Abstract
Roselle is one of the valuable plants grown in some regions of Egypt, which is used to make juices or as natural food color additive. Roselle seeds are waste, which can be used as a source of non-traditional oil, nutritious or functional compound. The evaluation of green extraction methods including supercritical CO2 (SC-CO2), screw, hydraulic press comparing to traditional method on oil yield, total phenolics, antioxidant activity (DPPH) and oxidative stability of roselle seeds oil were investigated. Fatty acid composition and tocopherol of the oil were also determined. The results showed that the roselle seeds oil extracted by solvent gave the highest oil content and extraction rate (17.98 and 98.34%, respectively) and the lowest peroxide and acid value. SC-CO2 gave the higher content of alpha, gamma, and delta tocopherol comparing to the other extraction methods. Fatty acid showed that linoleic acid, an essential fatty acid, was dominant followed by oleic and palmitic acids. These fatty acids were higher amounts in oil extracted by SC-CO2, followed by cold-press comparing to solvent extraction. The maximum stability (20 h), higher TPC (22.18 mg GAE/g) and antioxidant activity (DPPH, 65.15) were observed in oil extracted by SC-CO2 followed by hydraulic-press, solvent extraction and finally screw-press. The results revealed that SC-CO2 method is more efficient in determination of total tocopherol, oxidative stability, TPC and radical scavenging activity than the other extraction methods. Cold press extraction methods gave higher oil yield than SC-CO2 and more economically than other methods.
Highlights
Roselle (Hibiscus sabdariffa L.) seeds are the waste that is left behind during processing of roselle, known as hibiscus, for juices or other roselle-related products
There is a positive correlation between the total content of phenolic compounds and the antioxidant activity and over 95% of the antioxidant capacity is due to their phenolic components (Turkmen et al, 2007; Wang et al, 2017)
The results showed that supercritical CO2 (SC-CO2) extraction method exhibited the highest DPPH scavenging activity (65.47)
Summary
Roselle (Hibiscus sabdariffa L.) seeds are the waste that is left behind during processing of roselle, known as hibiscus, for juices or other roselle-related products. B-sitosterol, a phytosterol presence in roselle seeds, has secured an important place in the realm of health supplements with extensive scientific support for its prophylactic and therapeutic use for various physical ailments like arteriosclerosis, benign prostate cancer, and colon cancer (Nair et al, 2006; Yokota et al, 2006; Abdel-Razek et al, 2011; Hassanien et al, 2014; Rudzińska et al, 2016). Roselle seed contains about 20% oil and is considered to have high nutritional value and health-promoting properties due to the presence of natural balance between saturated: monounsaturated: polyunsaturated fatty acids (Abdel-Razek et al, 2017; Al-Okbi et al, 2017). Roselle seeds contain high levels of phytosterol, which have been associated with lowering total cholesterol and anti-carcinogenic effects in both animal and human studies. b-sitosterol, a phytosterol presence in roselle seeds, has secured an important place in the realm of health supplements with extensive scientific support for its prophylactic and therapeutic use for various physical ailments like arteriosclerosis, benign prostate cancer, and colon cancer (Nair et al, 2006; Yokota et al, 2006; Abdel-Razek et al, 2011; Hassanien et al, 2014; Rudzińska et al, 2016).
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