Effect of solvent composition on the extraction of proteins from hemp oil processing stream

Hempseed meal, a by-product of the hempseed oil processing stream, is a potential alternative source for food proteins. Efficient extraction of proteins from hempseed meal is challenging owing to differences in the structure and solubility of various protein fractions present in the seed. In the present study, protein was extracted from hempseed meal using four different solvents, including aqueous NaOH, KOH, NaHCO₃ and NaCl, at four different concentrations with the aim of improving the recovery of protein fractions rich in essential amino acids.

Extraction using alkaline solvents provided superior protein recovery (60-78%) compared with NaCl solution and control extractions (20-48% and 21%, respectively). The concentration of alkali or salt (0.25-1 mol L^-1 ) had a minor but significant impact on the yield. Amino acid composition analysis revealed that hempseed meal contains 24% (54.5 ± 0.19 mg g^-1 ) essential amino acids of total amino acids, and extraction with NaOH, KOH, NaHCO₃ or NaCl did not improve the selective extraction of essential amino acids compared to control experiments. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis allowed the identification of edestin and albumin in the extracts obtained with NaHCO₃ and NaCl solvents, with results further showing that the type of extraction solvent influences protein extraction selectivity.

Although alkali solvents provide superior extraction yields, extraction with water resulted in extracts containing the highest proportion of proteins bearing essential amino acids. According to the results of SDS-PAGE, extraction using alkali solvents induced protein crosslinking. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.