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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