Simple and efficient hydrolysis procedure for full utilization of the seaweed Mastocarpus stellatus to produce antioxidant films

Abstract

Three different hydrolysates were obtained from the red seaweed Mastocarpus stellatus using Alcalase: (H0) hydrolysis at 50 °C for 3 h; (H1) hydrolysis at 50 °C for 3 h followed by heating at 90 °C for 1 h; and (H2) hydrolysis at 50 °C for 3 h followed by heating at 90 °C for 2 h. The hydrolysates newly obtained were supplemented with glycerol and directly used as film-forming solutions for development of the corresponding films (FH0, FH1 and FH2). Viscoelastic properties of the film-forming solutions showed improved gel-like behaviour when the κ/ι-hybrid carrageenan extraction at 90 °C was promoted. FTIR analysis revealed that FH2 had the highest relative proportion of κ-carrageenan. All the films showed a high ultraviolet barrier property, but opacity increased markedly with prolonged heat treatment. Very slight differences in water solubility and water vapour permeability were found among the three types of film, but FH0 had the highest tensile strength and Young's modulus responses, whereas film elongation tended to increase with progressive carrageenan extraction in FH1 and FH2. No significant differences in puncture response were found. The enzymatic hydrolysis at 50 °C provided films with reducing power and radical scavenging capacity, which did not change as a result of subsequent heat treatment at 90 °C. The Folin-Ciocalteu-reactive substances content increased with both the hydrolysis process and the subsequent heating treatment.