Synthesis of Chitosan-ortho-vanillin/AgNPs Schiff Base Composite as Food Preservative

Abstract

Structural modification of chitosan (CH) may enhance the stability of silver nanoparticles (AgNPs) synthesized. This study aims to modify chitosan into chitosan-ortho-vanillin Schiff base (CHoVSB), which was used as a capping agent in the synthesis of AgNPs, and were evaluated as the food preservative through the antimicrobial testing. Composites of AgNPs were synthesized using AgNO₃ as an Ag precursor, ascorbic acid as a bioreductor, sodium tripolyphosphate (STTP) as a crosslinker and chitosan or CHoVSB. They were characterized by ultraviolet-visible (UV-Vis), Fourier transform infrared spectroscopy (FTIR), atomic absorption (AA) and scanning electron microscope-energy dispersive X-ray (SEM-EDX) analyses. CHoVSB was synthesized as a brownish-yellow solid with a yield of 57.6% and a degree of substitution of 44.09%. The composites of CH/AgNP were brownish-yellow solids with yields of 80.8–83.4% (w/w), and exhibited surface plasmon resonance (SPR) peaks at 420–439 nm. CHoVSB/AgNP-1 and CHoVSB/AgNP-2 composites produced were green solids with yields of 72.5 and 80.3% (w/w), and SPR peaks at 419 and 447 nm, respectively. CHoVSB/AgNP-2 composite was found the best product featuring spherical shape with a size of 21 nm and a uniform particle distribution. It has displayed the potential to be used as a food preservative with the highest percentage of bacterial reduction of 99.5 and 98.6% at a concentration of 1000 ppm for 3 and 7 days of observation, respectively.