Bananas are climacteric fruits and show climacteric patterns with respect to both their
ethylene production and respiration rates during the ripening process. Treatment with
ethylene accelerated the ripening process, evidenced by colour changes. Chlorophyllase
apparently synthesised chlorophyll in the 0.2 kGy irradiated fruit during the
post-climacteric period. Gamma irradiation of green bananas with doses of 0.4 kGy or
greater resulted in extensive tissue damage, undesirable colour development, and drastic
changes in respiration and ethylene production. Irradiation at 0.2 kGy, did however,
effectively delay ripening (without causing any phytotoxicity) of the fruit apparently by
decreasing its sensitivity to its own endogenous ethylene for a period up to 28 days when
kept at room temperature, provided that the relative humidity was maintained at 75 %
to prevent desiccation. Irradiation at this dose did not prevent the onset of ripening
when subjected to high concentrations of exogenous ethylene.
Ultrastructurally total cell collapse due to cell wall, middle lamella and membrane
damage was evident at doses of 0.4, 0.6 and 1.0 kGy. Irradiation with a dose of 0.2 kGy
did not cause cell wall softening and membrane breakdown and thus provided a banana
fruit of excellent postharvest quality with respect to ultrastructural features.
Glucose and fructose occurred probably directly from sucrose that may not accumulate
because it is transient after the banana fruit is harvested. The accumulation of sucrose glucose and fructose was not stimulated by ethylene in non-irradiated and irradiated
fruit. These results indicate a clear temporal separation between those biochemical
processes that appear to be stimulated by ethylene (respiration, fruit softening and
colour change) from those that are not (sugars). Pectin methyl esterase resulted in the
demethylation of pectin-like material in the cell walls of ripening bananas. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1991.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10502 |
| Date | January 1991 |
| Creators | Strydom, Gerhardus Johannes. |
| Contributors | Van Staden, Johannes. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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