Fatty Acids Composition of Selected Farmed and Wild Freshwater Fishes
(Komposisi Asid Lemak dalam Ikan Air Tawar Ternak dan Liar Terpilih) JUMAT SALIMON & NURASYIKIN ABDUL RAHMAN
ABSTRACT
Crude fat and fatty acids composition were examined in 16 different species of Malaysian freshwater fishes. Nine species of farmed and seven species of wild fishes lipids were extracted using chloroform: methanol sohxlet extraction. The results showed that the crude lipids in muscle of farmed fishes were higher than the wild fishes, ranging from 20 - 50%
(wt/wt) and 4 – 15% (wt/wt) respectively. Asian red-tail catfish showed highest total lipid among other fishes which was of 51.64% (wt/wt), followed by red pomfret and yellow-tail catfish which were of 46.2% and 43.2% respectively.
Eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA in wild fishes were found higher compared to captive fish.
Among the fishes studied, grey feather back contain high in EPA (2.9%) and DHA (12.1%) as well as snakeskin gouramy (EPA; 3.0% and DHA; 12.8%) and tengalan (EPA; 1.1% and DHA; 7.2%). Other fishes, on the other hand contain less percentage in !-3 fatty acids. The diet and the environment where the fishes were found are the main reason for the differences in fish fatty acids content.
Keywords: Fish oil; !-3 fatty acids; EPA and DHA; farmed and wild fish
ABSTRAK
Lemak kasar dan komposisi asid lemak telah dikaji dalam 16 jenis ikan air tawar di Malaysia. Sebanyak 9 ikan ternak dan 7 jenis ikan liar telah diekstrak kandungan lipidnya dengan menggunakan kaedah pengekstrakan soklet pelarut kloroform: metanol. Hasil kajian menunjukkan bahawa jumlah lipid dalam isi ikan ternakan lebih tinggi daripada ikan liar, dalam julat 20 - 50% (bt/bt) dan 4 – 15% (bt/bt) masing-masing. Ikan baung menunjukkan kandungan lipid jumlah tertinggi berbanding ikan kajian lain iaitu sebanyak 51.64%, diikuti oleh ikan bawal merah dan ikan patin dengan peratusan sebanyak 46.2% dan 43.2% masing-masing. Kandungan asid eicosapentaenoik (EPA) dan asid docosaheksaenoik
(DHA) adalah tinggi dalam ikan liar berbanding dengan ikan ternakan. Antara spesies ikan dikaji, ikan belida menunjukkan kandungan EPA (2.9%) dan DHA yang tinggi (12.1%), diikuti oleh sepat siam (EPA; 3.0% dan DHA; 12.8%) dan tengalan (EPA; 1.1% dan DHA; 7.2%). Ikan-ikan lain sebaliknya menggandungi asid !-3 dalam peratusan yang rendah. Persekitaran dan diet ikan di mana ianya ditemui menjadi faktor utama dalam perbezaan kandungan asid lemak tersebut.
Kata kunci: Minyak ikan; asid lemak !-3; EPA dan DHA; ikan ternak dan liar
fish are generally having low content of !-3 PUFA, which include EPA and DHA compared to that of marine fish. On the other hand, they show higher in !-6 PUFA, particularly linoleic acid (LA C18: 2) and arachidonic acid (ARA C20:4), due to the influence by their diet in natural environment (Sargent et al. 1999; Steffens 1997).
EPA and DHA fatty acids can be obtained by human only through daily diet. These fatty acids unfortunately cannot be synthesized by human due to the absence of desaturase enzymes required for producing PUFA (Haliloglu et al. 2004). Only marine seaweed and some fungi are able to synthesis these fatty acids (Uauy & Valenzuela 2000;
Shahidi & Wanasundara 1998).
Nowadays, there are high demands for !-3 PUFA
especially EPA and DHA for high value added foods consumed as supplement and pharmaceutical industry uses.
Cold water fish oils such as menhaden, mackerel, cod liver, sardine fish oils are known to be the world best available INTRODUCTION
It is known that lipids obtained from fish are rich in polyunsaturated fatty acids (PUFA) especially of omega-3 (!-3) fatty acids. Omega-3 PUFAs are classified as essential fatty acids (EFA) for human body. They have been reported to be able in protect and cure diseases such as cardiovascular, cancer, Alzheimer and inflammatory diseases (Furst & Kuhn 2000). Eicosapentaenoic acid (EPA
C20: 5 !-3) and docosahexaenoic acid (DHA C22: 6 !-3) are found to be the main omega-3 PUFAs in many fish oil (Gamez-Meza et al. 2002; Hidajat et al. 1995). It is reported that the delayed and abnormal growth, nerves symptoms, skin lesions, reduction in visual and learning ability are corresponding to sign of lacking in !-3 PUFA in diet (Kurowska et al. 2003; Sidhu 2003).
Fish uses !-3 PUFA for maintaining the internal homeostasis process and as a precursor of some valuable hormone (Shirai et al. 2001). It was reported that freshwater
sources of !-3 PUFA with high cost. This encouraged many researchers to explore cheaper resources of tropical common Malaysian farmed and wild freshwater fishes.
The aim of this investigation was to study the chemicals composition of selected farmed and wild Malaysian freshwater fish oils. Thus their commercial potential uses either for incorporation into human and animal feed or other higher value added food products can be evaluated.
MATERIALS AND METHODS
The nine matured farmed fishes were obtained from Sri Bayu Tekala Sdn. Bhd farm in Selangor, while seven different matured wild fish were bought from local market in Pahang (Tabel 1). All the fish were collected between June and July 2005. The fishes were put inside the polyethylene box containing ice and immediately gutted, cleaned and peel the skin off. The skinless filleted muscles were homogenized using National blender and then freeze-dried by Hector freeze-dryer for 3 days. The lipid was obtained using sohxlet extraction in chloroform: methanol (2:1 v/v). The extraction was carried out for 7 hours in 55°C. The solvent was removed using Buchi 461 evaporator and the lipid was weighed before further converted into fatty acids methyl ester (FAME)
according to PORIM Test Method (Siew et al. 1995). Fatty acids composition was then determined using gas chromatography (Shimadzu Model GC-17C) fitted with Column BPX 70 (30m × 0.25mm × 0.25µm) and equipped with FID detector. The column, injector and detector were programmed at 120°C, 250°C and 280°C respectively.
Nitrogen was used as carrier gas and the flow rate was set at 0.3 mL/min. Identification of the fatty acids composition was based on authentic standard fatty acid methyl esters and menhaden oil, obtained from Sigma. Twelve fatty acid
methyl esters C12:0, C14:0, C14:1, C16:0, C16:1, C18:0, C18:1!-9, C18:2!-6, C18:3!-3, C20:4!-6, C20:5!-3 and C22:6!-3 were used for internal individual fatty acids standard.
RESULTS AND DISCUSSION
Table 1 shows the percentage of total lipid extracted from selected common Malaysian freshwater fish. The results show that Asian redtail catfish contents the highest total lipid (51.7%) followed by other fish such as Red pomfret (46.2+1.1%) and Yellowtail catfish (43.2+0.5%). It is also found that the total lipid in wild fish was comparatively low compared to farmed fish. The highest total lipid in wild fish was shown byRiver barb (28.2+0.7%) followed by Hampala barb and Silver sharkminnow, which contain 13+0.2% and 10.5+0.2% lipids respectively.
It is found that the lipid and fatty acid compositions in farmed and wild fish are varies due to their diet supplied.
This is in agreement with the report (Cejas et al. 2003) that suggested that the lipid from tissue of fish reflects fatty acids content of the lipid in the diet supplied to the broad stock. These were due to the fish species and environment such as the water salinity and the temperature (Cejas et al. 2003; Hunter & Robert 2000).
Table 2 shows the percentage of fatty acid compositions in freshwater fish muscle. The primary fatty acids found in fish were palmitic acid (16:0) and oleic acid (18:1!-9). Farmed fish shows high in monounsaturated fatty acid (MUFA) due to high contents of oleic acids, ranging from 12-50 %. On the other hand, MUFA content in wild fish was lower than those found in farmed fish in the range of 5-40 %. Palmitic acid in wild fish was found in the range from 50-60 %. In general, the higher amount
TABLE 1. Total lipid content of selected Malaysian freshwater fish
Common name Local name Scientific name % Lipid
Farmed fish
African catfish Keli Afrika Clarius grapienus 39.0+0.2
Asian redtail catfish Baung Hemibagrus nemurus 51.7+0.2
Malaysia carp Lampam Jawa Barbodes gonionotus 16.6+0.1
Comman carp Leekoh Cyprinus carpio 19.0+0.1
Yellowtail catfish Patin Pengasius-pengasius 43.2+0.5
Red pomfret Bawal merah Colossoma macropomum 46.2+1.1
Common Snakehead Haruan Chana striatus 16.2+0.1
Red tilapia Tilapia merah Oreochromis niloticus 22.8+0.2
Rohu Rohu Catla-catla 13.2+0.1
Wild fish
Freshwater eel Belut Anguilla mauritiana 7.1+0.1
Greyfeather back Belida Notopterus notopterus 4.0+0.1
Hampala barb Sebarau Hampala macrolepidota 13.0+0.2
Snakeskin Gouramy Sepat siam Trichogaster pectoralis 7.7+0.1
River barb Lampam sungai Barbodes schwanenfeldii 28.2+0.7
Tengalan Tengalan Labiobarbus sp. 9.8+0.1
Silver sharkminnow Terbul Osteochilus hasselti 10.5+0.2
of palmitic acid will change fish oil into semi-solid or solid at room temperature.
Linoleic acid (18:2!-6) was found higher in both fish muscle, in the range between 4-20 % compared to linolenic acid (18:3!-3) that contributed around 12%. In general, these fatty acids exist naturally in vegetable oil in a small amount compared to oleic acid and palmitic acid.
However, linoleic acid was found higher in farmed fish rather than wild fish. Grun et al. (1999) reported that the higher amount of linoleic acid in farmed fish directly related to the food composition. The farmed fishes were fed with high protein, carbohydrate and fat contents such
as feed formulated from soybean and corn seeds based (unpublished data).
Arachidonic acids, C20:4n!-6 which are obtained in fish lipid, was found high in wild fish relatively compared to farmed fish in the range of 0.5-15.0% and 0.5-4.0%
respectively. Cejas et al. (2003) claimed that fish requires arachidonic acid as a precursor for the synthesis of eicosanoid acids (C20:0), which plays an important in physiological and biochemical functions. Bell et al. (1994) reported that prostaglandins obtained from eicosanoid acid were used to mediate fluid and electrolyte fluxes in fish gill and kidney. It is also used for maintaining the alteration
TABLE 2. Fatty acid compositions of farmed (A) and wild (B) freshwater fishes in Malaysia
A Percentage (%)
Fatty acids Menhaden Clarius Cyprinus Barbodes Pengasius- Colossoma Oreochromis Catla- Chana (standard) grapienus carpio gonionotos pengasius macropomum niloticus catla striatus
C12:0 0.1 ta ta 0.07 0.04 ta ta 0.14 0.03
C14:0 11.37 0.4 0.79 1.28 0.77 0.6 1.39 0.84 0.98
C14:1 0.39 ta 0.07 0.08 0.02 0.04 0.12 0.1 0.15
C16:0 21.45 25.84 23.1 33.58 26.5 25.42 24.97 32.51 27.33
C16:1 14.08 4.04 4.02 2.84 5.29 4.19 6.84 5.6 5.91
C18:0 9.03 7.18 7.64 1.42 9.27 8.29 6.62 5.01 0.18
C18:1 3.93 47.9 46.29 40.04 43.16 45.92 45.79 31.42 49.06
C18:2n-6 1.86 14.1 16.26 18.69 14.22 14.96 12.94 21.88 15.13
C18:3n-3 4.43 0.16 0.29 0.56 0.26 0.17 0.33 0.4 0.29
C20:5n-3 16.05 0.05 0.07 0.25 0.14 0.08 0.1 0.26 0.13
C22:6n-3 17.31 0.32 1.48 1.2 0.33 0.33 0.9 1.83 0.82
Saturated 41.95 33.42 31.53 36.35 36.58 34.31 32.98 38.5 28.52
MUFA 18.4 51.94 50.38 42.96 48.47 50.15 52.75 37.12 55.12
PUFA 39.65 14.63 18.1 20.7 14.95 15.54 14.27 24.37 16.37
!-3 37.79 0.53 1.84 2.01 0.73 0.58 1.33 2.49 1.24
!-6 1.86 14.1 16.26 18.69 14.22 14.96 12.94 21.88 15.13
B Percentage (%)
Fatty acids Notopterus- Anguilla Barbodes Hampala Trichogaster Labiobarbus Osteochilus notopterus mauritiana swarniferdii macrolepidota pectoralis sp. hasselti
C12:0 ta ta 3.91 0.13 ta ta ta
C14:0 1.11 0.7 3.05 1.38 2.73 0.89 0.98
C14:1 ta ta ta 0.32 1.33 1.02 ta
C16:0 38.82 42.29 37.37 36.37 38.11 23.28 40.62
C16:1 1.92 1.97 0.43 2.55 3.07 2.85 1.31
C18:0 18.33 24.11 7.13 12.48 13.4 17.52 14.67
C18:1 14.92 5.98 36.81 31.64 13.67 18.47 19.13
C18:2n-6 5.58 13.36 10.42 6.78 6.74 15.39 10.24
C18:3n-3 1.53 2.57 0.53 0.4 3.52 11.29 4.98
C20:5n-3 3.6 0.35 0.06 0.28 3.27 1.38 0.88
C22:6n-3 14.2 5.67 0.28 7.66 14.17 7.9 7.18
Saturated 58.26 67.1 51.46 50.36 54.24 41.69 56.27
MUFA 16.84 7.95 37.24 34.51 18.07 22.34 20.44
PUFA 24.91 21.95 11.29 15.12 27.7 35.96 23.28
!-3 19.33 8.59 0.87 8.34 20.96 20.57 13.04
!-6 5.58 13.36 10.42 6.78 6.74 15.39 10.24
MUFA: Monounsaturated fatty acid; PUFA : Polyunsaturated fatty acids
changes in water salinity especially in osmoregulation processes.
The percentages of omega-3 and omega-6 fatty acids composition in both farmed and wild freshwater fishes are shown in Table 3. The omega-3 fatty acids observed in fish samples are include EPA, DHA and linolenic acids while omega-6 fatty acids are ARA and linoleic acid. Farmed fish was found to contain less omega-3 and high contain of omega-6 fatty acids compared to the one in wild (Simopoulos 1996; Vaccaro et al. 2004). This is in agreement with the result in the present study. The percentages of EPA and DHA in wild fish range from 0.1- 3.0% and 0.2-15.0% respectively. On the other hand, EPA
and DHA contain in farmed fishes are lower contributing around 0.1-0.2% and 0.3-1.5% respectively. These percentages are far too low compared to those found in commercial menhaden fish oil.
It is observed that the wild Snakeskin Gouramy, Tengalan and Greyfeather back contain high percentage of omega-3 compared to the other fishes. Snakeskin Gouramy and Greyfeather back are herbivorous in nature, whereas Tengalan is omnivorous. Thus, the fish oils contain high in EPA and DHA. However the ARA is observed dominate the fatty acids composition in wild fish and the quantity of omega-6 is higher in the fish muscle. Freshwater eel is also a wild omnivorous fish which having high percentage in ARA.
In farmed fish group, high contain in EPA and DHA
were observed for Rohu followed by Malaysia carp and Asian redtail catfish, with composition in the ranges of 0- 0.3% and 0.3-1.5% respectively. These percentages were much lesser in wild fishes. Rohu and Malaysia carp are
herbivorous fish type whereas Asian redtail catfish is a carnivorous fish. The difference in dietary behaviors has been reported to influence the fatty acids composition in fish oil. In general, herbivorous fish eats more phytoplankton, containing large percentage of C18 fatty acid but small amount of C20 and C22 fatty acid. Whereas the carnivorous fish eats small fish and this raise the amount of omega-3 fatty acids (Hunter & Robert 2000). Most of the farmed freshwater fishes in this experiment were omnivorous which eat both phytoplankton and zooplankton and this may increase the linolenic acids (C18:3n-3) content. In general, the proportion of omega-3 fatty acids is less than the omega-6 for farmed fish whereas omega-3 fatty acid was found higher in the wild fish. The !-3/!-6 fatty acids ratio in this study was observed less than 0.2.
On the other hand, wild fish that fed on zooplanktons, insects and small fish, likely to contain more linoleic acid (18:2!-6), linolenic acid (18:3!-3) and eicosapentaenoic acids to (20:5!-3) compared to that of farmed fish that were fed on commercial pellets. The wild fish gained their
!-3 fatty acids from freshwater zooplanktons and insects that were able naturally converted C18 PUFA to C20 (EPA)
and C22 PUFA of DHA (Ghioni et al. 1996). Mild carnivorous fish such as greyfeather back, snakeskin gouramy, tengalan and silver sharkminnow were observed having potentially high in omega-3 compared to the others.
Steffens (1997) has reported that higher omega-6 in freshwater fish may increase the omega-3 fatty acids level due to the ability of freshwater fish to perform desaturation and the elongation processes in larger quantities from C18 w-6 to C20 and C22 !-3 fatty acids. The !-3/!-6 fatty acids ratio in these fishes was observed more than 0.8.
TABLE 3. Percentage of omega-3 and omega-6 fatty acid in freshwater fish
Common name Omega-3 Omega-6 !-3 / !-6
Menhaden 36.9 4.1 9
Farmed fish
African catfish 0.5 14.8 *
Asian redtail catfish 1.6 12.1 0.1
Common Snakehead 1.2 16 0.1
Rohu 2.4 24.9 0.1
Comman carp 1.8 18.5 0.1
Red tilapia 1.3 14.5 0.1
Malaysia carp 2 20.8 0.1
Red pomfred 0.6 15.6 *
Yellowtail catfish 0.7 15.2 *
Wild fish
River barb 0.9 10.8 0.1
Freshwater eel 6.9 30.5 0.2
Hampala barb 8 10.5 0.8
Snakeskin gouramy 18.9 16 1.2
Greyfeather back 16.2 19.5 0.8
Tengalan 18.7 24 0.8
Silver sharkminnow 12.7 14.9 0.9
* < 0.1 %
Selected Malaysian wild freshwater fish such as snakeskin gouramy, tengalan and greyfeather back also can be use as a !-3 PUFA rich oils in some extent industrial use such as in health food supplement. This is due to the fact that clinically, EPA and DHA can be taken from fish oil as much as 3 g/day as approved by FDA for maintaining a good health.
CONCLUSION
It is observed that most of the farmed fish studied contain high PUFA of !-6 fatty acids whereas the wild fishes show high !-3 PUFA content. The results show that local freshwater fish as well as selected wild freshwater fish can be further explored in their industrial use especially for their PUFA rich oils. Therefore it is plausible to conclude that although local freshwater fishes were not very good source of omega-3 fatty acids compared to those for marine fish, however they can be classified as good sources of
PUFA (!-6 and !-3 fatty acids).
ACKNOWLEDGEMENT
This research was supported by MOSTI under the IRPA Grant
# 09-02-02-0115EA277. We would like to express our gratitude and thanks to En. Abdul Hamid Takim, En. Amin Ahmad, En. Hassanudin Salleh and UKM staffs for their valuable supports.
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Oleochemistry Programme
School of Chemical Sciences and Food Technology Faculty of Science and Technology
Universiti Kebangsaan Malaysia 43600 Bangi, Selangor E.
Malaysia
Received: 29 March 2007 Accepted: 24 August 2007