Basic techniques for storage and preservation of t

2022-07-26
  • Detail

At present, the storage methods widely used at home and abroad can be divided into two categories: one is low-temperature storage, that is, using natural low temperature or artificial cooling (mechanical refrigeration or ice) to make the storage environment store at low temperature; The other is controlled atmosphere storage. This kind of storage method is to adjust the gas composition record data in the storage place under low temperature conditions, so as to achieve the gas index suitable for fruit and vegetable storage, so as to obtain better storage effect

with the continuous reform and innovation of fruit and vegetable storage technology and some treatment methods, in addition to the above methods, more attention has been paid to the research on radiation treatment, electromagnetic field treatment and decompression storage at home and abroad, which has avoided a new research path for fruit and vegetable storage

(I) simple storage and fresh keeping

simple storage includes three basic forms: pile storage, ditch storage (burial) and cellar storage, as well as the derived false planting storage and frozen storage. All of them use natural low temperature to maintain the required storage temperature as much as possible. The structure and equipment are simple, and all of them have a certain spontaneous preservation effect

1. stacking

is a temporary storage method that directly stacks fruits and vegetables on the ground or open space of fields and orchards. Stacking can also be used as a pre storage method. During storage, generally, fruits and vegetables are directly stacked on the ground or in shallow ditches (pits), and the coverage is thickened by times according to the temperature change, so as to provide shade or cold protection and heat preservation. The covering materials used are mostly local materials. The permanent covering materials include reed mat, straw curtain, crop straw, soil, etc. Because the storage is on the ground, the fruit is less affected by the ground temperature after storage, but more affected by the temperature. Especially in the early stage of storage, because of the high temperature, the storage temperature is difficult to decrease. Therefore, stacking storage should not be used in areas with high temperature. Generally, it is only used for short-term storage in autumn and winter. The width and height of the storage pile shall be determined according to the local climate characteristics and the types of fruits and vegetables

2. ditch storage

is a relatively simple method of fruit and vegetable storage. Root vegetables, chestnuts, walnuts, hawthorn, etc. are usually preserved by this method; Apples and other fruits are also preserved by this method. Ditches or pits shall be dug on the ground. The burial place shall be high and dry, with heavy soil, good drainage and low groundwater level. The ditch should be long from north to south in cold regions; In warmer areas, the east-west direction is often adopted. The depth of the ditch is generally determined according to the thickness of the local frozen soil layer, and it is stored below the frozen soil layer. The effect of burial is not only affected by soil temperature, but also related to its width. Generally, there are several methods for stacking fruits and vegetables in the ditch: first, stacking method, that is, fruits and vegetables are scattered in the ditch and covered with soil (sand); The second is the stratification method, that is, each layer of fruits and vegetables is put, a layer of sand is sprinkled, and after the stratification reaches a certain height, it is covered with soil (sand); Third, mixed sand burial method: after mixing fruits and vegetables with sand, they are stacked in the ditch and then covered; Fourth, put fruits and vegetables in baskets and bury them in ditches

3. cellar

there are many kinds of cellars, of which the shed cellar is the most common. In addition, in Shanxi, Shaanxi, Henan and other places, there are caves, Nanchong, Sichuan and other places where citrus is stored in the form of pits. Most of these cellars were built according to the characteristics of local natural and geographical conditions. It can not only use stable soil temperature, but also use simple ventilation equipment to adjust and control the temperature in the cellar. Fruits and vegetables can enter and leave the cellar at any time, and the storage condition can be checked in time. However, the shed cellar is reduced by the general ventilation of other cellars in Karachi

(II) ventilation storehouse storage and preservation

ventilation storehouse is the development of shed cellar, and its form and performance are similar to shed cellar. The shed cellar is a temporary storage place, ventilated and the warehouse is a permanent building. It uses brick, wood and cement structures. Although its cost is higher than that of the shed cellar, it has a large storage capacity and can be used for a long time. At present, the output of fruits and vegetables has increased significantly year by year, and the storage of fruits and vegetables can not completely rely on the cold storage. Therefore, the ventilated storage has great practical value in a considerable period of time

the ventilation storehouse also uses the principle of air convection to introduce external inspection and control the cold air in the visual world to cool down. It is mainly to set up a perfect and flexible ventilation system in the warehouse with good thermal insulation performance, use the temperature difference between daytime and liquid, introduce the low-temperature air outside the warehouse into the warehouse through the air guide equipment, and then discharge the hot air, ethylene and other harmful gases outside the warehouse through the exhaust equipment, so as to maintain a more suitable storage environment for fruits and vegetables. However, due to the fact that the ventilated storehouse is cooled and stored by natural temperature, it is greatly restricted by temperature, especially at the early and late stage of storage, the storehouse temperature is high, which is difficult to control and affects the storage effect. In order to make up for this deficiency, electric fan, blower, ice or mechanical refrigeration can be used to accelerate the reduction of storage temperature, so as to further improve the storage effect and prolong the storage period

the ventilated storage should be built in a place with high dry terrain, good ventilation, no air pollution and convenient transportation. The direction of ventilation silo shall be determined according to the local minimum temperature and wind direction. In the north, it is better to be long from north to south, so as to reduce the direct attack surface of winter cold wind and avoid the low temperature of the reservoir; In the south, the length from east to west is used to reduce the exposure of the sun to the East and West, and increase the windward side

there are generally three types of ventilated storage: above ground, semi underground and underground. The storehouse body of the above ground ventilated storehouse is all built above the ground, so it is greatly affected by the temperature; The semi underground ventilated storage is partly below the ground and partly above the ground. The temperature of the storage is affected by both the air temperature and the soil temperature; The underground ventilated storage is all built below the ground, which is most affected by the ground temperature and least affected by the air temperature. As for the type of ventilated storage, it should be determined according to the local climate (mainly air temperature, ground temperature), geography and other conditions. In severe cold areas in winter, underground type is often used, which is conducive to cold prevention and heat preservation; In warm areas, the above ground type shall be adopted to facilitate ventilation and cooling; In the warmer areas in winter, the above ground type shall be adopted to facilitate ventilation and cooling; in the warmer areas in winter, the semi underground type shall be adopted; In low-lying areas with high groundwater level, the above ground type shall be adopted

(to be continued)

rust and corrosion may also occur

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