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CO2 gas- One of the effective methods of preserving agricultural products

CO2 gas- One of the effective methods of preserving agricultural products

Cập nhật: 05-08-2021 03:42:38 | News | Lượt xem: 81

CO2 gas- One of the effective methods of preserving agricultural products

Store agricultural products in a well-ventilated state
Keeping agricultural products airy is to let the block of agricultural products come into contact with the outside air environment easily. To regulate temperature and humidity in the warehouse. And the mass of agricultural products in a timely manner adapts to the storage environment. Thus, keeping the water content and temperature of the agricultural products in a safe state. Preservation of agricultural products

Airy storage requires a well-ventilated warehouse system. It is both closed and has a reasonable ventilation system to prevent the agricultural product block from having water. And the temperature is higher than the outside air, natural ventilation is conducted. Or use a fan to take advantage of the cold, dry air outside. Conversely, when the temperature and humidity are higher in the air than in the warehouse. The warehouse must be closed to prevent hot and humid air from entering the warehouse. Preserving agricultural products

In the process of ventilation, taking advantage of nature to ventilate is called negative ventilation. And if it is also the mode of airy preservation. But we apply ventilation through machines called active ventilation.

Natural ventilation
It is a relatively simple and cheap method, but it is necessary to calculate and seize the right opportunity for ventilation to be beneficial. For natural ventilation, the following four conditions must be met:

– Weather: Outside there is no rain, no fog because that is when high humidity will be harmful to storage.

– Temperature: Outside, around the warehouse, the temperature should not be higher than 32°C and not lower than 10°C because if the temperature is too high, when opening the ventilation door, hot air will enter and increase the temperature in the warehouse. or if it is below 10°C, it will bring cold air into the warehouse to condense the steam in the warehouse. Preserving agricultural products

– Absolute humidity: Outdoor around the warehouse must be lower than the absolute humidity in the warehouse. If it is higher, the absolute humidity outside when opening the ventilation door. Can be inserted to make the relative humidity in the warehouse high, seeds and agricultural products are susceptible to moisture. Preservation of agricultural products

– Dew point: The dew point temperature in the warehouse must be lower than the temperature outside. Because the air temperature outside the warehouse is lower than the dew point in the warehouse. Water vapor will condense, causing adverse effects.

Conclusion on the method of preserving agricultural products by natural ventilation

Through many experimental observations found that natural ventilation . Can only be organized in case of dew point of high temperature environment. Do not exceed 1°C above the air temperature of the low-temperature environment. Through experience monitoring many warehouses shows that . Around 8 - 9 am and 17 - 18 pm can open the ventilation door. When the opportunity to ventilate is present, know how to open the warehouse door. First open the door from the direction the wind is blowing, then open the door on both sides of the warehouse, and finally open the door to let the air out. Such an opening does not cause sudden changes in temperature and humidity in the warehouse. Preservation of agricultural products

Active ventilation
Active ventilation is the treatment of a batch of grain by the amount of air that is allowed to pass through it according to its thickness. In practice, active ventilation is not used exclusively for grain cooling. But people also use it as a separate mode to preserve seeds. This is the most complete, cheapest method used to preserve . But the whole process is purely mechanical. Preservation of agricultural products

Method for performing ventilation for the purpose of air exchange. Between particles with new, cold or dry and hot air. Also thanks to ventilation, unripe seeds can continue to ripen. Maintain seed stability (germination and germination capacity)

Between the particles in the granules there are gaps and there a constant flow of air is created. In this environment there is always gas exchange. There is a process of adsorption and absorption from the particle to the atmosphere and vice versa. Between the air around the seed lot and the air in the seed lot. And the air in the capillary tubes of the particle performs a fixed exchange. As a result, the penetration of air into the vacancy of the grain lot is always variable. When we use cold air, the batch of seeds can cool quickly. When we use dry air, the batch of seeds is dried. In general, thanks to active ventilation, it is possible to dry or cool a batch of seeds for best preservation. Preservation of agricultural products

Active ventilation method

Positive ventilation leads to a decrease in the temperature of the seed lot, and the humidity of the seed lot also decreases. And change the amount of air in the space between the seeds and keep the seed quality.

Using active ventilation is subtle and easy. The energy required to use is less than with active vacuuming (passing light air through the particle lot). That energy is less than the energy needed to manually move the batch of seeds through the air stream.Preservation of agricultural products

To actively ventilate the seed mass, large-capacity fans must be used. Or air blower. The fan can be fanned in layers from the top down or from the bottom up thanks to the filler tubes throughout the seed lot.

With a seed moisture content of 13 - 15% when actively ventilated will give good results:. In 1 day the air in the grain lot can change 800 times. That means with that batch of seeds, we have to fan an amount of air 800 times. Larger than the volume of its voids. For more important particles, 2,500 times are needed. Change the atmosphere in the gaps in 1 day.Preservation of agricultural products

Outstanding advantages of active ventilation

The outstanding advantage of active ventilation is that the voids in the seed lot are continuously ventilated. In the seed lot, there is always an exchange of gas and moisture between the seeds and the surrounding environment. And finally the outside air. Preservation of agricultural products

The voidness of a particle can be determined by determining its density and specific gravity.

Ventilation can be done in two ways: continuous and intermittent. Continuous ventilation is often used in hot seasons such as summer and autumn. In the morning and afternoon hours of the day when it is a bit cold, and in winter, all day. Preservation of agricultural products

When fanning air into the particle block, the following requirements must be met:

– The air must be fanned evenly throughout the grain mass, avoiding the place where the fan is much, where there is no fan.

– It is necessary to ensure enough air to achieve the purpose of reducing the temperature and humidity of the grain mass.

– Only fan when the relative humidity of the outdoor air is low, that is, after the fan, the moisture content of the grain mass decreases.

– The outdoor air temperature must be lower than the temperature of the seed mass. Preservation of agricultural products

Sealed storage method
Closed storage is to stop the exchange of air between agricultural products and the outside environment. Keep the agricultural block always in a safe state. Closed storage also means storage in the absence of oxygen. The goal is to limit the respiration of the seeds, and at the same time control the generation. Destructive development of microorganisms and insects. Preservation of agricultural products

For example: Seeds with a small volume can be preserved in jars sealed with cement. Or put the seeds in a jar covered with kitchen ash and seal.

In common cases, people also give seeds . Agricultural products are put in sealed polyethylene bags, or sealed iron crates, etc. Through many studies, it has been found that sealed storage still retains the food properties of the seeds. However, during respiration, alcohol can be produced

- Storage equipment must ensure good heat resistance and moisture resistance.
 The initial quality of seeds and agricultural products must meet the prescribed standards and quality. Especially the water must be below the safe level, the impurities must be lower than the specified level. Cleanliness and purity must be below the maximum allowable level and absolutely free of pests. Preservation of agricultural products

In addition to the above requirements, there are 2 ways to prevent atmospheric oxygen from the outside environment from entering:

– Let the amount of CO2 accumulate and O2 gradually lose during the respiration of the seeds. This method often takes a long time, so it is not absolutely safe. For seeds because when a certain amount of CO2 accumulates, it is also the time when the grain has seriously reduced quality. Preservation of agricultural products

Normally, CO2 is added to the granule mass by using CO2 in the form of ice. Spread evenly in layers over the granules. CO2 not only works to prevent oxygen from entering, but also lowers the temperature of the grain mass.

Cold storage of agricultural products and food
The principle of this method is to use low temperature to paralyze the activities of microorganisms and insects. This method requires lowering the temperature of the product mass to a certain extent. The lower the better To implement this method, people use many ways to cool the seeds. However, there are two common ways: natural cooling and artificial cooling. Preserving agricultural products

Natural cooling means taking advantage of the low temperature of the air in the storage environment. To lower the temperature in the grain mass through active ventilation and artificial cooling. That is, using cold rooms, cold storage or air-conditioned warehouses to keep a certain temperature of the grain mass. Preservation of agricultural products

For fresh vegetables and food, people keep cold in 2 ways:

Preservation by refrigeration
It is a method of keeping the temperature of the product slightly above its cell lysate temperature. Usually between 0°C and 1ºC. Preserved by this method the quality of the food remains good because the cell fluid does not freeze. Preservation of agricultural products

For good preservation by this method, attention should be paid to reducing the humidity of the air. Preservation of agricultural products

Preservation by freezing method
This is a method of keeping the temperature of the product between -10°C and -30°C or less. Under such conditions, all microbial activities are paralyzed. In addition to the above direct effect, the water in the product is frozen, so microorganisms cannot perform the heterotrophic process. Normally, if you want to freeze fruits and vegetables, you must have a refrigeration environment. The cooling medium can be in liquid, solid or gaseous form. Preservation of agricultural products

– Liquid cooling medium such as water CaCl2, NaCl, Ethyleneglycol (HOCH2-CH2-OH). Propilenglycol (CH20 CH2OH-CH2) uses different refrigerants depending on the product. Preservation of agricultural products

– Solid refrigerant load medium: Ice + salt + CO2 snow in dry form.

– Air cooled medium: CO2 gas or cooled air. Preservation of agricultural products

After harvesting, vegetables and fruits are cleaned, then frozen, usually at a temperature of 25 - 28°C. After setting, store at 15-18°C. The method of cryopreservation is used to preserve all kinds of products used in the canned vegetable processing industry and is widely applied. However, this method has the disadvantage of changing some properties of the product. When thawing, there is usually a watery discharge in which many nutrients are lost and microorganisms are easy to penetrate. Preservation of agricultural products

Chemical preservation of agricultural products
For a long time, people have used chemical drugs to preserve them in certain concentrations. Depending on the type of drug, each type of agricultural product and the quality status of the agricultural product. The marinating time lasts from the time of storage to the time of using agricultural products. And changes depending on the purpose and requirements of the agricultural product. Chemical drugs have the effect of inhibiting the vital activities of agricultural products. And destroy all activity of insects, microorganisms and other rodents. Preservation of agricultural products

This is a highly effective method, which is increasingly being used on a large scale. When using chemical drugs for preservation, they must ensure thorough requirements. Protect human health and do not affect the quality of agricultural products. Preservation of agricultural products

Commonly used chemicals for nuts are chloropicrin, dichloroethane, bekaphot, ...

For fruits and vegetables, the food industry often uses anhydric sulfide, sorbic acid, oxalic acid, benzoic acid, etc. to preserve agricultural products.

Some anti-sprouting chemicals such as M-1 (methyl ester of a-naphtyl acetic); M-2 (esterdimethyl of a-naphthyl acetic), MH (Hydrazide of maleic acid). Widely used in the preservation of potatoes, carrots, onions and other tubers. Preservation of agricultural products

Fungicides such as T.M.T.D, anti-bacterial drugs that cause rot. During the preservation of fresh fruits and vegetables. Preservation of agricultural products

Store in a modified atmosphere
For many years, people have applied the method of preserving agricultural products. Especially vegetables and fruits in the atmosphere

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