Effects of the extraction temperatures on the protein contents, gelatin purities, physicochemical properties, and functional properties of tilapia scale gelatins.

Herein, the effects of the extraction temperatures (45, 55, 65, 75, and 85 °C) on the protein contents, gelatin purities, physicochemical properties, and functional properties of tilapia scale gelatins were studied. Among these temperatures, 65 °C was the best extraction temperature to obtain good production yield (16.0 % ± 0.3 %), good protein contents (excellent total amino acid composition of 94.20 ± 0.76 g/100 g of gelatin, the highest hydrophobic amino acids percentage of 32.68 ± 0.24 g/100 g of gelatin), appropriate ATR-FTIR spectra peaks (Amides A, B, I, II, and III), high β-sheet percentage (38.2 % ± 1.3 %), the highest purity of the gelatin structures (280, 140, and 125 kDa), the lowest nanoparticle sizes in atomic force microscopy results, the highest water-holding capacity (25.3 % ± 0.9 %), the highest fat-binding capacity (16.9 % ± 0.1 %), high foaming properties (foaming capacity of 151.7 % ± 7.6 % and foaming stability of 145.8 % ± 6.3 %), the lowest interfacial tension (2.1 ± 0.2 mN/m), the lowest emulsifying activity index (16.5 % ± 0.9 %), the highest emulsifying stability index (88.9 % ± 5.1 %), highest emulsion viscosity (1462 ± 17 mPa·s at the rotary speed of 6 rpm), the lowest initial droplet sizes, and lowest emulsion creaming index (6.9 % ± 0.7 %). This work provided a useful guide to choosing extraction temperature for gelatin extraction and a useful theory on the relationship between compositions and properties of a protein sample.