Browsing by Author "Rajapaksha, R.V.D.N."

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    Study on 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.
    Colour of 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. So the present study was undertaken to assess the effect of flesh colour in chilled storage on the quality of fresh yellowfin tuna by studying the changes in chemical (Histamine), microbiological (TPC) parameters and sensory attributes. Flesh of fresh yellowfin tuna received from Negambo landing site were categorised as bright red colour, light red colour, brown red colour and pale brown colour at the receiving. Forty samples were selected from each colour category to analyse the histamine content and TPC value. Flesh colour is significantly influenced to the histamine value. Furthermore, the mean histamine values are 0.66 ± 0.37 ppm, 1.70 ± 1.13 ppm, 5.19 ± 4.55 ppm and 10.14 ± 6.13 ppm in bright red, light red, brown red and pale brown colours respectively. The highest mean histamine value (10.14 ppm) and the highest variation (± 6.13 ppm) was represented in pale brown colour and lowest mean histamine value (0.66 ppm) and lowest variation (± 0.37 ppm) was represented in bright red colour. The flesh colour is significantly influenced to the TPC which means the microbial count of the flesh. Furthermore, mean TPC values are 2.62 ± 0.40 log CFU/g, 3.18 ± 0.28 log CFU/g, 3.54 ± 0.31 log CFU/g and 3.85 ± 0.22 log CFU/g in bright red, light red, brown red and pale brown colours respectively. The highest mean TPC value (3.85 log CFU/g) was represented in pale brown colour and the lowest mean TPC value (2.62 log CFU/g) was represented in bright red colour. The sensory scores by thirty two untrained panellists were judged bright red colour is the best quality colour grade and pale brown colour is the least quality colour grade. Key words: Yellowfin tuna, Histamine, Total Plate count, Colour grade, Chilled storage
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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.