Abstract: Polyelectrolyte composite nanoparticles were prepared by the electrostatic interaction between sodium caseinate with positive charges and pectin with negative charges. The effect of mass ratio between sodium caseinate and pectin on the particle size and polydispersity index (PDI) of composite nanoparticles was studied. A pectin/sodium caseinate composite delivery system loaded with lycopene was constructed to explore the effect of lycopene concentration on the encapsulation efficiency and loading rate of lycopene. Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to characterize the ternary composite nanoparticles and analyze its particle size distribution, chemical structure and apparent morphology. In order to determine the release efficiency of incorporated lycopene from the composite nanoparticles, an simulated gastric and intestinal digestion model in vitro was established. The release behavior of lycopene in simulated gastric and intestinal fluids with different pH values was evaluated. The results of TEM and FT-IR showed that pectin and sodium caseinate were not simply physically mixed, but could form a binary compound with stable core-shell structure, which could be used for the encapsulation of lycopene. The results of DSC and TGA showed that lycopene existed inside the powder particles in an amorphous form, thus forming a pectin/sodium caseinate-lycopene complex. The encapsulation rate of lycopene reached 96.93% when the ratio of pectin to sodium caseinate was 20% and the loading rate was 8%. Under these conditions, lycopene had good thermal stability, and it was released in a controlled in simulated gastric fluid and released in a large amount in simulated intestinal fluid.

Key words: lycopene; composite delivery system; pectin; sodium caseinate; controlled release