Physicochemical and functional properties of quinoa protein isolate

Abstract

This study was focused on the optimum conditions for preparing the protein isolate of quinoa seeds and investigates the physicochemical and functional properties of the isolated protein to assess the potential use of quinoa protein isolate in food applications and manufacturing. The protein isolate of quinoa was obtained by protein solubility at alkaline pH value (10), followed by precipitation at an acidic pH value (4.5). SDS–PAGE showed protein bands with 55 KDa corresponding to globulin and 31–33 KDa corresponding to chenoprotein in all extraction pHs. Quinoa protein had reasonable concentrations of essential amino acids (except tryptophan) with a high level of lysine (17.13%). A sharp minimum solubility was observed at the pH value (4.5), and the maximum value was observed at the alkaline pH value (10) (P > 0.05). Quinoa protein showed a high In Vitro digestibility (78.37 ± 1.08%). The quinoa protein showed water absorption (3.94 ± 0.06 ml/g) and (1.88 ± 0.02 ml/g) oil absorption. The foaming capacity of quinoa protein isolate was (69.28 ± 9.39% in average) and the foaming capacity was increased with the increase in the protein concentration. Quinoa protein isolate registered 54.54 ± 15.31% foam stability after 60 min. Emulsion ability index was ranged from 1.24 ± 0.05 m²/g for 0.1% protein suspension to 3.38 ± 0.31 m²/g for 3% protein suspension with average 2.10 ± 0.99 m²/g. The average of emulsion stability index was (38.43 ± 7.22 min). Quinoa protein isolate is a promising and impressive nutritive source, which is leading to candidate it as a food supplement and functional food but still needs more advanced research to improve and proof its functional properties to be convenient for using in food processing and additives.