Application of quick freezing equipment
The development of quick-frozen food started late in China, with the annual growth rate of more than 25%. Even now our annual per capita consumption is only one-tenth of that of developed countries. Therefore has the development space extremely.
With the development of food quick freezing industry and its industrial production, quick freezing machine has become an irreplaceable necessary equipment. At present, China's 28 kinds of food market access system stipulates that quick-frozen food, especially cooked food, must use a single quick-frozen device to ensure quality, and export commodity inspection also has requirements.
This article discusses why can not be replaced in the frozen food industry machine, quick-freezing machine and what is the difference between traditional frozen library, how to choose the suitable quick-freezing machine, quick-freezing machine how to meet the needs of the many different food and its processing technology, the direction of the further development of the quick-freezing machine, and how to energy saving, intelligent opportunities for quick-frozen production enterprise benefits.
First, the impact of food freezing factors
When the freezing speed of food is 5-50mm thick per hour, the number and size of ice crystals generated in the freezing process can be guaranteed to be basically unchanged, and the grains are relatively small, so as to achieve the reversibility of freshness preservation. There are two kinds of water in food, one is free water, whose ice crystallization stage is from 0 to -5 degrees, and the other is colloidal bound water, which is attached to the molecular surface of food. When the frozen product is at -18 degrees, the crystallization rate is above 95%. In addition, food stored at low temperatures after ice crystallization inhibits microbial activity and reproduction for long-term storage and preservation (fruits and vegetables inhibit respiratory heat).
The influencing factors of food quick-freezing can be divided into:
1. The temperature of cooling medium: food freezing rate and freezing point is proportional to the cooling medium temperature difference Δ t. The lower the temperature of the cooling medium, the faster the freezing speed.
2. Influence of frozen products on wind speed: the surface area, wind speed and cold wind circulation rate of frozen products influence the freezing speed: the test shows that green beans need 120 minutes at 0 wind speed under -30 degree cooling medium, and only 10 minutes at 4.5m/s wind speed.
3. Influence of latent heat and enthalpy difference: it needs 80kcal cooling capacity for 1kg of water to drop from 80 degrees to 0 degrees, and it also needs 80kcal cooling capacity for water to change from 0 degrees to 0 degrees of ice. The latent heat of crystallization requires more cooling. Similarly, when the enthalpy difference is large, such as the incoming temperature is high, it requires not only a large amount of cooling but also a long freezing time.
4. Influence of food ingredients: food with high thermal conductivity freezes faster than food with low thermal conductivity. If the food is coated with plastic film, it not only conducts heat slowly, but also hinders the wind. For example, the thermal conductivity of water is 0.604w/mk, the thermal conductivity of fat is 0.15, the thermal conductivity of plastic film is 0.028, and the thermal conductivity of wind is 0.066.
5. Influence of food thickness: the square of food thickness is proportional to the quick freezing time. The thicker the food, the longer the quick freeze.
Second, the transformation from the quick freezing storehouse to the quick freezing machine
It can be seen from the factors affecting quick freezing of food:
Because the frozen library open a better more, relatively high temperature of the food, the cooling medium temperature recovery fluctuations, reduce Δ t; The freezer keeps the temperature almost constant.
Because of the static food placed in the quick-frozen storage, the wind is not uniform, or even reduce the wind speed, the static one-way blowing hindered the crystallization speed of the frozen product center is the wind position; The wind surface area of each unit in the tunnel is large and uniform, and the freezing is accelerated due to the change of wind direction.
Since the food entering the quick freezing storehouse reaches latent heat at the same time, it needs to increase the cooling capacity suddenly and greatly to face the crystallization process, thus resulting in temperature recovery and prolonging the crystallization time. However, the continuous operation of the quick-freezing machine makes only a relatively small part of the originally limited storage capacity of frozen products have reached latent heat successively, and its cooling capacity is enough to complete the rapid crystallization process at a stable temperature and speed.
Thus, the pursuit of rapid food crystallization process so as to achieve reversible food preservation effect, quick freezer is essential.
Iii. Classification and characteristics of quick freezer with air as cooling medium
1) tunnel type quick freezer:
1. Plane mesh belt type quick freezer: suitable for meat, conditioning food, aquatic products, dishes, ice cream, etc. For the basic general - purpose quick - freezing machine. The output is from 100kg/h to 2000kg/h.
(2) multi-function vibration type network belt quick freezer: in the general plane network belt type single quick freezer on the basis of the addition of dynamic device. In addition to the general plane mesh belt type monomer quick freezer, it is also suitable for granular food monomer freezing.
(3) tunnel type pre-cooling quick-freezing machine: creative pre-cooling, quick-freezing combined for energy saving. Especially suitable for high temperature goods, cooked food and other fast cooling food.
(4) tunnel type multi-layer network with quick freezer: suitable for small area, longer freezing time of products.
(5) tunnel reciprocating quick freezer: suitable for small area, long freezing time and process reprocessing products.
Tunnel type plate with quick freezer: suitable for frozen aquatic products.
2) screw type quick freezer:
1. Single screw quick freezer: suitable for meat, conditioning food, aquatic products, dishes, ice cream, etc. Small footprint, high efficiency. The inlet and outlet is low in or high in and low out, and the output is 500-1500 kg/h.
(2) double spiral frozen machine: suitable for meat, conditioning food, aquatic products, dishes, ice cream and other frozen food frozen for a long time or large output. The inlet and outlet can be provided with various directions according to the process requirements of the user workshop; Low inlet and outlet. The output is 1000-3000kg /h.
(3) special ice cream freezer: single chain double rotating tray form, suitable for ice cream dumplings, etc.
3) fluidized quick freezer:
(1) fluidized monomer quick freezer: blowing type. Frozen products in the process of moving forward monomer freezing, applicable to fruits and vegetables, granular food. The output is 100-3000kg /h.
(2) surface fluidization monomer quick freezer, frozen varieties and categories expand, save energy. The combination of fluidization and quick freezing of tunnel is creative. Excellent freezing effect.
(3) fluidized monomer precooling quick-freezing machine. Precooling function is added on the basis of fluidized monomer quick freezer.
4) stepping type quick freezer:
(1) transmission without power supply, step into the track quick freezing, using dynamic and static friction near the point of gravity easy operation, avoid running cold.
(2) suitable for conditioning food, ice cream, large food, bags of food frozen box.
5) round trip type quick freezer
Round machine is a kind of framework structure of frozen equipment, used for frozen meat products in more can, chickens, ducks and other poultry, etc., compared with the traditional refrigerator freezing, frozen products back and forth with save manpower, save electricity, save the maintenance cost and save area etc, we design the machine running back and forth stability, design scientific and reasonable, loading capacity is big, can meet the demand of different products of frozen.
Four, about the quick freezing machine energy saving, reliable, reasonable and intelligent
Food freezing Δ t is proportional to the velocity and temperature difference. The low temperature in the quick-freezing machine is for fast crystallization of food, and the set temperature is -35 degrees. On the one hand, it considers fast freezing, and on the other hand, it considers energy saving. So the closer the temperature of the food is to freezing, the faster it freezes. The higher temperature before crystallization is reserved for the precooling section, so as to achieve the purpose of high quality quick freezing and energy saving. In addition, the temperature of goods near freezing point or the key to reduce the dry consumption of food.
Avoiding the loss of cooling of the quick freezer also lies in avoiding the loss of cooling of the joint gap of the insulation board of the enclosure structure. The insulation board of the enclosure structure of the quick freezer adopts the form of overall polyurethane foam, and all the butt joints of the storehouse board are sealed with double-sided special sealant and filled with secondary foam, so as to avoid the joint gap of the insulation board from running cold.
The requirements of air volume and wind speed are different in all kinds of quick freezer, and the methods of energy saving are also different. The tunnel type network belt monomer quick freezing machine, on the basis of guaranteeing the refrigerating air volume, designs the gershan strip regulating flow guide assembly, which greatly improves the surface wind speed of the frozen products. At the same time, it also increases the surface area of frozen products and the wind circulation rate. In addition, the grisham strip regulating flow guide assembly with symmetrical adjustable wind direction device can control the cooling of the cold air from the inlet and outlet. Reduce the fan motor running power, thereby reducing the fan motor cooling (reduce the wind pressure, improve the wind speed), thus improving the efficiency. In order to reduce the mechanical transmission, the method of conveyor belt cooling consumption, in this take mechanical transmission and conveyor belt system to maintain the operation at low temperature, the inlet and outlet of the material take heat preservation measures to use the air conditioning from the freeze-chamber to achieve the purpose of saving cooling consumption.
Tianjin ruier refrigeration equipment technology co. LTD
In August 2008