Study on the Effect of Chemical, Microbiological and Organoleptic Parameters Related to the Flesh Colour of Yellowfin Tuna (Thunnus albacares)
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Date
2013
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Journal ISSN
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
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.
Description
Keywords
Animal Sciences, Aquaculture and Fisheries, Fish, fish Industry, Food Science, Seafood