Effect of Extraction Temperature on the Physicochemical Properties of Gelatine from the Skin of Black Tilapia (Oreochromis mossambicus)

The physicochemical properties of gelatine from the skin of black tilapia (Oreochromis mossambicus) as affected by different extraction temperatures (45 degrees C, 55 degrees C, 65 degrees C and 75 degrees C) were investigated. The yield of gelatine increased significantly as the extraction temperature increased. Electrophoretic protein pattern and free amino acid content of tilapia gelatine showed that high extraction temperature (75 degrees C) contributed to the decrease in major protein components (alpha- and beta-chains) of the extracted gelatine. Fourier transform infrared (FTIR) spectroscopy showed a significant loss of triple helical structure in all samples. The gel strength, gelling temperature and melting temperature of tilapia gelatine decreased as the extraction temperature increased. The gelling and melting temperature of gelatine extracted at 45 degrees C (G45) was 18.9 degrees C and 26.2 degrees C, respectively, which was about 2 degrees C lower than those of the bovine gelatine tested. This suggested that G45 and bovine gelatine gel possessed similar thermal stability. In addition, the rheological test revealed that, as the extraction temperature increased, the storage modulus (G') of tilapia gelatine was frequency dependent and took a relatively long time to achieve maximum G' at 10 degrees C. Black tilapia gelatine showed higher emulsion ability and emulsion stability when lower extraction temperatures were used. The foaming properties of tilapia gelatine was similar among gelatine extracted from 45 degrees C to 65 degrees C. A significant decrease in foamability and stability was observed when extraction temperature further increased to 75 degrees C. Therefore, black tilapia gelatine extracted at 45 degrees C has the functional properties that are comparable to bovine gelatine.