Unlike conventional refrigeration units, which are unable to quickly and efficiently cool hot food products, shock freezers have enhanced cooling capacity and a progressive forced ventilation system
Intensive freezing chambers are used in the production of semi-finished products of maximum readiness, including for catering or fast food, and are capable of providing the highest level of sanitary and hygienic protection.
In any food at temperatures from +65 to +10 °C, microflora multiply rapidly: the number of bacteria doubles approximately every 20 minutes. With rapid cooling, many microorganisms simply do not have time to develop. Thanks to this, the shelf life of quickly chilled and quickly frozen products is much longer.
Very low temperature in the chamber (up to -40 °C) and intense airflow form ice microcrystals simultaneously in the cellular and intercellular spaces, which eliminates side effects: drying out, weight loss and destruction of the food structure, inevitable with other types of freezing
Weight loss during freezing in a conventional chamber can be 2%, in a shock freezer the maximum is 0.6%.
The freezing process in such cabinets is carried out for several hours at a temperature in the working chamber from -35 to -30 °C. Its duration does not exceed 240 minutes. The food storage temperature is most often -18 °C. The shelf life after freezing for semi-finished meat products is from 2 months, for dessert semi-finished products and salads - up to 12 months.
Products in blast freezers are frozen almost 10 times faster than in conventional refrigerators, which provides significant time savings
Blast cooling differs from blast freezing only in the product outlet temperature (+3 °C and -10...-20 °C, respectively).
Functional
Blast freezers are available in a wide range and may differ in capabilities (for example, cooling only or cooling plus freezing), performance, design features such as built-in or remote compressor, water or air cooling of the condenser, storage temperature, size (from small models, built-in under the table, to those into which products are rolled on carts).
The devices may have a standard or dynamic control panel. The second option allows you to automatically set the required temperature and cooling time depending on the type of semi-finished product. The electronic control system may have an alarm and a program that maintains the required temperature inside the chamber during breakdowns until the malfunction is eliminated.
The body of blast freezing cabinets and internal surfaces are usually made of stainless or galvanized steel coated with enamel.
The cabinets may include: an air pressure equalization valve, heating elements for doorways, trays for draining condensate, an electronic control unit (with programmability), fans with automatic speed control, and a control panel.
In addition, the package may include built-in handles along the entire length of the doors, lighting, locks, removable door seals, dust filters and much more.
Many models have a probe for monitoring the temperature inside the food.
Benefits of use
. Blast freezing is a fast and reliable way to intensify production without global structural changes and major investments.
. High security: Application helps to obtain food that meets the standards of the HACCP food safety management system.
. Reducing losses of finished products and semi-finished products. According to SanPiN 2.3.6.1079-01, the shelf life of most restaurant dishes should be no more than 1-2 hours from the moment of preparation. If the product is not purchased, it can be frozen and stored for up to 6 months.
. Time savings up to 30%. Thanks to a longer shelf life, it becomes possible to better plan production, prepare inventory, and repeat the production process less often.
. Increase in assortment prepared semi-finished products.
. Saving money for staff salaries.
. Long-term storage provides an opportunity to save money when purchasing seasonal ingredients (at lower prices and of higher quality).
. Increase in revenue from the sale of weight products to a 6% increase due to less weight loss.
Equipment selection
For small establishments, a batch blast freezing cabinet with a height of about 900 mm and 5-6 standard gastronomy containers is quite suitable. Such units can be equipped with a countertop, that is, the upper part can act as a working surface, or be built-in.
For larger production facilities and restaurants, equipment with greater power and a capacity of 10 or 20 levels is suitable. For industrial production, as a rule, fully automatic continuous equipment is used. Such systems are designed and manufactured for a specific customer.
According to specialists from the Trade Design company, all shock freezers can be divided into three categories in terms of price and quality ratio.
The second category includes blast freezing cabinets from companies Fagor(Spain) and Angelo Po(Italy). These companies are constantly upgrading their products.
The third category includes not very expensive products from domestic manufacturers, such as Abat And HiCold. The products are especially in demand for equipping small shops and catering establishments. Russian companies control production processes and improve technical indicators.
Carlos Martin Repetto,
hotel chef
The slow freezing process allows unwanted changes to occur in the food, turning it into bland, unhealthy food, while blast freezers preserve the nutrients in the food. After rapid cooling, food can be stored for a long time without loss of taste - and preserving cooked dishes reduces restaurant costs.
In our kitchen there are three “shockers”, or rather blast chillers: two large ones, Modular brand, and one medium size - Irinox. All show good results both in terms of cooling time and safety of use.
We use devices, firstly, to quickly cool dishes and pre-process products to avoid spoilage or crystallization.
Secondly, for preparations during banquets (then it is enough to heat them in a combi-oven).
Thirdly, for baking, as well as when making sorbets and ice cream: rapid cooling at a very low temperature helps to avoid ice crystallization.
As you know, the best way to increase the shelf life of freshly prepared products is rapid cooling and freezing.
When visiting abroad, many of us noted the abundance of various “frozen” foods 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 its often perishable products - anywhere and at any time. During perestroika times, frozen foods, mainly foreign-made, began to actively fill the shelves of domestic stores. Noticing interest in this product, our entrepreneurs began studying the technology of quick freezing (shock freezing).
The need to reduce work on night shifts, save human resources, as well as expand the range of products for the end customer is a key factor that makes blast freezing equipment an integral tool in all modern production workshops. Not only blast freezing to -18°C, but also rapid cooling to +3°C allows you to work more efficiently, reducing time for product preparation, reducing the amount of space required for storing finished products and increasing the quality and safety of products.
Let's consider the technology of blast freezing of 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 product temperature here is proportional to the amount of heat removal work.
At the second stage, a transition from the liquid phase to the solid occurs at temperatures from 0 to -5 ° C. The work of removing heat from the product is very significant, but the temperature of the product practically does not decrease, but crystallization of approximately 70% of the liquid fractions of the product occurs, which we call freezing.
At the third stage, freezing occurs at product temperatures from -5 to -18 °C. The temperature decrease is again proportional to the work performed by the refrigeration machine. Traditional freezing technology, implemented in the form of so-called low-temperature refrigeration chambers, assumes a temperature in the chamber of -18 and -24 °C. Freezing time in refrigeration chambers is 2.5 hours or more.
When freezing, the speed of the process plays a decisive role. A close connection between product quality and freezing speed has been established. Numerous experimental data indicate the influence of freezing speed on the size of ice crystals and on structural and enzymatic changes in products. The idea of blast freezing technology is to speed up the cooling, freezing and re-freezing modes. This boost is provided by two means of increasing the rate of heat extraction from the product: reducing the temperature of the environment to -30 - -35°C; accelerated movement of the coolant (which is air in the chamber), which is ensured by ventilation of the evaporator and, accordingly, intensive airflow 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 blast freezing
Compared to the traditional method of freezing on racks in refrigeration chambers, 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;
- Production personnel are being reduced by 25 - 30%;
- The payback period is reduced by 15 - 20%.
Let's consider the practical results of using blast 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 to complete the second stage is reduced from 1 hour to 15 minutes.
Reduce waste.
Rapid cooling and blast 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 or chemical treatment and, as a result, the invariability of protein types make rapid freezing a method that does not at all impair the environmental purity and biochemistry of the product.
Bacteriological purity.
When shock freezing is used, the period of activity of the bacteriological environment is also shortened. 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 and remain in the product, while when shock freezing is used, many of them simply do not have time to develop.
Reducing moisture loss.
The taste of a product is very often related to 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 products is longer than that of products frozen in conventional chambers. Quick-frozen foods retain their quality better during long-term storage than fresh ones. Thus, blast freezing ensures the preservation of the qualities of a fresh product and does this better than other methods of preparation and storage.
Blast freezing equipment
What can manufacturers recommend for freezing food and vegetables? In our opinion, the optimal solution is to use quick-freezers based on spiral conveyors.
The spiral belt conveyor is the most versatile and convenient 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 variety at the exit from the conveyor.
Conveyors are structurally designed in the form of one or two spirals; in addition, various relative positions of loading and unloading areas for products are possible.
The spiral conveyor provides:
- automatic loading of the product to be frozen and its distribution along the belt;
- freezing food and vegetables in the refrigerator compartment (quick freezer);
- automatic unloading of frozen product onto the outfeed conveyor, or directly into a plastic container (box).
Operating principle.
The product enters and moves through the apparatus using conveyor belts. The tapes are installed at different levels. The speed of the belts is adjusted smoothly and over a wide range. The tapes are made of fabric-polymer or rubber-woven materials approved for contact with food products. The frozen product is removed through the receiving hopper to be supplied for packaging.
Advantages.
- Product loss during freezing from drying is within 1.5-3%;
- maintaining product quality;
- reduction in unit cost of production;
- reduction of production space and maintenance personnel.
The quick freezer has a number of advantages compared to traditional freezing technology in refrigeration chambers. So, for example, if conventional refrigeration chambers are used to freeze dumplings or cutlets, it will take 2.5 hours. To reduce freezing time to 20-35 minutes. you need to use a blast freezer. In this case, ice crystals are formed of 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 preservation methods.
In any food that is cooked and left to cool slowly at temperatures from +65 to +10°C, microflora multiply rapidly (bacteria approximately double every 20 minutes). With a rapid decrease in temperature in the body of the product, there is a rapid reduction in the proliferation of microflora. Microorganisms of different species have different temperature limits for life. With a slow decrease in temperature, traces of the vital activity of many microorganisms appear in the product, while with a rapid decrease, many of them simply do not have time to develop. Thanks to this, the shelf life of quickly chilled and quickly frozen foods is longer.
When frozen, all water molecules turn into ice crystals and the faster the process, the smaller the crystals are. Thus, only during micro-crystallization the product molecules are not damaged. As a result, after defrosting there will be less loss of liquid, and the consistency and taste of the product will not change.
Blast freezing systems make it possible to reach a temperature of -18°C in the body of the product in less than 240 minutes - the maximum time during which it is necessary to carry out the freezing process for micro-crystallization, while maintaining the organoleptic properties of the product unchanged.
Blast cooling differs from blast freezing in the temperature of the product at the outlet. With shock freezing (shock freezing), the product comes out with a negative temperature of -10...-20°C, and with blast cooling it is usually +3°C (i.e., the process is simply completed earlier). In both technologies, the process of lowering the temperature of the product occurs quickly.
Blast cooling can be “soft” or “hard”. The first option is suitable for delicate and thin products, the second for dense, fatty and large ones.
In the West, devices for blast freezing are called shock freezers, and for blast cooling, blast chillers. For small product capacities (for example, in mini-bakeries), miniature serial samples of periodic equipment in the form of blast freezing cabinets are used. For industrial production, as a rule, they use fully automatic continuous equipment - a blast freezing chamber. Such systems are designed and manufactured for a specific manufacturer.
Advantages of using shock technologies:
1. Thanks to a longer shelf life, it becomes possible to better plan production, prepare inventory and repeat the production process less frequently. This results in a time saving of up to 30%.
2. Due to the long shelf life of products, it makes it possible to save money when purchasing seasonal ingredients (at lower prices and of higher quality (more fresh)).
3. Allows you to increase revenue from the sale of weight products (up to 6% increase) due to less weight loss.
4. The use of technology helps to obtain a product that truly meets the standards of the HACCP food safety management system.
5. Allows you to expand the range of products offered.
BLAST FREEZING OF BAKERY AND CONFECTIONERY PRODUCTS
In the West, frozen bread today occupies about 70-80% of the entire bread market, in Russia - so far only 10-15%. According to experts, the transition of large manufacturers (bakery factories) to new technologies and the production of frozen bread for the mass segment can provide increased profitability and quality compared to the traditional process. The difference in the production of regular and frozen bread is the increase in costs for freezing and storing products (from 15 to 30%), but the reduction in costs for returning unsold products from counterparties, logistics, damping surges and dips in demand due to long-term storage inventory.
The global frozen food market is developing much faster than the Russian market, where frozen baked goods appeared in the early 90s. For example, in Europe, the production of partially frozen baked goods has become widespread since the 70s.
Consumers of frozen bakery and confectionery products are the HoReCA sector - cafes, restaurants, the “street food” or street food segment, catering establishments and individual consumers. The largest portion of sales of frozen bakery products in Russia through retail channels occurs in grocery stores, markets and supermarkets.
As experts predict, the demand for such semi-finished products will grow not only in the capital, but also in the regions, and companies offering a wide range of products new to the market will be in demand.
In addition to traditional bread and rolls for Russian consumers, small-piece products are subjected to shock freezing - rye and wheat buns with various additives, mini-baguettes, classic baguettes of various sizes, almost ready-made frozen bread dishes (for example, sliced baguette with butter and herbs, baguette with garlic oil), which just need to be warmed up before use. The blast freezing method is also widely used for such products as bagels, pretzels, pizza, lasagna, sausages in dough, tartlets, flatbreads, khachapuri, panini, ciabatta, focacho, Finnish rye bread, Irish soda, strudels, cheese sticks, pretzels and envelopes with various fillings, cakes, pastries, pies, pancakes, pies, puff pastry (yeast-free and yeast), croissants, cheesecakes, cupcakes (muffins), donuts (donuts), puff pastries, denishes, cheesecakes, cookies (cookies), etc. d. In total, there are about 300 types of frozen bakery and confectionery products in the world. There are more than 100 represented on the Russian market. Only about 10 of them are the most universal and popular, the rest are narrowly targeted - for a specific cuisine, for a specific dish, etc.
In recent years, the demand for products made from frozen semi-finished products has increased significantly. As for the taste characteristics, according to experts, there is no pronounced difference between bread baked in a bakery or from frozen semi-finished products. As a rule, frozen products are made from natural ingredients without special additives or improvers. With proper adherence to the technology for producing bread from frozen preparations, the products turn out crispier (compared to bread produced in the classical way), which makes them especially appetizing. The stereotype that frozen products are obviously of lower quality than fresh ones is no longer so strong. Restaurateurs and their clients are convinced that “frozen” not only does not give itself away in appearance, but is absolutely identical in taste to its fresh counterparts.
What is the appeal of frozen foods? First of all, it is convenient. Convenient for both the consumer and the manufacturer. For the consumer, because such a product requires a minimum of time and labor to prepare. Is everything ready. And for the manufacturer, such products have a number of advantages. Thus, the use of frozen semi-finished bakery products in shopping centers does not require expanding the staff at the expense of specialists carrying out the dough making process. Also, when using, for example, frozen semi-finished bread products, there is practically no unsold goods, since new batches are baked as the previous ones are sold. As a result, the assortment always includes hot and fragrant bread.
Today there are three main ways to freeze baked goods and confectionery products:
1. Freezing dough pieces.
2. Freezing part baked products. This type is also called the “incomplete baking” production technology.
3. Take bake technology - freezing of finished products.
The first method may have variations. Here are two of them.
First option. The dough piece is allowed to rest a little. Then they are frozen and stored. Preparation: defrosting (defrosting) for 30 minutes, proofing for 2...4 hours at +20...+25°C and humidity 70...75%, baking for 10...25 minutes.
Second option. After molding, the dough pieces undergo a final proofing stage. Then the dough pieces are frozen in a blast freezing chamber at a temperature of -30...-40°C, packaged in the so-called “zero chamber” (0°C) and stored at a temperature of -18°C. Further actions with the workpieces are defrosting for 15-30 minutes. at room temperature, then bake in an oven or combi oven.
In the second method, the product is baked until 50-90% done. The bread is then deep frozen. Frozen bread is stored at -18°C. Today, many manufacturers use this technology. To prepare bread, it is removed from the freezer, defrosted and baked in ovens until ready. Fresh hot bread is ready.
The latest know-how in the production of frozen bakery and confectionery products is baking semi-finished products without prior defrosting, which further simplifies the process of preparing products.
With the third freezing method, the products are brought to readiness by heating them in a microwave oven.
The detailed technology for creating a semi-finished product, shock freezing, and preparation after storage is always individual for each specific type of product. As a rule, this technology is know-how and organizations using it are very reluctant to share it. The technology for different types of products can differ quite significantly due to their characteristics.
Depending on the additives used, the shelf life of some products can be up to 1.5 years. With strict adherence to technological parameters and careful quality control of raw materials, the resulting semi-finished puff pastry products can be stored frozen for up to 6 months without the slightest loss of their properties.
Deep freezing is suitable for products prepared according to a wide variety of recipes. Exceptions are butter cakes and products decorated with vegetable cream. The fact is that when defrosting, cracks appear on the surface of the cake and it loses its presentation.
When working with deep-frozen confectionery products, it is important to strictly follow the storage and defrosting rules. It is recommended to defrost the products gradually at a temperature of +2...+5°C (in a regular refrigerator) for 2 hours. The subsequent sales period is 72 hours, provided the product is stored in the refrigerator. If the storage and defrosting conditions are violated, the product shrinks, the taste deteriorates, and in addition, some deformation is possible. Note that manufacturers of frozen cakes and pastries also allow other defrosting methods: at room temperature or in a microwave oven in defrosting mode.
A few words should be said about the features of shock freezing of yeast dough. Keep in mind that flash freezing rates that are too high or too low can cause damage to yeast cells, even when using specialized yeast. Acceptable freezing technology for yeast dough is determined by professional technologists of the enterprise that produces such products. They determine the conditions under which maximum yeast survival is maintained.
EQUIPMENT FOR BLAST FREEZING BAKERY AND CONFECTIONERY PRODUCTS
Bakery and confectionery products are frozen at temperatures from -20 to -70 °C, depending on technological requirements. The duration of the freezing process depends on the size and thermophysical properties of the product and can vary from 15...20 minutes (puff pastry) to 3...4 hours (cake).
The fully automated blast freezing line consists of the following components
(types of equipment classified by functional purpose):
- Receiving conveyor system with the function of forming the required layout of products on the belt *
- Product rejection system based on a technical vision system
- Thermal insulation chamber made of sandwich panels
- Spiral or multi-tier cold conveyor with possible additional options (for example, a belt cleaning and washing system
- Refrigeration equipment (air cooler (special heat exchange unit with shock-frost type fans), compressor-receiver unit, condenser, oil cooler, etc.)
- Intermediate conveyor system*, which receives products from the chamber and transports them to the loading device in the packaging machine (feeder)
- Multifunctional control panels with alarm system
- Feeder
- Packaging machine with labeling capabilities
- Intra-plant logistics system (includes a conveyor system for containers (multiple packaging) and elements of its automation (product counters, robotic manipulators, palletizers, etc.)
*As additional options, belt cleaning systems can be supplied to equipment for confectionery production, removable trays can be installed on conveyors to prevent crumbs from falling off, protective covers against dust getting on the product (see more details), and more powerful refrigeration units can also be used installations (industrial).
Conveyor systems for lowering products between levels use inclined, steeply inclined, spiral, vertical conveyors, as well as straight (slides), curved and screw gravitational descents made of stainless steel.
The thermal insulation chamber is made of sandwich panels. Thermal insulation material can be different: polyurethane foam (PUR), non-flammable polyisocyanurate (PIR), etc. The most commonly used is polyurethane foam (PPU). The outer layers of the sandwich panel can be made of galvanized cold-rolled steel with various coatings or stainless steel. The design of the joints (tenon-groove connection) of the chamber can be of a locking type (with built-in eccentric locks and a deep profile at the ends), profile (with PVC profiles) and lockless types. With any type of chamber, a tight fit of the panels, structural rigidity and the absence of cold “bridges” are ensured. With a locking design, assembly of the camera is easier and faster because the use of seals, sealants, “additional” elements and hardware is not required. This reduces installation costs, but the cost of such a camera is higher than a lockless one. The chambers have reinforced floor panels. As a rule, the floor panel is reinforced with special plywood and corrugated aluminum sheet. In the room, a low-temperature chamber is installed on the vents. The chamber must be provided with drainage and a lighting system. The chamber has special windows for product entry and exit. As a rule, the exact location of these windows is determined during installation. In addition to these windows, the chamber must have at least one refrigeration door for service personnel. When designing a blast freezing system, it is necessary to take into account the ease of maintenance of the conveyor and heat exchange unit, and the required installation distances of the heat exchange unit.
A spiral conveyor is most often used as a technological conveyor for a blast freezing chamber for bakery and confectionery products. CJSC LIPSIA has extensive experience in the production of spiral conveyors (more than a hundred spiral conveyors for various applications have been installed).
As chamber equipment, heat exchange blocks with an increased finning pitch of the heat exchange surface are used, which allows increasing the operating time of industrial equipment refrigeration units between defrost cycles (6...8 hours). At the beginning of a shift in production with an automatic blast freezing system, the chamber is put into operation, then a long supply of product flow begins on the conveyor belt transporting it to the chamber. Thus, between defrost cycles, the freezing process mode does not change (remains consistently fast). This explains the higher quality of the frozen product compared to other methods.
Different heat exchange units are used for different products. Sometimes it is necessary to order heat exchange units of non-standard design (for example, with slowly blowing fans for freezing cream cakes).
An important role in shock freezing is the organization of air flows in the refrigerating chamber. To direct air flows, a special lining made of stainless steel sheets is installed. An incorrectly designed blast chiller system may not work or may not work efficiently.
CJSC LIPSIA has a division that designs climate control equipment. When creating refrigeration systems, components from various companies are used depending on the Customer’s preferences. However, to achieve the best results, the company strongly recommends using brands that have been proven over the years - such as: Bitzer (Germany), Güntner (Germany), GEA Goedhart (Netherlands), Thermofin (Germany), Alfa Laval (Sweden), Danfoss (Denmark).
Frozen products can be packed in film using flow pack packaging machines. It is also possible to package products in various trays with subsequent sealing. With these packaging methods, it is possible to carry out the freezing process of an already packaged product. However, this is often not possible due to a number of factors: difficult heat exchange prevents rapid freezing, the stickiness of an unfrozen semi-finished product prevents packaging, the quality of packaging material and printing does not allow it to maintain its presentation after the blast freezing process, etc.
Frozen products are often packaged in corrugated containers. For example, a given number of frozen pies needs to be packed into a corrugated cardboard box automatically. In this case, a Case Packer can act as a packaging machine for frozen semi-finished products. This is equipment for group packaging in corrugated boxes. The following operations are performed in automatic mode: forming a box from a blank, grouping and placing products in a box, closing the valves, sealing the box valves with tape.
In the in-plant logistics system, packaged products are automatically counted, placed in containers, which are then sent for storage (refrigerated warehouse of finished products) or into refrigerated transport for further shipment to points of sale.
The line described above is fully automatic. However, due to their high cost, such lines are not widely used in Russia. Most domestic enterprises have installed blast freezing lines that are partially automated (some of the line components are missing) or not automated at all.
A fully automated blast freezing line is as follows. Workers transfer semi-finished products ready for freezing onto trays into tiers of special mobile carts. Then these carts are rolled into a blast freezing chamber, where the products are frozen. The chamber is also equipped with appropriate heat exchange blocks of the “shock-froster” type. Then the carts are again manually removed from the chamber, the products are removed from the carts and packaged. Such cameras are periodic equipment. Unlike an automatic system, due to large heat inflows during loading and unloading, the chamber takes a long time to reach operating mode. Such lines are characterized by low product quality (damage to product tissues due to large ice crystals) and a large share of manual labor and, as a consequence, low profitability of production as a whole. At enterprises with such lines, there is irrational use of production space, a large wage fund, there is often confusion in the organization of intra-factory logistics and shortages of products, a high percentage of defects, downtime due to the “human factor”, and staff dissatisfaction with working conditions. A fully automated line is relatively cheap and therefore such equipment is still used at low production rates (up to 300 kg/hour).
Advantages of a blast freezing system based on a spiral conveyor:
- Reduction of wage fund
- Significant reduction in labor intensity
- Saving production space
- Reducing the number of defective products (eliminating the “human factor”, rough influence)
- Improving the consumer qualities of the finished product
- Increasing sales time (minimizing the development of microflora, eliminating or minimizing contact of products with people)
- Organization of a continuous technological process
- Reducing freezing time
The transition to full automation of production from the testing process to the receipt of products at the warehouse allows enterprises to take one of the leading positions in such important indicators as quality and price.
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 (see Fig. 1, curve 1).
At the first stage The product is cooled from +20 to 0 °C. The decrease in product temperature here is proportional to the amount of heat removal work.
At the second stage a transition occurs from the liquid phase to the solid at temperatures from 0 to -5 ° C. The work of removing heat from the product is very significant, but the temperature of the product practically does not decrease, but crystallization of approximately 70% of the liquid fractions of the product occurs, which we call freezing.
On the third- freezing occurs at product temperatures from -5 to -18 °C. The temperature decrease is again proportional to the work performed by the refrigeration machine.
Fig.1.
Traditional freezing technology, implemented in the form of so-called low temperature refrigeration chambers, assumes a temperature in the chamber of -18 ÷ -24 °C. Freezing time in refrigeration chambers is 2.5 hours or more. When freezing, the speed of the process plays a decisive role. A close connection between product quality and freezing speed has been established. Numerous experimental data indicate the influence of freezing speed on the size of ice crystals and on structural and enzymatic changes in products. The idea of blast freezing technology is to speed up the modes of cooling, freezing and freezing of products (see Fig. 1, curve 2). This boost is provided by two means of increasing the rate of heat extraction from the product: reducing the temperature of the medium to -30 ÷ -35 ° C; accelerated movement of the coolant (which is air in the chamber), which is ensured by ventilation of the evaporator and, accordingly, intensive airflow 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 blast freezing
Compared to the traditional method of freezing on racks in refrigerators, 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;
production personnel are being reduced by 25-30%;
the payback period is reduced by 15-20%; Let's consider one of the practical results of using blast 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 to complete 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 intensive airflow of the product, allows for a forced transition from the liquid phase to the solid phase. In this case, ice crystals are formed of much smaller sizes and almost simultaneously in the cell and intercellular partitions (the cells remain undamaged). As a result, the structure of the tissues of the fresh product is preserved almost unchanged, and better than with other methods of canning.
Ecology and biochemistry
The absence of any thermal and chemical treatment (with the exception of blanching and treatment with ascorbic acid, provided for by technology for some types of vegetables and fruits) and, as a result, the invariability of protein types makes quick freezing a method that does not at all impair environmental cleanliness and biochemistry product.
Bacteriological purity
Due to the speed of 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.
Loss of product weight resulting from evaporation of liquid (shrinkage) during freezing is usually 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 provides a significant economic effect.
Taste and nutritional value
By preventing drying out during fast freezing, aromatics and nutrients do not have time to escape from the product, which preserves its quality. Nutritional value and taste remain unchanged.
Shelf life
The shelf life of quick-frozen products is longer than that of products frozen in conventional chambers. Quick-frozen foods retain their quality better during long-term storage than fresh ones. Thus, blast freezing technology ensures the preservation of the quality of fresh product, and does this better than other methods of preparation and storage.
Frozen foods
Frozen foods, semi-finished and ready-made meals are popular all over the world. Their consumption in countries such as Great Britain, Denmark, Finland, France, Germany, Sweden, Switzerland, USA and Japan ranges from 40 to 100 kg per year per person. Moreover, their production in these countries increases annually by 5-7%.
In world practice, the range of products canned by quick freezing is extremely wide. Moreover, each country produces, first of all, products specific to a given region, climate, and traditions.
In recent years, quick-frozen products have been especially intensively produced:
fruits, berries, vegetables, melons, herbs and combinations of them;
ready-made first and second courses, pies, bakery and confectionery products;
semi-finished products (meat, fish, etc.), such as entrecotes, steaks, hamburgers, cutlets, sticks, sausages, dumplings and dumplings;
desserts, juices, puddings, jellies, ice cream, etc.
What is the appeal of frozen foods:
the product is almost completely free from inedible inclusions;
essentially “zero waste” (except for packaging);
practically no different from fresh - retains all the original, natural properties;
inherently dietary, conditioning;
packaged, dosed, portioned (this is convenient for any consumer);
a quick-frozen product is strategic (for trade, public catering, the end consumer);
does not require attention during storage and is always ready for use;
requires minimal time (minutes) and labor to prepare it.
Blast freezing technology opens up completely new possibilities. It takes the business to a higher stage 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 they are grown and the harvest season, but also by other regions and seasons. This is transport from summer to winter, from field to table. For example, for farms this is an opportunity to freeze part of their products and sell them directly to the consumer at a higher price than fresh, anywhere and at any time.
In Russia, the frozen food market was initially focused mainly on imported products. Now priorities are shifting towards domestically produced products. Although the share of imports of fresh frozen fruits and vegetables is still large. According to various sources, the share of imports in Russia accounts for about 40-60% of vegetables and fruits. At the same time, a very significant part of imported products enters the country illegally. According to various estimates, over the past five to six years, the share of imported vegetables has increased by approximately 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 vegetables - 4%, cabbage - 12%, other vegetables - 9%. According to Finam Management estimates, the entire Russian fruit market at the end of 2007 amounted to about $15-20 billion. According to various estimates, the share of imports is from 60 to 80%.
The undeniable advantages of blast freezing technology make it possible to recoup the reasonable costs of quick-freezing equipment in a fairly short time. In addition, blast freezing technology is becoming a kind of standard for producers and consumers of frozen products, without which their sales are difficult.
product losses are reduced by 2-3 times;
If previously 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 people don’t even think about how the structure of products changes when frozen, whether they lose their properties, or whether they can spoil. You will learn about this and more in this article.
How does freezing occur?
Complete freezing in refrigerators with low temperatures occurs in 2-3 hours. With normal freezing Products are frozen in three stages:- From +20 to zero. This stage is called preparatory. By gradually cooling the product is prepared for freezing.
- From zero to -5 degrees. This is an intermediate stage. Here the temperature fluctuations are insignificant. The main thing at this stage is the process of crystallization of the liquid in the tissues of the product.
- From 5 to 18 degrees with a minus sign. The final stage. At this stage, everything that was not completed earlier is frozen.
Rules for freezing food
In order not to spoil the product and preserve it for a long time, you need to follow simple freezing rules:- Products for freezing 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 purchase what you will cook and what you will leave “until better times.”
- Then the product needs wash and dry well, cut into pieces or boil.
- Select suitable dishes or special bags (the main thing is to keep the 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 won’t defrost two kilograms of minced meat. Therefore, it is better to share foods in small portions.
- So that they lose less vitamins and do not become chapped, try do not allow a lot of air into the packaging. But do not fill the containers to the top: when frozen, food expands in volume and can lift the lid.
Useful properties and freezing
If we talk about frozen cucumbers and those bought in the supermarket in winter, then the former, of course, has much more beneficial properties. After all, greenhouse products that are sold out of season are processed and lose most of their properties. But if you compare a product just picked from the garden and a defrosted one, then the first one is, of course, healthier.Vitamin C is lost the most during freezing. But any other processing also kills it. Thiamine (vitamin B1) is lost during freezing, approximately 25%, riboflavin (B2) - 4-18%. Freezing has no effect on vitamin A, 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, food will still spoil sooner or later. Here is a sample list of expiration dates for frozen foods:- minced meat - up to 2 months;
- sausages - up to 2 months;
- homemade meat and fish dishes - up to 3-4 months;
- small fish - maximum 3 months, large fish - twice as long;
- meat of rabbit, duck, goose and hare - 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 so that after defrosting it does not need to be washed.
- Freshly prepared dishes should be cooled to room temperature, and only then sent to the freezer.
- Only freeze fresh foods; those that have begun to spoil should be 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 frozen date so you know when it reaches its expiration date.
- If food has defrosted (due to a power outage), it cannot be frozen a second time. It is better to prepare their dishes right away.
Deep-frozen products
This term is more common on an industrial scale. Deep-frozen products include plant products and semi-finished products.In stores you can also find frozen berries, fruits, vegetables, mushrooms and various mixtures. Semi-finished products also occupy a special place today: cutlets, dumplings, pizza crusts and much more.
Blast freezing: technology
Blast freezing is very different from what everyone is used to. There are no separate stages; the product is cooled very quickly by reducing 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
Quick freezers have many advantages:- products lose 2-3 times less beneficial properties than during conventional freezing;
- food freezing time is reduced from 3 to 10 times;
- production area is reduced by one and a half to two times;
- we need 25-30% less staff;
- it pays off by 15-20%.
"Shock" equipment
For blast freezing the following quick freezers are used:- Fluidizing - most often used for freezing chopped vegetable and fruit raw materials.
- Conveyor - used for freezing prepared foods.
- Cradles - used for freezing packaged semi-finished products from fish, meat and poultry.
- Spiral - designed for freezing portioned dishes.
Housewives about freezing
Yana:“When I bought a refrigerator with a freezer, I tried to freeze everything I could get my hands on. I put everything in small portions and defrosted it every other day to try it. I liked the frozen melons and watermelons the most. Even now, when I defrost them in winter, there is such a smell in the house...”Nika:
“I am confident that freezing preserves more beneficial properties than any other canning method. Therefore, I put everything in my freezer: greens, mushrooms, herbs, fruits, berries. It's incredibly convenient."
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