Make sure your freezer is freezing your food correctly and not leaving your family vulnerable with our temperature and maintenance guide.
Don’t panic, you’re not alone. Not many people know the ideal temperature for a freezer - even though it’s important.
Our guide will run through the basics of how cold should a freezer be, plus the reasons why setting the correct temperature is so essential.
The Ideal Freezer Temperature
When stored correctly, frozen food is incredibly safe and can be kept for many months. However, the key to this is having a freezer which is operating at the right temperature.
The US Food and Drug Administration (FDA) recommend that all frozen food is stored at 0°F or colder. This ensures that it will stay safe while in the freezer and won’t allow any bacteria to multiply or grow.
Contrary to popular opinion, freezing food doesn’t kill the majority of bacteria but it will prevent any more from growing.
When stored at 0°F, food is safe for an indefinite period but over time the quality will deteriorate. This is why most items have a maximum recommended freezing time.
If a freezer is above 0°F (-18°C), you cannot trust that the food has been kept safe. In the event of a power cut, most freezers will be able to maintain a suitably cold temperature for up to 48 hours, providing the door is kept shut.
If the freezer door has been opened repeatedly, or it has been longer than 48 hours, the freezer temperature will have climbed above 0°F and will no longer be keeping your food safely frozen.
How to Know Precisely What Temperature Your Freezer Is At
As mentioned above, the FDA say that 0°F is the optimal temperature for a freezer. The difficulty is how to tell what temperature it really is. You can open the door and poke at your food but that won’t confirm the working temperature.
Some older or more basic models of freezer don’t include a temperature, just a numbered dial. This allows you to increase the chill factor, but it doesn’t tell you what the temperature is.
In contrast, modern or deluxe freezers have an integrated thermometer so you can see exactly the temperature. This allows you to tweak as needed, to make sure that your freezer stays below the recommended temperature.
But here’s the kicker: no matter what type of freezer you have, you should be measuring the temperature independently. Relying on the integrated thermometer is not advisable because if it isn’t working properly, you won’t be able to tell.
To stay safe, you’ll need a freezer thermometer. This is not the same as a regular thermometer as it’s specifically designed to be able to handle very cold temperatures.
For an accurate temperature, you’ll need to place the thermometer very precisely in your freezer. The tip shouldn’t be touching any frozen food or else it will be measuring the temperature of this item rather than your freezer!
Clear a small space in the center of your freezer and make sure it doesn’t touch anything. Before you put your thermometer in, it’s a good idea to give the area a quick wipe down. Any ice or debris can affect the performance and give you a false result.
Once clean, hang the thermometer from the central rack, or stand it up. Make sure it’s secure and won’t fall over, close the door and leave the thermometer to acclimatize.
It will take 24 hours to get an accurate reading of your freezer temperature, but the results will be accurate and reliable, providing you with peace of mind.
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Why Freezing Food at the Optimal Temperature is So Important
The vast majority of foods can be safely frozen, except for eggs in their shell and canned goods. However, even canned goods can be frozen once removed from their can.
Being able to freeze an item and retaining its quality are two different things. An item can be safely frozen while still degrading the quality enough to make it distinctly unpalatable.
Some goods just don’t freeze very well, no matter what you do. This includes mayonnaise, lettuce and cream sauces. Other types of food respond well to freezing, but the conditions must be correct.
If the temperature isn’t at 0°F, we already know the food can spoil. If your freezer is warmer than 0°F, microbes can start to grow and multiply; eating this food could make you very ill.
The right temperature wards off the microbes and also retains the freshness of the food. This is one of the benefits of freezing; nutrients are locked in and the food is preserved at peak quality. When the temperature isn’t what it should be, freshness and nutrients are both lost.
Freezer burn can be another issue for food which hasn’t been kept at the right temperature and fully protected. This can occur when the packaging isn’t airtight and the item has been squashed up against frost in the freezer.
You won’t get ill from eating foods with freezer burn, but you might not enjoy it much. Freezer burn dries the food out, making it tough and leathery. It’s possible to cut the bits of the food away which have freezer burn, but in bad cases, you might need to discard the whole item.
This is why freezer temperature settings should be checked carefully to make sure your appliance is operating within the ideal range.
The Difference Between Freezing & Deep Freezing
You may have heard the phrases ‘freeze’ and ‘deep freeze’ being used interchangeably but they refer to very different processes.
Freezing is what is carried out in most homes, with recommended freezer temperatures of 0°F. This freezes food slowly, taking up to 24 hours to completely freeze an item.
This is practical for home use, but slow freezing can cause problems. Large ice crystals can form and rupture the cell walls of the food. The most delicate and fragile flavors may vanish and water may evaporate, leaving the item dry and tasteless.
By comparison, deep freezing is carried out on an industrial level and is managed extremely carefully to prevent food poisoning. Food is rapidly frozen at temperatures of -30 to -50 °C, taking less than an hour to freeze. In some cases, food can be frozen in a few minutes.
The advantage of this rapid freezing process is that large crystals don’t have time to form. The textures, freshness and flavors are well-preserved, allowing the food to retain its nutrition and taste.
Carrying out deep freezing is a precarious job and to achieve the final result successfully without any risk of food poisoning, a very precise set of processes must be followed.
Freezer Temperature FAQs
Struggling to get your freezer to work optimally? We answer some common questions that might be just what you're looking for!
Q: What temperature should a freezer be set?
A: The FDA recommends a freezer should operate at 0°F to keep food safe.
Q: What is the correct chest freezer temperature - is it different from an upright freezer?
A: There is no difference with a chest freezer, this should operate at 0°F
Q: How can I monitor the temperature of my freezer?
A: You should keep a freezer thermometer in your freezer. This allows you to check the temperature of your freezer easily.
Q: Can’t I just take the freezer temperature when I need to, without keeping a freezer thermometer in there?
A: No. It takes 24 hours for the freezer thermometer to accurately read the temperature. It’s also useful if you have a power cut. When the power comes back on you can check the thermometer to see if the food has been kept cold enough or whether it needs to be thrown away.
Q: How long is food safe to be kept in the freezer for?
A: In theory, food can be frozen indefinitely without affecting the nutrients. However, the longer an item stays frozen, the more likely it is to dry out or lose flavor.
The FDA therefore have recommended maximum times for different types of frozen food. These limits aren’t for safety, but quality.
Q: Do I need to throw out the contents of my freezer is there has been a power cut?
A: You may be able to keep your food items, especially if the correct freezer temperature has been maintained. Keeping the door closed until the power comes back on will give you the best chance of preserving your food so don’t be tempted to check and see how it’s going!
When the power returns, you can safely keep your food items if the thermometer reads 40°F or lower. If you don’t have a food thermometer, look for ice crystals in the food. If you see ice crystals, the food item can be refrozen.
Still got questions? Leave us a comment down below and we'll do our best to help out.