Thermal characteristics of gelatin extracted from emperor (shaari) skin: effects of acid concentration and temperature of extraction (original) (raw)

Gelatin extraction yield increased with the increase of acetic acid concentration and temperature. Gelatin extracted from shaari skin using 0.1 N acid solutions and temperatures of 323 and 353 K gave highest protein content comparable to that of commercial bovine and porcine gelatins. In general, gelatin extracted from shaari gelatin showed lower onset of glass transition temperature than mammalian gelatins. For shaari skin gelatin, the onset of glass transition temperature decreased with the increase of extraction temperature up to 323 K and then remained nearly constant. The decrease in glass transition was more pronounced for gelatin extracted at 0.01 N compared to the 0.1 and 1.0 N samples. Unfolding temperature decreased exponentially with the increase of extraction temperature. The unfolding temperature shifted to lower temperature, and the decrease was more pronounced in the case of higher (1.0 N) concentrated samples. The extraction concentration and temperature did not show significant effect on the onset solids-melting temperature. Keywords Fish skin gelatin Á Glass transition Á Solidsmelting Á Shaari Á Amino acid List of symbols T gi Onset temperature of glass transition (K) T gp Peak temperature of glass transition (K) T ge End temperature of glass transition (K) T mi Onset temperature of solids-melting (K) T mm Maximum slope temperature of solids-melting (K) T mp Peak temperature of solids-melting (K) T me End temperature of solids-melting (K) T ui Onset unfolding temperature (K) T um Maximum slope of unfolding temperature (K) T up Peak of unfolding temperature (K) X w Moisture content (g/100 g sample) DC p Change of specific heat (J/kg K) DH u Enthalpy change for unfolding (kJ/kg) DH m Enthalpy change for solids-melting (kJ/kg)