Browsing by Author "Weththasinghe, M.P."

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    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, Weight
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    Study on the Effect of Chemical, Microbiological and Organoleptic Parameters Related to the Flesh Colour of Yellowfin Tuna (Thunnus albacares)
    (Uva Wellassa University of Sri Lanka, 2013) Rajapaksha, R.V.D.N.; Wijesundara, W.M.N.M.; Thushari, G.G.N.; Weththasinghe, M.P.
    The fishing industry is particularly important for Sri Lankans for the domestic supply and there is also a small but growing export market for high value products. Yellowfin tuna is one of the most important fish species in Sri Lankan export market (Amarasiri et al., 2004). Yellowfin tuna is sold as fresh in local markets and exported as frozen, chilled or fresh products. The local market is highly regulated and price oriented with low emphasis on quality. They sold products in fresh form with little or no processing other than drying. However, the export market is characterized by demand for quality and high prices. So the freshness of the fish is of high interest to both retailers and consumers. Colour grade of the fish flesh is the most important attribute when assessing the quality and price in industry. However, marine species like yellowfin tuna are highly susceptible to rapid spoilage. Therefore, loss of quality of flesh followed by spoilage is a complex combination of microbiological, chemical and physical processes. Therefore, the quality of fish can be estimated by sensory evaluation, microbial method and chemical method (Ozogul and Gokbulut, 2006). This study was designed to evaluate the chemical qualities of yellowfin tuna flesh by measuring histamine, microbiological qualities by measuring total plate count and sensory qualities in four colour grades. Methodology The research was carried out at the Ceylon Fresh Seafood (Pvt) Ltd. Fresh yellowfin tuna flesh colour was categorized into four colour grades such as, bright red, light red, brown red and pale brown using a reference colour chart. Forty fishes were selected from each colour grade making total sample size 160 individual fishes. Homogeneous samples were selected to get accurate results. Therefore, all the samples were collected from Negombo landing site with identical body weight and length and sex. The temperature of each fish was measured and samples were collected only from the fishes which contain body temperature below 4 °C. Appropriate 160 samples of four colour grades were collected from the area below the pectoral fin of each fish. Histamine values were measured by using competitive direct Enzyme Linked Immune Sorbent Assay (CD – ELISA) method (AOAC 977.13 method, 1992). Data were analysed by using one way Analysis of Variance (ANOVA) with 95% confidence interval using Minitab 16 software. Another 160 samples were collected from the area below the pectoral fin of above selected fishes to test the Total Plate Count (TPC) according to the AOAC (1992). Data were analysed by using one way Analysis of Variance (ANOVA) with 95% confidence interval using Minitab 16 statistical software. Organoleptic parameters such as odour, texture, appearance and overall acceptance of four colour grades were evaluated using thirty two untrained penalties. This sensory scale is based on the freshness quality grading system for yellowfin tuna mentioned in Act No. 1045/01 Gazette notification in 1998. Each assessor was given scoring demerit point from one to four. Data were analysed using non - parametric Freidman test in Minitab 16 software.