Controlled atmosphere
A controlled atmosphere is an agricultural storage method. An atmosphere in which oxygen, carbon dioxide and nitrogen concentrations as well as temperature and humidity are regulated.
Two major classes of commodity can be stored in controlled atmosphere:
- Dry commodities such as grains, legumes and oilseed. In these commodities the primary aim of the atmosphere is usually to control insect pests. Most insects cannot exist indefinitely without oxygen or in conditions of raised (greater than approximately 30%) carbon dioxide. Controlled atmosphere treatments of grains can be a fairly slow process taking up to several weeks at lower temperatures (less than 15 °C). A typical schedule for complete disinfestation of dry grain (<13% moisture content) at about 25 °C, with carbon dioxide, is a concentration above 35%(v/v) carbon dioxide (in air) for at least 15 days.[1] These atmospheres can be created either by:
- adding pure gases carbon dioxide or nitrogen or the low oxygen exhaust of hydrocarbon combustion, or
- using the natural effects of respiration (grain, moulds or insects) to reduce oxygen and increase carbon dioxide Hermetic storage.[2]
- Fresh fruits, most commonly apples and pears, where the combination of altered atmospheric conditions and reduced temperature allow prolonged storage with only a slow loss of quality.[3]
Long-term storage of vegetables and fruit actually involves inhibiting the ripening and ageing processes, thus retaining flavour and quality. Ripening is, in fact, postponed. This occurs as a result of modifying the gas conditions in the cool cell so that the respiration of fruit and vegetables is reduced. Controlled Atmosphere (CA) is a storage technique whereby the level of oxygen is reduced and CO2 is increased. Quality and the freshness of fruit andvegetables are retained under Controlled Atmosphere conditions without the use of any chemicals. Under CA conditions, many products can be stored for 2 to 4 times longer than usual.
See also
- Cold chain
- Modified atmosphere
- Modified atmosphere/modified humidity packaging
- Godwin agro
- Shelf life
References
- ↑ Annis, P.C. and Morton, R. 1997.The acute mortality effects of carbon dioxide on various life stages of Sitophilus oryzae. J. Stored Prod.Res. 33. 115-124
- ↑ Annis P.C. and Banks H.J. 1993. Is hermetic storage of grains feasible in modern agricultural systems? In “Pest control and sustainable agriculture” Eds S.A. Corey, D.J. Dall and W.M. Milne. CSIRO, Australia. 479-482.
- ↑ http://bestapples.com/washington-orchards/packing-process/
