Efficacy of ethanol-alkali blends for extracting sorghum protein with enhanced functionality

Authors: Hojillaevangelist, Milagros; Evangelista, Roque

Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 2/14/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Sorghum is a major export of the USA but utilized primarily as animal feed. Sorghum protein has attracted much interest in the booming alternative plant-based protein market and can add value to the crop. Kafirin, the major protein in sorghum, is very hydrophobic, which limits functionality and adversely affects extraction and protein quality using conventional isolation methods. The current work assessed a blended solvent approach (ethanol-alkali) with varying amounts of ethanol to improve sorghum protein yield and properties. Ground, defatted pearled sorghum samples were extracted with anhydrous ethanol:0.1 N NaOH (containing 15, 35, 45, or 55% ethanol, v:v) at 50°C and 250 rpm for 2 h, centrifuged, membrane-filtered, then freeze-dried. Protein recovery, composition, solubility, foaming, and emulsification properties were determined. Anhydrous ethanol amounts < 35% in the solvent blend resulted in reduced protein recovery (by 55%) and purity (by 33%). The recovered extracts had similarly high protein solubility index values (>94%). Protein extracted with 15 or 35% ethanol in the solvent blend showed downshifting of isoelectric point from pH 5.5 to 4.0-5.0 and markedly increased (by 2- to 3-fold) protein solubility within pH 5.5-7.5. All sorghum protein extracts produced abundant foams (110 ml) at pH 7, with protein extract from the 35% and 55% ethanol blend having the most stable foams (89% foam left). Protein foams were highly unstable at pH 10. All protein extracts showed least emulsifying activity at pH 7 and protein extracted by 55% ethanol blend had consistently lowest emulsifying activity at all pH tested. Protein emulsions became more stable at higher pH; the extracts from 55% or 45% ethanol blend produced the most stable emulsion at pH 7 and pH 10, respectively. This work demonstrated that using ethanol-alkali for extraction produced sorghum protein with markedly improved functional properties.