Preparation of novel seaweed nanocomposite film from brown seaweeds Laminaria japonica and Sargassum natans

Seaweed nanocomposite films were manufactured with brown seaweeds, kombu (Laminaria japonica) and sargassum (Sargassum natans). With the supernatant obtained after the acid-base pretreatment, a film-forming solution was prepared and seaweed biopolymer film formed using a cast-evaporating method. Additionally, cellulose nanocrystals (CNCs) were isolated from the residues of the film formulation process and were applied to seaweed biopolymer film. As a result, seaweed nanocomposite films were developed. Their physicochemical properties were investigated to determine viability as a packaging substrate. Kombu film was visible as a dark brown and sargassum film appeared light brown in color. The addition of CNCs did not affect the color of films. The morphological observation revealed the addition of CNCs could fill the void space including holes and fractures. FTIR spectra indicated hydrogen bonding was increased and XRD results showed higher crystallinity after the addition of the CNCs. The addition of CNCs into the film led to improving not only the physical properties such as thickness, moisture content, and water solubility, but also mechanical properties. Similarly, barrier properties to water, oxygen, and light were reinforced. It was found that CNCs also enhanced thermal properties in TGA and DSC tests. Total phenolic contents, DPPH radical scavenging effect, and reducing power assay indicated that kombu film showed higher antioxidant properties than sargassum film and not related to the CNCs addition. Results from this experiment indicate novel seaweed nanocomposite biopolymer films developed from brown seaweeds could be further developed for packaging applications such as food films used for preservation.