Ultrasound-reinforced encapsulation of proanthocyanidin by chitosan-chondroitin sulfate nanosystem

The polyelectrolyte complexation between chitosan (CH) and chondroitin sulfate (CS) and the ultrasonication assistance were adopted as the encapsulation strategy for preparing proanthocyanidin (PC) encapsulated nanoparticles (NPs) to protect bio-functions of PC. Conditions of 1.5 mg/mL of CH and CS, 1:3 wt ratio of CH/CS, 0.5 mg/mL of PC, pH 3.25, and 1 min ultrasonic treatment were recommended by the systematic research, respectively, with NPs appearing the smallest size (∼300 nm) and high entrapment efficiency (37.5%). Ultrasound crushed aggregates into nanoparticles by the acoustic cavitation and generated more amide bonds observed by XPS. Due to the physical barrier of NPs, PC in NPs still had a 94.4% DPPH radical scavenging rate after illumination of 10 d. Application of NPs for fabricating CH bio-films was carried out, and the bio-films containing CH/CS-PC NPs decreased aerobic bacteria count and lipid oxidation of fillets stored for 8 d by 2.2 log10 CFU/g and 51.1%, respectively, which was better than pure CH bio-films. The incorporation of PC-encapsulated NPs to CH bio-films inhibited the bacteria and oxidation induced spoilage for refrigerated grass carp flesh, providing a potential application for food preservation.