Some biophysical principles underlying the controlled atmosphere storage of plant material

Abstract

SUMMARYControlled atmosphere (CA) storage is of use for commodities which potentially can undergo rapid and unacceptable biochemical change. In air, the oxygen status of most plant material, including fleshy storage organs and fruits, suffices, even in the centre, for cytochrome oxidase to be fully saturated. Conflict of evidence exists as to possible O2 and CO2 gradients in fruit which, though physiologically unimportant in air, could be important under CA conditions. CA storage gives possible control of internal O2 from o to about 80–95%; internal CO2 from about 3–4 to 100%; and both simultaneously to intermediate values. Calculated molarities of dissolved O2, CO2 and ethylene are given for various atmospheres.The differences in the O2 concentrations recommended for different varieties of apple are not readily explicable. Varietal differences in susceptibility to CO2 injury could possibly result from anatomical, rather than biochemical, differences. This could be determined partly by resolving the conflict of evidence mentioned above. Variability of plant material prevents precise control of intercellular atmosphere; recommended atmospheres can be designed only to avoid completely anaerobic conditions and a harmful level of CO2 in the centre of the least permeable individual fruit or vegetable. Effects of low O2 and high CO2 are briefly described.