Investigating the Effect of Supercritical Carbon Dioxide Treatment on the Rheological, Thermal, and Functional Properties of Plum (Prunus domestica L.) Kernel Protein Isolates

Plum kernels are a promising source of dietary proteins that are irretrievably lost during processing. The recovery of these underexploited proteins could be eminently vital for human nutrition. Plum kernel protein isolate (PKPI) was prepared and exposed to a targeted supercritical carbon dioxide (SC-CO(2)) treatment to diversify its effectiveness in industrial applications. The impacts of SC-CO(2) treatment at different processing temperatures (30–70 °C) on dynamic rheology, microstructure, thermal, and techno-functional characteristics of PKPI were investigated. The results revealed that the dynamic viscoelastic characteristics of SC-CO(2)-treated PKPIs showed higher storage modulus, loss modulus, and lower tan δ value than native PKPI, indicating greater strength and elasticity of the gels. Microstructural analysis showed that the proteins experienced denaturation at elevated temperatures and resulted in the formation of soluble aggregates, which increased the heat requirement for thermal denaturation of SC-CO(2)-treated samples. SC-CO(2)-treated PKPIs demonstrated a decline of 20.74% and 30.5% in crystallite size and crystallinity. PKPIs treated at 60 °C showed the highest dispersibility, which was 1.15-fold higher than the native PKPI sample. SC-CO(2) treatment offers a novel path to improve the techno-functional properties of PKPIs and extend its use in food and non-food applications.