Physicochemical Analysis of Gelatin Extracted from African Catfish Skins using Nephelium lappaceum (Rambutan) Vinegar

Gelatin is a biopolymer with broad range of applications in food, pharmaceutical and photography industries. The main sources of gelatin are from the skins and bones of porcine and bovine. Due to religious sentiments by Muslim and Hindu communities as well as viral diseases such as bovine spongiform encephalopathy (BSE), an alternative was identified to replace mammal-derived gelatin which is from fish sources. In this study, African catfish was chosen for extraction of gelatin due to high content of collagen in its skin. Rambutan vinegar is used as pre-treatment acid in the study in order to identify whether natural vinegar could be a possible alternative to replace the use of synthetic acetic acid in gelatin pre-treatment process. Thus, the objective of this study is to optimize the gelatin extraction from catfish skin pre-treated with Rambutan vinegar and acetic acid of varying concentrations (2%, 4% and 6%). The physicochemical properties of gelatin extracted were evaluated in terms of yield, pH, colour, texture, moisture, ash and protein analysis. The highest yield is obtained from 6% acetic acid which is 17.36%. The pH of the gelatin pre-treated with acetic acid ranged from 4.67 to 4.91 whereas, the gelatin pre- treated with Rambutan vinegar ranged from 5.02 to 5.71. There were significant (p≤0.05) different in colour and texture of gelatin between all the gelatin treatments. All gelatin pre-treated with Rambutan vinegar gave positive results where low moisture (7.80- 8.91%), low ash (0.77-0.82%) and high protein content (89.70-95.77%) were obtained compared with gelatin pre-treated with acetic acid. The optimum concentration of Rambutan vinegar that is suitable for gelatin acid pre-treatments was 6% as it obtained the highest yield and better physicochemical properties compared with 2% and 4%. Therefore, Rambutan vinegar can be an alternative to replace acetic acid as gelatin pre-treatments acid