Extracting optimization and physical properties of yellowfin tuna (Thunnus albacares) skin gelatin compared to mammalian gelatins

This work is to optimize gelatin extraction from dorsal skin of yellowfin tuna (Thunnus albacares) using response surface methodology, and to compare physical properties of yellowfin tuna skin gelatin with those of two mammalian skin gelatins (bovine and porcine). Central composite design was adopted in gelatin processing for extracting optimization. Concentration of NaOH (X1), treatment time (X2), extraction temperature (X3) and extraction time (X4) were chosen for independent variables. Dependent variables were gel strength (Y1) and gelatin content (Y2). Optimal conditions were X1=1.89(%), X2=2.87 (days), X3=58.15(°C) and X4=4.72 (h), and predicted values of multiple response optimal conditions were Y1=429.1 (Bloom) and Y2=89.7 (%). In order to investigate physical properties of yellowfin tuna skin gelatin, gel strength, gelling and melting points, and dynamic viscoelastic properties were measured. The gel strength of yellowfin tuna skin gelatin (426 Bloom) was higher than bovine and porcine gelatins (216 Bloom and 295 Bloom, respectively), while gelling and melting points were lower. Dynamic viscoelastic properties of yellowfin tuna skin gelatin did not change at 20 °C, but increase at 10 °C as a similar pattern with mammalian gelatins.