Effect of defatting solvent type on the structure and function of Moringa stenopetala seed proteins

Abstract:
Growing consumer awareness of protein health benefits fuels demand for plant-based options. However, protein denaturation during isolation processes, especially during defatting with solvents, can compromise their native structure and biological functions.

This study assessed how three defatting solvents affected the structural and functional properties of isolated Moringa stenopetala (MS) seed proteins. Proteins were isolated from defatted MS seed meal using alkaline solubilization followed by isoelectric pH precipitation. The protein isolates from ethanol (EMG), hexane (HMG), and acetone (AMG) defatted meals were analyzed for their amino acid composition, protein solubility, heat coagulability, oil and water holding capacity, surface hydrophobicity, in vitro protein digestibility, and intrinsic fluorescence emission. The results were compared with those of the protein isolate obtained from undefatted meal (UMG).

AMG exhibited the highest protein content, while UMG had the highest protein yield. UMG displayed the lowest amino acid values, whereas AMG had the highest sulfur-containing amino acids and arginine-to-lysine ratio. HMG showed elevated levels of branched-chain, hydrophobic, and aromatic amino acids. AMG and HMG had the highest oil and water holding capacity, respectively. AMG and HMG had comparable surface hydrophobicity, which was higher than other proteins. AMG also had the highest in vitro protein digestibility. In terms of structural changes, intrinsic fluorescence spectra revealed two characteristic peaks at pH 5, 7, and 9, indicating tyrosine (303 nm) and tryptophan (348 nm), with a barely detectable tyrosine peak at pH 3. We conclude that defatting the MS meal with acetone had a comparatively less denaturing effect on the proteins when compared with ethanol and hexane.

This study significantly contributes to the AOCS community by having practical applications that improve plant-based protein quality, aligning with both consumer and industry needs.

Keywords: Moringa stenopetala seeds; protein isolates; acetone; hexane; ethanol; structural and functional properties