Introduction to above zero refrigerators
Above zero refrigerators are used to store fruits and vegetables because most fruits and vegetables lose their quality in sub-zero conditions. They also look bad. In order to increase the shelf life of the product, food must be kept at the lowest possible temperature. This prevents the growth and multiplication of microorganisms.
Above zero refrigerator for fruits and vegetables
In the storage of fruits and vegetables, the product should be in conditions close to the best quality in terms of appearance, smell, taste and amount of vitamins. Slight deterioration of the product that has caused obvious changes in its specifications will reduce its commercial value. For example, wilted vegetables or fruits, although usable, have lower prices due to changes in their appearance.
Decay of fruits and vegetables due to chemical changes begins after picking the fruit. Internal spoilage agents are natural enzymes that are present in all organic matter. External agents, on the other hand, are microorganisms that grow inside or outside fruits and vegetables.
Note that storing different fruits and vegetables together is possible provided that the conditions for storing them are exactly the same in terms of temperature, humidity and respiration. Otherwise food must be stored in different rooms with different storage conditions. Another problem that occurs in cold stores of mixed fruits and vegetables above zero is the smell of the products. For this reason, many fruits should not be stored together, even for a short time. Potatoes, for example, have a strong tendency to spread odors to other fruits and vegetables and should never be stored together.
Above zero refrigerator for fruits
Fruits are seasonal, and if they are not stored properly at temperatures above zero in the fruit Above zero refrigerator, we may have a shortage in the market during the seasons when we do not harvest. In the past, only durable fruits such as apples and pears were stored in cold places. This kept them safe for several months. But today, with fruit refrigeration, temperatures above zero can be simulated everywhere. For this reason, all fruits can be stored for a long time. It is also possible to move from where the product is grown to another place in the world to sell it.
At long distances, such as transporting bananas by ship, the fruit is harvested unripe and green. By controlling the temperature and humidity conditions, the fruit is taken to the place of consumption in the above zero refrigerator.
Today, large quantities of perishable food are transported by air. In these conditions, due to the high altitude and low pressure and temperature of the outside air, by creating positive pressure inside the consignment, food should be protected from the infiltration of outside air and the risk of over-cooling.
Fruit refrigeration temperature
The optimum storage temperature of products in the fruit Above zero refrigerator is usually above zero and slightly higher than their freezing point. Some fruits are sensitive to storage temperatures, and when stored at temperatures above or below their critical temperature, they develop fruit-freezing diseases, such as bananas, whose skin turns black at temperatures below 13 ° C.
Humidity and air flow in the fruit above zero refrigerator
The difference between product vapor pressure and air refrigeration is usually a function of relative humidity and air velocity. For this reason, stagnant air with relative humidity is the ideal condition for fruit refrigeration above zero. But this can cause the product to become moldy. Also, good flow in the Above zero refrigerator and around the products is essential for proper cooling of fruits. Therefore, the humidity should be slightly less than 100% and the air speed should be high enough.
Controling gas around fruits in fruit refrigerator
The fruits are alive after picking as they were when they were grown. Fruits breathe after picking oxygen and give back carbon dioxide. Because of this, they deteriorate and rot during storage. If the penetration of oxygen is controlled by atmospheric control fruit refrigerators, which are sealed and airtight, their shelf life can be increased to conditions above zero. When the products are kept in atmospheric control conditions (refrigeration c.a), after a few days, they consume the oxygen in the refrigeration space of the fruit. By removing excess oxygen by injecting nitrogen and by removing excess carbon dioxide, artificial sleep can be induced in fruits. This increases shelf life with precise control of oxygen, carbon dioxide and ethylene. For example, apples can be stored for up to 1 year with this method.
Above zero refrigerator for vegetables
Storage of vegetables in the refrigerator will stabilize the supply and demand in the market and increase profitability for farmers and reduce crop losses. If the following conditions are met, it is possible to store some fresh vegetables at above zero temperature in the refrigerator for up to 6 months. These conditions are as follows:
– The product should be placed at a low temperature. This causes bacteria, germs and other microorganisms to be inactive. Like celery, which rots if stored above 1 ° C.
– The product does not freeze. Because in this case, the freshness and freshness of the product is lost and the appearance of the product is spoiled.
– Maintain the optimum moisture for storing vegetables. This prevents the vegetables from shrinking and drying out in the refrigerator.
Reduce the contact of vegetables with oxygen. This minimizes the reactions caused by plant respiration.
The storage temperature of vegetables must be chosen correctly to maintain them for a long time. Celery, for example, rots if stored above 1 degree. Onions germinate at temperatures above zero.
Potatoes are sweetened at a temperature of less than 4 degrees. Peppers and green beans also produce pits at temperatures close to zero.
Damage to vegetables
Usually the damage to vegetables is due to the following reasons:
Fresh vegetables may be damaged during one of the harvesting, transportation, storage and retail stages before they are delivered to the consumer. Or during storage and transportation, if their temperature conditions are not observed it reduces the quality and loss of useful vitamins of vegetables. Also, not keeping vegetables at temperatures above zero and reducing their excessive temperature will lead to moisture loss and shrinkage.
With proper packaging and the use of refrigeration systems in storage and transportation, high-quality and fresh vegetables can be delivered to the consumer.
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