Khan, Ayesha Ashraf
(2025)
Advanced techniques for postharvest disease detection, control, and quality enhancement in papaya: electronic nose analysis and chitosan-zinc oxide nanoparticle coatings.
MRes thesis, University of Nottingham.
Abstract
Papaya (Carica papaya), a valuable tropical fruit in Malaysia, is highly susceptible to postharvest fungal diseases that can severely affect its quality and lead to economic losses. To address these challenges, this study explored a novel, non-destructive approach using electronic nose (EN) technology, a biosensor capable of detecting quiescent fungal infections by sensing changes in volatile composition, thereby avoiding the invasiveness of traditional methods. Additionally, an eco-friendly and cost-effective edible coating has been investigated as a means to control fungal diseases, providing a comprehensive solution to reduce postharvest losses in papaya.
EN was first investigated for its ability to differentiate between papaya ripening stages. Using the case-based reasoning (CBR) classification method, EN effectively detected differences in odour profiles across different storage days. The similarity percentages were 84.25% between days 1 and 3, 82.81% between days 1 and 5, and 94.19% between days 3 and 5—all below the 98% threshold, confirming distinct changes in volatiles over time. GC-MS analysis validated these findings by identifying potential biomarkers for each stage, including vinyl butyrate on day 1, acetone on day 3, and cyclobutanol on day 5, demonstrating EN's accuracy and sensitivity of EN in tracking papaya ripening.
EN technology was then investigated to determine how early and accurately it could detect quiescent fungal diseases in papayas, focusing on pathogens such as Colletotrichum gloeosporioides (CG), Fusarium solani (FS), and Lasiodiplodia theobromae (BC). EN successfully distinguished volatile profiles between healthy and infected samples, with CG-infected samples showing 94.36% similarity between days 1 and 3, and 91.58% similarity between days 1 and 5, reflecting disease progression. By day 5, BC-infected papayas exhibited distinct profiles with only 83.40% similarity to CG, and GC-MS identified specific potential biomarkers for each pathogen, further supporting EN’s pathogen differentiation capability.
Finally, an eco-friendly edible coating combining chitosan with green-synthesised zinc oxide nanoparticles (ZnO NPs) from pandan leaf extract was tested for its efficacy in controlling anthracnose disease in papaya. Increasing concentrations of ZnO NPs in the chitosan solution demonstrated a trend of progressively reduced disease incidence, with 2.5 g/L of ZnO NPs emerging as the optimal concentration. Papayas treated with this chitosan-2.5 g/L ZnO NP coating showed a 63% reduction in disease incidence compared to those treated with chitosan alone. Moreover, the disease severity was reduced by 36.5%, highlighting the effectiveness of the coating in delaying anthracnose onset.
This study highlights EN technology as a rapid, non-destructive tool for detecting ripening stages and fungal infections in papayas, complemented by an eco-friendly ZnO-chitosan coating that offers a sustainable solution to mitigate postharvest losses by delaying onset of infections and extending shelf life, particularly in tropical regions where papaya is economically vital.
| Item Type: |
Thesis (University of Nottingham only)
(MRes)
|
| Supervisors: |
Muthoosamy, Kasturi
Ali, Asgar |
| Keywords: |
papaya (Carica papaya); tropical fruit; Malaysia; postharvest fungal diseases; economic losses |
| Subjects: |
S Agriculture > SB Plant culture |
| Faculties/Schools: |
University of Nottingham, Malaysia > Faculty of Science and Engineering — Science > School of Biosciences |
| Item ID: |
80160 |
| Depositing User: |
Khan, Ayesha
|
| Date Deposited: |
08 Feb 2025 04:40 |
| Last Modified: |
08 Feb 2025 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/80160 |
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