Processing of watermelon seed shells nanocellulose with electron beam irradiation and esterification modification: Consequences on fundamental characteristics, molecular structure, physicochemical properties, functional performance, and associated mechanisms.

This study developed an electron beam irradiation (EBI)-assisted esterification strategy to convert underutilized watermelon seed shells into amphiphilic esterified nanocellulose (ENC). The multiscale structural evolution associated with EBI-enhanced esterification, as well as its feasibility for emulsion stabilization, was investigated. Native nanocellulose (NNC) was subjected to EBI (50, 100, 150 kGy) followed by lauric acid esterification. The degree of substitution of irradiated ENC was 0.28-0.77, which was 40-285% higher than unirradiated ENC (0.20). The decrease in hydrophilic-lipophilic balance indicated improved interfacial compatibility in nonpolar solvents. Fourier transform infrared spectroscopy confirmed successful lauric acid grafting. Transmission electron microscopy revealed that esterification induced nanocellulose to change from strip-like structures into aggregated particles (21.52-33.72 nm). Pickering emulsions prepared with ENC exhibited droplets (3.29-3.79 μm) and outstanding oxidative stability, underscoring ENC'S interfacial stabilization capability. This work integrates EBI-induced structural activation with lauric acid esterification, providing a new way to produce high-performance nanocellulose from agro-waste.