Balancing the benefits of protein content and the risks of trace metal toxicity exposure from Skipjack tuna (Katsuwonus pelamis) consumption in Sri Lanka
No Thumbnail Available
Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
Uva Wellassa University of Sri Lanka
Abstract
Fish is considered as an excellent source of protein that can provide immense health benefits to human
being. Protein is the major nutrient in fish consumption and it is highly digestible and consist all the
essential amino acids. However, recent claims that marine fish are contaminated with trace metals
exceeding the recommended maximum allowable limits have raised concerns among consumers
regarding fish consumption. This may lead to rejection of marine fish both by local and export
markets (Liyanage, 2009) as fish contaminated with toxic trace metal can lead to acute and chronic
effects in human being. In the present study, protein content and major toxic trace metal
concentrations in skipjack tuna (Katsuwonus pelamis) which is a major commercial marine fish
species were studied with the aim of assessing benefits and risks in consumption of skipjack tuna in
Sri Lanka.
Materials and Methods
Samples of skipjack tuna fish (n = 44) were collected to represent all fish landing site areas around
Sri Lanka during April-July, 2014. Concentrations of toxic trace metals Hg, Cd, Pb and As were
analysed individually for all the samples while the protein content analysis was carried out for
composite samples that were prepared based on gender and standard length of each fish. Crude
protein content was analysed according to 928.08, AOAC 2000 standard method. Crude protein
content was determined using UDK 132 (VELP Scientifica, Usmate, Italy) semi-automated Kjeltec
system. All composite samples were analysed in triplicates. Hg, Cd, Pb and As trace metal
concentrations were analysed by Atomic Absorption Spectrophotometer (AAS; Varian240 FS,
Varian Inc., Australia) following the standard method in AOAC 1998. All analyses were strictly
adhered with quality control procedures. Protein content of skipjack tuna was assessed in terms of
benefits with reference to its Recommended Dietary Allowance (RDA) value whereas the toxicity of
each trace metal was assessed based on the stipulated Provisional Tolerable Weekly Intake (PTWI)
with the Probable Weekly Intake (PWI) values. Average consumption of skipjack tuna flesh in Sri
Lanka was considered as 2.8 g/person/day (MFARD, 2013) and the average body weight of a Sri
Lankan adult person was assumed as 55 kg. In addition, resulted mean toxic trace metal
concentrations were compared with the established maximum allowable limits for toxic trace metals
in Sri Lanka and European Union standards for skipjack tuna.
Results and Discussion
In order to determine the recovery percentage in crude protein analysis, spiked samples with
(NH4)2SO4 were used and the recovery values were maintained within the acceptable range of 90-
110%. The method of trace metal analysis was evaluated for its suitability in terms of their respective
Limit Of Detection (LOD) and recovery levels using spiked samples and certified quality control
materials. Calculated recovery values for all the trace metals were within the expected recovery range
of 80%-120%.
The mean standard length of the analysed skipjack tuna fish was 47.4±3.9 cm and the range was 36-
56 cm whereas the mean total weight was 2.2±0.5 kg and it had a variation of 1.1 - 4.2 kg. Among
the analysed specimens 24 were males and 20 were females.
Description
Keywords
Food Science, Fish, fish Industry, Aquaculture and Fisheries, Aquatic Products, Animal Sciences