Preparation and Stability Study of Co-Encapsulated Particles of Curcumin or Quercetin with Lactobacillus rhamnosus GG

This study developed and characterized a hierarchical co-encapsulation system for the delivery of hydrophobic polyphenols (curcumin or quercetin) and the probiotic Lactobacillus rhamnosus GG (LGG). The system was constructed through the self-assembly of zein to form a hydrophobic core for the polyphenols, followed by complex coacervation with debranched starch and chitosan to form an outer hydrophilic layer for LGG. Structural analyses using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and confocal laser scanning microscopy verified the successful formation of the core–shell structure and the transformation of crystalline polyphenols into an amorphous state. The co-encapsulated particles exhibited high encapsulation efficiency (>95% for both polyphenols and LGG) and encapsulation yield (>80% and >75%, respectively). The encapsulation significantly enhanced the antioxidant capacity of both polyphenols in DPPH and ABTS assays, with co-encapsulation of LGG providing a further enhancement. Moreover, the hierarchical structure effectively protected LGG, markedly improving its survival under simulated gastrointestinal conditions and during storage at 4 °C and −20 °C, with quercetin offering stronger protection than curcumin. These findings demonstrate that this co-encapsulation strategy delivers simultaneous protection to both probiotics and polyphenols, providing a robust approach for improving the stability and functionality of multiple bioactive components.