Collagen films from swim bladders: Preparation method and properties

This paper describes the preparation and characterization of collagen films extracted from swim bladders of three species of tropical fishes: Arius parkeri (Gurijuba), Cynoscion acoupa (Pescada Amarela) and Cynoscion leiarchus (Pescada Branca). Collagen was extracted under acidic conditions (CH3COOH, 2.5 pH) and precipitated by the addition of NaCl up to 3.0 mol L−1. The films were prepared in acrylic containers and dried in a vacuum atmosphere. The collagen films were characterized by hydroxyproline contents, thermal analysis, scanning electron microscopy and impedance spectroscopy. The determined values of 4-hydroxiproline and collagens in the films were: 105.23 ± 4.48 and 873.2; 102.94 ± 4.42 and 854.1; 100.65 ± 4.80 and 835.8 mg g−1 for A. parkeri, C. acoupa and C. leiarchus, respectively. Differential scanning calorimetry revealed high denaturation temperature peaks at temperatures ranging from 65.9 to 74.8 °C. The micrographs showed no fibrillar organization along the material, but spongy structure, with cavity diameters relatively uniform, at around 2 μm. The impedance spectroscopy presented a distributed relaxation process. A. parkeri's films showed piezoelectricity.