L-class preservation warehouse is mainly used for storing fruits and vegetables, eggs, medicinal materials, preservat.
L-class preservation warehouse is mainly used for storing fruits and vegetables, eggs, medicinal materials, preservation and drying, etc.; D-class cold storage is mainly used for storing meat, aquatic products and products suitable for the temperature range; J-class cold storage is mainly used for storing ice cream, ice cream, low-temperature food and medical supplies, etc.;
Food storage in the fresh-keeping warehouse generally does not affect its internal organization, fresh-keeping can keep the original flavor and freshness of food, while customers should not pursue too low storage temperature, temperature reduction will directly bring equipment initial investment and operating costs increase.
Fresh-keeping storage is to inhibit the activity of microorganisms and enzymes, extend the longevity of fruits and vegetables a storage method.
Freshness is the main way of modern fruit and vegetable low-temperature preservation.
The fresh-keeping temperature range of fruits and vegetables is 0 ℃~15 ℃.
Fresh-keeping storage can reduce the incidence of pathogenic bacteria and the decay rate of fruits.
It can also slow down the respiratory metabolism process of fruits, thus preventing decay and prolonging the storage period.
Perfect original refrigeration unit, high efficiency and energy saving, excellent quality; Efficient ceiling evaporator; Advanced microcomputer control system and advanced control method (negative pressure parking); High quality double-sided color steel polystyrene cold storage board, small footprint, good insulation performance; More than 20 years of cold storage design, installation work experience, large and efficient technical group; advanced construction machinery, advanced installation technology; professional construction team, each construction personnel have long-term refrigeration engineering construction experience.
The temperature of the refrigerator is generally (-15 ℃~-18 ℃) Cold storage is to store chilled food and frozen food at different temperatures for short or long term storage.
It is mainly suitable for meat, aquatic products and other food storage.
Generally speaking, refrigeration is to store food with such requirements in order to maintain its required temperature.
Because the temperature drops below-15 ℃, the freezing rate of food is high, microorganisms and enzymes basically stop their activities and growth, and oxidation is also very slow.
Therefore, food can be stored for a long time and has good refrigeration quality.
In addition, refrigerated food also requires that the temperature in the warehouse be relatively stable, and excessive fluctuations in temperature will cause food spoilage.
Is the storage body for polystyrene foam (EPS) as the sandwich, with plastic coated steel plate and other metal materials as the surface layer, the material superior thermal insulation performance and good mechanical strength combined together.
With simple and fast assembly, long insulation life, simple maintenance, low cost and high strength and light weight characteristics, it is one of the best materials for cold storage insulation.
Cold storage characteristics: Perfect original refrigeration unit, high efficiency and energy saving, excellent quality; Efficient ceiling evaporator; Advanced microcomputer control system and advanced control method (negative pressure parking); High quality double-sided color steel polystyrene cold storage board, small footprint, good insulation performance; More than 20 years of cold storage design, installation work experience, large and efficient technical group; advanced construction machinery, advanced installation technology; professional construction team, each construction personnel have long-term refrigeration engineering construction experience, after strict job training, certificate on duty.
The so-called rapid freezing refers to the rapid passage of food through its maximum ice crystal formation zone and the rapid freezing method when the average temperature reaches-18 ℃.
Food will undergo various changes during the freezing process, such as physical changes.
(volume, thermal conductivity, specific heat, dry loss changes, etc.), chemical changes (protein denaturation, color change, etc.), cell tissue changes, biological and microbial changes, etc.
Fast frozen foods are characterized by maintaining the original nutritional value, color and flavor of the food to the maximum extent.
That is to say, in the freezing process, it must be ensured that the above-mentioned changes in the food achieve maximum reversibility.
Rapid freezing of food has the following advantages:(1) Avoid large ice crystals between cells (2) Reduce the external precipitation of water in cells, and reduce the loss of juice during thawing (3) The contact time between concentrated solute and food tissues, colloids and various components in cell tissues is significantly shortened, and the harmfulness of concentration is reduced to a minimum.(4) Quickly reduce food to below the temperature of microbial growth and activity.
Advantageously resist the growth of microorganisms and their biochemical reactions (5) food in the freezing equipment for a short time, conducive to improving the utilization of equipment and continuous production Most foods begin to freeze when the temperature drops to-1 ℃, and most ice crystals are generated between-1 ℃ and-5 ℃.
This stage is called the highest ice crystallization stage.
Rapid freezing can greatly shorten the freezing time at this stage, and can eliminate this part of heat at the fastest speed, which is of great significance to improve the quality of quick-frozen foods.
(+2 ℃/-2 °C) controlled atmosphere storage, referred to as "CA" storage, is an advanced new method of fruit and vegetable preservation and storage.
Controlled atmosphere storage is essentially to increase the adjustment of gas components on the basis of preservation.
By controlling the temperature, humidity, carbon dioxide, oxygen concentration and ethylene concentration in the storage environment, the respiration of fruits and vegetables is inhibited, and the metabolism process is delayed.
Compared with ordinary refrigeration, it can better maintain the freshness and commodity of fruits and vegetables, and prolong the storage period and sales shelf life.
Controlled atmosphere storage can reach the most suitable conditions for fruit and vegetable storage, and its effects are as follows: Inhibiting respiration, reducing the consumption of organic substances, maintaining the excellent flavor and aroma of fruits and vegetables.
Inhibiting water evaporation, maintaining the freshness of fruits and vegetables.
Inhibiting the breeding and reproduction of pathogenic bacteria, controlling the occurrence of some physiological diseases, and reducing the rot rate of fruits and vegetables.
4 Inhibit the activity of some post-ripening enzymes, inhibit ethylene production, delay the post-ripening and aging process, maintain fruit hardness for a long time, and have a long shelf life.
5 Fruits and vegetables are stored in a low oxygen environment, which can inhibit the growth of molds and pests to avoid harmful substances to the human body.
Controlled atmosphere warehouse has higher requirements than ordinary cold storage in building structure and equipment installation.
In addition to good thermal insulation performance, it also requires strict control of gas exchange inside and outside the warehouse.
It also requires a series of controlled atmosphere equipment.
A few problems should be paid attention to in the use of fruit and vegetable controlled atmosphere storage and its use: Controlled atmosphere storage is developed on the basis of fruit and vegetable cold storage, on the one hand, it has many similarities with fruit and vegetable cold storage, on the other hand, it has great differences with fruit and vegetable cold storage, mainly in: (1) The volume of controlled atmosphere storage.(2) The CA storehouse must have good airtightness, because it is necessary to form the required gas composition in the CA storehouse, maintain the set index for a long time during the storage of fruits and vegetables, and reduce the gas exchange between the inside and outside of the storehouse.(3) the safety of the atmosphere.
Because the atmosphere is a closed cold storage, when the temperature rises and falls in the library, the gas pressure also changes, often causing the formation of pressure difference inside and outside the library.
For this reason, there are usually balance bags and safety valves installed on the atmosphere to limit the pressure within the design safety range.(4) The climate control warehouse should generally be built into a single-story building.
When fruits and vegetables are transported, stacked and stored in the warehouse, the ground must bear a large load.
The building height of a larger climate control warehouse is generally about 6 m.
The configuration of the refrigeration equipment and temperature sensor of the climate control warehouse (1) Refrigeration system: Refrigeration equipment of CA storehouse mostly adopts piston type single-stage compression refrigeration system, using Freon R22 as refrigerant, and the cooling mode in the storehouse can be direct evaporation cooling of refrigerant.(2) Configuration of temperature sensor: A well-designed CA storehouse can realize temperature difference less than 0.5 ℃ during operation.
The main atmosphere control equipment and auxiliary equipment of the atmosphere control warehouse (1) Nitrogen generator.
At present, there are two main types of nitrogen generator used in the atmosphere control warehouse: adsorption separation carbon molecular sieve nitrogen generator and membrane separation hollow fiber membrane nitrogen generator.(2) Carbon dioxide removal machine: Carbon dioxide removal unit is divided into intermittent type (commonly referred to as single tank machines) and continuous (Usually called double tank machine) two kinds.(3) ethylene removal machine.
There are two main methods to remove ethylene: potassium permanganate oxidation method and high temperature catalytic decomposition method.(4) humidification device.
Water and gas mixed humidification, ultrasonic humidification and centrifugal atomization humidification are three common humidification methods in the current atmosphere controlled warehouse.
Reasonable use and management of controlled atmosphere storage (1) Reasonable and effective use of space (2) Fast forward and rectification (3) Good air circulation controlled atmosphere storage group (+2 ℃~+5 ℃) The temperature of the freezer is generally-22~-25 ℃.
The temperature of the cryogenic library is below-20 °C, because seafood and cold drinks need to be below-20 °C to not deteriorate.
If it does not reach-20 °C, the fresh taste of seafood is completely different.
The characteristics of low temperature library is to put the instrument into the cold storage step by step from time to time.
After a period of time, the temperature of the cold storage reaches-20 °C.
There is no special requirement for this period of time, but the temperature of the library is strict.
Between-18 °C and-23 °C is a typical low temperature library, but the cold drinks containing dairy products are stored.
The temperature of the library should be set at-20 °C~-28 °C.
However, these two different temperatures require different levels of equipment.
There is a big gap in equipment investment.
Professional refrigeration personnel think that the lower the temperature of the freezer, the better, the shelf life of ice storage can be extended, but sometimes it should be determined according to the storage temperature required for various items, with fruits and vegetables, too low storage temperature is easy to cause frostbite, and meat products can be stored for a long time at a low temperature.
However, from the perspective of economy and energy, the storage temperature should be selected for a long time.
For example, meat can be stored for 4 - 6 months at-18 °C and 8 - 12 months at-23 °C.
Because meat will arrive at consumers within 5 months, it is sometimes considered whether to choose a storage temperature of-23 °C.
Therefore, the freezer design must depend on the commodity life cycle of the object, and its effective storage environment to select the appropriate storage temperature.
Precooling method Air precooling: Air precooling method has the advantages of easy adjustment of air temperature and humidity, can be used for various food cooling and refrigeration transportation, and low equipment cost.
Vacuum precooling: According to the physical properties of water that its boiling point decreases with the decrease of pressure, the pre-cooled food is placed in a vacuum tank to evacuate.
When the pressure decreases to a certain value, the moisture on the surface of the food begins to evaporate and absorb the latent heat of vaporization.
The method of cooling the food itself is vacuum pre-cooling method.
The method of using water to reduce the cooled food from the initial temperature to the required end temperature is called water precooling method.
Features of cryogenic warehouse: Perfect original refrigeration unit, high efficiency and energy saving, excellent quality Efficient ceiling evaporator; Advanced microcomputer control system and advanced control method (negative pressure stop); high-quality double-sided color steel polystyrene cold storage board, covering a small area, good insulation performance; more than 20 years of cold storage design, installation work experience, a large and efficient technical group; advanced construction machinery, advanced installation technology; professional construction team, each construction personnel have long-term refrigeration engineering construction experience, after strict job training, certificate on duty.
Prefabricated cold storage is a fast and simple assembly of refrigeration equipment, with excellent thermal insulation and moisture resistance performance.
According to different classification standards, prefabricated cold storage can be divided into a variety of types.
From the use of performance
Classification, prefabricated cold storage mainly includes fresh-keeping cold storage, cold storage, low-temperature cold storage and quick-frozen cold storage.
The temperature range of these cold storage is different to meet the preservation and storage needs of different foods.
The temperature range of fresh-keeping cold storage is +2 ℃~+5 ℃, mainly used for storing fruits, vegetables, eggs and medicinal materials; the temperature range of cold storage is-15 ℃~-18 ℃, mainly used for the storage of meat and aquatic food;
The temperature range of cold storage (freezer) is-22 ℃~-25 ℃, mainly used for storing seafood and cold drinks; the temperature range of frozen storage is-35 ℃~-2 ℃/+2 ℃, which is used for quickly freezing food and maintaining the original nutritional value and appearance of food.
From the structural composition classification, assembled cold storage is composed of cold storage plates, steel components and insulation materials, which have detachable assembly and flexible variable characteristics.
These components can be disassembled, transported and installed according to the needs of users.
At the same time, the size of walls, roofs and floors can also be adjusted to meet different storage needs.
In addition, according to the classification of tightness, fully enclosed cold storage refers to completely sealed cooling rooms, which can control factors such as air pressure, temperature and humidity to achieve the best storage environment.
Such cold storage is usually used for refrigeration, freezing or specific atmosphere control storage environment.
