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rmoA HOi
CHEMICAL COMPOSITION AND POTENTIAL USES OF YELLOWFIN TUNA (Thunnus albacares) DARK MUSCLE
THANH PHAN HOA HOC VA TIEM NANG SU" DUNG COTHITDO CA NGlT VAY VANG (Thunnus albacares)
Huynh Nguyen Duy Bao '
A B S T R A C T
Yellowfin tuna (Thunnus albacares) dark muscle is an edible by-product fivm tuna processing. Il has a low commercial value and is underutilized. The present study was conducted lo characterize chemical composition of yellowfin tuna dark muscle and reviewed in relation lo potential uses. The results indicate that the tuna dark muscle is a promising source of material that can be used in the preparation of fish protein isolate, histtdine-rick foods and antioxidants.
Keywords: Tuna, by-product, dark muscle, fish protein, histidine T O M T A T
Ca ihit do Id phv phdm dn duac tir chi biin cd ngir vdy vdng (Thunnus albacares). Bdy la phdn kem gid tri vd chira duoc su difng hi?u qud. Nghien cuu ndy phdn tich thdnh phan hoa hgc ciia ca thit do cd ngir vdy vdng de xdc dinh tiem ndng img di^ng cho phdn phu phdm kem gid tn nay Kit qud nghien cuu chi ra rdng ca thit do ciia cd ngif la nguon nguyin liiu day hua hen cho sdn xudt protein cd, thuc phdm gidu histidine vd chdt chong oxy hoa.
Tie khoa: Cd ngir, phiiphdm, ca thit do, protein cd, histidine
I. INTRODUCTION
Tuna (Thunnus spp.) species are significant sources of food and thus play a very important role in the economy of many countries. More than 48 species of tuna are known in the Atlantic, Indian, and Pacific Oceans, and the Mediterranean Sea. Seven principal market tuna species are identified, including albacore, Atlantic bluefin, bigeye, Pacific bluefin, southern bluefin, yellowfin and skipjack.
Among the principal market tuna species skipjack and yellowfin represent the largest share of total catch, 84.4% (Table 1).
Table 1. Principal Market Tunas (FAO FIGIS) Tuna species
Skipjack Yellowfin Bigeye Albacore Atlantic bluefin Southern bluefin Pacific bluefin Total
Total catch (%) 54.0 30.4 9.4 4.9 0.8 0.4 0.1 100
' Faculty of Food Technology, Nha Trang University
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Yellowfin tuna Thunnus albacares is an intensely exploited fish. Large quantities of yellowfin tuna are commercially used in canned and dry-salted products, like cured tuna loin and as sashimi (Herpandi et al., 2011). Because only the white meat of tuna is used in canning or sashimi, the tuna industry generates a large amount of waste or by-products. Guerard et al. (2002) reported that solid wastes generated from the processing Industry are composed of muscle (after loins are taken), viscera, gills, dark muscle, head, bone, and skin, and these wastes can constitute as much as 70%
o f t h e original material. Some o f t h e by-products are used to produce fish sauces and food products such as dry-salted roe, also could be used In animal feed, but much of it is discarded and is a source of environmental contamination. The amount of hazardous waste produced from fish processing has tended to increase annually (Shahidi, 1994). Therefore, optimal utilisation of fishery by-products is becoming increasingly important (Siziyte et a l , 2005).
Vietnam is among the top ten world exporters of seafood, total seafood exports In first 3 quarters of 2013 reached USD 4.7 billion. The tuna export value expected more than USD580 million in 2013.
Main products (fillets and loins) and rest matenal from tuna processing are shown in figure 1.
H Fillets and loins
• B o n e s , f i n s , s k i n D Head D Others
• Viscera H Dark m u s c l e
Figure I. Main products (fillets and loins) and rest material from tuna processing The dark muscle is more than 6% of material used In tuna processing, it is a band of dark tissue that lies beneath the skin throughout the body and also located near the backbone. Dark muscle of tuna has so far mainly been used as a source of pet food. Therefore, the present study was conducted to characterize chemical composition of the yellowfin tuna dark muscle and identify their potential uses in foods.
II. MATERIALS AND METHODS 1. Materials and Chemicals
The yellowfin tuna dark muscle was obtained from a seafood processing company in Nha Trang.
It had been frozen and then stored at -IB^C. The frozen tuna dark muscle was transported to the Seafood Processing Laboratory, at the Nha Trang University under refrigerated conditions (4''C). The tuna dark muscle was thawed overnight in a 2"C to 6°C reft-jgerator before each analysis.
All chemicals of analytical grade were obtained from Aldrich Chem. Co. (Milwaukee, Wis, U.S.A.) and Sigma-Aldrich (St. Louis, Mo, U.S.A.).
2. Methods of analysis 2.1. Chemical composition analysis
The proximate analysis was carried out according to the procedures of &ie Association of Official
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1 ap cm Khoa hoc - Cong nghe Thuy Sdn So Dac biet - 2013
Analytical Chemists (AOAC, 1995). Moisture was determined by drying the samples in an oven at 105°C to constant weight, crude ash was determined by incineration in a furnace at 550^0 to whiteness, crude protein was determined by the Kjeldahl method (N x 6.25) and lipid was determined according to the method described by Bligh and Dyer (1959).
2.2. Determination of fatty acid composition
Fatty acid methyl ester (FAME) was prepared according to the Official Method and Recommended Practices of AOCS (1989). The FAME was analyzed with a Shimadzu gas chromatograph model GC-14B (Kyoto, Japan) equipped with an open tubular capillary column (0.25 mm i.d x 30m, 0.25 pm In film thinckness, Supeico, Bellefonte, PA). The initial oven temperature was kept at 140°C for 1 mm and subsequently programmed to a final temperature of 240°C at a rate of 1 °C/min. The temperature of both the injector and detector was kept at 250°C. Helium was used as carrier gas at the column inlet pressure of 2 kg/cm^.
2.3. Determination of amino acid composition
The amino acid composition of tuna dark muscle was analyzed according to the procedures of Wang et al. (2012). Briefly, the amino acids in tuna dark muscle were released by hydrolysis with 6M HCI in an oxygen-free solution, gives complete release of most ammo acids. The amino acids were analyzed using RP-HPLC system.
3. Statistical analyses
Microsoft Excel 2003 was used to calculate means and standard deviations for all multiple measurements and to generate graphs. Analysis of variance (ANOVA) was applied to the data using R software version 2.4.1 (http://cran.R-project.org). Significant differences were determined by one-way ANOVA and Tukey's Multiple Comparisons of Means was used to determine the statistical difference between samples.
III. RESULTS AND DISCUSSION
1. Chemical composition of tuna dark m u s c l e
The result of the proximate composition of the tuna dark muscle is shown in Figure 2 Chemical composition of fish varies greatly from one species and one individual to another depending on age, sex, environment and season The protein, lipid, ash and moisture contents o f f i s h range between 16-28%, 0.2-25%, 1.2-1.5% and 66-81 %, respectively (Huss, 1995) The present study found that the lipid contents of tuna dark muscle was 2.8 ± 0.2%, 1.05 ± 0.1 % and 71.5 ± 1 3%, respectively.
The protein content of tuna dark muscle was 26.2 ± 1.1%, this result strongly suggest a potential utilization of tuna dark muscle as a material for production offish protein isolate or fish protein hydrolysate.
£ 80 i
weight S 1 40
Percentage
1 •
ix
Moisture Protein• ^
Proximate Upid -ompos'rtion
Ash
Figure 2. Proximate composition of tuna dark muscle
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2. Fatty acid composition of tuna dark m u s c l e
The fatty acid composition of tuna dark /nuscle is shown in Table 2.
Table 2. Fatty acid composition of yellowfin tuna dark muscle Saturateil
fatty acids 14:0 15:0 ISO 16.0 16:0 Iso 17:0 17 0 Iso 18'0
180 19:0 20.0 22:0 24:0
Total
Contents (mg/g oU) 20.49 5.77 2.28 172.00 5.72 7.52 1.24 53.40 3.28 3.59 1.64 1.12
- -
278.04
Monounsaturateil fatty acids 14:ln-7 14:ln-5 15;ln-6 16:ln-9 16:ln-7 16:ln-5 18:ln-9 18:ln-7 18:111-5 20:ln-9 20'ln-7 2 2 : l n - l l 22:ln-9
-
Total
Contents (mg/g oU)
0.53 0.78 0.57 2.59 38.81 1.09 205.27 25.48 2.61 25.52 1.90 3.84 4.75
.
313.74
Polyunsaturated fatty a c i d s 16:2ii-6 16:3n-6 16:3n-4 16:3n-l 16:4n-3 18:2n-6 18:2n.4 18:3n-6 18:3n-4 18:3n-3 18:4n-3 20:2n-6 20:3n-6 20.4n-6 20:3ii-3 20:4n-3 20:5n-3 22:4ii-6 22:5n-6 22:5n-3 22:6n-3 Total
Contents
(mg/goU)
0.87 6.90 6.52 2 65 1.89 7.83 2.75 2.92 1.66 2.54 2.67 3.16 1.07 20.10 2.31 4.50 43.55 3.37 8.46 11.70 183.22 320.64 Although the role of polyunsaturated fatty adds in the human diet is not completely understood, unsaturated fatty acids ottier than essential fatty acids have been shown to play a part in physiological processes. The present study found that the fatty acids dominant in the tuna dark muscle were 16:0, 18:1n-9 and 22:6n-3. Approximately three-fourths of the fatty acids in the tuna dark muscle are composed five fatty acids 16:0, 18:0, 18:1n-9, 20:5n-3 and 22:6n-3. These results suggest that the tuna dark muscle can be used for recovery of omega 3 fatty acids or high quality oil for human.3. Amino acid composition of tuna dark muscle
The amino acid composition of tuna dark muscle is shown in Figure 3.
Figure 3. Amino acid composition of tuna dark muscle 6 • T R U S N G D A I HOC NHA TRANG
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The method used in this study only allowed the analysis of 17 amino acids. The essential amino acids were identified in the tuna dark muscle including phenylalanine, valine, threonine, isoleucine, methionine, leucine, lysine, and histidine. Tryptophan is destroyed upon acid hydrolysis, thus was not measured in this study. The result showed that tuna dark muscle contains high level of histidine (28.4 mg/kg). Histidine has demonstrated a variety of medicinal properties both anecdotally and in clinical studies, it can bind and transport several metals, including copper and iron. It also increases calcium absorption, reduces histamine levels, and in turn controls diarrhea. Histidine is also an important mechanism in clotting factors and can minimize internal bleeding from microtrauma Furthermore, histidine is known as a source ofthe antioxidants. Peptides containing histidine demonstrated metal-ion chelation, active-oxygen quenching, and hydroxyl radical scavenging activities as the modes of inhibiting lipid oxidafion (Mine et a l , 2010). This observation shows the possibility of using the tuna dark muscle as a raw material for production of functional foods.
IV. CONCLUSION
Yellowfin tuna dark muscle has a high nutritional value, and it is especially high in protein content.
The protein from tuna dark muscle contains high level of histidine which has bio-functions in human health. These indicate that the tuna dark muscle is a promising source of material that can be used In the preparation offish protein isolate, histidine-rich foods and/or antioxidants.
REFERENCES
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8. F. Shahidi, "Seafood Processing By-Products," In: F. Shahidi, Ed., Seafoods Chemistry, Processing, Technology and Quality, Blackie Academic & Professional, Glasgow (UK), (1994), pp. 320-334.
9. R. Slziyte, E. Dauksas, E. Falch, L StoiT0 and T. Rustad. (2005). Characteristics of Protein Fractions Generated from Hydrolysed Cod (Gadus morhua) By-products Process Biochemistry, 40 (6), 2021-2033.
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