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In the present study, to establish the optimum gelatin extraction conditions from pangasius catfish (Pangasius sutchi) bone, Response Surface Methodology (RSM) with a 4-factor, 5-level Central Composite Design (CCD) was conducted. The model equation was proposed with regard to the effects of HCl concentration (%, X 1 ), treatment time (h, X 2 ), extraction temperature (°C, X 3 ) and extraction time (h, X 4 ) as independent variables on the hydroxyproline recovery (%, Y) as dependent variable. X 1 02.74 %, X 2 021.15 h, X 3 074.73°C and X 4 05.26 h were found to be the optimum conditions to obtain the highest hydroxyproline recovery (68.75 %). The properties of optimized catfish bone gelatin were characterized by amino acid analysis, SDS-PAGE, gel strength, TPA and viscosity in comparison to bovine skin gelatin. The result of SDS-PAGE revealed that pangasius catfish bone gelatin consisted of at least 2 different polypeptides (α 1 and α 2 chains) and their cross-linked chains. Moreover, the pangasius catfish bone gelatin was found to contain 17.37 (g/100 g) imino acids (proline and hydroxyproline). Pangasius catfish bone gelatin also indicated physical properties comparable with that of bovine and higher than those from cold water fish gelatin. Based on the results of the present study, there is a potential for exploitation of pangasius catfish bone for gelatin production. Furthermore, RSM provided the best method for optimizing the gelatin extraction parameters.

Summary Lizardfish (Saurida tumbil), threadfin bream (Nemipterus japonicus) and purple‐spotted bigeye (Priacanthus tayenus) surimi were freeze‐dried to produce surimi powder. The resulting surimi powder contained 72.8–73.4% protein and 16.8–17.5% carbohydrate. Functional properties such as solubility, gelation capacity, water‐holding capacity (WHC), emulsification, foaming properties and colour varied from species to species. The surimi powder formed gels and produced about 90% emulsification at a concentration of 1.0%. Threadfin bream was found to be the best source for surimi powder production, followed by purple‐spotted bigeye and lizardfish, respectively.

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Edible bird's nest (EBN) is widely consumed as a delicacy and traditional medicine amongst the Chinese. In the present study, for the first time, the antioxidant properties of an EBN pepsin-trypsin hydrolysate of the swiftlet species Aerodramus fuciphagus and its ultrafiltration fractions were investigated. Thirteen peptides with molecular weights between 514.29 and 954.52 Da were identified in the EBN fraction with the use of mass spectrometry. Two novel pentapeptides Pro-Phe-His-Pro-Tyr and Leu-Leu-Gly-Asp-Pro, corresponding to f134-138 and f164-168 of cytochrome b of A. fuciphagus, indicated the highest ORAC values of 14.95 and 14.32 μM of TE μM peptide, respectively. Both purified peptides showed resistance against simulated gastrointestinal proteases. In addition, both peptides had no in vitro cytotoxicity on human lung MRC-5 cells and prevented human liver carcinoma HepG2 cellular damage caused by hydroxyl radicals. Therefore, it is suggested that EBN protein hydrolysates are a good source of natural antioxidants and could be applied as nutraceutical compounds.