Parametric Evaluation and Material Characterization of Garlic Peel-Derived Polyphenol Encapsulation in Water-Soluble Chitosan-Tripolyphosphate Matrices

Garlic peels remain an underutilized lignocellulosic biomass within the agro-industrial value chain despite their inherent bioactive polyphenol content. However, the thermal and oxidative instability of polyphenols limits high-value valorization of garlic peel biomass and requires stabilization strategies such as encapsulation. This study investigates how water-soluble chitosan (CS) and sodium tripolyphosphate (NaTPP) concentrations affect the encapsulation efficiency of garlic peel polyphenols (GPP) in water-soluble chitosan-tripolyphosphate (CS-TPP) matrices through ionotropic gelation. The highest encapsulation efficiency (EE) observed was 53.02 ± 10.92% with 7% w/v CS and 1% w/v NaTPP. Reduced model ANOVA revealed moderate goodness of fit (R² = 0.70; p < 0.0001) and a non-significant lack-of-fit (p = 0.46), with CS concentration (p < 0.0001), NaTPP concentration (p = 0.01), and NaTPP concentration * NaTPP concentration (p = 0.002) having significant effects on the encapsulation efficiency. Particle size analysis of GPP encapsulated in CS-TPP (GPP@CS-TPP) and CS-TPP matrices revealed an average particle size of 2.71 mm and 2.55 mm, respectively. Fourier-Transform infrared spectroscopy confirmed the presence of polyphenols in the matrices and the electrostatic interactions between the amide and phosphate groups of CS and TPP. Scanning electron microscopy revealed low crosslinking density at the center of both CS-TPP and GPP@CS-TPP matrices. These findings demonstrate the feasibility of CS-TPP encapsulation in agricultural-waste-derived crude polyphenol extracts and provide insights into concentration-dependent encapsulation performance.