- Title
- Gac oil extraction and encapsulation by spray drying
- Creator
- Kha, Tuyen Chan
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2014
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Gac fruit (Momordica cochinchinensis Spreng) aril contains extraordinarily high levels of β-carotene and lycopene and unsaturated fatty acids, especially oleic and linoleic acids. These bioactive compounds have been proven to be beneficial to human health and are linked with a reduced risk of cardiovascular disease and cancers. Importantly, it has been found that a significant improvement in the absorption of the carotenoids into the human body occurs when they are digested with fat. The current study hypothesised that optimisation of conditions for several processing steps, including oil extraction, emulsion preparation conditions and spray drying process using response surface methodology (RSM), is expected to maximise the oil yield and increase the retention of bioactive compounds. The aim of this study was therefore to develop optimal conditions for the extraction of Gac oil enriched in β-carotene and lycopene, and the preparation of the Gac oil rich in β-carotene and lycopene encapsulated powder, for use as nutrient supplement or natural food additive and natural food colourant. The objectives of this study were to investigate the effect of (1) pre-treatments prior to supercritical carbon dioxide extraction, (2) ultrasound-assisted aqueous extraction, (3) microwave-drying followed by pressing on the Gac oil extraction efficiency, and β-carotene and lycopene contents. Moreover, this study was also to optimise the conditions for spray-drying encapsulation of Gac oil using RSM: (1) wall material concentration and ratio of Gac oil to wall material, and (2) spray-drying conditions including air inlet and outlet temperatures. The shelf life and stability of the encapsulated Gac oil powder were also evaluated. The results showed that high extraction efficiencies in terms of Gac oil, β-carotene and lycopene were obtained using the three different extraction methods. Supercritical carbon dioxide extraction gave the highest oil extraction efficiency (95%), followed by ultrasound-assisted extraction (90%) and microwave-drying followed by pressing (86%). The Gac oil extracts from the different extraction methods contained high concentration of β-carotene and lycopene and had low peroxide value. For encapsulation, the results indicated that the response surface model was sufficient to describe and predict the response variables with high R²value. Under optimal conditions for wall material (whey protein and gum Arabic, 7/3) concentration (29.5%) and the ratio of Gac oil to wall material (0.2, g/g), the encapsulation efficiencies in terms of Gac oil, β-carotene and lycopene, peroxide value, moisture content and total colour difference were predicted and validated. For spray-drying, using optimal conditions (inlet and outlet temperatures of 154 and 80 oC, respectively), the encapsulation efficiencies in terms of Gac oil, β-carotene and lycopene, encapsulation yield, moisture content, water solubility and peroxide value were predicted and confirmed. Furthermore, physicochemical (Aw, pH, bulk density, fatty acid composition, and particle morphology), reconstitution and colour properties of the optimally encapsulated Gac oil powder were also evaluated. The results indicated that the encapsulated Gac oil powder could be stored for a long time due to low Aw and good protective structure of particles against light, oxidation, and unwanted release of the oil droplets and carotenoids. A storage study was conducted to determine preservation of quality in the encapsulated Gac oil powder. Findings from the storage study confirmed that preservation of colour, β-carotene and lycopene in the encapsulated Gac oil powder with a lower peroxide value was more effective when vacuum-packed into laminated aluminum bag and stored at ambient temperature or lower for up to 12 months. The results also showed that during storage, the incorporated Gac oil in yoghurt, pasteurised milk and cake mix were found to be satisfactory in terms of preserving an attractive colour and β-carotene and lycopene contents, and having a low peroxide value. In summary, the hypothesis was supported and the aims were achieved in this study. The high extraction efficiency for Gac oil containing high level of β-carotene, lycopene and unsaturated fatty acids was obtained using different extraction methods. The Gac oil rich in those bioactive compounds was effectively encapsulated by spray drying. The encapsulated Gac oil powder was highly stable at ambient temperature or lower. Furthermore, the encapsulated Gac oil powder was found to be easily incorporated into a range of food products. Finally, the Gac oil encapsulated powder is considered suitable for use as natural food colourant, a nutraceutical or an additive in the food industry.
- Subject
- gac oil; gac fruit; carotenoids; extraction; encapsulation; spray drying; fortification; storage study
- Identifier
- http://hdl.handle.net/1959.13/1310242
- Identifier
- uon:22008
- Rights
- Copyright 2014 Tuyen Chan Kha
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Abstract | 445 KB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 8 MB | Adobe Acrobat PDF | View Details Download |