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An improved method for extraction of sorghum polymeric protein complexes

B.P. Ioerger, S.R. Bean, M. Tilley, H. Lin
Journal of cereal science 2020 v.91 pp. 102876
albumins, digestibility, disulfides, gel chromatography, germplasm, globulins, kafirins, molecular weight, polyacrylamide gel electrophoresis, polymers, protein composition, protein structure, reducing agents, reversed-phase high performance liquid chromatography, solvents, sorghum flour
A method for fractionating sorghum proteins using extraction solvents and techniques designed to obtain polymeric protein structures (especially disulfide linked) was developed. Extraction and separation conditions were optimized in terms of completeness of protein extraction, sample stability, and analytical resolution. After pre-extraction of albumins and globulins, a 3-step sequential procedure involving no reducing agents was applied to ground whole sorghum flour. The three fractions obtained represented proportionally different protein polymer contents and molecular weight distribution as evidenced by comparative size exclusion chromatography. Protein composition also varied among the extracts with differences in kafirin composition and non-kafirin proteins detected in the fractions by RP-HPLC and SDS-PAGE analysis. The ability to quantify and further characterize sorghum polymeric protein complexes will be useful for additional studies linking protein structures with functionality and digestibility and variations for these properties within diverse sorghum germplasm.