Physiochemical properties such as colour, amino acid composition, melting temperature and hydroxyproline content determines the quality of gelatin. In this study, 4% of acetic acid was used to produce gelatin powder from Pekin, Muscovy and Khaki Campbell duck feet. The duck feet gelatin powders were analysed for their physiochemical properties and compared with commercial bovine gelatin. For colour analysis, Pekin duck feet gelatin (PDFG) had the highest L* value (21.41), followed by Khaki Campbell duck feet gelatin (KCDFG, 20.57) and Muscovy duck feet gelatin (MDFG, 17.85). KCDFG and PDFG had the same a* values (redness) which was -0.05, while the a* value of MDFG was -1.49. Lastly, the b* values of duck feet gelatin powder were 6.17, 8.47 and 9.47 for PDFG, MDFG and KCDFG, respectively. Duck feet gelatin powder had a melting temperature value of 61.91°C, 48.62°C and 44.81°C for KCDFG, MDFG and PDFG, accordingly. PDFG had the highest hydroxyproline content, which was followed by KCDEG and MDFG with the values of 9.15, 8.00 and 7.63 g/100g, respectively. The main amino acids present in the duck feet gelatin powder were glycine (21.73%, 13.62%, 13.46% and 15.33%), proline (13.08%, 8.71%, 8.39% and 9.34%), hydroxyproline (12.57%, 8.05%, 7.84% and 9.39%) and alanine (8.79%, 5.77%, 6.03%, 6.65%) for CBG, KCDFG, MDFG and PDFG, respectively. Furthermore, the lowest amino acids observed were tyrosine, histidine, methionine and isoleucine. No trace of cysteine was observed. Pekin duck feet produced the best quality gelatin compared to Khaki Campbell and Muscovy duck feet.

Malaysia is one of the main producers of duck meat globally with increasing demands. Increasing in duck production will also increase the number of duck by-products such as skin, feet and bones. Pekin duck (Anas platyrhyncos domestica) is one of the famous duck breeds. Gelatin that was extracted from Pekin duck feet has shown a potential raw material for the production of bioactive peptide that can involve in various functions of the organism physiologically for example antioxidant effects. Pekin Duck feet gelatin was hydrolyzed by using five commercial enzymes (Alcalase, Esperase, Flavourzyme, Neutrase and Protamex) to identify radical scavenging potencies of derived bioactive peptides. All the five enzymes were studied under three different enzyme-substrate ratio (1:10, 1:15, 1:20) with every enzyme optimum pH and temperature. Scavenging activities studied included DPPH radical scavenging activity and ABTS radical scavenging activity. In DPPH radical scavenging activity, all the five enzymes showed the highest percentage of radical scavenging activity at (1:20) enzyme-substrate ratio condition. Among the five enzymes studied, gelatin hydrolyzed with Protamex showed the highest activity (54.83%), followed by Alcalase (53.12%), Esperase (49.81%), Flavourzyme (49.32%) and lastly Neutrase (47.49%) at sample concentration 4.5 mg/ml. The half-maximal inhibitory concentration (IC50) value of the bioactive peptide for ABTS radical scavenging activity was measured. Alcalase has produced the duck feet gelatin hydrolysate that has the lowest IC50 value against ABTS radical scavenging activity with value (0.45%) followed by Esperase (0.54%), Neutrase (0.57%), Protamex (0.60%) and lastly Flavourzyme (0.74%).