Abstract
Fatty acid composition and antioxidant content are major determinants of vegetable oil quality. Antioxidants are important food components, and there is an increasing interest of replacing synthetic antioxidants with those from natural sources for food industry. The objective of this study was to evaluate fatty acid composition, total phenolic, carotenoid and chlorophyll contents, and antioxidant capacity of different varieties of two oilseed crops. Five niger seed and eight linseed varieties were used. For the analysis of fatty acid composition of the seed oil, gas chromatography method was used. Standard methods were used for total phenolic, carotenoid and chlorophyll contents, and antioxidant properties. In niger seed oil, linoleic acid (C18:2) was the dominant fatty acid, accounting for 73.3% (variety Esete) to 76.8% (variety Ginchi) of the total fatty acids. In linseed oil, linolenic acid (C18:3) was the dominant fatty acid accounting for 55.7 (variety Chilalo) to 60.1 (variety Belaye-96). The total phenolic content ranged from 22.4 mg GAE/g (variety Esete) to 27.9 mg GAE/g (variety Ginchi) in niger seed and from 20.5 mg GAE/g (variety Belay-96) to 25.4 mg GAE/g (variety Ci-1525) in linseed. In niger seed, variety Fogera had the highest values for FRAP and radical scavenging activity. The carotenoid content also showed significant variation among the varieties ranging from 2.57 (Esete) to 8.08 (Kuyu) μmol/g for niger and 4.13 (Tole) to 8.66 (Belay-96) μmol/g for linseed. The FRAP assay showed that variety Fogera of niger seed and variety Chilalo of linseed came on top among their respective varieties with values of 57.2 and 30.6, respectively. Both niger seed and linseed were shown to be rich in bioactive compounds. However, significant variation was observed among the varieties of each crop and among the two crops in their total phenolic and carotenoid contents as well as ferric reducing potential and radical scavenging capacity. Principal component analysis revealed the presence of more than one group in both niger seed and linseed. Hence, genetic variation among the varieties should be utilized for improving their desirable characteristics through breeding. Both oil crops can be used as the source of antioxidants for replacing synthetic compounds.
Highlights
Oilseed crops are vital sources of nutrients for both humans and animals in addition to their use for various industrial applications
Linoleic acid (C18:2) was the principal unsaturated fatty acid in all niger seed varieties included in the present study ranging from 73.3 to 76.8% (Table 1)
The monounsaturated fatty acids (MUFA) accounted for 4.7% to 7.3%, which needs be exploited to increase the content of MUFA as they enhance the oxidative stability of the oil [50]
Summary
Oilseed crops are vital sources of nutrients for both humans and animals in addition to their use for various industrial applications. Various molecular marker based population genetics studies revealed high genetic diversity in these crops [e.g., [2,3,4,5,6,7,8]]. These crops are primarily used as sources of edible oil for local consumption. Ethiopia exports different types of oilseeds to various countries, especially China, India and the European Union [10] Among these oil crops, sesame, niger seed, and linseed account for about 90, 6, and 1%, respectively. Besides increasing the production of these oilseed crops, there is a need to improve their nutritional qualities [11] so that it is possible to satisfy consumers’ nutritional requirements
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