. 2023 Sep 30;7:100604. doi: 10.1016/j.crfs.2023.100604

Table 2.

Modification of quinoa protein.^a

Modification techniques	Modification treatment	Characterization techniques	Major findings	References
Physical modification	Heat treatment •Different temperatures from 25 to 121 °C with different time intervals from 5 to 30 min •Controlled heat-treatment (80–100 °C) at variable time (15–30 min) •Microwave heating at 560 W for 3 min •Steaming at 100 °C for 15 min •Boiling at 100 °C for 15 min •Baking at 160 °C for 5 min •81 ± 2 °C for 30 min	Intrinsic fluorescence UV-VIS FTIR CD SDS-PAGE XRD DSC	Solubility, WBC, OBC, EA, and ES were significantly improved after hydrothermal treatment. Moderate heat treatment resulted in the improvement of foaming capacity and foaming stability. Microwave heating and boiling improved solubility, emulsification and gelling properties while steaming and baking decreased such functional properties. Viscosity and elasticity of quinoa protein isolate gels increased after moderate heat treatment.	He et al. (2022a); Mir et al. (2021); Wang et al. (2020a); Luo et al. (2021)
	Sonification •HIUS at variable intervals from 5 to 35 min •HIUS at variable intervals and on-off pulses •HIUS at variable intervals for 5 and 15 min	Dynamic rheometer SDS-PAGE FT-IR Intrinsic fluorescence SEM CD UV-VIS DSC	Sonication significantly improved EA, ES, WBC and OBC compared to native quinoa protein isolate. EA, ES, WBC and OBC reached maximum for 25 min-HIUS-treated quinoa protein isolate. Sonication resulted in strong gelling behaviour and improved flow properties. Increased solubility was detected for HIUS treated quinoa protein isolate.	Mir et al. (2019); Vera et al. (2019); Luo et al. (2022b)
	HHP •250 and 600 MPa at room temperature for 15 min •HHP at room temperature at variable pressure form 100 MPa–600 MPa	SDS-PAGE FT-IR Rheometer CLSM SDS-PAGE	Quinoa protein isolate solubility increased to a small extent after HPP (600 MPa) treatment at pH 7 and pH 9. Viscosity and elasticity of quinoa protein isolate gels increased with the increase in pressure levels.	Luo et al., 2021, Luo et al., 2022b
	HPH •Pressure varied from 10 MPa to 50 MPa •Pressure varied from 30 MPa to 150 MPa	SDS-PAGE FT-IR SLS CLSM Rheometer Intrinsic fluorescence UV-VIS DSC	Enhanced emulsifying capacity, foaming capacity, solubility, and viscoelasticity. HPH treatments increased the solubility of quinoa protein. The peak value of EAI, ESI, FC, FS were obtained at 120 MPa. Shear stress and apparent viscosity of quinoa protein decreased as the pressure increased.	Luo et al. (2022a); Zhao et al. (2022)
	Extrusion •Semolina incorporated with quinoa protein isolate at variable levels •Quinoa flour	Colorimeter Rapid-Visco Analyzer Texture analyzer SEM SE-HPLC X-ray microtomography	Addition of quinoa protein isolate to produce pasta increased the optimal cooking time, water absorption, volume expansion, pasting temperature and firmness. Extrusion increased protein crosslinking and aggregation, and decreased protein solubility.	Gupta et al. (2021); Kuktaite et al. (2022)
Chemical modification	pH-shifting treatment •Acidic pH and basic pH (above 8.0) •pH 3.5 and 7.0	CD	Solubility shifted from low (less than 10%) to high (more than 70%) as the pH increased from acidic condition to alkaline condition. Quinoa protein isolate gel at pH 3.5 showed more stable to cooling than at pH 7.0.	Kaspchak et al. (2017); Elsohaimy et al. (2015)
	Presence of salts •The addition of CaCl₂ or MgCl₂ to quinoa protein isolate suspension •The addition of CaCl₂ to quinoa protein concentrate suspension •The addition of NaCl and CaCl₂ to quinoa protein isolate suspension	Rheometer SEM USANS SAXS SANS CLSM	The divalent ions resulted in stronger gels and crosslinking structure at pH 3.5, but had detrimental effects on gelation at pH 7.0. The incorporation of Ca²⁺ increased the quinoa protein concentrate suspension’s elastic behaviour. The gelation of quinoa protein isolate could occur at lower temperatures with increasing NaCl or CaCl₂ concentration. Increasing the concentration of either NaCl or CaCl₂ led to a greater gel strength.	Kaspchak et al. (2017); Quintero et al. (2022); Yang et al., 2022a, Yang et al., 2022b
	Glycosylation technology •Quinoa protein isolate grafted with mannose or xylose at variable levels	SDS-PAGE	Solubility, EA, ES, WAC and OAC were significantly improved, especially with 3 g of mannose.	Teng et al. (2021)
Enzymatic modification	•Limited Alcalase hydrolysis •Limited protease hydrolysis • Limited pancreatin hydrolysis	CLSM SDS-PAGE FT-IR Rheometer CSLM	Limited Alcalase hydrolysis could promote the thermally induced quinoa protein isolate gel strength, but the gel strength was strongly related to the hydrolysis time. Alcalase-hydrolysed quinoa protein showed higher solubility, emulsifying stability, and foaming capacity, but lower emulsifying activity index and foaming stability. The gel-forming ability and gel properties of acid-induced gels was affected by limited protease hydrolysis. Pancreatin hydrolysate of quinoa protein showed higher solubility, emulsifying and foaming activities but lower emulsifying and foaming stabilities than that of the control.	Wang et al. (2022); Aluko and Monu (2003); Galante et al. (2020); Daliri et al. (2021)

Abbreviations: CD, circular dichroism. CLSM, confocal laser scanning microscopy. DSC, differential scanning calorimetry. EA, emulsion activity. ES, emulsion stability. FTIR, Fourier transform infra-red spectroscopy. HHP, high hydrostatic pressure. HIUS, high intensity ultrasound treatment. HPH, high pressure homogenization. OAC, oil absorption capacity. OBC, oil binding capacity. SANS, small-angle neutron scattering. SAXS, small-angle X-ray scattering. SDS-PAGE, sodium dodecyl sulfate–polyacrylamide gel electrophoresis. SE-HPLC, size exclusion-high-performance liquid chromatography. SEM, scanning electron microscopy. SLS, static light scattering. USANS, ultrasmall angle neutron scattering. UV-VIS, ultraviolet–visible spectroscopy. WAC, water absorption capacity. WBC, water binding capacity. XRD, X-ray diffraction.