Lipid Classes and Fatty Acid Profile of Cultured and Wild Black Rockfish
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Journal of Oleo Science Copyright ©2014 by Japan Oil Chemists’ Society doi : 10.5650/jos.ess13217 J. Oleo Sci. 63, (6) 555-566 (2014) Lipid Classes and Fatty Acid Profile of Cultured and Wild Black Rockfish, Sebastes schlegeli Hiroaki Saito＊ and Satoru Ishikawa† National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fuku-ura, Kanazawa-ku, Yokohama-shi 236-8648, Japan † Present address: Shimokita Brand Research Institute, Aomori Prefectural Industrial Tech-nology Research Center (154, Ueno, Ohata, Mutsu 039-4401, Aomori, Japan). Abstract: The lipid and fatty acid compositions of the muscle and liver of adult and juvenile black rockfish, Sebastes schlegeli, and that of its stomach contents were examined to clarify its lipid characteristic and the difference between aquacultured and wild samples. Triacylglycerols were the dominant depot lipids of all samples, while phospholipids, such as phosphatidylethanolamine and phosphatidylcholine, were found to be the major components in the polar lipids. The cultured juvenile and young samples had high levels of 18:2n- 6 (linoleic acid, 5.0% and 4.0–5.9% for TAG of juvenile and young samples) with low levels of 22:6n-3 (docosahexaenoic acid: DHA, 9.7% and 3.3–6.7% for TAG of juvenile and young samples), whereas the adults (both cultured and wild) had only trace levels of 18:2n-6 (0.6–1.3% and 1.0–1.3% for TAG of cultured and wild samples) with noticeable levels of DHA (3.3–19.7% and 5.2–11.9% for TAG of cultured and wild samples). Similar to the fatty acid profiles in TAG of both cultured and wild adult samples, those in the phospholipids of both the samples were very similar to each other. The lipid characteristics of the cultured adult S. schlegeli samples were similar to those of the wild ones, whose muscle phospholipids contained markedly high levels of DHA (38.3–40.2% for cultured and 40.1–43.5% for wild). Therefore, the nutritional values of cultured and wild adult S. schlegeli are expected to be similar. Key words: aquaculture, docosahexaenoic acid, fish lipid, icosapentaenoic acid, linoleic acid, polyunsaturated fatty acid 1 Introduction and black（Korean）rockfish, Sebastes schlegeli, are utilized It is generally known that all marine animals, not only as a healthful and popular seafood15）. Unfortunately, in marine fishes but also invertebrates, characteristically ac- recent years, overfishing in Japan has reduced the produc- cumulate various sorts of long-chain n-3 polyunsaturated tion of wild Sebastes fishes. Black rockfish, S. schlegeli fatty acid（s PUFA）in their lipids, such as docosahexaenoic Hilgendor（f Scorpaenidae, Scorpaeniformes）, is the most acid（DHA, 22:6n-3）and icosapentaenoic acid（EPA, important commercial rockfish in Japan and Korea. Re- 20:5n-3）1）. Much attention has been brought to the lipids cently, it has been aquacultured because of its desirable and fatty acids of seawater fishes, with growing recognition taste and high value16－18）. For both consumers and produc- of the benefits of dietary fish oils1, 2）. However, compared to ers, it is important to produce good quality cultured S. pelagic fish species1－3）, little information is available on the schlegeli with high nutritious value, rich in n-3 PUFA. lipid classes and fatty acid composition of demersal fish Although a great deal of attention being paid to the eco- species except for some cultured fishes, such as sea logical and biological aspects of S. schlegeli15, 19－21）, few bream（s Pagrus major4）, Pagellus bogaraveo5）, Sparus studies on the lipid composition of the flesh of S. schlegeli aurata6－10））, and flounder（s Paralychthys olivaceous11）, Solea solea11－14） and Solea senegalensis12））. Abbreviations: DHA, docosahexaenoic acid; DMA, dimethylacetals; DMOX, 4,4-dimethyloxazoline; EPA, Rockfish（genus Sebastes, Sebastidae, Scorpaeniformes） icosapentaenoic acid; GC/MS, gas chromatography/mass is circumglobal demersal fish, the largest genus in the Se- spectrometry; MUFA, monounsaturated fatty acids; PC, bastidae family, and is present in all the world′s oceans. As phosphatidylcholine; PE, phosphatidylethanolamine; PUFA, for important sport and commercial fishes in Japan, two polyunsaturated fatty acids; TAG, triacylglycerols; TFA, total typical Sebastes species, red rockfish Sebastes inermis, fatty acids; TL, total lipids. ＊Correspondence to: Hiroaki Saito, National Research Institute of Fisheries Science, 2-12-4 Fuku-ura, Kanazawa-ku, Yokohama 236-8648, Japan. E-mail: [email protected] Accepted February 5, 2014 (received for review December 11, 2013) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/ http://mc.manusriptcentral.com/jjocs 555 H. Saito and S. Ishikawa for the nutritive value have been published22）, in particular, lipids）were dissected, while whole body of each juvenile fatty acid composition23, 24）. was sampled（except for stomach）. The ordinary muscle, In the present study, comprehensive analyses of lipid liver, and stomach contents were separately homogenized classes and fatty acid compositions of cultured and wild S. in a mixture of chloroform and methano（l 2:1, v/v）, and a schlegeli were conducted to examine the differences in portion of each homogenized sample was extracted ac- lipid classes and fatty acid profile in an effort to produce cording to the Folch procedure25）. Each crude lipid was good quality cultured fish. separated into classes on silicic acid column（s Merck and Co. Ltd., Kieselgel 60, 70-230 mesh）, and quantitative anal- ysis of the li-pid constituents was performed using gravi- metric analysis of fractions collected from column chroma- 2 Material and methods tography4）. The first eluate（dichloromethane/n-hexane, 2.1 Materials 2:3, v/v）was collected as steryl ester, wax ester, and diacyl- The biological data of S. schlegeli are listed in Table 1. glyceryl ether fraction（s Table 2）. This was followed by The aquacultured S. schlegel（i samples 1, 2, and 3）were eluting the triacylglycerol（s TAG）with dichloromethane collected in October 2009 at“ Wakinosawa Fisheries Coop- and eluting the sterols with dichloromethane/ethe（r 35:1, v/ erative Association,” an aquaculture farm in Mutsu Ba（y 41° v）; eluting the diacylglycerols with dichloromethane/ether 09′N and 140°50′E）on Honshu Island in Japan. All cultured （9:1, v/v）; eluting the free fatty acids with dichlorometh- samples were raized in the aquaculture farm for one year ane/methano（l 9:1, v/v）; eluting the phosphatidylethanol- and six month（s from spring to autumn of the next year）. amine（PE）with dichloromethane/methano（l 1:5, v/v）; The juvenile and young sample（s Nos. 1 and 2）were cul- eluting other minor phospholipids with dichloromethane/ tured with the similar artificial feed（s Tables 2 and 3）. methano（l 1:20,v/v）; and eluting phosphatidylcholine（PC） From May to Jul（y 2 months）, samples 1 were fed a juvenile with dichloromethane/methano（l 1:50, v/v）4）. feed（Otohime A, Maruha Ltd., Japan）, while from July to Individual lipids from each lipid class, such as the phos- Decembe（r 6 months）, samples 2 were fed another feed pholipid class, were qualitatively identified with standards （EP-3 and EP-4, Maruha Ltd., Japan）. December to by comparing the Rf values using thin-layer chromatogra- October in the following yea（r 10 months）, the feeds for ph（y Merck & Co. Ltd., Kieselgel 60, thickness of 0.25 mm the samples 2 were changed to raw whole fish, such as for analysis）. All sample lipids were dried under argon at sardin（e Sardinops melanostictus）and anchovy（Engrau- room temperature and stored at －40℃ under argon. lis japonica）, and the samples were fed during 10 months （sample 3）. 2.3 Preparation of methyl esters and gas-liquid chroma- In January 2010, wild S. schlegel（i samples 4）were col- tography（GLC）of esters lected near the coast of Fukaura in the Japan Se（a 40°45′N Individual components of TAG, PE, and PC fractions and 140°06′E）. After their biological data were measured, were converted to fatty acid methyl esters by direct trans- the specimens were immediately frozen at －40℃. esterification with methanol containing 1％ concentrated hydrochloric acid under reflux for 1.5 hr, as previously re- 2.2 Lipid extraction and analysis of lipid classes ported, to produce the fatty acid methyl esters4）. These From each adult and young individual of S. schlegeli, methyl esters were purified using silica gel column chroma- the muscle tissue（edible part）and live（r representative of tography by elution with dichloromethane/n-hexane（2/1, viscera）with stomach content（s influence of the prey v/v）. Table 1 Locality of Capture and Biological Data of Sebastes schlegeli Hilgendorf. 556 J. Oleo Sci. 63, (6) 555-566 (2014) Lipid Classes and Fatty Acid Profile of Cultured and Wild Black Rockfish, Sebastes schlegeli Hilgendorf. Sebastes schlegeli The Lipid Contents and Classes of Table 2 Table 557 J. Oleo Sci. 63, (6) 555-566 (2014) H. Saito and S. Ishikawa The composition of the fatty acid methyl esters was de- 3 Results termined by gas-liquid chromatograph（y Table 3–6）. Analy- 3.1 Lipid content of S. schlegeli under two different condi- sis was performed on HP-5890（Hewlett Packard Co. Ltd., tions（cultured and wild） Yokogawa Electric Corporation, Tokyo, Japan）gas chro- The biological data of the S. schlegeli samples are listed matographs equipped with an Omegawax-250 fused silica in Table 1 with other relevant data. As shown in Table 2, capillary column（30 m×0.25 mm i. d.; 0.25 μm film, the muscle lipid content of the cultured adult sample Supelco Japan Co. Ltd., Tokyo, Japan）. The temperatures （sample No. 3, cultured adult; 0.6％ for muscle and 13.9％ of the injector, the detector, and the column were held at for liver）was similar to that of the wild adult sample 230, 240, and 215℃, respectively, and the split ratio was （sample No.