The mechanism of action of high-intensity ultrasound, high hydrostatic pressure, and heat treatments on Grass pea (Lathyrus sativus L.) protein isolate: From structural denaturation to functional performance

In this study the effects of high-intensity ultrasound (HIU), high pressure (HP), and heat treatment on the structural, functional, and thermal properties of grass pea protein isolate (GPPI) were investigated. While HIU improved the solubility of GPPI (74.03%) by reducing the particle size and exposing the functional groups, heat-treated GPPI exhibited the lowest solubility (39.98%) due to its larger particle size (465.04 nm). The secondary structure was significantly altered by all treatments. The native α-helix content of 30.2% decreased to 10.0% with HIU and 20.3% with heat treatment. Conversely, the β-sheet content increased from 15.8% in the native protein to a maximum of 32.5% following HIU treatment. These structural alterations led to the exposure of buried hydrophobic and sulfhydryl groups. The SDS-PAGE pattern showed higher band intensity in treated samples, indicating that the treatments reduced the GPPI aggregation. All treatments lowered the denaturation enthalpy and thermal degradation temperature from that of the native sample (115.3 J/g and 89°C), with the heat-treated GPPI showing the highest stability among these samples (74 J/g and 76°C). Although HP treatment improved the emulsion and foam properties, HIU was the superior non-thermal method for enhancing the overall GPPI functionality. HIU significantly increased the surface hydrophobicity, and improved the emulsifying (66 m²/g) and foaming (92.5%) capacities. These findings indicate that the non-thermal HIU treatment was highly effective in enhancing the functional properties of GPPI, particularly for applications requiring high solubility, emulsification, and foaming capacity.