Effect of Boiling on the Nutritional Composition and Antioxidant Properties of Beniseed (Sesamum indicum L.)

Abstract

Beniseed has been considered to be a valuable oilseed, not only because of its high oil content, but also because of its medical effects. The present study sought to investigate the effect of boiling on the proximate and mineral composition of beniseed. In addition, the effect of boiling on the antioxidant properties of beniseed extract was evaluated. Proximate and mineral composition of raw beniseed and beniseed boiled for 5, 10, 20 and 30 min were assessed. The amount of phenols, flavonoids and vitamin C were determined in the aqueous extracts of raw and boiled beniseed. In addition, the antioxidant mechanisms of the extracts of raw and boiled beniseed were assessed by measuring their reducing property, iron (II) chelating ability and their ability to scavenge 1, 1-diphenyl-2-picryhydrazyl (DPPH) radicals. Results showed that boiling significantly (p < 0.05) improved the crude fat (49.23 to 56.78%) and calcium content (757.13 to 975.54 mg/100g). However, boiling caused a significant (p < 0.05) reduction in levels of protein (18.87 to 14.12%), fiber (6.17 to 4.45%) and potassium (831.47 to 727.42 mg/100g) while iron levels were unchanged. The total phenolics levels of the raw beniseed (0.15 mg/g) showed a remarkable increase as the boiling time was increased to 30 min with a level of 0.35 mg/g. In addition, boiling caused a significant (p < 0.05) increase in the total flavonoid levels from 0.22 mg/g to 0.55 mg/g while a decrease in the vitamin C content of raw beniseed was observed within the period of boiling. Furthermore, the aqueous extracts of boiled beniseed exhibited greater antioxidant properties than that of the raw seeds. It was concluded that boiling for 30 min caused a significant loss of some nutrients but potentiated the antioxidant activities of the aqueous extract of the seed.

Keywords: Antioxidant, beniseed, boiling, radicals, nutritional, oilseed