Impact of Sonication Duration on Oil Yield, Phenolic and Flavonoid Contents, Antioxidant Capacity, Fatty Acid Profile, and Phenolic Composition of Bitter and Sweet Lupine (Lupinus albus L.) Seeds

Lupine seeds are not consumed directly because they are bitter. Therefore, differences in the phytochemical, lipidomic, and bioactive properties of bitter and sweetened lupine seeds were revealed using analytical and chromatographic methods. In this study, influence of ultrasound treatment time on extraction efficiency, phenolic and flavonoid contents, antioxidant capacity, fatty acid and phytochemical profile of bitter and sweet lupine (Lupinus spp.) seeds was investigated. The oil quantities of the bitter and sweet lupine seeds were specified to be between 8.60% (control) and 9.90% (5 and 10 min) to 11.0% (25 min) and 13.00% (5 min), respectively. The total phenolic content of bitter lupine seeds ranged from 124.32 mg gallic acid equivalent (GAE)/100 g (15 min) to 142.0 mg GAE/100 g (control), while sweet lupine seeds ranged from 4.21 to 6.61 mg GAE/100 g, respectively. Total flavonoids in bitter seeds varied between 35.00 mg/100 g (control) and 52.30 mg/100 g (15 min), whereas sweet seeds contained between 5.00 and 9.92 mg/100 g. Gallic acid, catechin and kaempferol were detected as the predominant phenolic compounds in sweet and bitter lupine seeds. Oleic acid quantities of bitter and sweet lupine oils were demonstrated to be between 36.78% (25 min) and 52.47% (15 min) to between 55.89% (15 min) and 56.69%, respectively. The phenolic compound amounts of bitter lupine were slightly higher than those of sweet lupine seeds. The highest phenolic compounds detected in both lupine seeds were catechin, kaempferol and rutin. As the sonication time increased, the amount of linoleic acid in bitter lupine oil became higher than in the control sample. In contrast, sweet lupine oil showed a slight decrease in linoleic acid content compared to its control.