What is the source of the unique smell in freezers?
Sometimes, when you open your freezer, you might notice a strange, distinctive smell, even if nothing has been spilled or any food is spoiled. The YouTube channel
What is 'freezer smell'? - YouTube
According to MinuteFood, a major cause of the distinctive, strange smell in freezers is 'sublimation.' While melting is when a solid turns into a liquid and evaporation is when a liquid turns into a gas, sublimation is the phenomenon of a solid instantly turning into a gas. Common examples of sublimation include dry ice and air fresheners.
Water is basically in a liquid state at room temperature. When ice is left at room temperature, it melts into liquid water and then turns into gaseous water vapor. However, in a freezer, water remains in the state of ice and does not melt, but constantly sublimes little by little.
As an example of water continuously sublimating from its ice state, MinuteFood proposes the following experiment: Make a certain amount of ice, weigh it, and leave it in a freezer. If ice only turns into gas through the process of melting and evaporation, then it should maintain its weight in a freezer where it doesn't melt. However, in an experiment conducted by MinuteFood, the initial ice made lost 7g in just one week, about 3% of its total weight.
The same thing happens with food in the freezer: the water inside the food solidifies due to the low temperature, and sublimation begins wherever this solid water comes into contact with the air. This phenomenon, where food deteriorates due to sublimation and drying, is called '
Sublimation creates holes where water molecules once were. This allows oxygen to come into contact with food more easily, which is the cause of the strange smell in freezers. Oxygen is a highly reactive molecule that easily triggers chemical reactions, and oxidation can generate odor-causing compounds.
While food stored in the freezer is less likely to spoil, it will emit a certain unpleasant odor due to freezer burn and oxidation, even if it's not to the point of spoilage. These odors mix with aromatic compounds emitted from plastic packaging and the materials that make up the freezer itself, creating the distinctive smell of a freezer. Because sublimation and oxidation are constantly occurring, the smell of a freezer worsens over time. These odors can also cling to other foods, which is why ice that has been in the freezer for a while may develop a strange smell or taste.
One way to prevent freezer odors from becoming strong is to store food in airtight containers. If food is not exposed to air, water molecules will not be released into the freezer, and chemical reactions between food and oxygen will be suppressed. One reason why many cups of ice cream use a film in addition to a lid is to seal it and suppress sublimation and oxidation. Also, with frozen seafood and other foods, a 'glaze' is sometimes used, which covers the food with a thin layer of ice to prevent direct contact with air.
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