Enhancing quinoa protein properties: Pulsed electric fields as a sustainable green innovation for structural and functional excellence

Abstract

Pulsed electric field (PEF) processing is an emerging non-thermal technology capable of modifying plant protein functionality through controlled structural rearrangements. This study systematically investigated the effects of electric field strength (3, 5, and 7 kV/cm) and pulse number (80, 100, and 120) on the structural, technofunctional, thermal, and rheological properties of quinoa protein concentrate (QPC). The results demonstrated that pulse number was the primary factor governing protein functionality, exerting a stronger influence than electric field strength. Compared with the control sample, moderate PEF treatment (5 kV/cm-80 pulses) significantly increased protein solubility (43.75 %), foaming capacity (36 %), and emulsion stability during centrifugation (14 %), while reducing surface tension and improving viscoelastic behavior. Structural analyses revealed a marked increase in free sulfhydryl groups (up to 27.6 mu mol/g), a decrease in alpha-helix content accompanied by a corresponding increase in beta-sheet structures, and reduced crystallinity, indicating partial protein unfolding without alteration of the primary structure, as confirmed by SDS-PAGE. Thermal analysis showed a substantial increase in denaturation enthalpy (9.24 J/g), reflecting enhanced structural ordering. In contrast, higher pulse numbers (120 pulses) promoted protein aggregation, leading to reduced solubility, foaming stability, and water-holding capacity. Microscopy revealed a smoother surface with cracks and sheetlike features in PEF-treated proteins compared to the control. These findings demonstrate that moderate PEF treatment improves QPC functionality by balancing molecular unfolding and aggregation, providing mechanistic insight into PEF-induced protein modification and highlighting its potential as a sustainable green technology for the development of high-performance plant-based food ingredients.