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

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.