This study was conducted to investigate the effect of storage temperatures on the shelf life of yellowfin tuna (YFT) loins by studying of microbial, chemical and organoleptic changes. Shelf life of YFT was determined through changes in total aerobic bacterial plate counts (APC), total volatile basic nitrogen (TVB-N) trimethylamine (TMA), organoleptic properties and histamine development during storage at 0, 4 and 7°C. Based on TVB-N value indices, YFT maintained an acceptable shelf life for 21, 17 and 12 days at 0, 4 and 7°C, respectively. Nevertheless, YFT was rejected earlier by the sensory panellists than their TVB-N value indicated. Histamine development was found to be lower than the European Union safety level for 100 mg/kg fish during storage at 0 and 7°C for 21 and 17 days, respectively. Aerobic bacteria initially dominated the micro-flora on YFT; however, as storage time increased, aerobic bacteria became dominant at cold storage, but the numbers exceeded the International Commission on Microbiological Specifications for Foods (ICMSF) limit of 10 7 cfu/g in storage at 7°C after 17 days. Therefore, it can be concluded that the storage of fresh YFT in below 4°C has good enough to the shelf life of products (two weeks).

Total mercury (Hg), cadmium (Cd) and lead (Pb) levels were determined in the muscle of four commercialised exported fish species Thunnus albacares (yellowfin tuna), Xiphias gladius (swordfish), Makaira indica (black marlin) and Lutjanus sp (red snapper) collected from the Indian Ocean, Sri Lanka, during July 2009-March 2010 and measured by atomic absorption spectrophotometry. Results show that swordfish (n = 176) contained the highest total Hg (0.90 ± 0.51 mg/kg) and Cd (0.09 ± 0.13 mg/kg) levels, whereas yellowfin tuna (n = 140) contained the highest Pb levels (0.11 ± 0.16 mg/kg). The lowest total Hg (0.16 ± 0.11 mg/kg), Cd (0.01 ± 0.01 mg/kg) and Pb (0.04 ± 0.04 mg/kg) levels were found in red snapper (n = 28). Black marlin (n = 24) contained moderate levels of total Hg (0.49 ± 0.37), Cd (0.02 ± 0.02) and Pb (0.05 ± 0.05). Even though there are some concerns during certain months of the year, this study demonstrates the safety of main export fish varieties in terms of total Hg, Cd and Pb.

Mercury (Hg) is a global environmental pollutant that has been the cause of many public health concerns. It is transferred through trophic level and bio magnification in the food chain. Total Hg level was measured by cold vapour atomic absorption spectrometry in muscle tissue of 176 Swordfish (Xiphiasgladius) samples ranging from 11.8-112.0 kg total weight and 45-278 cm total length, collected from major fish landing sites in Sri Lanka during July 2009 to March 2010. Total Hg concentration varied between 0.18-2.58 mg/kg wet weight (ww), with a mean value ± standard deviation of 0.90 ± 0.52 mg/kg ww. Of the investigated samples 32% exceeded Hg limits as set by the European Union and Sri Lankan legislation (1 mg/kg, ww). Hg concentration of swordfish showed a significant positive relationship (P value < 0.05) with the fish length and weight. Consequently, consumption of larger fish leads to an increase in the exposure level for consumers.

Most heavy metals which bio-accumulate in fishes, especially predatory species do not have any biological significance or beneficial use, but due to the presence of heavy metal fish can pose a health risk to consumers. The objective of this research is to determine mercury (Hg), cadmium (Cd), and lead (Pb) levels in samples of yellowfin tuna, Thunnus albacores (n=25), swordfish, Xiphias gladius (n=35), and red snapper, Lutjanus sp (n=12). Samples were prepared by dividing edible parts into small pieces and homogenizing. Total Hg was measured by cold vapor atomic absorption spectrometry whereas the Pb and Cd were analysed by graphite furnace atomic absorption spectrometry after microwave-assisted digestion. Swordfish contains highest mercury and cadmium concentrations while yellowfin tuna contained the highest lead concentrations. The mean concentrations of heavy metals in fish muscles were found to be 1.24± 0.72 mg/kg (Hg), 0.13±0.83 mg/kg (Cd) and 0.03±0.04 mg/kg (Pb) in swordfish and 0.39± 0.19 mg/kg (Hg), 0.02±0.02 mg/kg (Cd) and 0.06±0.06 mg/kg (Pb) in yellowfin tuna. In red snapper concentrations were 0.17± 0.06 mg/kg (Hg), 0.02±0.01 mg/kg (Cd) and 0.04±0.05 mg/kg (Pb).

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