During the freezing process, three temperature ranges can be distinguished in the center of the product: from +20 to 0 °С, from 0 to -5 °С and from -5 to -18 °С (see Fig. 1, curve 1).
At the first stage the product is cooled from +20 to 0 °С. The decrease in the temperature of the product here is proportional to the amount of heat extraction work.
At the second stage there is a transition from the liquid phase to the solid at temperatures from 0 to -5 ° C. The work on the removal of heat from the product is very significant, however, the temperature of the product practically does not decrease, and about 70% of the liquid fractions of the product crystallize, which we call freezing.
On the third- there is a freezing at product temperatures from -5 to -18 °C. The decrease in temperature again goes in proportion to the work performed by the refrigeration machine.
Fig.1.
Traditional freezing technology, implemented in the form of so-called low-temperature refrigerators, assumes a temperature in the chamber of -18 ÷ -24 °С. Freezing time in refrigerators is 2.5 hours or more. During freezing, the speed of the process acquires a decisive role. A close connection between the quality of the product and the rate of freezing has been established. Numerous experimental data testify to the influence of the freezing rate on the size of ice crystals, on structural and enzymatic changes in products. The idea of shock freezing technology is to force the modes of cooling, freezing and freezing of products (see Fig. 1 curve 2). This forcing is provided by two means of increasing the rate of heat removal from the product: lowering the temperature of the medium to -30 ÷ -35 °С; accelerated movement of the coolant (in the role of which air acts in the chamber), which is ensured by the ventilation of the evaporator and, accordingly, by intensive blowing of the product. It should be noted that a further decrease in temperature leads to unjustified power consumption and increased deformation of the product, the unevenness of the process becomes too great.
Benefits of shock freezing
Compared to the traditional method of freezing on racks in cold rooms, the advantages of using quick freezers are as follows:
freezing time is reduced by 3-10 times;
production areas are reduced by 1.5-2 times;
the production staff is reduced by 25-30%;
the payback period is reduced by 15-20%; Consider one of the practical results of the application of shock freezing technology.
total freezing time. If with traditional technology the total freezing time for dumplings and cutlets is 2.5 hours, then with quick freezing it is ~ 20-35 minutes, which gives a significant economic effect. The time for passing the second stage is reduced from 1 hour to 15 minutes.
Fabric structure
The high cooling rate ensured by the shock temperature in the chamber (-30 ÷ -35) °C and the intensive blowing of the product allows for a forced transition from the liquid phase to the solid phase. In this case, ice crystals are formed in much smaller sizes and almost simultaneously in the cell and intercellular partitions (cells remain intact). As a result, the tissue structure of a fresh product is preserved almost unchanged, and better than with other methods of preservation.
Ecology and biochemistry
The absence of any thermal and chemical treatment (with the exception of blanching and ascorbic acid treatment, provided for by the technology for some types of vegetables and fruits) and, as a result, the invariance of protein types make quick freezing a method that absolutely does not impair environmental cleanliness and biochemistry product.
Bacteriological purity
Due to the speed of freezing, the periods of activity of the bacteriological medium are also reduced. Bacteria of different types have different (including below 0 °C) temperature zones of vital activity. During slow freezing, traces of the vital activity of each of these types of bacteria appear and remain in the product. During shock freezing, a number of types do not have time to develop.
The weight loss of the product resulting from the evaporation of the liquid (shrinkage) during freezing is normally up to 5-10% (depending on the temperature in the chamber and the product being frozen). The forced freezing mode reduces weight loss to 0.8%, which also gives a significant economic effect.
Taste and nutritional value
Due to the prevention of drying during quick freezing, aromatics and nutrients do not have time to leave the product, which preserves its quality. Nutritional value and taste remain unchanged.
Shelf life
The shelf life of quick-frozen foods is longer than those frozen in conventional chambers. Quick-frozen foods retain their qualities better during long-term storage than fresh ones. Thus, the technology of shock freezing ensures the preservation of the quality of a fresh product, and does it better than other methods of harvesting and storage.
Quick frozen foods
Frozen products, semi-finished products and ready meals are popular all over the world. Their consumption in countries such as the UK, Denmark, Finland, France, Germany, Sweden, Switzerland, the USA and Japan ranges from 40 to 100 kg per person per year. Moreover, their production in these countries increases by 5-7% annually.
In world practice, the range of products preserved by quick freezing is extremely wide. Moreover, each country produces, first of all, products specific to the region, climate, and traditions.
In recent years, quick-frozen products have been especially intensively produced:
fruits, berries, vegetables, gourds, herbs and combinations of them;
ready-made first and second courses, pies, bakery and confectionery products;
semi-finished products (meat, fish, etc.), such as entrecote, steaks, hamburgers, meatballs, sticks, sausages, dumplings and dumplings;
desserts, juices, puddings, jelly, ice cream, etc.
What is the attraction of quick-frozen foods:
the product is almost completely free from inedible inclusions;
essentially "waste-free" (other than packaging);
practically does not differ from fresh - retains all the original, natural properties;
inherently dietary, conditioned;
packaged, dosed, portioned (this is convenient for any consumer);
the quick-frozen product is strategic (for trade, public catering, end consumer);
does not require attention during storage, and is always ready for use;
requires minimal time (minutes) and labor for its preparation.
Shock freezing technology opens up completely new possibilities. It brings the business to a higher level of its development. Quick freezing allows you to delay the sale of agricultural products in time and move the place of sale in space. This is a kind of transport that expands the scope of sales of products not only by the region where it is grown and the harvest season, but also by other regions and seasons. This is a transport from summer to winter, from the field to the table. For example, for farms, this is the opportunity to freeze part of their products and sell it directly to the consumer at a higher price than fresh, anywhere and at any time.
In Russia, the market for quick-frozen products was initially focused mainly on imported products. Now the priorities are shifting towards domestic production. Although the share of imports of fresh frozen fruits and vegetables is still large. According to various data, about 40-60% of vegetables and fruits fall on the share of imports in Russia. At the same time, a very significant part of imported products enters the country illegally. According to various estimates, over the past five or six years, the share of imported vegetables has increased by about two to two and a half times. According to the Federal Customs Service of the Russian Federation, in the structure of "white" vegetable imports, the largest share is occupied by onions (38%) and tomatoes (27%). The share of other vegetables is relatively low: root crops - 4%, cabbage - 12%, other vegetables - 9%. According to Finam Management estimates, the entire Russian fruit market in 2007 amounted to about $15-20 billion. According to various estimates, imports account for 60 to 80%.
The undeniable advantages of shock freezing technology make it possible to recoup the reasonable costs of quick-freezing equipment in a fairly short time. In addition, shock freezing technology is becoming a kind of standard for producers and consumers of frozen products, without which it is difficult to sell them.
product losses are reduced by 2-3 times;
Shock freezing does not cause changes in the structure and chemical composition of food products. It is based on the features of liquid freezing. The essence of the method is to cool food at a rate at which water microcrystallization occurs. But this is not a simple freezing, because the volume of ice crystals in relation to the initial volume of the liquid substance does not increase. Here the main criterion is the rate of freezing, and not the temperature regime.
The essence of the process of shock freezing
Speaking about this method of preserving products, we are not talking about a set of special technological equipment, but about achieving the result of liquid microcrystallization. Shock freezing includes three stages: cooling, freezing and freezing. The temperature of the chamber reaches -40°C, and due to the ventilation of the evaporator, there is an accelerated movement of air in this chamber. A greater decrease in temperature and an increase in airflow is not advisable, because in this case power is unjustifiably spent, and the products begin to deform. If at the stage of freezing, then the process will be significantly accelerated.The main difference between shock freezing and conventional freezing is explained simply. In the usual, ice crystals are formed, the size of which is larger than the size of a water molecule. Because of this, the moisture that freezes in the product changes the structure of the food and destroys it. Food frozen in the usual way, when defrosted, loses its shape and valuable nutritional qualities. In the process of shock freezing, the resulting ice crystals do not exceed the size of a water molecule. The structure of the product in this case does not suffer, and when defrosted, the beneficial properties of food will not go anywhere.
Advantages of quick freezing
The advantages of shock freezing are obvious. If you freeze cutlets in the usual way, it will take at least 2.5 hours, and with a fast one, 30 minutes will be enough. Shock freezing produces smaller ice crystals. At the same time, the products retain their attractiveness for buyers, since their shape is not affected. Also, the advantage of quick freezing is that there is no weight loss of the product and the development of bacteria. At a high freezing rate, bacteria simply do not have time to develop and leave traces of their vital activity in food. The period of activity of pathogenic bacteria is minimal. In terms of shelf life, quick-frozen foods have a much longer shelf life than foods frozen in a conventional freezer.As you know, the best way to increase the shelf life of freshly prepared products is rapid cooling and freezing.
When traveling abroad, many of us noted how abundant a variety of "freezing" is represented there. Probably, the reason for this phenomenon lies in the fact that the Western buyer appreciates the opportunity to load the refrigerator for several weeks in advance and not waste time on daily shopping trips, and the manufacturer understands the convenience of selling his often perishable products - anywhere and at any time. In perestroika times, frozen food, mainly of foreign production, began to actively fill the counters of domestic stores. Noticing the interest in this product, our entrepreneurs began to study the technology of quick freezing (shock freezing).
The need to reduce night shift work, save human resources, and expand the range of products for the end customer is a key factor in the fact that blast freezing equipment is an indispensable tool for all modern production shops. Not only shock freezing down to -18°C, but also rapid cooling up to +3°C allows you to work more efficiently, reducing the time for product preparation, reducing the amount of space required for storing finished products and increasing the quality and safety of products.
Consider the technology of shock freezing products.
During the freezing process, three temperature ranges can be distinguished in the center of the product from +20 to 0 °C, from 0 to -5 °C and from -5 to -18 °C.
At the first stage, the product is cooled from +20 to 0 °C. The decrease in the temperature of the product here is proportional to the amount of heat extraction work.
At the second stage, there is a transition from the liquid phase to the solid phase at temperatures from 0 to -5 °C. The work on the removal of heat from the product is very significant, however, the temperature of the product practically does not decrease, and about 70% of the liquid fractions of the product crystallize, which we call freezing.
At the third stage, freezing occurs at product temperatures from -5 to -18 °C. The decrease in temperature again goes in proportion to the work performed by the refrigeration machine. Traditional freezing technology, implemented in the form of so-called low-temperature refrigerating chambers, assumes a temperature in the chamber of -18 and -24 °C. Freezing time in refrigerators is 2.5 hours or more.
During freezing, the speed of the process acquires a decisive role. A close connection between the quality of the product and the rate of freezing has been established. Numerous experimental data testify to the influence of the freezing rate on the size of ice crystals, on structural and enzymatic changes in products. The idea of shock freezing technology is to force cooling, freezing and freezing modes. This forcing is provided by two means of increasing the rate of heat removal from the product: lowering the temperature of the medium to -30 - -35°C; accelerated movement of the coolant (in the role of which air acts in the chamber), which is ensured by the ventilation of the evaporator and, accordingly, by intensive blowing of the product. It should be noted that a further decrease in temperature leads to unjustified power consumption and increased deformation of the product, the unevenness of the process becomes too great.
Benefits of shock freezing
Compared to the traditional method of freezing on racks in cold rooms, the advantages of using quick freezers are as follows:
- Product losses are reduced by 2-3 times;
- Freezing time is reduced by 3-10 times;
- Production areas are reduced by 1.5 - 2 times;
- The production staff is reduced by 25 - 30%;
- The payback period is reduced by 15 - 20%.
Consider the practical results of the application of shock freezing technology. total freezing time. If with traditional technology the total freezing time for dumplings and cutlets is 2.5 hours, then with quick freezing it is 20-35 minutes, which gives a significant economic effect. The time for passing the second stage is reduced from 1 hour to 15 minutes.
Waste reduction.
Rapid cooling and shock freezing increases the shelf life of products, which allows you to use all prepared products and raw materials, while reducing possible waste.
Reducing weight loss.
After cooking, the product releases moisture through evaporation. Rapid cooling immediately after cooking stops the evaporation process, thereby reducing the loss of water and weight of the product. If a product is sold by weight, savings on purchases can be up to 7%.
Ecology and biochemistry.
The absence of any thermal and chemical treatment and, as a result, the invariability of protein types make quick freezing a method that absolutely does not impair the ecological purity and biochemistry of the product.
bacteriological purity.
When shock freezing is used, the period of activity of the bacteriological medium is also reduced. Bacteria of different types have different temperature zones of vital activity. With slow freezing, traces of the vital activity of each type of bacteria appear in the product, and remain, while shock freezing is used, many of them simply do not have time to develop.
Reducing moisture loss.
The palatability of a product is very often associated with the optimal amount of moisture in the product. Rapid cooling immediately stops the evaporation of moisture from the product, thereby preventing excessive dehydration.
Shelf life.
The shelf life of quick-frozen foods is longer than those frozen in conventional chambers. Quick-frozen foods retain their qualities better during long-term storage than fresh ones. Thus, shock freezing ensures the preservation of the qualities of a fresh product and makes it better than other methods of harvesting and storage.
Shock freezing equipment
What can be advised to manufacturers for freezing food and vegetables? In our opinion, the best solution is the use of quick freezers based on spiral conveyors.
The spiral belt conveyor is the most versatile and easy to use. They allow you to freeze products of various sizes and shapes, both in bulk and in trays, in addition, it is possible to simultaneously freeze products and vegetables of different types with further separation by grade at the exit from the conveyor.
Conveyors are structurally made in the form of one or two spirals, in addition, a variety of mutual arrangement of the loading and unloading sections of products is possible.
The spiral conveyor provides:
- automatic loading of the product to be frozen and its distribution along the belt;
- freezing food and vegetables in a refrigerator (quick freezer);
- automatic unloading of the frozen product on the outfeed conveyor, or directly into a plastic container (box).
Operating principle.
The product enters the machine and moves in it with the help of conveyor belts. Tapes are installed at different levels. The speed of the belts is regulated smoothly and in a wide range. Tapes are made of fabric-polymer or rubber-woven materials approved for contact with food products. The frozen product is taken out through the receiving hopper for feeding for packaging.
Advantages.
- Product losses during freezing from drying within 1.5-3%;
- maintaining the quality of the product;
- reduction in unit cost of production;
- reduction of production space and maintenance personnel.
The quick freezer has a number of advantages compared to the traditional technology of freezing in refrigerating chambers. So, for example, if conventional refrigerators are used to freeze dumplings or cutlets, it will take 2.5 hours. To reduce the freezing time to 20-35 minutes. you need to use a blast freezer. In this case, ice crystals are formed in much smaller sizes and almost simultaneously in the cell and in the intercellular partitions. As a result, the tissue structure of the product is preserved better than with other methods of preservation.
During shock freezing products three temperature ranges can be distinguished in the center of the product from +20 to 0 °С, from 0 to -5 °С and from -5 to -18 °С.
At the first stage the product is cooled from +20 to 0 °С. The decrease in the temperature of the product here is proportional to the amount of heat extraction work.
At the second stage of shock freezing there is a transition from the liquid phase to the solid at temperatures from 0 to -5 ° C. The work on the removal of heat from the product is very significant, however, the temperature of the product practically does not decrease, and about 70% of the liquid fractions of the product crystallize, which we call freezing.
At the third stage freezing occurs at product temperatures from -5 to -18 ° C. The decrease in temperature again goes in proportion to the work performed by the refrigeration machine.
Traditional freezing technology, implemented in the form of so-called low-temperature refrigerating chambers, assumes a temperature in the chamber of (-18) - (-24) °C. Freezing time in refrigerators is 2.5 hours or more. During freezing, the speed of the process acquires a decisive role. A close connection between the quality of the product and the rate of freezing has been established. Numerous experimental data testify to the influence of the freezing rate on the size of ice crystals, on structural and enzymatic changes in products.
technology idea shock freezing of products (meat, vegetables, fruits, berries) consists in forcing the modes of cooling, freezing and freezing of products. This forcing is provided by two means of increasing the rate of heat removal from the product: lowering the temperature of the medium to (-30) - (-35) ° С; accelerated movement of the coolant (in the role of which air acts in the chamber), which is ensured by the ventilation of the evaporator and, accordingly, by intensive blowing of the product. It should be noted that a further decrease in temperature leads to unjustified power consumption and increased deformation of the product, the unevenness of the process becomes too great.
Benefits of shock freezing
Compared with the traditional way of freezing on racks in cold rooms, the advantages of using shock freezing products are:
- Product losses are reduced by 2-3 times;
- Freezing time is reduced by 3-10 times;
- Production areas are reduced by 1.5-2 r
- The production staff is reduced by 25-30%;
- The payback period is reduced by 15-20%;
Consider the practical results of the application of the technology of shock freezing of products.
total freezing time
If with traditional technology the total freezing time for dumplings and cutlets is 2.5 hours, then with quick freezing it is 20-35 minutes, which gives a significant economic effect. The time for passing the second stage is reduced from 1 hour to 15 minutes.
Fabric structure
The high cooling rate provided by the shock temperature in the chamber (-30)-(-35)°С and intensive blowing of the product allows for a forced transition from the liquid to the solid phase. In this case, ice crystals are formed in much smaller sizes and almost simultaneously in the cell and intercellular partitions (cells remain intact). As a result, the tissue structure of a fresh product is preserved almost unchanged and better than with other methods of preservation.
Ecology and biochemistry
The absence of any thermal and chemical treatment (with the exception of blanching and ascorbic acid treatment, which are required by technology for certain types of vegetables and fruits) and, as a result, the invariance of protein types make shock freezing vegetables and fruits a method that absolutely does not impair environmental cleanliness and biochemistry product.
Bacteriological purity
Due to the speed of shock freezing, the periods of activity of the bacteriological environment are also reduced. Bacteria of different types have different (including below 0 °C) temperature zones of vital activity. During slow freezing, traces of the vital activity of each of these types of bacteria appear and remain in the product. During shock freezing, a number of types do not have time to develop.
Weight
Weight loss of the product, resulting from the evaporation of the liquid (drying) during freezing, in the usual mode is up to 5 - 10% (depending on the temperature in the chamber and the product being frozen). Shock freezing mode reduces product weight loss up to 0.8%, which also gives a significant economic effect.
Taste and nutritional value
Due to the prevention of drying during quick freezing, aromatics and nutrients do not have time to leave the product, which preserves its quality. Nutritional value and taste remain unchanged.
Shelf life
The shelf life of products subjected to shock freezing (for example, meat) is longer than products frozen in conventional chambers. Quick-frozen foods retain their qualities better during long-term storage than fresh ones. Thus, the technology of shock freezing ensures the preservation of the qualities of a fresh product and makes it better than other methods of harvesting and storage.
Quick frozen foods
Frozen products, semi-finished products and ready meals are popular all over the world. Their consumption in countries such as the UK, Denmark, Finland, France, Germany, Sweden, Switzerland, the USA and Japan ranges from 40 to 100 kg per person per year. Moreover, their production in these countries increases by 5-7% annually.
In world practice, the range of products preserved by shock freezing is extremely wide. Moreover, each country produces, first of all, products specific to the region, climate, and traditions. In recent years, quick-frozen products have been especially intensively produced:
- Fruits, berries, vegetables, gourds, herbs and combinations of them;
- Ready-made first and second courses, pies, bakery and confectionery products;
- Semi-finished products (meat, fish, etc.) such as entrecote, steaks, hamburgers, meatballs, sticks, sausages, dumplings and dumplings;
- Desserts, juices, puddings, jelly, ice cream, etc.
What is the attraction of quick frozen products: The product is almost completely free from inedible inclusions. It is essentially "waste-free" (other than packaging); practically does not differ from fresh, retains all the original, natural properties; inherently dietary, conditioned; packaged, dosed, portioned. It is convenient for any consumer; For trade, public catering, for the end consumer, a quick-frozen product is strategic. It does not require attention during storage and is always ready for use;
Such a product requires minimal time (minutes) and labor for its preparation; The technology of shock freezing of products opens up completely new possibilities. It brings the business to a higher level of its development. Quick freezing allows you to delay the sale of agricultural products in time and move the place of sale in space. This is a kind of transport that expands the scope of sales of products not only by the region where it is grown and the harvest season, but also by other regions and seasons. This is a transport from summer to winter, from the field to the table.
For example, for farms, this is the opportunity to freeze part of their products and sell it directly to the consumer at a higher price than fresh, anywhere in Russia, the market for quick-frozen products was initially focused mainly on imported products. Now the priorities are shifting towards domestic production. Although the share of imports of fresh frozen fruits and vegetables is still large. The share of imported products in the total consumption of frozen vegetables and fruits in Russia in 1998 was 99.4%, and in 1999 it was 99.7%. From the foregoing, it follows that the undeniable advantages of shock freezing technology make it possible to recoup the reasonable costs of quick freezing equipment in a fairly short time. In addition, shock freezing technology is becoming a kind of standard for producers and consumers of frozen products, without which it is difficult to sell them.
Shock freezing equipment
The following types of equipment are used for shock freezing of meat, berries, vegetables, fruits and other products, semi-finished products and ready meals:
Fluidized quick freezers are mainly designed for freezing small-piece or chopped fruit and vegetable raw materials: fruits (plum, peach, apricot), berries (strawberries, currants, cranberries, blueberries), vegetable stews and soup mixtures (beets, carrots, zucchini, bell peppers, cabbage ), french fries. Possible shock freezing of mushrooms(whole or in pieces), as well as small fish and shrimp. This class of equipment provides the highest (among air) speed of shock freezing, minimum shrinkage and maintains high quality of products. After freezing, the product retains its original crumbly structure and is perfectly packaged.
Conveyor quick freezers are designed for shock freezing of meat, fish, dairy, flour semi-finished products and ready meals: pancakes, puff pastry, pastries, meatballs, steaks, hamburgers, sausages, dumplings and dumplings, ravioli, etc. The thickness of the frozen products can be up to 25 mm, and the length and width up to 100 x 100 mm. These devices allow freezing up to 80% of the range of products traditionally frozen on imported spiral quick freezers.
Shock freezing with cradle equipment
It is also possible shock freezing of products of the plant group: mushrooms, strawberries, peaches, apricots. Cradle quick freezing equipment is designed for shock freezing packaged semi-finished products from poultry, meat and fish: meatballs, meatballs, steaks, hamburgers, sausages (including vacuum-packed), confectionery, as well as various side dishes and ready-made second courses. The thickness of the frozen products can be up to 80 mm, and the length and width up to 200 x 150 mm. The mass of one product (serving) can reach 1 kg, and the freezing time is 2.5 hours.
Shock freezing with spiral equipment
Spiral quick freezing equipment designed for shock freezing portioned dishes from meat, fish, fruits, vegetables, as well as breaded semi-finished products. When designing quick freezers, shockfrosters (air coolers with a large heat exchange surface, an increased distance between the lamellas to prevent ice rusting and a high air exchange rate) by GUENTNER (Germany) of the GFN series are used. As a compressor and condenser unit, they are usually used. More powerful shock freezing units are equipped with central units (refrigeration units consisting of two or more reciprocating or screw refrigeration compressors) with air condensers from GUENTNER (Germany) series GVV (vertical), GVH (horizontal), GVW (V-shaped).
If earlier frozen products could only be seen in supermarkets, today every housewife freezes everything on her own and leaves everything “until better times”. But the trouble is that not everyone knows the rules for freezing food, how long and under what conditions they can be stored. Some do not even think about how the structure of products changes during freezing, whether they lose their properties, whether they can deteriorate. You will learn about this and more in this article.
How does freezing work?
Complete freezing in refrigerators with low temperatures takes 2-3 hours. With normal freezing Food is frozen in three stages:- From +20 to zero. This stage is called preparatory. Due to the gradual cooling, the product is prepared for freezing.
- From zero to -5 degrees. This is an intermediate stage. Here the temperature fluctuation is insignificant. The main thing at this stage is the process of liquid crystallization in the tissues of the product.
- From 5 to 18 degrees with a minus sign. Final stage. At this stage, everything that did not have time before is frozen.
Food freezing rules
In order not to spoil the product and keep it for a long time, you must follow the simple rules of freezing:- Freezing Products must be fresh. If something has already gone bad, don't expect the freezer to do a miracle. It is better to decide immediately after the purchase what you will cook and what you will leave "until better times."
- Then the product must wash and dry well cut into pieces or boiled.
- Choose suitable dishes or special bags (most importantly, keep food away from air and moisture) and lay out the prepared product in small portions. Why small? If you need to cook ten cutlets, you will not defrost two kilograms of minced meat. Therefore, it is better to divide the products in small portions.
- So that they lose less vitamins and do not get chapped, try prevent too much air from entering the package. But do not fill the containers to the top: when frozen, the products increase in volume and can lift the lid.
Useful properties and freezing
If we talk about frozen cucumber and bought in the winter in a supermarket, then in the first, of course, there are much more useful properties. After all, greenhouse products that are sold out of season are processed and lose most of their properties. But if we compare the product just plucked from the garden and defrosted, then the first, of course, is more useful.Vitamin C is lost the most during freezing. But any other treatment also kills it. Thiamine (vitamin B1) is lost during freezing about 25%, riboflavin (B2) - 4-18%. Freezing does not affect vitamin A in any way, but long-term storage kills it. Therefore, do not keep frozen carrots for too long, cook them.
Shelf life of frozen foods
Nothing lasts forever, including frozen foods. Even with the most proper storage, products will still deteriorate sooner or later. Here is a sample list of frozen food expiration dates:- minced meat - up to 2 months;
- sausages - up to 2 months;
- homemade meat and fish dishes - up to 3-4 months;
- small fish - a maximum of 3 months, large - twice as much;
- rabbit, duck, goose and hare meat - six months;
- turkey and chicken meat - 9 months;
- liver - 3 months;
- milk and dairy products - from six months to a year;
- vegetables - 10-12 months, in soup sets - 6-7 months;
- mushrooms - 5-6 months;
- fruits and berries - up to a year;
- greens - 3-4 months;
- flour products - up to 3 months.
- Before freezing, the product is prepared in such a way that it does not need to be washed after defrosting.
- Freshly prepared dishes should be cooled to room temperature, and only then sent to the freezer.
- Freeze only fresh foods, those that have begun to deteriorate are best cooked immediately.
- For better preservation, food should be frozen quickly.
- The packaging in which this or that product will be stored must be airtight.
- Label each bag with the freeze date so you know when the expiration date is.
- If food is defrosted (due to a power outage), it cannot be refrozen. It is better to cook their dishes right away.
Deep frozen products
This term is more common on an industrial scale. Deep frozen products include vegetable products and semi-finished products.You can also find frozen berries, fruits, vegetables, mushrooms and a variety of mixtures in stores. A separate place today is occupied by semi-finished products: cutlets, dumplings, pizza crusts and much more.
Shock freezing: technology
Shock freezing is very different from the one that everyone is used to. There are no separate stages here, the product is cooled very rapidly by lowering the temperature to -30-35 degrees and increasing the air flow. With this technology the product is exposed to frosty air from all sides and freezes much faster.Advantages and disadvantages
Freezers have many advantages:- products lose 2-3 times less useful properties than with conventional freezing;
- the freezing time of products is reduced from 3 to 10 times;
- the production area is reduced by one and a half to two times;
- need less staff by 25-30%;
- pays off more by 15-20%.
"Shock" equipment
For shock freezing, the following freezers are used:- Fluidizing - most often used for freezing chopped vegetable and fruit raw materials.
- Conveyor - used for freezing ready meals.
- Cradle - used for freezing packaged semi-finished products from fish, meat and poultry.
- Spiral - designed for freezing portioned dishes.
Mistresses about freezing
Yana:“When I bought a refrigerator with a freezer, I tried to freeze everything that came to hand. I folded everything in small portions, and thawed it every other day to try it. I liked the most frozen melons and watermelons. Even now, when I defrost them in winter, there is such a smell in the house ... "Nika:
“I am sure that freezing retains more of the health benefits than any other canning method. Therefore, I put everything in my freezer in a row: greens, mushrooms, herbs, fruits, berries. It's incredibly convenient."
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