The effect of the triethanolamine: glycerol deep eutectic solvent on the yield, fatty acid composition, antioxidant activity, and physicochemical properties of black mustard (Brassica nigra L.) seed oil

Abstract

This study reports the yields, physicochemical properties, fatty acid compositions, and antioxidant activities of black mustard (Brassica nigra L.) seed oils extracted by cold pressing and the solvent extraction using different solvents (n–hexane, trichloroethylene, and a mixture of trichloroethylene and the triethanolamine:glycerol deep eutectic solvent (TEOA:G DES) with no or after pretreatment with the TEOA:G DES. Density (0.9791 ± 0.0003–0.9851 ± 0.0003 g/cm3), viscosity (121.15 ± 1.62–123.32 ± 0.10 mPa⋅s), boiling point (179–185 ± 1 °C), refractive index (1.4692 ± 0.0006–1.4758 ± 0.0011), acid (2.08 ± 0.19–3.22 ± 0.15 mg KOH/g), iodine (99.2 ± 1.6–105.4 ± 1.5 g I2/100 g), peroxide (1.68 ± 0.01–1.82 ± 0.03 mmol O2/kg), and saponification values (165.1 ± 2.7–169.4 ± 2.3 mg KOH/g), fatty acid composition and antioxidant activity of the extracted oil were determined in order to evaluate its potential use as a foodstuff, a pharmaceutical or a feedstock for biodiesel production. Although the maceration of black mustard seeds with sole trichloroethylene yielded the highest oil yield of 31.10 ± 0.42 g/100 g, it required almost twice the volume of trichloroethylene compared to the volume applied in the macerations after the pre–treatment with the TEOA:G DES and with the mixture of trichloroethylene/TEOA:G DES. The oil extracted by the extraction in the presence of TEOA:G DES has similar physicochemical properties but better antioxidant activity than the oil extracted by cold pressing.