Activity of polyphenol oxidase, concentration of 3, 4-
dihydroxyphenylethylamine (dopamine), and concentration of ascorbic
acid in the pulp of bananas as they ripened were measured and relationships
between these factors and both the extent of browning and the
susceptibility to discoloration of the fruit during a 30-minute holding
period were studied. Moisture and protein content were determined
also. Bananas from three lots were analyzed as purchased and after
either two or four days of additional ripening.
Initial browning of the filtrates of bananas and the increase in
browning upon standing were greater as the fruit ripened. Protein
content also increased with ripening. Moisture content of bananas
increased significantly in those bananas held for four additional days.
The specific activity of polyphenol oxidase (units of activity/mg
protein) in bananas decreased with ripening, but when the activity was calculated on a basis of dry weight of banana no significant change was
observed. Both the dopamine and ascorbic acid contents decreased in
individual bananas with ripening.
Decrease in the concentration of dopamine was the variable
with the highest correlation to the increase in browning in ripening
bananas. Both the increase in browning and the decrease in dopamine
in ripening bananas were associated with a decrease in ascorbic acid
content. Thus, the concentration of dopamine as influenced in part by
concentration of ascorbic acid appears to be the limiting factor in the
browning of bananas. The specific activity of polyphenol oxidase did
not appear to be a limiting factor in the browning of bananas.
Dopamine was located histochemically in the vacuoles of the
latex vessels and in a few isolated parenchyma cells of banana.
Polyphenol oxidase appeared to occur throughout the pulp. / Graduation date: 1974
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26955 |
| Date | 04 January 1974 |
| Creators | Weaver, Connie Marie |
| Contributors | Charley, Helen G. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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