Structural modification of plum (Prunus domestica L) kernel protein isolate by supercritical carbon-dioxide treatment: Functional properties and in-vitro protein digestibility

The effect of supercritical carbon dioxide (SC-CO2) treatment at different processing temperatures (30–70 °C) on the physico-functional properties, structural features, and in-vitro digestibility (IVPD) of plum kernel protein isolates (PKPI) was examined. The results revealed remarkable changes in the secondary structures of SC-CO2-treated PKPIs, including a decrease in α-helix proportion, a concomitant increase in β-sheet content, and a considerable variation in random coils and β-turn structures. The temperature rise increased the negative zeta potential to a maximum of 31.35 mV at 60 °C, exhibiting the colloidal stability of PKPI dispersions. SDS-PAGE analysis showed variations in the intensities of protein bands, indicating denaturation and aggregation at higher temperatures. These structural and molecular changes improved water-binding capacity (1.22-fold) and oil binding capacity (1.11-fold), wettability (1.12-fold), and the highest value in all the properties was recorded at 60 °C. Moreover, the highest IVPD value (21.58 %) and a distinguishable colour difference (∆E) of 8.11 was also obtained at 60 °C of the processing temperature. Therefore, SC-CO2 treatment-induced modification of PKPI contributed to the enhanced digestibility and techno-functional properties, which offered new prospects to extend its use in food applications. [Display omitted] •SC-CO2 treatment at 30–70 °C was applied to modify structural properties of PKPIs•Circular dichroism spectra revealed notable changes in secondary structures of PKPI•Modification of α-helix and β-sheet contents indicates a flexible and loose structure•Wettability, water and oil holding ability improved by 1.12, 1.22 & 1.11-fold at 60 °C•Zeta-potential of −31.35 mV at 60 °C exhibited colloidal stability of PKPI dispersions