Degreening Characteristic of Musa AAA 'Berangan' and "William Cavendish' Bananas
A study was conducted on the changes in cellular structure, physiology and physiochemical of Musa AAA 'Berangan' and 'Cavendish' as the ripening progressed at 18+2 and 2722 OC. Mature green (ripening stage (RS) 1) bananas were initiated to ripen using 0.02% acetylene from calc...
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Format: | Thesis |
Language: | English |
Published: |
2004
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Subjects: | |
Online Access: | http://psasir.upm.edu.my/id/eprint/6137/1/FP_2004_22.pdf http://psasir.upm.edu.my/id/eprint/6137/ |
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Summary: | A study was conducted on the changes in cellular structure, physiology and physiochemical
of Musa AAA 'Berangan' and 'Cavendish' as the ripening progressed at
18+2 and 2722 OC. Mature green (ripening stage (RS) 1) bananas were initiated to
ripen using 0.02% acetylene from calcium carbide (CaC2) source (with an equivalent
of 1 g cac2.kg-' fruit) for 24 h. A hand of Berangan and Cavendish fmit was split
into 2 clusters. One of the clusters was initiated and ripened at 18t2 OC RH 90-
94%, while the other was initiated and ripened at 2722 OC RH 75-80%. The
experiment was conducted using randomized complete block design with four
replications. Five fruits per replicate were used. The various ripening stages were
evaluated with the aid of FAMA visual colour score until the fruit turned intosdl?
yellow at RS 6. For the Cavendish ripened at 27+2 OC (C27) where the fruit failed
to degreen, the evaluation was done daily until senescence, when brown specks
appeared on the peel. Data from measurements of ripening duration, L*, C* and h0
values, chlorophyll a, b and total chlorophylls, water loss, stomatal density, stomatal
length and opening, peel thickness, peel and pulp fresh and dry weight, cell length
and width of photosynthetic, epidermal, crystalliferous, tanniferous and starch
granules, pulp firmness, soluble solids concentration (SSC), titratable acidity and pH
were analysed using analysis of variance and differences between means were
determined by Duncan Multiple Range Test. Data from starch iodine test, cellular
structure and ultrastructure were documented as photographs or micrographs.
Berangan degreened naturally under tropical ripening temperature of 27+2 OC, and a
golden yellow fruit of RS 6 was obtained within 4 d of ripening. In contrast,
Cavendish failed to degreen at 27+2 OC even though the pulp had softened. By day 5
after the acetylene treatment brown specks started to appear on the fruit surface
indicating senescence had commenced. Cavendish could only degreen when ripened
at 1822 OC, and a yellow fruit of RS 6 was obtained after 9 d of ripening. On the
contrary, Berangan could not degreen and ripen under 1822 OC thus the fruit was
discarded. TEM revealed that at RS 6 the grana-thylakoid membrane of chromoplast
Berangan ripened at 2722 OC (B27) and Cavendish ripened at 1852 OC (C18) had
lysed. Besides, plastoglobuli increased in number, and types of staining density and
vesicles increased in number and size. However at day 5 of C27, the grana-thylakoid
membrane retained and this was in concurrent with the high retention of chlorophyll
content in fruit peel. The total chlorophyll retained in C27 was 57%, while only 25
and 40% of total chlorophyll was retained in B27 and C18 respectively. The high
retention of chlorophyll content in C27 had caused it to correlate significantly with
L*, C* and h0 values. Among B27, C18 and C27, C27 encountered the most water
loss. However, there was no correlation between water loss and stomata1 density and
opening. The existence of cracks and pores on the banana peel surface could be the
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passage for water loss. The severe water loss caused the peel thickness of C27 to be
the thinnest among the bananas studied although initially its peel was thicker than
B27. The fruit pulp and peel behaved differently towards ripening temperature. The
moisture content in pulp increased, while no moisture content in peel decreased as
ripening progressed. This led to increase of pulp to peel fresh weight ratio and C27
had the highest ratio as compared to C18 and B27. The softening of the banana fruit
was due to starch degradation and dissolution of middle lamellae. SEM revealed
that the pulp starch granules decreased in size and density as ripening progressed.
The blue-black stained area of starch-iodine complex cleared from the central core
of fmit towards the periphery of peel in all the bananas studied. The clearing pattern
was most rapid in C27. The hydrolysed starch increased the SSC of all the bananas
studied but the most significant increase was in C27. The titratable acidity of the
three bananas studied increased then decreased as ripening progressed. In contrast,
the pH decreased then increased as contrary to the trend of titratable acidity. The
tropical temperature of 2722 OC, besides failing to degreen, had caused poor keeping
and eating quality of Cavendish. |
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