of these foods. People no longer had to make a trip to the market every day, and had more time to spare.
The modern advances
Today, perishable food is shipped around the world by way of ocean, railway and highway. Modern advances in mobile refrigeration technology have made this even more efficient than in the past. Refrigerated trucks are more likely to use liquid carbon dioxide in their cooling units as opposed to ice, and larger boats and freight trains largely rely on cyclic refrigeration, in which heat is mechanically pumped from the cooling unit into a heat sink. It's impossible to tell what the future may hold in terms of technological advances, but it's clear that mobile refrigeration has had an enormous effect on human progress, and isn't likely to diminish in importance anytime soon.