Extraction of gelatin from sardine scales by pressurized hot water

Abstract

In the present study, gelatin was extracted from sardine scales using a novel pressurized hot water extraction method, and the extraction behavior and properties of of the extracted gelatin were investigated. The present method enabled stable extraction using only water, and no clogging of extraction tube filters was observed. The hydrolysis reaction became more pronounced at an extraction tube outlet temperature of 143-153°C, and virtually all sardine scale collagen was eluted within 8 min at an extraction tube inlet temperature of 225°C (tube outlet temperature, 156-203°C). Extracted proteins consisted mostly of gelatin, but also a small percentage of ash thought to be apatite. In addition, no significant amino acid thermal decomposition was observed. Molecular weights of extracted gelatin ranged from approximately 443 to 6.5 kDa at the peaks of the GPC curve, and decreased as extraction temperature increased. Gelatins in the peptide region that had narrow molecular weight distributions were obtained in the 400-1000 mL fraction at an inlet temperature of 225°C.