Sorghum oleoresins: Effect of extraction on compositional and structural characteristics

Oleoresins are resin-like viscous materials obtained from plants, oilseeds, or spices with functional properties. The objectives of this study were to obtain oleoresins from waxy burgundy sorghum grain, and to characterize the effects of extraction process and solvents on their composition and functional properties. Oleoresins were obtained by using the following solvents with and without ball milling: two types of novel ionic liquids (IL₁: 1-n-Hexyl-3-methylimidazoliumchloride, IL₂: 1-Ethyl-3-methylimidazoliumchloride), ethanol and dichloromethane. The effects of processing were evaluated for the extraction yield, protein, fat and total phenolic content, fatty acid composition, particle size and zeta potential, and FTIR spectra. The use of ILs and ball mill process significantly (p < 0.05) affected the extraction yield and physicochemical properties. The highest extraction yields increased (31.35% ± 0.58) when ball milling used with IL2 in comparison to the lowest (18.37% ± 0.77) obtained by traditional ethanol extraction. In a similar way, protein concentration and phenolic content were the highest (1.37% ± 0.05 and 0.57% ± 0.01, respectively) with ball milling extraction and IL1. The FTIR spectra indicated higher phospholipids (at 1200 cm⁻¹) and protein-phospholipid bonding (at 1700 cm⁻¹) by ILs, and ball milling as compared to traditional extraction. Overall, wet milling-assisted extraction by using a ball mill and ILs provided control over the composition of the oleoresins important for value-added food applications and higher extraction efficiencies as compared to traditional techniques.