Anthracnose Incidence, Biochemical Changes, Postharvest Quality and Gas Exchange of Chitosan–Coated Papaya
A study was conducted to investigate the effect of chitosan -1. on growth of Colletotrichum gloeosporioides, the causal organism of anthracnose; 2. mechanisms involved in controlling anthracnose disease; 3. biochemical changes; 4. physico-chemical quality characteristics and extension of storage...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2006
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/426/1/t_fp_2006_22.pdf |
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| Summary: | A study was conducted to investigate the effect of chitosan -1. on growth of
Colletotrichum gloeosporioides, the causal organism of anthracnose; 2.
mechanisms involved in controlling anthracnose disease; 3. biochemical
changes; 4. physico-chemical quality characteristics and extension of storage
life; 5. fruit surface study using SEM and 6. gaseous exchange of papaya fruit
during storage at 12 + 1°C. Data were analyzed using analysis of variance and
differences between treatments mean were determined by LSD. The results
revealed that mycelial growth of C. gloeosporioides was reduced significantly (P
≤ 0.05) at all concentrations as compared to the control. The maximum percent
inhibition in mycelium growth (100%) was obtained at 2% chitosan. Similarly,
conidial germination inhibition was 100% for 2.0% and 80.4% for 1.5% chitosan
coating. Microscopic studies revealed that when chitosan solution was brought
in direct contact with conidia there were marked deformities accompanied with
shrunken conidia cellular damage and finally death of the cells at 1.5 and 2% coatings. Chitosan (1.5%) was found highly effective in reducing of anthracnose
disease upto 93.0% during five weeks storage. The reduction was found to be
85.4% during four days of ripening after five weeks of storage. There was no
added advantage of 2.0% chitosan on disease reduction during storage. Marked
effect on reducing disease demonstrated the fungicidal effect of chitosan. In
addition to its direct microbial activity, the study strongly suggested that chitosan
induces a series of defense reactions through production of inducible
compounds such as phenols, peroxidase, chitinase and β-1, 3-glucanase in
papaya fruits with 1.5% chitosan showing greatest activities. 1.5% chitosan
coating showed maximum beneficial effect in reducing weight loss, maintaining
firmness, delaying changes in peel colour and the slowing changes in soluble
solids concentration (SSC) after five weeks of storage. Non-coated and 0.5%
coated fruits gave significantly higher SSC compared to fruits coated with higher
percentages of chitosan (1, 1.5 and 2%). The titratable acidity declined
throughout the storage period with slower rate in coated fruits.
Overall sensory assessment of quality after ripening showed fruits were
significantly better in quality when coated with 1.5% chitosan which were
assigned higher sensory score than 1% chitosan coated fruits. Two percent
coated fruits were rated as zero because of their inability to ripen.
Scanning Electron Microscopy (SEM) showed that there were no deep cracks
on the surface of 1.5% chitosan coated fruits whereas in non-coated fruit cracks
were found on the surface after four weeks of storage.
Chitosan coatings significantly reduced respiration rate and ethylene evolution.
The coating also reduced oxygen and increased carbon dioxide level inside the
fruits, thus created modified atmosphere within fruits. Modification of
atmosphere was inversely proportional to the concentration applied. The two
percent chitosan extremely modified the atmosphere which might be the reason
for the fruits being unable to ripen when transferred to ambient temperature.
Treatment with 1.5% chitosan seems to produce ideal atmosphere for
maintenance of quality of papaya during storage.
The results from all experiments carried out in the study showed that 1.5%
chitosan coating reduced the anthracnose disease by 93.0% and extended
postharvest life upto five weeks while maintaining acceptable quality. One
percent resulted in poorer quality fruits as compared to 1.5% coated fruits. Two
percent chitosan seems non-physiological for Eksotika papaya-II in term of
maintaining quality. As a non-toxic, biodegradable byproduct from sea food,
chitosan has the potential to become a natural preservative for protecting
papaya fruits, thus assisting the goal of sustainable agriculture. Extension of
storage from up to five weeks would facilitate the export of fruits to long distance
markets by sea and thereby cost of export would be reducing making the fruits
more competitive in the world market. |
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