Basic principles of long-term storage of fruit
The main form of interaction of fruits and vegetables with the environment is the process of respiration, which can be described by the formula:
C6H12O6 + 6O2à 6CO2 + 6H2O + energy
During storage, fruits absorb oxygen from the environment and emit carbon dioxide CO2. The heat of respiration is released during storage. However, not all heat is released into the air, as some of it is used by the cell for metabolic reactions and the evaporation process, some is stored in the form of chemically bound energy.
The biological role of respiration is to provide the living tissues of fruits and vegetables with the energy they need to function.
Along with the evaporation of moisture, the process of respiration is inevitably accompanied by a decrease in the weight of fruits and vegetables. Therefore, such losses are called natural. They can be reduced by regulating the intensity of respiration and evaporation of moisture, which is important in practice.
Storage under normal conditions involves a normal air environment with a normal content of oxygen, carbon dioxide and other gases in the atmosphere. The total content of oxygen and carbon dioxide in the air is about 21%.
The reaction rate depends on the temperature and the concentration of the reactants. In order to slow down the rate of the above reaction, it is necessary to reduce the temperature and oxygen concentration. Also, to avoid the conversion of glucose into alcohol, it is necessary to maintain a CO2 concentration of not more than 2%, thus, the optimal conditions for long-term storage of fruit are (O2 content, 0.5-1.5%, CO2 content 0.03-2%, storage temperature +1 - +4 Co). Such storage conditions are provided by modern equipment consisting of two main systems:
1. Air filtration system to create a special air environment in the chambers.
2. Refrigeration equipment
Air filtration system to create a special air environment in the chambers.
The required composition of the air environment in the storage is achieved by a complex combination of air filtration using the Scrubber "Scrubber ST" and Nitrogen Generator "N2 generator" of the appropriate capacity and associated accessories. At the same time this or that structure of air is selected so that to keep normal respiratory gas exchange of fruits.
Fruits placed in a closed environment, due to the natural respiratory exchange, change the partial pressure of CO2 and oxygen in the surrounding atmosphere.
In a controlled gaseous medium, compared to storage in a normal air environment, the quality of the fruit is better preserved, the color lasts longer, the hydrolytic processes of protopectin decomposition are slowed down - the fruit stays firm longer.
In order to slow down the ripening processes and prolong the shelf life of fruits while maintaining their high quality, it is necessary to create an air composition corresponding to each variety.
Depending on the composition of the air there are 3 main types of regulated atmosphere:
1. Traditional Controlled Atmosphere - oxygen content 3-4%, carbon dioxide 3-5%.
2. With low oxygen content LO (Low Oxygen) - 2-2.5% O2 and 1-3% CO2.
3. With ultra-low oxygen content ULO (Ultra Low Oxygen) - oxygen concentration in the chamber in the range of 0.5-1.5%, CO2 content 0-2%. It is established that at low oxygen storage hardness, freshness, acidity of fruits are better kept, the probability of sunburn decreases or is completely eliminated. Therefore, a regulated ULO atmosphere will be used in this storage.
The composition of the atmosphere will be maintained at a level determined for each type of product according to the recommendations of the technologist. Management and control of operation of all installations in storage is carried out by means of the computerized control system.
It is well known that ambient air contains 78% nitrogen, 21% oxygen and carbon dioxide, 1% impurities. By processing it with a nitrogen generator "N2 generator" we get almost pure nitrogen (97 - 99%), feeding
which in the storage chamber we can bring the percentage of oxygen to the specified parameters (eg 5%). After some time, the level of carbon dioxide in the storage air will increase as a result of fruit respiration. At this point, the Scrubber ST will be indispensable, which will filter excess oxygen and carbon dioxide from the air of the chambers. During the year, the amount of carbon dioxide emitted by fruits varies greatly, so to avoid frequent switching on the equipment use air buffers corresponding to the size of the chamber volume, which stores air with a given oxygen content and without carbon dioxide. Air buffers also serve to compensate for the pressure drop in the chambers in relation to the environment. As the external air pressure increases, the difference in air pressure in the chamber and in the environment is compensated by the air stored in the buffers. At decrease in external air pressure different
Скруббер углекислого газа - STOREX CO2 Scrubber
Генератор азота STOREX VSA N2 Generator
Буферные емкости из полиуретана.
