Controlled atmosphere is the precise regulation of a storage rooms’ concentration of humidity, oxygen concentration, nitrogen, temperature, and carbon dioxide concentration.
Historically, the Controlled atmosphere is seen to be practiced by ancient Samarians and Egyptians around the second entry in the storage of their crops in crypts sealed with limestone to increase the storage life of their foods like grains. However, the first recorded CA, through control of how fruit could ripe at a slower rate, was done by Jacquet Beard in 1821 in France.
Years later, in Cleveland, Ohio, Benjamin M Nyce, a commercial storage operator, experimented by reducing the oxygen level of an ice-cold store and realised this improved the storage life of fruits. Later, CA experiments have been carried out, and by 1933 scientists and researchers from all over the globe began studying at Ditton Laboratory. This scientist referred to the prolonging of the storage life of commodities as gas storage. However, a group of scientists and researchers assembled in New York in 1940 and renamed gas storage as Controlled Atmosphere Storage.
The controlled atmosphere is commonly used in the storage of dry commodities, vegetables, and fresh fruits.
Although controlled atmosphere mostly involves the regulation of oxygen and carbon dioxide concentration, Controlled Atmosphere Temperature Treatment (CATT) is very vital in this method of storage. Moreover, in a controlled atmosphere, pest control to stored commodities is achieved through Controlled Atmosphere Disinfestation(CAD). CAD is done by reducing the oxygen level of a temperature-controlled store. This treatment through C.A.D is lethal to pests, non-toxic, and does not have any harmful effects on stored commodities.
The controlled atmosphere helps in prolonging the storage life of commodities by reducing physiological and fungal deterioration and slowing respiration down. In this process, the oxygen level is reduced by replacing it with nitrogen, while some are converted to CO2 to extend the storage of perishable goods. The precise level of oxygen, nitrogen, carbon dioxide, and temperature required to prolong the room varies from commodity to commodity. Depending on the degree of control of gases or the method used in CA, there are different types of controlled atmosphere. First, the static controlled atmosphere storage is a type of CA where the product generates the atmosphere. Secondly, a flushed controlled atmosphere is a type of CA where the atmosphere is supplied from a flowing gas stream, which purges continuously into the store.
Controlled Atmosphere Disinfestation (CAD) is involved in getting rid of rodents and pests in a controlled atmosphere storage system.
C.A.D is a type of treatment that does not harm the stored commodities for consumption and other use but prolongs its storage life by keeping away pests and rodents. Insects and pests in storage are aerobic organisms that require oxygen for survival. Therefore CAD helps in altering gas composition within a controlled atmosphere and making it have high levels of carbon dioxide and low oxygen level. The lower the humidity and moisture content in CA, the higher the mortality due to the dehydration effect on pests caused by high concentrations of CO2 and low level of O2.
Therefore in Controlled Atmosphere Disinfestation (C.A.D), sufficiently high levels of carbon dioxide and reduced oxygen levels are created through a metabolic process that is based on pests respiration and the moisture content of the stored commodity. CAD is highly suitable in the storage of products like rice, soya, grain, cacao, and tobacco. Therefore, C.A.D is done depending on physical factors such as relative humidity, gas concentration, and temperature. Moreover, biological factors such as insect species, development stage, and strain are also considered in Controlled Atmosphere Dis-infestation.
Dry commodities such as legumes, grains, and oilseeds are usually stored in a CA to control pests through the Controlled Atmosphere Disinfestation(CAD). Such treatments, like C.A.D, may take several days or weeks to lower the temperature level of the store below 15 degrees. Dry grains need a complete schedule of Disinfestation, with most content below 13% and carbon dioxide level being high for at least fifteen days. This is easily achieved by adding pure nitrogen or carbon dioxide to the controlled atmosphere. Moreover, the Controlled Atmosphere Disinfestation can be made by the use of natural effects of respiration such as molds or grains to increase carbon dioxide level and reduce oxygen level.
In the case of fruits and vegetables, the combination of CAD and CATT (Controlled Atmosphere Temperature Treatment) is vital to prolonging the storage life of these commodities.
With controlled atmosphere, the long term storage of fruits and vegetables involves the slowing down of the ripening process in fruits and reducing aging in plants. In a Normal atmosphere, there is usually a 78 percent level of nitrogen, 21 percent oxygen, 0.3 percent carbon dioxide, and other rare gases. In CA, the percentage level of oxygen is reduced up to about 1.5 to 2 percent, depending on the type of fruits or vegetables. Therefore the quality of these commodities is maintained, and they can be stored up to 4 times the usual storage.
Controlled Atmosphere Temperature Treatment (CATT) has been used in controlling the pest in stored products for centuries. Ancient Egypt, for example, sealed cribs tightly for the storage of grains to prevent insects’ growth and infestation by lowering the oxygen level within. Historically, Controlled Atmosphere Temperature Treatment (C.A.T.T.) was designed for long term storage in the preservation of quality of the commodity. The controlled atmosphere is vital in the room of products; low temperatures in a CATT are essential in the storage life of commodities.
Controlled Atmosphere Temperature Treatment(C.A.T.T) provides more time in the storage of commodities since low temperatures affect the mortality rate of insects.
Scientists have reported that CATT has effects on insect physiology, including the reduction of energy charge of these insects to reduce the production of ATP. Researchers have also studied the impact of CATT on stored fruits like apples. These fruits, after CATT, do not show any form of loss of quality in terms of sweetness, decay, and firmness. However, there is a limitation of using CATT in the transportation of commodities. These were under CA due to the sophisticated technology used in this type of storage.