Effect of High-Pressure Isostatic Treatment with pH Shifting on the Modification of Techno-Functional Properties of Quinoa Protein Isolate (Chenopodium quinoa Willd)

Plant proteins, particularly those from pseudocereals like quinoa, are gaining attention for their nutritional benefits and potential in food formulations, especially in dairy and meat alternatives. To enhance their functionality, techniques such as high hydrostatic pressure (HHP) combined with pH adjustments are being explored. This study evaluated how HHP and pH treatments affect the techno-functional properties of quinoa protein isolate (QPI), including water and oil retention, foam capacity (FC), foam stability (FS), emulsion ability (EAI), emulsion stability (ESI), and solubility. QPI dispersions were adjusted to pH 4.5, 7.0, and 12.0, and pressurized at 200, 400, and 600 MPa for 10 minutes at 25°C. Unprocessed quinoa protein isolate (U-QPI) was used as a control. The results showed that alkaline pH with intermediate pressure (400 MPa) promoted better water and oil retention (3.73 g/g and 2.70 g/g, respectively), while acidic pH with higher pressure (600 MPa) reduced these properties (2.67 g/g and 2.15 g/g, respectively). Foam capacity was highest at 200 MPa with pH 7 (102.5% ± 3.54), and foam stability increased with higher pressures (77.50% ± 3.54) at alkaline pH. For emulsions, EAI decreased with increasing pressure, with the highest values recorded at 400 MPa for pH 7 (18.70 m²/g ± 0.09) and pH 4.5 (18.66 m²/g ± 0.24). Emulsion stability was optimal at pH 7 and 200 MPa (643.80 min ± 9.95). Solubility was highest in the control group (20.08%) and decreased under pressure treatments, particularly at 200 MPa with pH 4.5 (11.05%). These results demonstrate the potential to modulate quinoa protein functionality through pressure and pH adjustments, offering valuable insights for tailoring plant proteins to specific food applications.