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% O2 and 0.03% CO2. However, it was found that low oxygen and high carbondioxide 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 O2 and increased CO2 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: • 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: • 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 O2 and to high CO2 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 O2 concentrations
Tolerance of various commodities to high CO2 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.
Transportation of strawberries in CO2 – enriched atmosphere – TransFresh (Tectroll) technology
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.
Acta Hortic. (2003) 600: 737-740 The above recent publication from the 8th Int. CA Conference (2002) provides a list of the optimal CA conditions for 35 selected horticultural commodities.
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 5C 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% O2 and 8-12% CO2). It is possible to improve gas control in MAP by adding absorbers of ethylene, carbon dioxide and oxygen.
Individual seal packaging of oranges China, 2007
MAP of mangoes Bangkok, 2007
MAP of apples Bangkok, 2007
MAP of peppers Bangkok, 2007
Perforated bags Bangkok, 2007
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.
Water condensation and decay development Bangkok, 2007
Water condensation in fresh-cut pineapple Thailand, 2011
In commercial practice, CA is applied especially in apples and pears, whereas MA is successfully applied in a wide range of produce
The following pictures explore some applicable uses of CA and MAP storage:
Effects of MAP on the inhibition of ripening in Mango fruit
Effects of MAP on the quality of pomegranate fruit