Unlike most food products, fruits and vegetables continue to respire after harvest. This process absorbs oxygen and produces carbon dioxide and water vapor.
The main thing to keep these products fresh is packaging that can reduce the amount of breathing as much as possible and does not damage the quality, taste, texture and appearance of the product.
In general, by keeping the temperature low and creating a lower level of oxygen in the indoor atmosphere and increasing a higher level of carbon dioxide, the rate of breathing can be reduced.
However, not everything will be that simple, for example, if there is not much oxygen in the space inside the package, a process called anaerobic respiration will occur, which will cause unwanted flavors and odors in the product and finally It will damage the food product. In addition, too much carbon dioxide can damage some products.
Also, taking into account that the high amount of water in this category of food products, along with the fact that the fruit is naturally acidic, can lead to spoilage, mold and yeast. Also, the pulp of the fruit can become soft and be attacked by enzymes through microbes and eventually rot.
How to choose the type of film and container used in the packaging of fruits and vegetables is of particular importance, because the important factor in choosing the right type is the degree of permeability or breathability.
If the product is sealed (sewn) and packed inside the container, the oxygen inside the package will decrease soon and unfavorable anaerobic conditions can be created. On the other hand, if the packaging materials are very porous, the modified atmosphere will escape from inside the package and will be of no use.
The goal is to achieve equilibrium in the product, which is called the Equilibrium Modified Space or EMA. Here, oxygen and carbon dioxide can pass inside and outside the package, so that when the oxygen inside the package is consumed, it is replaced by oxygen outside the package, and in the same way, a constant amount of carbon dioxide is maintained inside the package. to be Another advantage of modified atmosphere is that it can reduce the natural ripening of fruits and vegetables by ethylene gas, which can accelerate this ripening process.
For a package of mixed salad, a practical EMA might include 5% oxygen, 15% carbon dioxide, and 80% nitrogen. This gaseous composition can increase the shelf life of the product up to 8 days, while outside of these conditions and in the best possible case, it can stay fresh for 4-5 days.
Also, a modified atmosphere can have a significant effect on the browning of chopped fruits and vegetables, such as potatoes and apples, which is a result of the oxidation reaction by enzymes that are released when damaging the skin of the fruit. be
In these cases, having a combination of carbon dioxide and nitrogen in the package, without the presence of oxygen, can prevent the browning process for several days, while under normal conditions, only a few minutes or a few hours. It can be exposed to air and the browning process takes place immediately.