Alginate-based nanocomposite films reinforced with halloysite nanotubes functionalized by alkali treatment and zinc oxide nanoparticles.

Functionalized halloysite nanotubes were prepared by surface activation of halloysite (Hal) with sodium hydroxide and deposition of zinc oxide nanoparticles (ZnONP). The surface charge of Hal was changed from 0.18 ± 0.6 mV to -35.2 ± 2.8 mV after alkali treatment. The functionalized Hal (AT-Hal/ZnONP) was incorporated into alginate biopolymer as a reinforcing filler with different concentration of AT-Hal/ZnONP (1, 3, 5, and 7 wt% of alginate). Alginate films with AT-Hal/ZnONP exhibited a significant increase in the mechanical, water vapor barrier, and UV light barrier properties. The thermal stability of composite films has not changed after AT-Hal/ZnONP incorporation. The AT-Hal/ZnONP incorporated alginate films demonstrated strong antibacterial activity against food-borne pathogenic bacteria, Escherichia coli and Listeria monocytogenes. The nanocomposite film with 7 wt% of AT-Hal/ZnONP exhibited complete sterilization of E. coli and L. monocytogenes after 3 and 9 h of treatment, respectively.