How to

2 June 2016

The Science behind Refrigeration/Freezing for Preservation

Refrigeration and home freezing have been a prevalent form of food preservation for generations. In fact, we know that snow and ice were harvested solely for the preservation of food as far back as 1000BC. Refrigeration as we think of it, however, began with Scottish professor William Cullen in 1755.

Cullen created the world’s first artificial refrigeration system, which was publicly demonstrated for the first time the following year, using a system of pumps to create a partial vacuum around a container of diethyl ether. When boiled, the diethyl ether absorbed heat from the surrounding air. Although the experiment was a success, it was deemed to have no practical application at the time.

From there, research shifted into vapour-compression refrigeration. As far back as 1758, a collaborative effort between Benjamin Franklin and John Hadley proved that by evaporating volatile liquids such as alcohol and ether, you could lower temperatures to below the freezing point of water. It was not until 1834 that Jacob Perkins made the world’s first working vapour-compression refrigeration system. A success in theory, the system failed commercially.

Since that point, the exact methods have steadily evolved. Generally these changes involved making use of new, safer chemicals intended to make home refrigeration viable. A big leap came in 1930, when Frigidaire successfully synthesised Freon, also known as CFC. The new chemical gained widespread use due to the perceived safety of the product, but since it was proven in the 1970s to be damaging to the atmosphere, today’s refrigerators make use of another type of gas. Known as tetrafluoroethane or HFC-134a, the modern gas is a much safer substitute.

So that covers the basics of how home refrigeration as we know it came about, but why does it work? We know that certain bacterial life forms can withstand conditions much more severe than the inside of your freezer, so how does your freezer manage to put a stop to the bacteria?

Simply put, it doesn’t. Refrigeration doesn’t actually kill the bacteria present; it just slows it down dramatically. Refrigeration slows down bacterial growth to the point that a day’s worth of normal growth takes around a week, give or take, whereas freezing renders the bacteria completely inactive. Make no mistake though, it’s not dead, merely safe to consume.

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.