Structural Properties of Quinoa Protein Isolate: Impact of Neutral to High Alkaline Extraction pH
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Date
2023-07-03
Open Access Location
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI (Basel, Switzerland)
Rights
(c) 2023 The Author/s
CC BY 4.0
CC BY 4.0
Abstract
In this work, we extracted proteins from white quinoa cultivated in the northeast of Qinghai-Tibet plateau using the method of alkaline solubilization and acid precipitation, aiming to decipher how extraction pH (7-11) influenced extractability, purity and recovery rate, composition, multi-length scale structure, and gelling properties of quinoa protein isolate (QPI). The results showed that protein extractability increased from 39 to 58% with the increment of pH from 7 to 11 whereas protein purity decreased from 89 to 82%. At pH 7-11, extraction suspensions and QPI showed the similar major bands in SDS-PAGE with more minor ones (e.g., protein fractions at > 55 or 25-37 kDa) in suspensions. Extraction pH had limited effect on the secondary structure of QPI. In contrast, the higher-order structures of QPI were significantly affected, e.g., (1) emission maximum wavelength of intrinsic fluorescence increased with extraction pH; (2) surface hydrophobicity and the absolute value of zeta-potential increased with increasing extraction pH from 7 to 9, and then markedly decreased; (3) the particle size decreased to the lowest value at pH 9 and then increased to the highest value at pH 11; and (4) denaturation temperature of QPI had a large decrease with increasing extraction pH from 7/8 to 9/10. Besides, heat-set QPI gels were formed by loosely-connected protein aggregates, which were strengthened with increasing extraction pH. This study would provide fundamental data for industrial production of quinoa protein with desired quality.
Description
Keywords
extraction conditions, functionality, plant protein, structure
Citation
Liu S, Xie Y, Li B, Li S, Yu W, Ye A, Guo Q. (2023). Structural Properties of Quinoa Protein Isolate: Impact of Neutral to High Alkaline Extraction pH.. Foods. 12. 13. (pp. 2589-).