Characteristics of the gelatin extracted from Channel Catfish ( Ictalurus Punctatus) head bones

Three gelatins were prepared from channel catfish head bones by hot water after the head was pretreated with alkali protease, quickly desalted by 0.4 mol/L HCl and soaked in 9 g/L Ca(OH) 2. The extraction conditions of gelatins were 5 °C, pH 4.0, 4 h, 82 °C, pH 2.5, 2 h and 90 °C, pH 3.0, 3 h, respectively. The studies showed there were many differences between these gelatins. The first head bone gelatin contained high content of imino residues and more high molecular weight proportions of β and γ components. Gel strengths of the second and third gelatins were 209 ± 7 g and 117 ± 5 g, lower than that of the first head bone gelatin (282 ± 11 g). Furthermore, the first head bone gelatin achieved the highest gelling and melting points. The first head bone gelatin showed strong ability of clarification when it was used to clarify apple juice. At the same time, the nutritional components of apple juice changed a little except Vitamin C.