Effect of pH and holding time on the characteristics of protein isolates from Chenopodium seeds and study of their amino acid profile and scoring.

Highlights • Isoelectric pH of both quinoa (QPI) & album protein isolates (API) was 4.5. • The yield and purity of QPI & API was 12.22%; 85.07% & 10.98%; 86.12%. • pH-10 suitable for protein extraction on the basis of purity, solubility & colour. • Quinoa seed protein had improved functional property than the album seed protein. • Protein quality and amino acid score of both the protein indicated higher values. Abstract Alkali extraction and acid precipitation methods were adopted to isolate protein from quinoa and album seeds of variety Chenopodium. Different pH dispersions (3–11) of isolated proteins were prepared and effects of pH and holding time on protein characteristics were evaluated. The pH-10 of extraction medium was found suitable for protein extraction on the basis of yield, purity, solubility and colour having isoelectric pH of 4.5. Yield and purity of protein isolates (PI) of quinoa and album varied from 8.12 to 12.22%; 74.19 to 85.07% and 7.71 to 10.98%; 77.16 to 86.12%, respectively. Overall, pH and time had significant effect on functional properties of PI of both seeds. Quinoa PI had higher emulsifying activity, emulsion stability, water binding capacity and dispersibility, whereas, foaming capacity and stability were higher for album PI. Nutritional indices were 64.20 and 64.58 for quinoa and album PI, respectively, whereas, amino acid scoring (FAO, 2013) indicated, isoleucine, leucine and valine as the limiting amino acids. [ABSTRACT FROM AUTHOR]