Properties of fish skin gelatin film incorporated with seaweed extract

Fish skin gelatin films incorporated with 6% oxygenated seaweed (Turbinaria ornata) extract (based on protein content) with pHs 9 or 10 were prepared and characterized in comparison with the control film (without seaweed extract). Films incorporated with seaweed extract at both pHs exhibited the higher elongation at break (EAB) than the control film (p < 0.05). However, no differences in tensile strength (TS) and transparency between films without and with seaweed extract were observed (p > 0.05). Water vapor permeability (WVP), and film solubility decreased as seaweed extract was incorporated, regardless of pH (p < 0.05). This was associated with the formation of non-disulfide covalent bond in the film matrix, most likely induced by the interaction between oxidized phenols in seaweed extract and gelatin molecules. Coincidentally, the second transition temperature of gelatin film shifted from 170.54 to 178.36 °C when incorporated with 6% seaweed extract at pH 10. Film without seaweed extract had smooth surface while the rougher surface was noticeable in film incorporated with seaweed extract for both pHs. Thus, the addition of seaweed extract had the impact on the property of fish skin gelatin film, most likely due to the enhanced formation of protein cross-links.