Isolation of quinoa protein by milling fractionation and solvent extraction

• Twenty hours of conditioning with 15% moisture enables fractionation of quinoa (flour/bran).
• Quinoa bran contains 28% protein (db) in comparison to 12% (db) in whole grain.
• Using quinoa bran instead of whole grain improves protein extractability.
• Maximum quinoa protein yield was achieved with aqueous alkaline extraction.
• The color of quinoa milling fractions indicates their mineral and protein content.

Quinoa is an attractive non-animal protein source, because of its absence of gluten and the favorable amino-acid profile. The objective of this study was the extraction of quinoa protein by two consecutive approaches. Initially, the protein-rich bran was isolated by optimizing the conditioning parameters of a milling fractionation procedure. In contrast to the protein content of the whole grain, 11.75% in dry base (db), the bran fraction contained 27.78% (db) protein when conditioned with 15% moisture at 20 ̊C for 20 h. Subsequently, an aqueous extraction was developed, resulting in a protein solubility of 60% at pH 10 and 20 ̊C for 1 h. For purification at the isoelectric point, the pH-value and the separation method were varied. After drying, an extraction of proteins from bran yielded 68% (db) as compared to 52% (db) protein from quinoa whole grain flour.

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