Presentation on theme: "Controlled Atmosphere and Modified Atmosphere Storage Dr. Ron Porat Dept. of Postharvest Science of Fresh Produce ARO, The Volcani Center, Bet Dagan, Israel."— Presentation transcript:
Controlled Atmosphere and Modified Atmosphere Storage Dr. Ron Porat Dept. of Postharvest Science of Fresh Produce ARO, The Volcani Center, Bet Dagan, Israel
Normal room air contains 21% O 2 and 0.03% CO 2. However, it was found that low oxygen and high carbon dioxide levels slow ripening, reduce the development of some peel disorders and inhibit pathogen growth.
The terms controlled atmosphere (CA) and modified atmosphere (MA) imply using an atmospheric compositions that is different from air, but they differ in the degree of their control of the gases concentrations. Control atmosphere (CA) – generally refers to decreased O 2 and increased CO 2 concentrations, by a precise control of the gas composition. Modified atmosphere (MA) – is used when the control of the storage atmosphere is not closely controlled, such as in plastic film packaging.
CA and MA are usually used as a supplement to cold storage, but in some cases they may replace cold storage.
Potential benefits of CA: 1) Retardation of ripening and senescence. 2) Inhibits ethylene effects. 3) Reduction of certain physiological disorders. 4) Inhibition of pathogen growth. 5) May be used for insect control.
Potential harmful effects of CA: 1) May cause irregular ripening after storage. 2) May cause certain physiological disorders. 3) May enhance anaerobic respiration and development of off-flavors. 4) May cause susceptibility to decay.
Fruits and vegetables differ in their tolerance to low O 2 and to high CO 2 concentrations. Extreme oxygen and carbon dioxide concentrations (above the limits for each cultivar) may cause physiological and pathological deterioration, interrupt with normal ripening and enhance anaerobic respiration and development of off-flavors.
Tolerance of various commodities to low O 2 concentrations
Tolerance of various commodities to high CO 2 concentrations
Fruits and vegetables can be grouped according to their storage potential under optimum temperature, RH and CA conditions as followed: Up to 1 year – apple and pear Up to 6 months – kiwi, persimmon, pomegranate Up to 3 months – avocado, banana, cherry, grape, mango, nectarine, peach, plum Up to 1 month – apricot, fig, papaya, pineapple, strawberry
CA or MA may be applied to improve the storage potential of either short- or long- lasting commodities.
CA recommendations A CD-ROM entitled: “CA Recommendations (2001)” was published by the University of California, Postharvest Technology Center. The CD-ROM can be ordered through website access at http://postharvest.ucdavis.edu.
The above recent publication from the 8 th Int. CA Conference (2002) provides a list of the optimal CA conditions for 35 selected horticultural commodities. Acta Hortic. (2003) 600: 737-740
Recent developments in CA storage: Recent improvements include maintaining CA during transport in refrigerated marine containers - this allows to continue the CA chain of apple, pear and kiwi during transport. CA transport of banana permits the harvest at a more fully-mature stage. CA transport of avocado permits to use a lower temperature of 5 C without the development of CI.
In addition to CA, there is also a continuing increase in the use of plastic films and MAP. The greatest use of MAP is for fresh-cut products (to maintain 2-5% O 2 and 8-12% CO 2 ). It is possible to improve gas control in MAP by adding absorbers of ethylene, carbon dioxide and oxygen.
In addition to gas exchange properties, new polymeric films have been developed with various water vapor transmission rates, which allow to control the RH inside the package and to avoid problems caused by water condensation.