Research Symposium-2010
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Browsing Research Symposium-2010 by Subject "Aquatic Resources"
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Item Investigation of Occurrences of Mercury Level in Tuna Fesh (Thunnus albacares) in Relation to it Habitat and Size Variation(Uva Wellassa University of Sri Lanka, 2010) Weththasinghe, M.P.; Abeyrathne, E.D.N.S.; Jayamanne, S.C.; Karunarathne, B.Mercury is poisonous to human being and the level of mercury in fish is regarded as high when it exceeds 0.3 ppm. Mercury level is a hazard point in fish processing and finding ways in reducing the hazards of mercury is important for export market. In this study, distribution of mercury in yellowfin tuna in relation to its habitat and size was investigated. Three hundred and sixty samples of fish were collected from 120 individuals from four fish landing sites; Galle, Trincomalee, Dondra, and Negombo. From each fish three samples were collected from head, underneath the pectoral fin and tail end respectively. Mercury content in each part was analysed using Atomic Absorption Spectroscopic method. Total mercury levels in four landing sites; Galle, Trincomalee, Dondra, and Negombo ranged from 0.0733 ppm to 0.2225 ppm with reference to yellowfin tuna. Highest mean mercury level (0.1668 ppm) and highest variation of mercury (±0.0327) was recorded at L.ondra. The lowest mean mercury level (0.1048 ppm) was recorded at Galle. Mercury level in tuna harvested from eastern coast of Sri Lanka was significantly higher than the mercury level in tuna harvested from western coast. This suggests that mercury gets distributed through oceanic currents. Weight and mercury level of tuna showed a positive correlation (R2 = 0.123) while fork length of fish and mercury level of fish has shown a negative correlation (R2 = 0.123). Body location of the fish has no significant effect on the deposition of mercury in tuna. Keyword: Mercury level, Yellowfin tuna, Landing site, Body location, WeightItem Investigation on the Effect of Addition of Sugar into ice on TVB-N Content, Microbial Growth, pH and Histamine Formation during the Ice Storage of Skipjack Tuna in Boats(Uva Wellassa University of Sri Lanka, 2010) Wimalakeerthi, K.K.M.M.; Ginigaddarage, P.H.; Ariyawansa, K.W.S.; Ganegama, A.G.J.; Jayamanne, S.C.Skipjack tuna comprises about half of the world tuna production, being the number one species in every ocean in terms of catch. Addition of sugar into ice is done on storage as an ad-hoc practice to improve the external appearance of Skipjack and present study reports the effect of this practice on quality parameters of Skipjack. Forty eight Skipjack samples were obtained from Beruwala landing site and divided into two equal lots. Control sample set was kept in normal ice and the treated in sugar added ice (ice: sugar = 200:1). Samples were kept for 20 days and analyzed for histamine by AOAC method, Total Volatile Bases Nitrogen (TVB-N) by Conway-Byrnes method and microbial assay by Aerobic Plate Count (APC) at 3 days intervals. In the initial period of storage TVB-N increased slowly, then increased rapidly and in the later stage increased slowly whilst APC increased gradually in both samples. Histamine level gradually increased in both samples Initially and in the latter period (16th and 20th days) histamine content of treated sample was low (44.6±32.50 ppm, 60.0±17.72 ppm) over the control (57.8±22.47 ppm, 64.1±21.25 ppm). pH decreased initially in both samples and then increased. Tuna was found safe for consumption up to 16th day and 12th day on the basis of TVB-N and histamine respectively and never exceeded the rejected level for APC during the study period. Treated and control samples were not significantly different for histamine content, TVB-N, APC and pH (respective P values 0.376, 0.974, 0.411 and 0.617) but there was a significant difference in above quality parameters of both samples with the storage time (P<0.05). Since addition of sugar into ice did not negatively affect the quality parameters of Skipjack, this can be applied as a desirable practice to improve the buying quality of consumers. Key words: Skipjack, Microbial growth, Histamine