Influence of alginate extraction conditions from the brown seaweed Dictyota mertensii on the functional properties of a novel glycerol plasticized alginate film.

Abstract

Alginate films were prepared from the brown seaweed Dictyota mertensii using glycerol as a plasticizer. The effects of extraction conditions-time, temperature, and Na₂CO₃ concentration-on the optical, barrier, and mechanical properties of the films were investigated using a central composite design (CCD). ANOVA and F tests confirmed the models' statistical significance at p ≤ 0.05, 95 % CI. Na2CO3 concentration significantly influenced moisture absorption, water vapor permeability, solubility, opacity, L*, b*, and elongation at break. Temperature mainly affected the color parameter a* and tensile strength, while time was more relevant for the modulus of elasticity. The properties of alginate from Dictyota mertensii were correlated to the film properties. Optimization through numerical desirability function yielded a global desirability index of 0.767, with optimal conditions at 1.390 h, 54.927 °C, and 0.361 mol.L^-1 Na₂CO₃. Under these conditions, the films showed low moisture content (0.277 %), moderate WVP (31.278 g.mm/kPa.m².h), low solubility (18.825 %), appropriate color parameters (Opacity: 12.411 AU.nm/mm, L*: 49.655, a*: 17.680, b*: 44.657), and balanced mechanical properties (TS: 13.270 MPa, EB: 20.638 %, and E: 64.592 MPa). These findings emphasize the potential of alginate films from Dictyota mertensii and promote sustainable use of marine resources.