- Title
- Recovery of phenolic compounds from banana (Musa cavendish) peel and encapsulation of its phenolic-rich extract
- Creator
- Vu, Thi Hang
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Banana is one of the most popular fruits with annual production of 112 million tonnes, mainly from the Musa Cavendish variety. Banana peel accounts for about 38% of the fruit weight and is generally known as waste. Although the peel has been traditionally used for the treatment of various ailments and has been found to exhibit potent antioxidant and antimicrobial activities, the majority of the peel usually ends up in landfill. Our review (Chapter 2) revealed that banana peel is a rich source of phenolic compounds, with dopamine and levodopa among the major individual phenolic compounds present. The peel can be potentially used as functional ingredients in food, cosmetic or pharmaceutical industries; however limited studies have been conducted in depth to answer the following questions, which includes (1) whether or not phenolic compounds are affected by different ripening stages with and without ethylene treatment; (2) how the drying methods and conditions affect retention of phenolic compounds in banana peel during the dehydration process; (3) what are optimal extraction conditions for maximum recovery of phenolic compounds from dried banana peel; (4) how to prepare the powdered extracts and their fractions enriched with phenolic compounds and assess their biological properties; and (5) what are the best conditions for encapsulation of the banana peel enriched extracts to improve their stability. To answer these research questions, this thesis aimed to maximise recovery of bioactive compounds from banana (Musa Cavendish) peel by selecting the most suitable ripening stage and applying optimal drying, extraction, isolation and encapsulation conditions for further utilisation in food products as functional ingredients. The results are presented in the six research articles (Chapters 4 to 7). This study found that the banana peel without ethylene treatment had a relatively higher phenolic content and antioxidant power than those of the peel treated by ethylene. Fully ripened peel had higher phenolics and antioxidant capacity than less or overripe peels (Chapter 4). This study also found that drying significantly affected retention of phenolics and antioxidant capacity. Microwave drying at the power level of 960 W for 6 min was the best technique to dehydrate banana peel for further extraction and isolation as it was faster and retained higher phenolics and antioxidant capacity than other drying methods, such as freeze-drying, vacuum oven, hot air oven, dehumidified air, and sun drying (Chapter 5). The optimal extraction conditions of the two common advanced extraction techniques, including ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE) were then investigated for maximizing extraction yield of phenolics from dried banana peel. The results (Chapter 6) showed that the optimal UAE conditions were 30°C, 5 min, 150W, sample to solvent ratio of 8:100 mg/mL, and acetone concentration of 60%. Whereas, the optimal MAE conditions were found at solvent pH of 1, ratio of 2:100 mg/mL, 6 min of continuous irradiation, and microwave power of 960W. The optimal UAE obtained 23.49 mg of phenolics, while the optimal MAE achieved 50.55 mg phenolics from 1g of banana peel. MAE also gave higher extractable solids than that of UAE (Chapter 6). The extracts were used for further preparation of powdered extracts and fractions. The results (Chapter 7) indicated that more powder can be obtained from MAE extract but concentration of phenolics was lower in MAE extract as compared to UAE extract. Both extracts exhibited potent antioxidant and antimicrobial activities. Fractions were prepared from UAE and MAE extracts using a liquid-liquid partition technique with n-hexane, dichloromethane, and n-butanol as the solvents. The n-butanol and aqueous fractions derived from the UAE extract had higher TPC, dopamine content and antioxidant capacity than the corresponding fractions derived from the MAE extract. Of those, the n-butanol fraction from UAE extract had the highest level of TPC, dopamine and thus this fraction is recommended for further isolation of phenolic compounds and dopamine. The results also revealed that all fractions prepared from UAE and MAE possessed inhibitory activity against E. aero, E. coli and E. faecalis. Fractions prepared from MAE demonstrated higher inhibitory activities, indicating that these fractions are potential sources of antimicrobial agents and possess many potential useful industrial properties. Considering the more environmental friendly method of extraction, recovery yield of extractable solid content and biological properties of the extract, the MAE extract was selected for preparation of a powdered extract for further applications. Different spray drying conditions and wall materials were tested to identify the optimal encapsulation process. The results (Chapter 8) found that the optimal encapsulating conditions for preparation of powdered extract enriched with phenolic compounds from banana peel were at inlet air temperature of 150°C, feed rate of 9 mL/min, and ratio of dry-mater in fresh extract – to – wall material of 1:1 (w/w) with the wall material being a combination of gum acacia and maltodextrin M100. The powdered extract prepared under optimal conditions had a spherical shape with a rough surface, good solubility and high dopamine content as well as phenolic compounds. Encapsulation protected the phenolic compounds from degradation under storage conditions of 40 °C for 4 weeks. In conclusion, the overall aim of this study was achieved. This study illustrated the impact of different ripening stages with and without ethylene treatment, different drying methods and conditions, and two advanced extraction methods (MAE and UAE) on phenolics and antioxidant properties of the peel, and revealed the best conditions to recover phenolic compounds from fresh banana peel. Composition and properties of the enriched extracts and their fractions were also identified. Finally, a suitable encapsulation conditions were also developed to prepare the powdered extract, ready for further applications. Future studies are recommended to prepare and test properties of powdered extracts from the fractions of the peel, and to apply these powdered extracts as functional ingredients in food, cosmetic or pharmaceutical products.
- Subject
- banana peel; antioxidant; food waste utilisation; encapsulation; optimisation; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1412758
- Identifier
- uon:36529
- Rights
- Copyright 2020 Thi Hang Vu
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 35 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 612 KB | Adobe Acrobat PDF | View Details Download |