Development, antimicrobial properties and mechanical properties of starch-based biodegradable films incorporated with antimicrobial-nanoparticle system

Abstract

Increasing plastic waste has led to a shift in the use of materials for food packaging from plastic to natural polymers. Antimicrobial agents (AM) and Nanoparticles (NP) have been used to improve certain properties of the bio-based films. In particular, two AM agents, sodium benzoate (Bz) and natamycin (Nat), were incorporated into starch to form starch-based films. Two incorporation methods were studied, directly incorporating AM into starch matrix, and incorporating AM-NP systems into starch matrix. In the latter method, AM were first loaded onto NP, layered double hydroxide (LDH), called LDH-Bz and LDH-Nat, and then incorporated into starch. Five films were prepared: starch without AM, starch with Bz, starch with Nat, starch with LDH-Bz, and starch with LDH-Nat. Mechanical properties were tested using the Tensile Strength Tester for Elongation, Tensile Strength and Elasticity. The results showed that addition of AM has significant effect on elongation at break but no significant effect on tensile strength. The elongation increased for films with 2% of LDH-Bz. Antimicrobial tests revealed that films most effective in inhibiting the molds were all Natamycin films i.e. Standard Nat 0.4% (50% salt and 50% lactose) and Starch LDH-Nat, whereas none of the films showed effectiveness against bacterial species.