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How A Freezer Works: Science Behind Your Cold Food & Drink

For many of us, fortunate enough to live in a world of Wifi, electricity, and the usual mod-cons found in the west, a refrigerator is one of the essential items on the checklist when we move into our first home. Then, barring catastrophes, we will never be without one again.

Most people have a freezer unit attached to the refrigerator, but some go even further and have a dedicated freezer on the side. Hunters, homesteaders, and folk living a long way from the stores trust a freezer to keep food fresh even longer than a refrigerator will.

How A Freezer Works

Typically located behind the fridge, a compressor is an electric pump pushing refrigerant around a closed system of pipes inside and outside the refrigerator and freezer. This is how a freezer works:

The compressor pumps refrigerant gas into the coils seen outside the older units’ back, cooling to a liquid. High pressure forces the fluid along the line to an expansion valve, which drops the pressure, and low-pressure liquid refrigerant flows into the evaporator coils inside the freezer.

Any warmer food than the refrigerant will become colder by losing heat to the evaporator. The refrigerant converts to gas en route to the compressor, where the cycle repeats.

The warmer food releases heat to the refrigerant and thus cools down. The refrigerant will then heat up with the radiated heat, turning to gas. This transference takes the heat away from the freezer and returns the gas to the compressor. The gas is pumped back to the cooling coils from the compressor, continuing the cycle.

These coils are hidden from our sight in modern machines, but rest assured, they’re still there. Many old fridges/freezers had shelves made from the evaporator coils, but mainly for vanity, these coils are now hidden in the unit’s walls.

The basics are, of course, a little easier than the details, and if you’re cat-like in your curiosity, you will undoubtedly want to learn more. I’ll clarify several other aspects of freezers in the following few sections.

What Refrigerants Are Used In Our Freezers?

A refrigerant needs to be a substance that can quickly turn from a liquid to a gas and return to a liquid again with no degradation. Manufacturers initially used ammonia, but authorities found it toxic when leaked. 

Freon, a brand name of the Chemours company, is a Chlorofluorocarbon (CFC) used for many years but was blamed for the damage to the Ozone layer and phased out under the Montreal Protocol.

Companies primarily use hydrofluorocarbons (HFCs) as refrigerants; int. al. Iso-butane, a colorless, odorless gas, is one example.

Why Refrigerant Is Important To Keep Freezers Cold

Even though there are several refrigerant properties, if we look at the situation from an environmental perspective, we can see that the most important ones are ozone depletion potential (ODP), global warming potential (GWP), and level of flammability. 

Since the refrigerant stays inside the refrigeration system, why are ODP and GWP considered necessary? Refrigeration systems all tend to leak. These leaks may occur through contraction and expansion at welds in refrigerant piping, systems recharging, or during the freezer’s eventual disposal. The lower the ODP and GWP numbers are, the less risk to nature.

Modern refrigerants have an ODP of zero, making them perfectly safe for the Ozone layer. Still, if you’d like to know what refrigerant your freezer is using, check the nameplate of your unit – it should be noted.

I suggest you always use an EPA-certified refrigerant reclaimer when you finally dispose of your freezer, and then ensure that natural refrigerants cool the replacement fridge/freezer.

How Long Can Food Last In a Freezer?

No one can give you a definitive answer, but provided microorganisms are not permitted to thrive in and on your food, you may be good to go indefinitely. According to the United States Department of Agriculture (USDA), your freezer must remain at 0 degrees F (-18 degrees C) to do this. However, just one power outage and your temperature chain will be compromised.

Since you and I don’t live in extremes, but in the real world, let’s consider something infinitely more practical:

The USDA recommends that you toss all frozen food in adherence to the following timeline:

  • Cooked food after three months
  • Uncooked ground meat after four months, and
  • Un-cooked meat after 12 months.

You’ll notice that fish, fresh vegetables, and fruit are not covered here, so I contacted the biggest fishmonger in my city, and he recommends we toss fish after four months if vacuum sealed. He adds that adding newspaper wrapping to the pre-sealed fish will help prevent freezer burn. 

Vegetables can last eight to ten months in a freezer if adequately frozen. Fruit will need to be blended, possibly into smoothies, or used in baking and last a year.

Foods You Can Freeze In A Freezer

Done carefully, you can freeze just about any food, though some will not thaw as well as others and may have to be used by you in different ways. 

Vegetables with high moisture content are most tricky as the freezing process breaks down the cell walls resulting in mushy veg when defrosted, but these can be blended or added to ratatouille, stews, soups, etc.

I generally avoid freezing leafy greens like cabbage, spinach, and lettuce which are lifeless when thawed, but I know folk who will add defrosted spinach to smoothies. 

You may freeze peas, carrots, corn, broccoli, cauliflower, squash and green beans, and more for pasta, casseroles, and soups.

Blanching can be helpful. Vegetables benefit from being blanched before freezing. You need to rinse and prepare veg for cooking as you normally would. Remove stems, roots, any damaged bits, and shell fresh peas and beans. 

If you usually peel the vegetable before cooking, do so now. Chop larger pieces into a uniform size for even blanching.

Preparing Food for Freezing

If you click on the hyperlink below, it accesses a page where The National Center for Food Preservation offers guidelines on how long to blanch different foods before freezing.

  • Blanch one type of food at a time as different foods take different times to blanch properly
  • Heat a pot of fresh water to boiling point
  • Have an Ice Bath ready nearby
  • Place the food into the boiling water for the recommended time
  • When done (they should still be firm,) place them in the cold water
  • Once cool, remove and pat dry with paper towels. Do this correctly to avoid freezer burn later.

You may want to freeze the veg on a sheet pan in the freezer. Spread the individual pieces out to not touch one another and leave them in the freezer overnight. Once they are frozen, you should transfer them to clean, freezer-proof bags or other containers. Remember to date them. 

Common Freezer Problems

Setting The Temperature Too High

We best store food at, or colder than, 0 degrees F (-18 degrees C), so don’t try to save money by setting it a little warmer to avoid requiring a chisel for the ice cream, say. This belief may cost you far more in the long run.

Freezing Food For Too Long

Label your food well, as we discussed earlier, and perhaps even rotate the items if you have a large freezer so you forget nothing until you discover it years later.

Losing Small Items Like Herbs and Chili Peppers

You might want to dedicate a freezer-safe container into which all small objects are placed and never overlooked.

Whenever cooking, I consider the possibility that freezing might be required, and if it is, I do so as soon as the food cools. This seals in the most flavor possible.

Keeping The Freezer Nearly Empty

You might think this will save power costs, but it does just the opposite. Frozen food helps cool the freezer box, whereas the empty area will not retain cold as efficiently as the food can and requires more cooling.

Despite carefully packing the freezer according to date, types of food, etc., We should take care never to close any vents off, as this will undoubtedly lead to extra running costs and could lead to repairs being required by yourself later.


Learn more about refrigerators below.

Is a Smart Fridge Worth It? Here’s The Truth!

Is It Safe To Have a Mini Fridge In The Bedroom? Learn Here

What Refrigerators Make Craft Ice (Ball Ice)?

Where Does The Water Come From In a Refrigerator?

Why Does A Refrigerator Need Wifi?

Why Does A Refrigerator Freeze Up? Learn Here

What Refrigerators Are Made In The USA

How Does a Refrigerator Make Ice? Full Tutorial

A freezer – and a refrigerator – can last you for many years. Treat it well, and it will keep your family safe from spoiled foodstuffs and supplied with the essential things in life, like ice cream.

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