Effect of Extraction Temperature on Functional Properties and Antioxidative Activities of Gelatin from Shark Skin

Physico-chemical properties, functional properties, and antioxidative acitivities of gelatin from the skins of brownbanded bamboo shark (BBS; Chiloscyllium punctatum) and blacktip shark (BTS; Carcharhinus limbatus), as affected by extraction temperature, were investigated. α-Amino acid group content and surface hydrophobicity of both gelatins from both species increased as the extraction temperature increased (P < 0.05). Both gelatins had a high solubility (more than 80%) in a wide pH range (1–10). Both gelatins extracted at 60 °C exhibited the highest emulsion activity index (EAI), emulsion stability index (ESI) and foam expansion (FE). The lowest foam stability (FS) was obtained when gelatin was extracted at 75 °C (P < 0.05). The BBS gelatin had lower EAI, ESI, and FE than did BTS gelatin. Nevertheless, a higher FS was found in the former (P < 0.05). Antioxidative activities of both gelatins increased with coincidental increase in α-amino group content as the extraction temperature increased (P < 0.05). The BTS gelatin generally exhibited the higher antioxidative activities, compared with the BBS gelatin (P < 0.05). Gelatin extracted at 60 °C showed the highest interfacial properties, while those extracted at higher temperature (75 °C) had enhanced antioxidative activities. Extraction temperature may therefore be regulated to maximize applications.