ISHS Acta Horticulturae 343: Physiological Basis of Postharvest Technologies
ROLE OF SKIN RESISTANCE TO GAS DIFFUSION IN THE RESPONSE OF FRUITS TO MODIFIED ATMOSPHERES |
| Authors: | B.K. Dadzie, N.H. Banks, D.J. Cleland, E.W. Hewett |
| Abstract:
Internal atmospheres of fruits are always different in composition from the external atmospheres in which fruits are kept: fruits are themselves modified atmosphere packages within which their tissues reside. For a fruit of a given surface area (A, cm2) and respiratory O2 flux (Fo2, cm3 s-1), the resistance of its surface to O2 diffusion (Ro2, s cm-1)2 is the proportionality constant which determines the magnitude of difference between internal oxygen ([O2]i, atm) and external oxygen ([O2]e) concentrations: [O2]e = [O2]i + Fo2 R02 A. The internal anaerobic compensation point for tissues within a fruit (ACPi, atm O2) therefore differs from the anaerobic compensation point for the atmosphere external to the fruit (ACPe) in an analagous way: ACPe = ACPi +F02 R02/A, where F02 ACPi is the respiratory O2 flux at ACPi. A steady state mathematical model incorporating these relationships was used to show that, even if temperature has no effects on ACPi, the strong dependence of respiration rate upon temperature would make ACPe vary with temperature, particularly for fruit with high R02. Thus, the lowest O2 level to which a given crop can be safely exposed is not constant but is temperature dependent, to an extent which would vary with its R02 and its O10 for respiration rate. | |
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