Sorghum oleosomes: effect of extraction on physicochemical characteristics

Abstract: Oleosomes are triacylglycerol spherosomes surrounded by a protein-phospholipid membrane and show remarkable stability with health-beneficial components.It is essential to set up an effective extraction process since extraction parameters affect the physicochemical properties of oleosomes:ball mill extraction using poly-ionic innovative and green ionic liquids provides unique multidirectional beating decreasing solvent use, yielding higher extraction and time efficiency compared to traditional methods with organic solvents.We hypothesized that extraction efficiency and physicochemical properties of oleosomes can be significantly improved by novel ball milling and ionic liquids.

Objective: The aim of this study was to enhance the extraction yield and physicochemical properties of oleosomes from waxy burgundy whole grain sorghum containing high lipid and amylopectin.

Methods: Dry milling was performed by soaking sorghums in 0.1M NaHCO3 solution for overnight at 20±2^oC and grinding via blender for 15 min (1:1 (w/v).Serial dilution was performed (3x in (1:4) w/v) using the following solvents: ionic liquids(i.e.,IL1:1-n-Hexyl-3-methylimidazoliumchloride,98% and IL2:1-Ethyl-3-methylimidazoliumchloride,97%),ethanol and dichloromethane (99.5%).Wet (ball) milling was done (30 min. (1:4) w/v)).Excess solvent was evaporated using refrigerated vapor trap (SpeedVac™).Yield of extraction, protein (LECO) and total phenolic content (Folin Ciocalteu), fatty acid profile (FAME, GC-MS) and FTIR spectra (ATR-FTIR) of oleosomes were determined.

Results: Ionic liquids and ball mill treatment significantly (p < 0.05) affected the extraction yield and physicochemical properties.The highest extraction(31.35±0.58) yield(%) was obtained with ball milling assisted IL2 and the lowest one(%)(18.37±0.77) was with traditional ethanol extraction.The concentration (%) of protein which anchored to stabilize triacylglycerol and phospholipid units was the highest (1.37±0.026 by ball assisted extraction with IL1.FTIR spectra peak of O-H(3200 cm^-1) protein-phospholipid, C=O(1700 cm^-1) and PO-2(1200 cm^-1) symmetrical stretching between phospholipid bilayers were higher by ILs and wet milling.Essential fatty acid contents(%)werehigher(oleicC18:1 ω9-cis(23.66±0.891) and linoleic acid(C18:2)(16.649±1.336)) with IL1 and wet extraction.Significance:Ionic liquids and ball milling can be used in an efficient oleosome extraction process to improve the yield and physicochemical properties.