Dragon Fruit ( Hylocereus spp.) Seed Oils: Their Characterization and Stability Under Storage Conditions
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ORIGINAL PAPER
Dragon Fruit (Hylocereus spp.) Seed Oils: Their Characterization and Stability Under Storage Conditions Wijitra Liaotrakoon • Nathalie De Clercq Vera Van Hoed • Koen Dewettinck
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Received: 31 July 2012 / Revised: 22 August 2012 / Accepted: 18 September 2012 / Published online: 29 September 2012 Ó AOCS 2012
Abstract Oil was extracted from the seeds of white-flesh and red-flesh dragon fruits (Hylocereus spp.) using a cold extraction process with petroleum ether. The seeds contained significant amounts of oil (32–34 %). The main fatty acids were linoleic acid (C18:2, 45–55 %), oleic acid (C18:1, 19–24 %), palmitic acid (C16:0, 15–18 %) and stearic acid (C18:0, 7–8 %). The seed oils are interesting from a nutritional point of view as they contain a large amount of essential fatty acids, amounting to up to 56 %. In both dragon fruit seed oils, tri-unsaturated triacylglycerol (TAG) was mainly found while their TAG composition and relative percentage however varied considerably. Therefore, they showed a different melting profile. A significant amount of total tocopherols was observed (407–657 mg/kg) in which the a-tocopherol was the most abundant (*72 % of total tocopherol content). The impact of storage conditions, cold and room temperatures, on the oxidative stability and behavior of tocopherols was monitored over a 3-month storage period. During storage, the oxidative profile changed with a favorably low oxidation rate (*1 mequiv O2/week) whilst tocopherols decreased the most at room temperature. After 12 weeks, the total tocopherol content, however, still remained high (65–84 % compared to the initial oils). Hereto, the dragon fruit seed oils can be considered as a potential source of essential fatty acids and tocopherols, with a good oxidative resistance.
W. Liaotrakoon (&) N. De Clercq K. Dewettinck Laboratory of Food Technology and Engineering, Faculty of Bioscience Engineering, Department of Food Safety and Food Quality, Ghent University, 9000 Ghent, Belgium e-mail: [email protected] V. Van Hoed Faculty of Bioscience Engineering, Department of Sustainable Organic Chemistry and Technology, Ghent University, 9000 Ghent, Belgium
Keywords Dragon fruit seed oil Fatty acid composition Triacylglycerol Essential fatty acids Tocopherols Physicochemical properties Thermal properties Oxidative stability Storage conditions
Introduction Dragon fruit (Hylocereus spp.), known as pitaya or pitahaya, is a cactus fruit originating from South America generally growing in tropical climate countries including Southeast Asia. In this region (Thailand, Malaysia and Vietnam), there are two types of commercial dragon fruits, white-flesh dragon fruit (Hylocereus undatus) and red-flesh dragon fruit (Hylocereus polyrhizus). The dragon fruit has a distinctive appearance and has the potential to be used as a source of functional ingredients [1]. The flesh of the dragon fruit contains numerous tiny black seeds covered with a gelatinous carbohydrate layer. The dragon fruit seeds contain oil like
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