Some biophysical principles underlying the controlled atmosphere storage of plant material

Abstract

SUMMARY Controlled 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 O 2 and CO 2 gradients in fruit which, though physiologically unimportant in air, could be important under CA conditions. CA storage gives possible control of internal O 2 from o to about 80–95%; internal CO 2 from about 3–4 to 100%; and both simultaneously to intermediate values. Calculated molarities of dissolved O 2 , CO 2 and ethylene are given for various atmospheres. The differences in the O 2 concentrations recommended for different varieties of apple are not readily explicable. Varietal differences in susceptibility to CO 2 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 CO 2 in the centre of the least permeable individual fruit or vegetable. Effects of low O 2 and high CO 2 are briefly described.