Strategies to improve the mechanical strength and water resistance of agar films for food packaging applications

•Agar solutions easier to process with locust bean gum (LBG) addition (viscosity increase and decrease in gelling ability).•Film-forming properties of native (NA) and alkali-modified (AA) agars clearly improved by LBG addition.•NA/LBG films exhibited similar or better properties than AA/LBG films.•NA/LBG films are more cost-attractive for the transformation industries.•Integrated multi-trophic aquaculture can enable tunability and quality control of biomass for transformation industries. Agar films possess several properties adequate for food packaging applications. However, their high cost-production and quality variations caused by physiological and environmental factors affecting wild seaweeds make them less attractive for industries. In this work, native (NA) and alkali-modified (AA) agars obtained from sustainably grown seaweeds (integrated multi-trophic aquaculture) were mixed with locust bean gum (LBG) to make ‘knife-coated’ films with fixed final concentration (1wt%) and variable agar/LBG ratios. Agar films were easier to process upon LBG addition (viscosity increase and gelling character decrease of the film-forming solutions observed by dynamic oscillatory and steady shear measurements). The mechanical properties and water resistance were optimal for films with 50 and/or 75% LBG contents and best in the case of NA (cheaper to extract). These findings can help reduce the cost-production of agar packaging films. Moreover, the controlled cultivation of seaweeds can provide continuous and reliable feedstock for transformation industries.