�Who doesn't have some frozen food in their fridge? It is so convenient that few chefs can resist. But do we really know the properties of these foods, what processes they undergo and whether they are healthy? Although they meet minimum health standards, it is not a bad idea to know a bit more about these foods we keep at sub-freezing temperatures and which have become regulars at our dinner table.

What are they?
Freezing is a process of conserving things at temperatures below zero degrees centigrade. It lets us eat food long after it has been harvested and cooked. But to do it with guarantees of safety takes care, speed, strict hygiene and foods that are at just the right point of freshness and ripeness.

The big advantage of freezing is that it barely changes foods' composition, flavor, look and nutritional qualities

The process consists of lowering a food's temperature, generally to -20 or -30 degrees centigrade. This slows down biochemical processes and microbacteria present inside the foods. Be they friend or foe, microorganisms don't die, they simply go into a state of dormancy. During freezing the water inside food solidifies and salts become concentrated.

In order to achieve the desired conserving effect and minimize physical, chemical and microbiological changes, the speed of the process must be optimal (the faster, the better), the packaging adequate and the storage temperature the right one.

The foods which have the longest freezing tradition are fish and vegetables. In the case of fish, the process is done at sea on huge freezer ships as soon as the creatures are caught. No more than three hours should go by from the time the fish are pulled from the sea. In the case of vegetables the freezing is done immediately. Before being frozen, the vegetables are washed and blanched, which destroys part of their nutrients, mainly vitamin C. This is why you should not thaw vegetables to cook them because it would mean losing nutrients yet again. The frozen water contains most of the vegetables' minerals.

Many studies say loss of other substances such as B vitamins, present in fish and meat is negligible, but nearly 60 % of vitamin A is lost to oxidation.
Neither fish nor vegetables should lose flavor because of freezing. If they do, they have not been frozen properly.

The quality of frozen and pre-cooked foods (empanadillas, croquettes and lasagna) - which fill freezers at supermarkets - depends on how they have been prepared and the raw material used. It must be pointed out that freezing does not make this kind of food less advantageous.

Buying frozen, freezing at home
Because of their busy work schedules and a lack of time, more and more families cook once a week, then freeze. The makeup and origin of the food is known in these cases, so if there is a problem it has to be in the process of freezing.

It should be done right after a dish is prepared, once it has cooled. Don't use a lot of salt because it makes freezing more difficult, or a lot of fat. In making sauces it is best to use cornmeal as opposed to wheat flour, which does not freeze well, and recipients which can be placed in the oven.

It is best to freeze small portions of food depending on how much is going to be eaten and use adequate bags which are to be marked with the date of cooking. Keep food that is to be frozen from touching food that is already frozen, and make sure the freezer is at its coldest. There is a basic rule which must be observed always: no frozen food should be thawed then frozen again.

Another maxim is never break the so-called chain of cold. That is, if you buy a product frozen keep it as short a time as possible at room temperature if you are not going to cook it right away. Thus, at the supermarket, choose frozen foods last.

In order to thaw the best technique is to put the food in the refrigerator, and when there is no longer any ice visible, cook it. Other equally good and faster options are to put the food under a faucet with hot water running or in a microwave oven, so long as you set the time and temperature to thaw. Frozen foods can be stored for three to six months, depending on the food in question and the strength of the refrigerator.
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