All temperatures in this article are expressed in degrees Celsius.
Remember the formula
ºF = ℃ * 1.8 + 32
When we are not going to consume a product in the next few days or we buy it already frozen, we take it for granted that we will be able to keep it in the freezer for a long time without fearing it will spoil. This is true if we take a series of precautions, if we choose foods that are suitable for freezing and if our freezer is adequate. Therefore, to ensure that the food does not lose nutrients or properties with freezing and remains equally safe, we have to carry out a series of guidelines and recommendations.
Freezing is one of the oldest and most effective ways to preserve food. By keeping food below zero degrees, the water it contains freezes, which prevents microorganisms, such as bacteria, from reproducing, at least at the same rate. In addition, we avoid oxidation and rancidity and the food is preserved without decomposition for longer. The time that this food can remain in the freezer without deteriorating will depend on both the type of food and the temperature of the freezer, which is determined by the stars in the freezer. Roughly speaking, according to these stars will be discussed:
- 1 star: -6ºC minimum temperature, the food should only remain in it for a few hours.
- 2 stars: Minimum temperature of -12ºC. Food can be kept frozen for up to three days.
- 3 stars: Minimum temperature of -18ºC. This is the most common conservation temperature, and the food can last for months frozen without deteriorating.
- 4 stars: -24ºC the freezing is faster and allows to freeze more food and for longer time.
Depending on the food, there is a maximum time that the food can remain without deteriorating. Thus, while minced meat, pork or fatty fish are not recommended to be frozen for more than three months, lean fish will be preserved perfectly for about six months and whole meat of lamb, chicken or have it and vegetables can remain between 8-12 months without deteriorating.
Except for some parasites, freezing does not eliminate microorganisms, but stops their growth for a certain time. Therefore, as with fresh food, a series of precautions must be taken when handling them.
- Package the products in small portions. In this way, as well as organising the portions better, freezing will be quicker and involve fewer food risks.
- Use airtight plastic bags for freezing. They should only be used once, with the least amount of air possible, and it is convenient to remove as much air as possible, but with a little space so that they do not explode when expanding. Airtight containers and transparent film are also a good option.
- Put a date on all packages, and use the “First in, First out” criterion.
- The best temperature to keep frozen food at home is -18º. To freeze them, you can go down to -25.
- It is not recommended to refreeze a thawed food. Successive freezing reduces the quality of the food and facilitates contamination. Freezing a cooked food that is made with thawed food would not be as problematic.
- Be careful to break the cold chain, because it favors the oxidation of the food and the greasy rancidity, yellow tones and burns that cause a loss of quality in the product.
- Before freezing cooked food, it is necessary to let it cool down completely so as not to break the cold chain of already frozen food.
- Fill the freezer and do not leave much space between the foods. Freezers work better when they are full and, with less air inside, the food dries out less.
When defrosting it is recommended:
- Leaving defrosting for 24 hours in the lower part of the refrigerator is the best option. If we do not have time, we can use the defrosting function of the microwave, although the defrosting will not be homogeneous and its texture can be damaged, especially in meat and fish.
- Stews defrost in the microwave much better.
- It is not safe to defrost at room temperature or in the sink, much less in the sun, as this allows bacteria to grow quickly.
- Some vegetables can be cooked directly frozen.
- Once thawed, food must be cooked quickly, and at a temperature of at least 70 degrees.
Both when freezing and defrosting, food must be handled with the utmost hygiene: with hands and on clean surfaces, without mixing it with other foods…
There are foods that, due to their characteristics, it is not advisable to freeze them, mainly because they lose properties, quality and textures and are no longer suitable for consumption.
- Fatty meats. All greasy foods, in general, resist freezing poorly. In case we want to freeze a fatty meat, it is advisable to remove the fatty part first, because the process of freezing the fat is slower than the lean part.
- Foods rich in starch, such as cooked potatoes, rice or pasta. These foods can be frozen, but their texture, once thawed, will be much less appetizing, especially that of the potato. Vegetable stews or broths, on the other hand, do hold up quite well.
- The fruit. With the exception of some red fruits, the fruit does not stand freezing well, as it loses its texture and flavor. It is only recommended to freeze it peeled and cut and if we are going to cook it later.
- Vegetables that are intended to be eaten raw. Like fruit, vegetables in general, lose their texture with freezing, so in case of vegetables that are not going to be cooked, it is better not to freeze them, like tomatoes, cucumbers or lettuce.
- Cakes and pies. If we buy them already frozen it is because they have gone through an industrial deep-freezing process that guarantees that they retain their properties, but this is not something we can do at home, so homemade cakes should not be frozen, especially those with a high content of cream and other fatty ingredients.
- Eggs. They cannot be frozen because, with their shells, they explode, both raw and cooked. Milkshakes can be frozen, although this is not very common.
- Fish. A fish that we buy frozen is suitable for freezing as long as the cold chain has not been broken. If we buy it fresh, we should previously remove all the viscera and scales.
- Dairy products. In general, they do not freeze well and the texture once thawed is very different. The most cured cheeses are those that best endure freezing after a few months, never more than six.
- Seafood. It depends on the seafood, since some, like barnacles, should not be frozen and others, like spider crabs or crab, must be previously cooked.