A study on lipid properties and heavy metal contents on fin fish in Pulau Tuba, Langkawi, Malaysia

Abstract

With the increase of knowledge on the beneficial consumption of fish oil, the consumer demand for it is increasing. However, fish oil stability and concentration of heavy metals in the fish inhibit the production of fish oil. This study examines the lipid properties of the fin fish oil, the storage stability of the oil and heavy metal concentration of some of the samples collected in order to evaluate the fish oil profile and the possible risk of fish consumption. Wild marine fin fish commonly found in Pulau Tuba, Langkawi in Malaysia and the sea water of the area were used as samples. Thirteen (13) fish species namely “jenahak” (Lutianus agentimaculatus), “kebasi” (Anadontostoma chacunda), “duri” (Arius cumatranus), “tenggiri batang” (Scomberomorus commersoni), “kembong” (Rastrelliger kanagurta), “kintan” or “sebelah” (Psettodes crumei), “kerisi” (Pristipomodes typus), “kerapu” (Epinephelus sexfasciatus), “gelama kling” (Sciaena dussumieri), “malong” (Congresax talabon), “laban” (Cynoglossus lingua), “yu 9” (Scolidon sorrakowah) and “bagi” (Aacnthurs nigrosis) were collected. The total lipid contents and fatty acid composition of all 13 species were determined using a gas chromatography- (GC-FID). All fish showed a considerable amount of unsaturated fatty acids particularly those with 4, 5 and 6 double bonds. Two physiologically important omega-3 polyunsaturated fatty acids (PUFAs), i.e. eicosapentaenoic acid (EPA) and docasahaexaenoic acid (DHA), made up more than 50% of the total PUFAs. For saturated fatty acids, palmitic was found to be the major one in all types of fish studied. Based on DHA, EPA and arachidonic acid (AA) contents, “gelama kling” was found to be the best source (23, 11 and 7%, respectively) followed by “kerapu” (21, 10, 9%) and “kintan/sebelah” (19, 14, 4%). However, fish oils extracted from only 6 species (“kerapu”, “kembong” “kerisi”, “malong”, “gelama kling” and ”tenggiri batang”) were evaluated at -27 and 4 C temperature storage stability. Results showed that the stability of oils stored at -27 C was better than that of oils stored at 4 C. Iodine value (IV) of oils decreased during storage, while other parameters, namely peroxide value (PV), anisidine value (AnV), acid value (AV) and thiobarbituric acid (TBA) value increased. However, the rate of quality deterioration of oil samples was relatively low, meaning that both storage temperatures might be used for storage purposes of fish oil. IUPAC (1987), PORIM (1985) methods and MV-UV spectrometry were used to evaluate storage stability. For the heavy metals study, metal concentration in water and eight species from the study area were studied using the flame atomic absorption spectrometry (F-AAS). The species studied are “jenahak”, “duri”, “tenggiri Batang”, “kembong”, “kintan” or “sebalah”, “kerisi”, “kerapu” and “malong”. Mercury (Hg), cadmium (Cd), and lead (Pb) as toxic elements and copper (Cu), zinc (Zn), calcium (Ca) and manganese (Mn) as vital elements were analyzed. The result revealed the consumption of fish from the human health point of view is safe though the metal studied are almost two times higher than the early reports.