Composition of Quinoa Protein Fractions

Abstract

Proteins of quinoa and roasted-quinoa flours were fractionated and analyzed. The protein content of the flours was 11.7-12.5%(w/w). In quinoa flour, water-soluble protein (albumin) and NaCl-soluble protein (globulin) constituted 28.5%(w/w) and 34.1%(w/w) of total protein, respectively. Amino acid profile of each protein fraction showed a balanced content of essential amino acid for quinoa flour when compared with reference patterns from the World Health Organization. The lysine level of each protein fraction of quinoa flour (4.5-7.0%, w/ w) was high, compared with major cereals such as rice and wheat. On the other hand, insoluble protein comprised 54.4%(w/w) of total protein in roasted-quinoa flour. The level of water-soluble and NaCl-soluble proteins decreased in the roasted flour. SDS-polyacrylamide gel electrophoresis revealed that polypeptides of high molecular mass found in each protein fraction of quinoa four were degraded by roast. The lysine level of each protein fraction was decreased by the roast. The amino acid score for each protein from roasted-quinoa flour was lower than that of quinoa flour. Lysine was the first limiting amino acid in all fractions of proteins from the roasted flour. These results showed that quinoa could be used as a nutrient substitute for the cereals, but the balance of essential amino acid in roasted quinoa was lowered resulting from the decrease of lysine level.