Frozen foods: properties and conservation

Frozen food they can be much more nutritious than many fresh foods because they are able to retain most of the original nutrients present in freshly picked foods and retain, with minimal alterations, the organoleptic characteristics and nutritional properties. Let's find out better. 

> 1. History of food preservation

> 2. What is deep freezing

> 3. What are the differences between deep-frozen and frozen foods

> 4. Properties of frozen foods

> 5. Precautions for storing frozen food

Frozen foods: properties and conservation




History of food preservation

The history of food preservation we can say that it marches hand in hand with the history of the man who from the beginning felt the need to take advantage of the moments of great availability of food to stock up for the most difficult moments.

Of course, at the beginning it was a rudimentary conservation due to instinct and observation of natural phenomena. The salt of the sea, the heat of the sun first and the fire afterwards were the first means that man used to preserve food.

At the time of the Romans we find more advanced techniques; they had intuited that there must be something in the air that did not allow the preservation of food and that they called the "air corrupting principle". To remove the foods from this "corrupting principle" they had to avoid contact with the air and so they kept them by placing them in large amphorae which, completely covered with melted wax or cedar oil, closed in the best possible way and buried them.

However, they were always conservation techniques based on empirical notions because the existence of bacteria and enzymes was not yet known. We have to get to modern times for the problem of food preservation to be scientifically re-proposed.

Compared to the past, the need to preserve food does not arise from the need to preserve food for times of famine but rather from the fact that many foods are not available at all times of the year, having productions, a seasonal and non-seasonal trend. they can be found everywhere for geographical and environmental reasons.

Conservation, the purpose of which is to stop the biochemical processes of decomposition, allows the use of foodstuffs over time and space.


What is deep freezing

Freezing is a preservation method with physical means (including heat preservation) in which a change in the state of the water contained is created both inside and outside the cells that make up the food.

Water passes from a liquid to a solid state and in freezing it forms crystals, the number and size of which are closely related to the cooling rate.

Since the number and size of the crystals play a fundamental role in the preserve the nutritional value and organoleptic characteristics of the food, faster cooling allows the formation of "microcrystals" that only partially damage the cell walls without breaking them and thus preserving all the original organoleptic characteristics of the food.

It is in this context that frozen foods are inserted in which freezing is defined "ultra-rapid freezing". Since the temperature to which a frozen food is subjected is -40 ° C and -50 ° C, there is a simultaneous freezing cells and all its constituents while preserving all the components of the food.

Furthermore, it is not only the temperature that counts in freezing, but also the speed with which freezing occurs which takes place from a minimum of a few minutes to a maximum of 4 hours in relation to the size of the product put to freeze.


What are the differences between frozen and frozen foods

The substantial difference between the two types of food lies in the different freezing speed foods are subjected to.

A slower freezing speed means that, in frozen foods, the crystals that derive from freezing water are "macrocrystals" and therefore sometimes larger than the cells with consequent breakage of the same (the cells seem emptied of their contents) and unavoidable spill of cellular content.

At the time of defrosting, therefore, there is a dripping of liquids rich in nutrients and a depletion of the food, both in nutritional and organoleptic terms. 

The substantial difference therefore between the two types of food is that in the frozen one there is considerable alteration of the product both of a physical nature, especially in terms of color and flavor and chemical with an increase in protein degradation products. In the frozen food, on the other hand, the original organoleptic characteristics of the food are almost completely maintained.

We can only buy a frozen food because it is one technique feasible only industrially because of the low temperatures to be reached while a frozen food can be obtained both at an industrial level and at a domestic level thanks to the widespread use of the refrigerator and the use of the freezer.


Properties of frozen foods

Since the growth of microbes is inhibited by cold (microbiostatic action), deep-freezing is one of the most effective ways of preserving of foodstuffs with minimal alterations of organoleptic characteristics and nutritional properties.

Freshly picked fruits and vegetables immediately begin to lose nutrients when they arrive at the supermarket counter after several days or weeks. Frozen food is ultimately much more nutritious because it can retain most of the original nutrients present just picked at a lower cost.

A possible deterioration of food stored in this way occurs only if it is the cold chain is broken.
It is good to point out that the cold however, it does not have a healing or sterilizing action; therefore foods to be stored at low temperatures must be hygienically perfect.


Tips for storing frozen foods

The tricks to keep frozen foods at the best of their nutritional and quality characteristics are simple.

At the moment of dell´acquisto:

  • buy frozen foods at the end of the shopping and place them in the appropriate thermal bags or thermal boxes to slow down thawing;
  • go home as quickly as possible and immediately place them in the freezer compartment;
  • if the packaging has traces of frost on the surface, it means that the cold chain has been interrupted at some point and thawing has begun, the food could be damaged and even polluted;
  • check the thermometers placed inside the refrigerator, one is placed in correspondence with the maximum loading surface, the other at half height. Both must report a temperature equal to or below -18 ° C. If one of the two thermometers shows higher temperatures (-16 ° C / -14 ° C) perfect preservation of the products is not guaranteed.

At home:

  • periodically check the freezer temperature which must always operate at -18 ° C. Frozen foods cannot be stored at higher temperatures, otherwise they will be damaged;
  • la shelf life varies depending on the freezer. Check the international symbols for temperatures, such as: **** (- 25 / - 30 C) and *** (- 18 C) you can keep frozen foods until the date indicated on the package; ** (- 12 C) allows you to keep frozen foods for a month; (- 6 C) frozen foods can only be kept for a few days.


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