Controlled atmosphere
CA storage (English controlled atmosphere ) are an agricultural storage technology, especially, but not only, for the pome fruit storage, especially for apples, rare even for vegetables and meat (eg ham). CA storage have significance in the Silo. In an atmosphere storage system, the aging process is slowed perishable goods.
Operation
CA stands for controlled atmosphere, in a controlled, controlled atmosphere, and designates a storage technique which is used for delaying the ripening of climacteric fruit. In CA storage temperature, humidity, oxygen and carbon dioxide content be monitored by measurement and control technology and maintained at the desired levels.
Thanks to CA storage certain fruit and vegetables are available regardless of the harvest throughout the year. Compared with the traditional cold storage, the cost of the controlled atmosphere storage are considerably higher. In addition, the CA storage is not suitable for all fruit and vegetables.
The following conditions are in CA storage before:
- Low temperature ( -1 to 6 ° C, depending on crop and variety)
- High humidity (usually 92%)
- Of low oxygen content (typically 2 to 3% )
- Elevated carbon dioxide concentration (2 to 5 % depending on the crop and variety)
The metabolic activity of the stored material and therefore the loss of valuable ingredients to be possible significantly reduced. This is achieved firstly through a lowering of the temperature by cooling and removal of respiratory heat. On the other hand, the fruit is stored in storage cells, which allow a control of the gas exchange. By respiration and subsequent delivery of dosed oxygen content is lowered into the storage cells such that the respiratory activity and thus the metabolic activity is greatly reduced. However, a decrease in the O2 concentration to 0% has to be avoided at all costs, as are formed under anaerobic conditions and ethanol fermentation aromas musty. At the same time, the resulting CO2 should be absorbed by so-called scrubber, as it may cause a concentration of 5% metabolic damage. A constant high humidity ensures that the fruits do not dry out.
In particular CA camps in addition, the natural " ripening gas " ( phytohormone ) ethene is removed or inhibited its formation. A further possibility is to block the Ethenrezeptor, for example with 1-methylcyclopropene.
Background
Fruits have a metabolism. They also consume oxygen after the harvest, producing heat, carbon dioxide, water vapor and aromatic compounds. This tire is dependent on the oxidation of carbohydrates, sugars, and acids in the tissue of the fruit.
There is a relationship between the respiration in fruits and vegetables and its durability. Onions keep normally refrigerated up to 250 days and produce approximately 3 mg of carbon dioxide per kilogram and hour. Keep strawberries, however, cooled only 8 days, but produce ( "breathe" ), about 65 mg of carbon dioxide per kilogram and hour. The stronger the intensity of respiration of a fruit, the faster it ages.
The reduction of the oxygen content and the increase in Kohlenstoffdioxidgehalts are for slowing aging in the storage room of importance. The breakdown of vitamins and acids is slowed, reducing the production of ethylene in the fruit, the decomposition of chlorophyll inhibited (and thus the core house tan decreased) and the decrease in fruit firmness delayed.
In particularly low oxygen damage can occur in the fruits. Large fruit trees with low income are more sensitive to storage diseases.
History and Origins
1821 saw Jacques Etienne Berard, a researcher of plant physiology that fruits and vegetables stored have a reduced metabolism at a low oxygen content. At the beginning of the 20th century, the term CA received a precise scientific definition by the researchers Kidd and West. The real economic introduction of CA began simultaneously in the U.S. and in Europe, but only at the end of the 50s.
Developments
A variant of the CA storage are the so-called ULO-storage (English Ultra Low Oxygen ), which contain very little oxygen. Apples stay fresh until well into next year.