Skip to main content
ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Plant Polymer Research » Research » Publications at this Location » Publication #411644

Research Project: New and Improved Co-Products from Specialty Crops

Location: Plant Polymer Research

Title: Sorghum protein: Ethanol extraction to improve yield and properties

item Hojilla-Evangelista, Milagros - Mila
item Evangelista, Roque

Submitted to: American Oil Chemists' Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/14/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Sorghum, an ancient grain used as a staple food, animal feed and biofuel source, is among the crops generating much interest in the rapidly growing alternative plant-based protein market. Sorghum’s major protein is the alcohol-soluble kafirin, whose hydrophobicity and limited functionality have posed challenges for extraction, recovery, and protein quality using conventional extraction methods. The current work involves an evaluation of a blended solvent approach (ethanol:alkali) to improve sorghum protein yield and properties. Ground, undefatted pearled sorghum (UPS), defatted pearled sorghum (DPS) and sorghum protein meal from wet-milling (control; WSPM) were each extracted with anhydrous ethanol:0.1 N NaOH (1:1.2, v:v) at 50°C and 250 rpm for 2 h, centrifuged, ultrafiltered-diafiltered, then freeze-dried. Protein recovery, composition, solubility, and foaming properties were determined. The sorghum samples contained only prolamins and glutelins. DPS has almost double the prolamins but four-fold less glutelins compared to WSPM. The ethanol-alkali method had high protein recoveries (78-83%) and produced high-purity (87-97%) protein extracts, with WSPM having the greatest protein content. Starting UPS and DPS protein solubility index (PSI) values (30%) were five-fold greater than that of WSPM. The recovered protein isolates showed markedly improved solubility, with PSI of 99% (practically fully soluble) for UPS or DPS and 20% for WSPM. The solubility-pH curve affirmed that UPS and DPS protein isolates are much more soluble than WSPM protein isolate, especially at pH>6.0. UPS and DPS protein isolates’ surface hydrophobicity indices at pH 7 (500) were five-fold greater than that of WSPM, indicating more unfolded configuration. DPS and WSPM protein produced substantial foams (100 ml), but only DPS showed moderately stable foam (64% remaining foam after 15 min). This work demonstrated the significantly enhanced yield and solubility of sorghum protein obtained by using ethanol:alkali for extraction.