Introduction to basic
Controlled atmosphere storage is now the most advanced methods of fruit and vegetable fresh-keeping and storage. It is on the basis of the refrigeration, increased gas composition adjustment, through the storage environment temperature, humidity, carbon dioxide, oxygen and ethylene concentration conditions control, inhibition of respiration of fruits and vegetables, slow the metabolic processes, betterpreserve the freshness and quality of fruits and vegetables, extended shelf life of fruits and vegetables during storage and sale. Often than ordinary cold storage controlled atmosphere storage can extend the storage period 2-3 times.
Traditional methods of storing and fresh keeping fruits and vegetables easy storage, ventilation, storage, preservation of radiation, chemical storage, cold storage.Simple easy storage, ventilation equipment, low investment, poor storage, storageperiod is short, serious decay losses. Radiation and chemical preservation on thepart of the fruit have some applicability, but radiation and chemical residues, not all fruits and vegetables can be used. Gas adjustable storage can in suitable low temperature conditions Xia, through change storage environment gas components, and relative humidity, maximum degree to created fruits and vegetables storage best environment, its effect performance in following aspects: gas adjustable storage create of low oxygen (General O2 content for l%-5%), and appropriate CO2 concentration can effective to inhibit breathing role, reduced fruits and vegetables in the nutrition material of loss, while inhibit disease original bacteria of breeding breeding, control some physiological disease of occurred; clear storage environment gas in the of vinyl, to inhibit its on fruits and vegetables of ripening role, Delayingripening and senescence; increase the relative humidity of ambient gas in order toreduce the transpiration of fruits and vegetables, so as to achieve the objective oflong-term storage and fresh-keeping of fruits and vegetables. Therefore, after controlled atmosphere storage of fruits and vegetables have the following characteristics: (1) very well keeping the original shape, color, scent, (2) hardness than regularrefrigerated; (3) storage date; (4) low rate of decay, natural losses (loss of) low (5)to extend shelf life. Due to prolonged low 02 and on the fruit and vegetables highC02 effect, atmosphere State of when fruits and vegetables is still there after a long time of "lag effect" or dormant period (6) suitable for long distance transportation and export. Fruit and vegetable quality improved, creating conditions for export and distribution; (7) numerous quarter can be achieved annual sales of annual supply of fruits and vegetables, to create a good social and economic benefits.
Folding editor this controlled atmosphere storage
Controlled atmosphere storage library requires not only has good insulation, reducing the impact of external heat to the air temperature, more importantly requiresa good air-tightness, reducing or eliminating the outside air pressure on the gas composition in the warehouse, ensuring fast gas composition adjustment in the warehouse, small fluctuations, so as to improve the quality of storage and reduce storage costs. Controlled atmosphere storage is mainly composed of gas-tight insulation layers and layers. Modified atmosphere library building can be divided into 3 types: Assembly-style, brick, jacket. Fabricated airproof structure using steel polyurethane sandwich panels are assembled, has the role of heat, moisture and air. Thelibrary building fast, elegant, but slightly higher cost, new controlled atmosphere storage at present is the most commonly used type. Controlled atmosphere storage special tone, the door should have good thermal insulation and air tightness. Inaddition, in controlled atmosphere storage after being snowed in during long term storage, generally does not permit the indiscriminate open tone, so as to avoidinternal and external gas exchange, causing fluctuation of gas composition in thewarehouse, for ease of understanding within the fruit and vegetable storage, observation window should be set. After controlled atmosphere storage building, to conduct air tightness test. Airtight 300Pa, half-relief time of not less than 20-30min.
Folding editor this paragraph characteristics and effects
1. modified atmosphere library features:
(1) wide application range: suitable for China's North and a variety of fruits, flowers and other controlled atmosphere fresh-keeping effect of fruit storage.
(2) long storage period and high economic benefits. Such as grapes fresh 7 months, Apple 6 months, garlic after 7 months of quality fresh as ever, total loss less than 5%. Grape production price of only 1.5 Yuan/kg, and storage before and after the Chinese new year priced at up to 6 Yuan/kg. Once put into cold storage, service life of up to 30 years, economic benefits are significant. Year investment take effect that year.
(3) simple operation, easy maintenance. Microcomputer control temperature refrigeration equipment, automatic startup, shutdown, without special care, supporting technical and economic utility.
Modified atmosphere library it can adjust temperature and humidity within the library, is in control of the content of gases such as oxygen, carbon dioxide, make fruits and vegetables in a dormant state within a library, libraries retain their originalquality.
2. effect of controlled atmosphere storage
(1) inhibition of respiration, reduce the consumption of organic matter and keeping excellent flavor and aroma.
(2) inhibit evaporation, keeping freshness of fruits and vegetables.
(3) inhibition of pathogenic bacteria breeding and reproduction, control the occurrence of physiological diseases, reduce the rate of fruit rot.
(4) inhibit the activity of ripening enzymes, inhibiting ethylene production, delayingripening and senescence, keep fruit firmness, has a longer shelf life.
Folding editor this controlled atmosphere systems
Gas gas composition of storage required and remain relatively stable, apart fromhaving to meet the requirements of air tightness in vitro, also must have the appropriate gas regulation equipment, piping system, valves, controlled atmosphere system. Controlled atmosphere systems as a whole, including nitrogen-making system, the carbon dioxide removal system, ethylene removal systems and gas composition, temperature, humidity automatic control system.
Nitrogen system
Nitrogen is the main equipment of the gas system (that is, oxygen). Nitrogen machine roughly went through the catalytic combustion nitrogen ¡ú carbon molecular sieve making nitrogen, the development of hollow fiber membrane separation nitrogen processes. Now commonly used hollow fiber membrane separation nitrogenand carbon molecular sieve.
Carbon molecular sieve making nitrogen machine carbon molecular sieve makingnitrogen PSA nitrogen is used, due to molecular oxygen and nitrogen dynamics ofdifferent diameters, the diffusion of oxygen molecules hundreds of times faster than nitrogen molecules. Adsorption capacity is proportional to the pressure, oxygen, nitrogen adsorption characteristics vary greatly within a short time, by the program controller is in a specific program to quickly switch between the two towers, combined with hyperbaric oxygen adsorption and desorption of oxygen decompression process, separates the oxygen from the air. Carbon molecular sieve making nitrogen machine has high nitrogen purity (up to 99.9%), the characteristics of simplicity and low price, but the device valve, switching frequency, each valve switch 20.4 million times a year, equipment noise. Requirements ensure the quality of valve, otherwise it will affect the reliability of the equipment.
Inside the air conditioned storehouse measurement and control system for: in thecontrolled atmosphere storage temperature and humidity, O2, CO2 gas checks inreal time measurement and display, to determine whether they meet the gas regulating specifications and automatic (manual) adjusting to make it in the best atmosphere parameters. In automation degree high of modern gas adjustable library in the, General used automatically detects control equipment, it by (temperature, and humidity, and O2, and CO2) sensor, and controller, and computer and the sampling tube, and valve, composition, whole system all by a Taiwan central control computer achieved far distance real-time monitoring, both can gets all points library within of O2, and CO2, and temperature, and humidity data, displayed run curve, automatically print records and started or close the system, while also can according to library within material situation at any time change control parameter. Central control computers use Windows interface, operators can be convenient and intuitive access to all relevant information.
Refrigeration system
Refrigeration system is essential for mechanical refrigeration machines, equipmentand to connect the machines, equipment, piping, valves, control elements consisting of closed-loop systems. Controlled atmosphere storage refrigeration system refrigeration system is basically the same with the common cold. Controlled atmosphere storage and refrigeration systems with high reliability, high degree of automation, and controlled atmosphere storage of fruits and vegetables maintain the required temperature in the library for a long time. Commonly used ammonia refrigeration system or direct expansion refrigeration system for liquid freon single stage compressor.
Humidification systems
Compared with conventional cold storage of fruits and vegetables, due to the controlled atmosphere storage of fruits and vegetables during storage of long, fruits and vegetables high water evaporation in order to contain evaporation of fruits and vegetables, reduces storage environment and storage of fruit and vegetable water vapour partial pressure difference between requiring controlled atmosphere storage has the best storage environment relative humidity, which reduce fruit and vegetable consumption is important to keep fruits and vegetables fresh and crisp.Relative humidity within the General Library best kept between 90%-95%. Air humidification methods commonly used are as follows: (1) ground water humidification;(2) chassis of cooler water, (3) spray humidification; (4) centrifugal atomizing humidification; (5) ultrasonic atomizing humidification.
Pressure balance system of controlled atmosphere storage