Isolation of Prunus persica kernel protein and its physicochemical properties and aggregating performance modulated by heating and ultrasonication

Prunus persica kernel (PK), a by-product discarded from fruit processing, poses a threat to the environment if not disposed of properly. While previous studies have focused on the recycling oil from PK to reduce environmental risks, little attention has been paid to the recovery of proteins. The present work aimed to investigate the structure and physicochemical properties of Prunus persica kernel protein (PKP) and evaluate its suitability as a carrier material for delivering bioactive substances. PKP was extracted by salt fractionation and identified as a 250 kDa albumin, consisting of approximately 40 kDa acidic (PKP-A1 and PKP-A2) and 20 kDa basic subunits (PKP–B). Further physicochemical properties assay revealed that PKP possessed abundant free sulfhydryl (FSH) groups (17.23 μmol/g), high denaturation temperature (89.26°C), and low hydrophobicity (3.37). Additionally, PKP can self-assemble into nano-aggregates (155.8 ± 31.1 nm) after heating at 90°C for 60 min, which is correlated with the oxidation of FSH in PKP-A1; while PKP aggregate with a particle size of 253 ± 61.7 nm is induced by the disintegration of PKP-B and the reaggregation of PKP-A2 upon ultrasonication at 200 W for 10 min. Besides, PKP and its acidic subunits had no obvious cytotoxic effects on Caco-2 cells. The well aggregation behavior and minimal cytotoxicity imply that PKP is suitable for loading bioactive compounds as a self-assembled nanocarrier. Overall, this study provides a basis for the recovery of protein from PK and exhibits the utilization potentiality as nutraceuticals and delivery vehicles in the food and pharmaceutical areas.