Eli5: How does freezing food at -5 or -15°C make a difference, if water already freezes at 0°C?

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Hi! While unfreezing my ice box I put various groceries on the porch, as it is around -5°C at the moment. When I checked the packaging, I noticed that the date the food was supposed to be consumed by, varied widely, depending on the temperature. From 3 days (-5°C) to around a year (-15°C). How does it make that big of a difference? Is the water not equally frozen at both temperature points?

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Anonymous 0 Comments

Regular kitchen freezers usually go through a regular defrost cycle. That means the freezer shuts off and is allowed to warm to just above freezing for short periods of time. This reduces frost buildup, but it comes at the cost of food not lasting as long due to the slight thawing and refreezing. The food never completely thaws, it never comes even close to that…but the cycle takes a toll.

Deep freezers both achieve a colder temperature (better at reducing bacterial growth) and they hold that constant cold temperature forever…so no wear and tear on the food due to temperature cycling.

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