Evaluation and characterisation of Citrullus colocynthis (L.) Schrad seed oil: Comparison with Helianthus annuus (sunflower) seed oil
Highlights
► Citrillus colocynthis seeds contain 23.12% of oil which is mainly composed of linoleic and oleic fatty acids. ► The tocopherol content of C. colocynthis was 121.85 mg/100 g and γ-tocopherol was the major one. ► C. colocynthis oil was thermally stable up to 286.57 °C and showed four decomposition stages at high temperature. ► C. colocynthis oil can supplement or replace some of the conventional oils such as sunflower oil. ► C. colocynthis oil can be used for food and non-food applications.
Introduction
Vegetable oil is a valuable food commodity whose consumption has increased in the past decade, particularly in emerging countries such China and India. The increase is mainly due to, among other things, population growth, improving living standards and changing diets (Rosillo-Calle, Pelkmans, & Walter, 2009). Global vegetable oil consumption has grown by over 5% per year since the mid 1970s. Furthermore, the increase of the needs of their derivatives, especially biodiesel, has led to a growing demand for conventional vegetable oils, especially sunflower, soybean, rapeseed and palm oils. This trend combined with droughts, bad weather circumstances, speculation, and a low growth in total oil production, has led to a gradual decline in world supplies of vegetable oils.
Oil World indicated in its 2012 report (Mielke, 2012) that world production of 7 oilseeds (soybean, sunflower, rape, cotton, peanut, palm kernel, copra) will turn out to be smaller than expected, enforcing an unprecedented decline in oilseed stocks, as well as demand rationing. This may lead to a price spike of vegetable oils and to an insufficiency to satisfy global demand for food and oleo chemical industries as well as for the energy sector. All these facts highlighted there is a need to find other unconventional oils that can partially replace some of the conventional oils and thus lower their prices.
One of the possible alternative oils is the non-conventional oil from seeds of Citrullus colocynthis (L.) Schrad. It belongs to the species of the genus Citrullus of cucurbitaceae family, which usually consists of a large number of varieties that are generally known as melons (Mabaleha, Mitei, & Yeboah, 2007). The fruits of C. colocynthis, commonly named bitter apple, egusi melon, ground melon, Handhal, Dellaa El-Wad were gathered as deadly poison. The pulp is an effective hydragogue, cathartic and laxative because of its glucosides content such as colocynthin (Dane, Liu, & Zhang, 2007). The ripe fruit of C. colocynthis is nearly globular, yellow in colour and characterised by a thin but hard rind. The fruits have a soft, white spongy pulp which is filled with numerous ovate compressed seeds, which are edible and when ground provide a rough bread for the Bedouins living in desert (Dane et al., 2007). The seeds contain approximately 17–19% oil (Zohary & Hopf, 2000), and consist mainly of unsaturated fatty acids (80–85%) (Schafferman, Behazav, Shabelsky, & Yaniv, 1998). It is estimated that the oil yield is approximately 400 l/ha (Schafferman et al., 1998).
C. colocynthis native from tropical Asia and Africa (Dane et al., 2007), is now widely distributed in the Saharo-Arabian phylogeographic region of Africa, in the Mediterranean region, eastward through Iran to India and other parts of tropical Asia. This perennial herb is a drought tolerant species, which can survive arid environments by maintaining its water content without any wilting of the leaves or desiccation, even under severe stress conditions. This is accomplished by extending its root system into deep ground water (Dane et al., 2007). Therefore, C. colocynthis can be placed as a serious oilseed crop candidate for medicinal, food and non-food applications. The first objective of this study was to determine tocopherol, fatty acids and thermal profiles, physicochemical properties, 1H NMR, FTIR and UV–Visible spectra of the non conventional C. colocynthis seed oil grown in Saudi Arabia. The second objective was to compare the properties of this non conventional seed oil with the common Helianthus annuus (sunflower) seed oil.
Section snippets
Seed material and lipid extraction
Mature fruits of C. colocynthis were collected in December 2011 from about 30 herbs from Wadi Hanifa in Al-Diriyah (Riyadh, Saudi Arabia) located in: latitude 46°24′16.N; longitude 31°46′30.E; altitude: 664 m. Damaged seeds were removed, and the remaining seeds were oven-dried at 60 °C for 24 h. The dried seeds were milled in a K/IKA-WERKE M20 grinder and oil was extracted using hexane for 8 h in a Soxhlet apparatus. Hexane was removed by rotary evaporation (R-210 BUCHI, Flawil, Switzerland) at 80
The physicochemical properties of seeds and oils
Table 1 summarises the physicochemical properties of the C. colocynthis and sunflower seeds and their oils. The oil content, moisture and ash values of C. colocynthis seed were lower than those of sunflower seed. However, the oil content of C. colocynthis (23.16%) was higher than this of soybean seed (20.9%) (Piper & Boote, 1999). Thus, this high oil yield coupled with the ease of cultivating and seed collection make C. colocynthis a good candidate for commercial exploitation. The free fatty
Conclusion
This study revealed that C. colocynthis seed oil possessed physicochemical properties, antioxidant properties, fatty acids and tocopherol compositions that may be of interest for food and non-food applications. The oil showed a high content of ω-6 polyunsaturated fatty acid and γ-tocopherol, suggesting that this oil might be used as seasoning or frying oil, mayonnaise and table margarine, and commercial natural antioxidant formulations. C. colocynthis seed oil is desirable in terms of
Acknowledgement
The Deanship of Scientific Research at King Saud University is thanked for funding the work through the research group project RGP-VPP- 048.
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