BOVINE AND FISH GELATIN COATINGS INCORPORATING TANNINS: EFFECT ON PHYSICAL PROPERTIES AND OXIDATIVE STABILITY OF SALMON FILLETS

Fish gelatin provides an alternative source of gelatin for Halal and Kosher applications and is prion and zoonotic agent free. However, applications of fish gelatin have been limited due to inferior mechanical and barrier properties. The physical properties of fish gelatins can be improved by crosslinking using natural polyphenolic compounds such as tannic acid. The objectives of this study were to develop fish gelatin films incorporated with tannic acid and evaluate their antioxidant, thermal, tensile, water vapor permeability and water solubility properties. Also, the effect of tannin-incorporated gelatins on the oxidative stability of salmon fillets was examined at 4 and 10 °C. Comparative data with bovine gelatins were generated. Fish gelatin (6.75% wt/wt) films were prepared at a gelatin:tannic acid ratio (wt/wt) of 1:0.05, 1:0.10 and 1:0.15. Tensile strength of bovine gelatin control was approximately 49 MPa and that of fish gelatin was 21 MPa. Tensile strength of bovine gelatins increased with tannic acid incorporation (P > 0.05) and did not vary significantly for fish gelatin films. Percent elongation of films increased and elastic modulus decreased with tannic acid incorporation. Water solubility of bovine gelatin films was reduced significantly (P < 0.05) and there was no significant effect of tannin on the solubility of fish gelatin films. The water vapor permeability was not significantly different for both the gelatins (P > 0.05) and the values ranged between 1.62 and 2.01 g mm/kPa h m2. Bovine and fish gelatin films with highest level of tannic acid showed an increase in glass transition temperature of approximately 12 and 6 °C, respectively. Films with tannic acid possessed antioxidant activity and were able to reduce oxidation (TBARS values) in gelatin coated refrigerated salmon held for 12 days.