Characterization of Redistilled Liquid Smoke of Oil-palm Shells and its Application as Fish Preservatives

Oil-palm shells as an agricultural waste can be pyrolysed producing gaseous material that can be condensed into liquid smoke. Redistilled liquid smoke has been proven effective as fresh fish preservative due to its antibacterial activity. In the present study, the redistilled liquid smoke is evaluated as fish preservative of fresh catch and as fly repellent in fish salting-fermenting process. The tests included total volatile base-nitrogen levels in fish muscle and antibacterial activity using agar diffusion method. The content of various organic acids in liquid smoke reached 9.2%, mainly consisting of acetic acid and phenolics, at pH of 3.2. There were no harmful compounds such as tar and polycyclic aromatic hydrocarbons. The redistilled liquid smoke concentrations of 8, 9, and 10% were able to maintain the freshness of pomfret fish up to 24 h. In these levels of redistilled liquid smoke solution, diameters of clear zone formed on the antibacterial test ranged 10-20 mm, meaning that the liquid smoke fell into strong antibacterial category. It is suggested that the content of carboxylic acids, phenolic compounds and carbonyl serve as a natural preservative to replace the use of synthetic preservatives in salting fermented fish.