Ethylene Removal in Cold Storage: Ozone versus Potassium Permanganate
The preservation of fruit and vegetables in cold storage is currently an indispensable fact, although the cold in itself does not resolve the problem of preservation.
Ethylene is a gas that is produced naturally by vegetable tissues. It acts as a vegetable hormone and principally controls the processes of ripening and senescence. Ethylene accumulates in low concentrations in areas where fruit and vegetables are preserved, and thus reduces the postharvest life of the products stored. That is why eliminating it from these areas reduces the loss of quality in the fresh produce and consequently brings financial benefits.
To ethylene removal, systems that eliminate ethylene from the air through oxidation (with ozone or potassium permanganate) catalysis or combustion are installed in the cold stores .
For these technologies to be safe and efficient, they need to meet certain requirements. In general terms these are as follows:
- The capacity to reduce ethylene concentrations to safe levels under practicable conditions.
- They must not cause damage to the fresh produce.
- They must not cause damage to the cold storage equipment.
- They must be safe for staff, the consumer and the environment.
According to an article published by the University of California, Davis (*), ethylene elimination systems that consist in emitting ozone into the air in the cold stores at safe concentrations are not an efficient way to eliminate ethylene. That is because using ozone at low concentrations means that contacts with molecules of ethylene or other volatile substances are fleeting, making the process of their elimination too slow. In addition, according to the same article, ozone can cause damage to the vegetable tissues and to the cold storage equipment, since it is very corrosive.
If ozone is not directly introduced into the cold store, but air is forced through an ozone chamber, the problems of corrosion and damage to the fruit disappear. However, the low flow provided by the equipment on the market (far below the volume per hour in cold storage) impedes the fast elimination of ethylene that is needed to maintain the concentration of ethylene at safe levels.
On the other hand, the Bioconservacion systems force the air through a granulate with potassium permanganate (Bi-On), with a high capacity for absorbing ethylene from a flow that is equal to or higher than the cold storage volume per hour. That enables a rapid elimination of the ethylene being produced by the fruit and impedes its accumulation to harmful levels. It also meets the other requirements suggested above and is a safe and cost-effective system for eliminating ethylene.
(*) Trevor V Suslow. Ozone Applications for Post-harvest Disinfection of Edible Horticultural Crops. Extension of Vegetable Crops, University of California, Davis
Article available at: http://anrcatalog.ucdavis.edu/pdf/8133.pdf