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Mackerel Lipids and Fatty Acids
Mackerel Lipids and Fatty Acids R. G. Ackman and C. A. Eaton Fisheries Research Board of Canada Halifax Laboratory Halifax, Nova Scotia
Abstract The light and dark muscle of Atlantic spring mackerel differed sharply in lipid content, the dark muscle showing about 12% in spring males and 9% in females as against values of 2-3% for light flesh from both sexes. Fall mackerel had nearly twice as much fat in the dark muscle and three times as much in the light muscle. The fatty acid compositions of the total lipids of different muscle samples from three lots of fish and of triglycerides and phospholipids from muscles of another lot of fish are compared.
Resume Le muscle clair et Ie muscle fonge du maquereau de l'atlantique printanier different considerablement en contenu lipide. Le muscle fon<;;e a montre- environ 12% pour les males et 9% pour les femelles en ,comparison de 2-3% !pour Ie muscle clair des deux sexes. Le maquereau d'automne a montn~ presque 2 fois autant de gras dans Ie muscle fon<;;e et 3 fois autant dans Ie muscle clair. Les compositions en acides gras des lipides totaux de differents echantillons provenant de trois lots de poissons et des triglycerides et phospholipides provenant d'un autre lot sont comparees.
Introduction The Atlantic mackerel (Scornber scombrus), and related species caught in other parts of the world, are highly esteemed as food fish. In the Atlantic provinces landings were 29,268,000 lbs in 1969, of which at least 10 million pounds were sold round or dressed in fresh or frozen form for human consumption, with a distinctly lesser amount being put up in brine and/or vinegar, canned, or lotherwise preserved (Anon, 1970). The muscle lipids of mackerel are of special interest as both light and dark meats are eaten, whereas in SOllIe other fatty species with distinctly different muscle type the dark muscle may not be utilized for human food (e.g., tuna; Roubal, 1963). This study was undertaken to indicate the proportions of major lipids and of their fatty acids in the two types of muscle, and to compare spring and fall mackerel in these and other respects.
Experimental Mackerel destined for this study were obtained from the gillnet and trap fisheries in the area immediately outside Halifax harbour. Those landed on June 10, 1965, were immediately frozen and kept at -40 0 until April, 1966, when they were thawed and examined. Fish landed on June 11, August 31 and October 3, 1966, ,vere analysed within a few hours of landing. The muscle was freed of skin and coarse bones and dissected carefully into light and dark meats, with the belly flaps being examined separately from the other white meat. These samples, the livers, and the gonads (spring fish lonly) were extracted by the method of Bligh and Dyer (3). The recovered lipids, except for the October, 1966 sample, were saponified and unsaponifiable material removed by American Oil Chemists' Official Method Ca-6b-53. The 169
fatty acids were th'en recovered and converted to methyl esters by refluxing for five minutes with 7% boron trifluoride in methanol. 'Vater was added and the esters were extracted into petroleum ether. This extract was washed once with water, once with sodium bicarbonate solution, once with saturated sodium sulphate solution, and dried over sodium sulphate prior to recovery of the esters. In the case of the October, 1966 sample the recovered lipid was fractionated on a styrene-divinylbenzene copolymer bead column as described elsewhere (Drozdowski and Ackman, 1969). The phospholipids and triglycerides were recovered quantitatively for fatty acid analyses. These were subjected to transesterification in a centrifuge tube (Teflon-lined screw cap) and the esters recovered by the same procedure as used for esterification. Some additional samples of fish collected in conjunction with these studies were measured, the muscle extracted for total lipid, and in some cases the IV (iodine values) determined on the total lipid. Most samples of methyl esters were analysed for fatty acid composition by gas-liquid chromatography on polar packed columns (EGSS-X and EGSS-Y) as described elsewhere (Ackman and Eaton, 1966). An additional analysis of the fall, 1966 samples was carried out on an open-tubular GLC column coated with butanediol-succinate polyester (Fig. 1) as described elsewhere (Ackman et al., 1967b; Ackman et al, 1970). Parts of all ester samples were hydrogenated and the resulting saturated esters used to verify accurate determination of unsaturated acids by chain lengths and to determine minor saturated components. Two decimal places are given in the results solely to show the relative proportions of these; accuracy would normally be within + 5% for major components with larger potential errors for lesser components.
Results and Discussion The mackerel is an interesting migratory species. The ,vestern Atlantic population, in part, winters along the eastern coast of the United States and spawns in coastal waters off New England in the spring. Another portion of the population migrates along the Atlantic coast of Nova Scotia to the Gulf of St. Lawrence, an important spawning and summer feeding ground. The fishery can be broadly broken down into three phases:- the spring northbound migration, usually of sexually maturing fish; a summer fishery in the Gulf of St. Lawrence; and the fall southbound migration. Further details of the biology and economic importance of these two groups of mackerel ,viII be found in recent publications (Hoy and Clark, 1967; MacKay, 1967). The fish studied were of common market size (Table 1) and several years of age (compare MacKay, 1967). The lipid contents of muscles and organs (Table Can. Inst. Food Techno!. J. Vol. 4, No.4, 1971
MACKEREL TRIGLYCERIDE METHYL ESTERS
16:0
I
21:S?
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I
-5,
18:0
1
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90
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22:1
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20:1 18:2w6 I 18:3w3
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18:1
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22:6"" 3
s
14:0
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HYDROGENATED METHYL ESTERS
w a:: 19.0
22:0
210
-5, 120
130
1
I
40
TI ME (Min. ) Figure 1
Open-tubular gas chromatographic analyses of fresh methyl esters from mackerel dark flesh triglycerides (A, continued on A') and the same sample after hydrogenation (B). Butanediol-succinate coated stainless steel .column 50 m in length x 0.25 mm I.D. operated in Perkin-Elmer Model 226 at 170· and 40 psig helium. Attenuation changes (marked x), and retention times are noted below baselines.
male fish, then the dark muscle is also higher in fat in the fall fish. The belly flap is in all cases remarkably high in total lipid, a characteristic also notable in coho salmon (Karrick and Thurston, 1964), or herring (Fraser et al., 1961). December, 1958, mackerel had 37.2% lipid in the belly flap (Mannan et al., 1961). As indicated in Table 3 the light muscle contains 0.5% phospholipids, the dark muscle 1.6% or three times as much. These relative proportions of phospholipids are found in comparable muscles in other species including fish as lean as cod (Ackman, 1972; Ackman and Cormier, 1967). The proportion
2) clearly reflect the nutritional status of the fish. In fall fish, which have been feeding heavily, the lipid levels in the light muscle are distinctly higher than in spring fish, and if allowance is made for the definite lower levels in the spring female fish relative to the
Table 1. Sex, size, and other pertinent data for mackerel studied for lipids and fatty acids Date landed Sex No. Av. Length Av. Weight Av. Weight Av. Weight Av. Weight fish (cm) (g) eviscerated liver(g) gonads ~)
June 10, 1965 June 10, 1965 May 31, 1966 May 31, 1966 August 31, 1966 Oct. 3, 1966 Table 3.
M F M F F F
5 4 7 5 6 4
35.4 35.2 36.1 36.9 36.7 35.5
486.3 458.6 563.6 561.0 540.2 439.3
389.0 367.1 452.6 449.5 493.2 410.4
(~
5.1 10.0 7.4 15.2 9.3 6.8
65.0 51.1 69.1 61.1
Recoveries of triglycerides and phospholipids from October 3, 1966 mackerel lipids and calculated iodine values for methyl esters of fatty acid from lipids. Triglycerides Percent in lipid in tissue
Light flesh Dark flesh Liver
89.5 74.2 79.5
J. lnst. Can. Techno!. Aliment. Va!. 4, No 4. 1971
9.1 10.7 14.4
Ester iodine value 152.3 144.3 130.9
Phospholipids Percent in lipid in tissue 4.7 11.3 9.3
0.5 1.6 1.7
Ester iodine value 242.9 208.1 242.1
170
OOO ...... "!<"!<
<:6<:60005
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of phospholipid to muscle should be approximately constant and the balance of the lipids indicated in Table 2 should be mostly triglycerides. Unpublished observations for mackerel from the Fish Inspection Laboratory, Halifax, indicate that fat contents for whole fish of about 8% in "spring" fish can rise in the course of three or four weeks to about 22% for "fall" fish with a maximum of 25.5% for 39 cm fish taken south of Halifax in November, 1965. Comparable figures (for fillets only) of Norwegian mackerel are:- spring, 5.4%, fall, 20.2% (Taarland, 1958). The methyl ester IV offer a rough guide to fatty acid compositions (Table 2) when considered from the view point of the typical high IV fatty acids of phospholipids blended into greater or lesser proportions of triglyceride fatty acids. The detailed aspects of overall fatty acid compositions are presented in Table 4 and 5. In Table 6 are given some additional details revealed by open-tubular GLC (Fig. 1). In 1965 spring male and female fish could clearly be differentiated in overall aspects of fatty acid composition (Table 2). In 1966 spring fish this was less obvious, and muscle fat IV were higher than in 1965 fish for both sexes. Lipid IV of both lots of fall (1966) spent (presumed to be female) fish differed a little from spring (female) fish for the muscle lipids, especially in the belly flap overall composition. This was principally due to the total monoethylenic acids decreasing in the belly flap from 50.8-53.7% (spring) female to 43.4% (fall) as shown in Tables 4 and 5, with a concurrent rise in polyunsaturated acids. Overall, the lower IV of the dark flesh lipid for spring male (1965) fish compared to female fish is reflected in the former Table 6.
Additional details of fatty acid information from open-tubular GLC of fall 1966 (October) mackerel lipids which were not included in Table 5.
Fatty Acid"+ C') C"l t- <>1 C')C'lt-CO
dm""';d
4, 8, 12-TMTD Pristanic Phytanic I 14 I 15 AI 15 1 16 I 17 AI 17 I 18 16:1 w 9 w7
w5 18:1 w 11 and 9
w7 w5
.....o
20:1 w 11 w9
w7 w5
22:1 w 13 and 11 w9
w7
Light Flesh TG PL
Dark Flesh TG PL
TG
0.05 0.04 0.03 0.04 0.31 0.16 0.13 0.32 0.15 0.14 0.96 4.27 0.26 17.40 6.01 0.48 0.46 4.50 0.83 0.11 4.08 1.38 0.16
0.06 0.02 0.13 trace 0.14 0.03 0.09 0.20 0.12 0.25 0.86 3.99 0.23 12.55 3.11 0.78 0.70 6.38 0.75 0.06 10.18 2.13 0.19
0.12 trace trace trace 0.03 0.02 0.08 0.20 0.08 0.20 0.60 2.72 0.10 30.45 7.76 0.64 0.59 5.41 0.54 0.05 2.82 0.99 0.05
trace 0.04 0.07 0.10 0.08 0.01 0.06 0.21 0.06 0.10 0.24 1.26 0.27 5.51 3.51 0.21 0.10 1.33 0.13 trace 0.81 0.15 0.06
0.03 0.06 0.13 0.13 0.06 0.01 0.06 0.26 0.13 0.22 0.27 0.99 0.14 8.67 5.05 0.68 0.19 2.80 0.34 0.11 1.16 0.29 0.08
Liver PL 0.01 0.01 0.02 0.01 0.04 0.01 0.07 0.47 0.24 0.21 0.65 0.82 0.22 10.03 3.51 0.17 0.08 1.38 0.13 0.05 0.32 0.08 0.04
" Shorthand notation for chain length, number of double bonds anteiso and position relative to methyl group - I = iso, AI + 4 8 12-TMTD 4,8,12-trimethyltridecanoic acid p~i~tanic = 2,6,10,14-tetramethylpentadecanoic acid phytanic 3,7,11,15-tetramethylhexadecanoic acid
= =
171
=
Can. lnst. Food Technol. J. Vol. 4, No.4, 1971
Table 4.
Fatty acid composition (Weight %) derived from total lipids of portions of spring mackerel. Spring 1965
Fatty Acid ~ 12:0 14:0 AI 15 I 15:0 I 16 16:0 I AI 17 17:0 18:0 19:0 20:0 Total 14:1 15:1 16:1 17:1 18:1 19:1 20:1 22:1 24:1 Total 16:2(J)6 & 4 16:3 w4 & 3 16:4 w 1 18:2 w6 18:3 w6 18:3w 3 18:4 w3 20:2 w6 20:3 w 6 20:3 w3 20:4 w6 20:4w 3 20:5 w3 21:5· ? 22:5w 6 22:5 w 3 22:6 w3 Total
+
+
~Shorthand
Light Flesh
Male Dark Flesh
Belly
0.16 6.05 0.48 0.60 0.10 17.07 0.35 0.40 3.15, 0.15 0.26 28.77 5.53 0.58 15.57 0.10 10.53 14.48 1.66 48.45 0.81 0.41 0.22 1.59 0.16 0.91 1.41 0.34 0.13 0.10 0.35 0.61 4.62 0.55 0.42 1.34 8.83 22.80
Spring 1966 Belly Flap
Light Flesh
Female Dark Flesh
Belly
Flap
Light Flesh
Male Dark Flesh
0.10 5.39 0.41 0.55 0.17 15.27 0.46 0.76 3.56 0.19 0.19 27.05
0.24 7.28 0.60 0.80 0.18 13.84 0.70 0.59 2.54 0.07 0.07 26.91
5.92 0.19 0.35 0.23 19.64 0.23 0.31 3.63 trace trace 30.50
0.14 5.81 0.58 0.72 0.25 15.88 0.54 0.52 2.95 0.19 0.13 27.71
0.12 6.00 0.42 0.54 0.11 14.51 0.44 0.51 2.38 0.12 0.09 25.24
0.15 4.94 0.25 0.46 0.12 16.02 0.23 0.29 3.53 0.09 0.05 26.13
0.19 5.67 0.33 0.48 0.14 16.34 0.54 0.49 3.18 0.09 0.05 27.50
0.36 6.13 0.52 0.75 0.23 13.72 0.42 0.47 2.65 0.11 0.04 25.40
4.59 0.41 13.68 0.06 9.84 14.39 1.73 44.70 0.64 0.44 0.27 1.72 0.17 1.05 2.05 0.33 0.17 0.13 0.43 0.66 6.44 0.40 0.29 1.27 11.82 28.28
6.09 0.64 17.39 0.06 12.15 15.74 1.60 53.67 0.86 0.51 0.34 1.83 0.14 1.25 2.52 0.27 0.10 0.08 0.27 0.51 4.86 0.18 0.11 0.85 4.72 19.40
7.09 0.23 14.05 0.07 6.42 10.89 1.50 40.25 0.31 0.27 0.23 0.89 trace 0.27 1.13 0.23 trace trace 0.53 0.53 7.66 0.58 0.28 1.24 15.10 29.25
5.86 0.51 12.75 0.08 8.50 12.96 1.60 42.26 1.07 0.42 0.38 1.33 0.21 0.90 1.38 0.37 0.21 0.19 0.62 0.67 7.26 0.61 0.64 2.90 10.85 30.01
6.15 0.55 15.52 0.12 10.33 14.20 1.27 47.38 0.79 0.47 0.36 1.75 0.20 1.30 2.54 0.41 0.20 0.12 0.62 0.78 7.06 0.46 0.25 1.38 7.92 27.37
5.41 0.40 13.38 0.05 9.13 12.23 1.14 41.74 0.67 0.21 0.33 1.81 0.20 0.90 1.74 0.47 0.11 0.21 0.61 0.70 7.58 0.52 0.39 1.60 14.08 32.13
5.93 0.35 15.34 0.14 8.43 13.04 1.72 44.95 0.88 0.31 0.56 1.47 0.21 0.58 1.28 0.34 0.07 0.09 0.60 0.64 7.16 0.44 0.20 1.33 11.43 27.59
7.03 0.56 17.78 0.13 9.92 14.23 1.19 50.84 0.99 0.30 0.43 1.67 0.28 1.01 2.18 0.29 0.17 0.18 0.41 0.51 7.35 0.36 0.20 0.97 6.43 23.73
Belly
Flap
Light Flesh
Female Dark Flesh
0.12 6.06 0.22 0.51 0.12 15.69 0.49 0.73 3.57 0.17 0.16 27.85
0.05 6.18 0.49 0.60 0.12 15.24 0.27 0.71 2.83 0.09 0.22 26.80
0.15, 5.05 0.41 0.49 0.10 16.63 0.53 0.36 3.04 0.13 0.12 27.01
5.87 0.33 14.77 0.10 10.28 14.81 1.68 47.84 0.60 0.47 0.13 1.64 0.19 1.18 1.98 0.38 0.26 0.17 0.54 0.80 4.80 0.28 0.82 1.39 8.66 24.29
6.42 0.42 16.91 0.u4 10.65 15.04 1.92 51.40 0.70 0.55 0.07 2.02 0.21 1.39 2.30
4.44 0.40 13.97 0.10 9.18 13.35 1.61 43.05 0.80 0.33 0.43 2.08 0.31 1.16 1.91 0.36 0.09 0.13 0.45 0.49 6.04 0.30 0.43 1.06 13.57 29.94
O.lt)
0.04 0.19 0.39 0.68 5.05 0.25 0.23 1.26 6.29 21.80
----
notation for chain length, number of double bonds and position relative to methyl group -
having 47.8% monoethylenic acids in the dark flesh as against 44.7% in the latter. As there is little difference in total saturated acids the affected balance must be in the polyunsaturated acids, especially the 22 :6w3. The 1966 spring and fall (August) flesh samples differ only a little in details of the saturated acids but the totals are lower in fall fish for all three muscle samples (Tables 4 and 5). The total monoethylenic fatty acids also differ little except in the belly flap, where they are lower in fall fish. However there are interesting differences as 18:1 is lower in the spring fish samples, a factor offset by higher 20:1 and especially 22 :1. The decrease in relative proportions of the latter acids in the fall suggests deposition of fatty acids typical of small crustaceans such as copepods or euphausiids, where these two acids are of minor ilUportance (Ackman et al., 1970). These animals are kno"rn to be a principal food for mackerel in the Gulf of St. Lawrence (MacKay, 1967). Fatty acids from the triglycerides of October (1966) fish confirmed the J. lnst. Can. Techno!. Aliment. Vol. 4, No 4, 1971
I
=
iso, AI
--~
Flap
= anteiso.
results for August fish. As suggested by. the similar IV, the polyunsaturated fatty acids differed but little in spring and fall (fenlale) 1966 light and dark muscle. Essentially the proportions of 20 :5w3 and 22 :6w3 and their relationship to the minor polyunsaturated fatty acids are also typical of the euphausiid crustacean fats (Ackman et al., 1970) although 22 :6w3 is 1/2 20 :5w3 in one species of small copepods potentially included in the diet (Ackman and Hooper, 1970). The percentage of unsaponifiable nlaterials in the muscle lipid varied inversely with the total lipid. Although the composition was not investigated, occasionally thin films crystallized in a pattern similar to that of cholesterol. Small proportions of hydrocarbons are also known to occur (Dubravic and Na,var, 1969). A tocopherol level of 310 p,g/g lipid, typical of many marine oils, has been recorded for mackerel lipid (Ackman and Cormier, 1967). Analysis of fall (1959) Atlantic mackerel fillets containing 12.9% oil (Gruger et al., 1964) differed especially from the Table 5 data in 16:0 (28.2%), 172
Table 5.
Fatty
Fatty acid composition (Weight %) derived from total lipids of portions of fall 1966 (August) mackerel and of principal lipids of portions of fall 1966 (October) mackerel. The latter were analysed on open-tubular GLC column.
acid~
12:0 14:0 I and AI 15 15:0 I 16 16:0 I and AI 17 17:0 18:0 19:0 20:0 Total 14:1 15:1 16:1 17:1 18:1 19:1 20:1 22:1 24:1 Total 16:2 16:3 16:4 18:2w6
3w 6
3 w3 4 w3 20:2 w6
3w6
3 w3 4 w6 4 w3 20:5.w3 21:5 ? 22:4 w6 22:5 w 6 5w3 22:6 w3 Total ~Shorthand
Fall 1966 August Light Flesh Dark Flesh Belly Flap 0.16 5.09 0.17 0.50 0.05 18.40 0.28 0.74 3.41 0.07 0.21 29.08
0.10 5.23 0.15 0.37 0.07 18.72 0.21 0.69 3.56 0.12 0.10 29.32 0.05
0.22 5.51 0.37 0.67 0.07 17.80 0.44 0.59 3.36 0.08 0.17 29.28
6.00 0.16 20.77 0.07 5.36 7.06 0.67 40.09 0.66 0.33 0.09 1.73 0.09 1.18 1.97 0.43 0.12 0.14 0.59 0.99 8.04 0.28
5.45 0.07 19.52 0.16 6.70 9.50 1.04 42.49 0.19 0.10 0.07 1.94 0.27 1.21 2.03 0.53 0.12 0.03
6.52 0.23 21.55 0.05 6.75 7.18 1.09 43.37 0.51 0.32 0.16 2.44 0.10 1.15 2.55 0.44
0.24 1.02 13.00 30.90
0.6D
0.90 7.04 0.19 0.02 0.27 0.94 11.75 28.20
0.11 0.58 0.77 7.44 0.30 0.26 1.19 9.00 27.32
Flesh
TG
PL
TG
PL
0.19 4.96 0.47 0.87 0.13 15.07 0.48 0.88 3.89 0.23 0.16 27.33 0.05 trace 5.49 0.34 23.89 0.11 5.90 5.62 0.98 42.38 0.47 0.12 0.13 1.41 0.08 1.30 2.15 0.39 0.07 0.11 0.40 0.69 7.65 0.34 0.10 0.12 1.38 13.38 30.29
trace 0.50 0.09 0.22 0.06 20.42 0.27 0.53 7.40 0.08 0.04 29.61 0.03
0.06 4.18 0.17 0.63 0.09 16.92 0.32 0.75 3.04 0.10 0.14 26.40 0.02
1.77 0.14 9.23 0.11 1.56 1.02 0.45 14.31 0.22 0.08 0.04 1.56 0.10 0.51 0.23 0.38 0.10 0.22 1.71 0.74 10.66 0.60 0.10 0.98 1.57 36.28 56.08
5.08 0.35 16.44 0.11 7.89 12.50 2.11 44.50 0.73 0.13 0.24 1.65 0.13 1.45 2.38 0.54 0.18 0.27 0.42 0.83 6.63 0.26 0.08 0.42 1.53 11.15 29.02
0.04 0.94 0.07 0.31 0.06 14.65 0.39 0.89 13.15 0.26 0.16 30.92 0.04 0.03 1.40 0.10 14.40 0.18 3.44 1.53 0.22 21.34 0.20 0.04 0.07 2.97 0.04 1.16 0.30 0.53 0.19 0.29 1.04 1.71 7.25 0.15 0.10 0.43 1.75 29.54 47.76
notation for chain length, number of double bonds and position relative to methyl group -
20:1 (3.1 %) and 22:1 (2.8%). Possibly some material listed as 20:4 should be included in 22 :1. Mackerel oil cold pressed from fillets of fish caught off Massachusetts is comparable, insofar as detail for fatty acid composition is given, to the spring 1966 oils (Dubravik and Nawar, 1969) . .A.\driatic mackerel seem to have broadly the same composition as Atlantic fish (Montefredini and Testa, 1964). Fatty acids obtained in France by hydrolysis of mackerel (presumed to be Sco1'nber 8oombru8) flesh had an iodine value of 251.5 but the fatty acid analysis does not agree with any well-known analysis reported for triglyceride-based fats of marine teleost fishes (Ploquin et al., 1969). The oil from Soomber japoniou8 has been analysed (Ueda, 1967) and bears some resemblance to the fall (1966) analyses of Atlantic fish. It had an IV of 143.3, but 18.1 at 23.9% apparently to some extent replaced 20:1 and 22 :1. These were possibly about 4.5% each; the details are obscured for 20 :1. Mackerel which were netted at Jeddore Harbour, N.S., on September 30, 1969, were relatively small, 173
Fall 1966 October Dark Flesh
Light
Liver
I
==
TG
PL
1.16 0.05 0.22 0.08 15.27 0.28 0.40 4.40 0.03 0.04 21.93 0.01
0.52 0.05 0.28 0.07 16.33 0.71 0.43 6.62 0.11 0.10 25.22 0.01
3.42 0.50 39.55 0.20 6.59 3.86 0.95 55.08 0.74 0.03 0.02 1.6H 0.08 0.71 0.93 0.20 0.15 0.36 0.57 1.06 4.86 0.39 0.45 0.34 1.89 8.53 23.00
1.69 0.18 13.71 0.10 1.64 0.44 0.08 17.85, 0.30 0.02 0.01 0.78 0.04 0.47 0.20 0.16 0.06 0.20 2.17 1.39 12.08 0.15 0.28 0.49 3.81 34.32 56.93
iso, AI
=
anteiso.
averaging 26.6 cm in length and 191 g in weight (six fish). The headed, eviscerated bodies weighed an average of 136 g and yielded 8.6% total lipid. The average weight of livers was 3.2 g with a lipid yield of 8.9%. These small fish ("tinker mackerel") probably had spent the summer in that vicinity. Two sizes of mackerel were represented in a catch in Long Harbour, Placentia Bay, Newfoundland, landed on July 29, 1970. Six larger fish, including both ripe and spent fish of both sexes, were an average of 34.2 cm in length and 425 g in weight. Three smaller fish appeared to be immature and averaged 30.2 Clll in length as against 305.3 g in weight. The dark flesh of the large fish contained 11.1 % lipid of IV 133.5, that of the small fish 14.6% lipid of Iv'" 148.2. The corresponding light flesh samples had lipid contents of 4.6% and 7.2%. These samples represent additional years, locations and sizes of fish, but do not appear to differ materially in either lipid content or triglyceride fatty acid composition from the 1965-1966 fish from Nova Scotia which had been examined in detail. Can. Inst. Food Techno!. J. Vol. 4, No.4, 1971
Table 7.
14:0 16:0 16:1 18:0 18:1 18:2 w6 18:4w3 20:1 20:4 w6 20:5 w3 22:1 22:5 w3 22:6 w3
Principal or nutritionally important fatty acids of mackerel livers and gonads (as percent of total fatty acids) Spring 1965 Male Female Liver C'onad Liver Gonad
Spring 1966 Male Female Gonad Gonad Liver Liver
2.12 11.63 5.03 6.81 17.54 2.66 2.06 8.80 0.82 10.35 7.57 2.31 10.45
1.37 11.99 3.15 7.93 22.63 1.01 0.99 6.23 0.70 11.28 10.49 3.51 9.59
1.43 20.01 2.46 4.48 15.78 1.52 0.59 2.24 1.51 13.08 1.28 2.14 28.16
1.92 17.56 4.13 5.51 28.46 1.50 0.76 4.33 1.20 8.91 3.21 1.23 14.63
It is possible to conclude that although commercial sized mackerel show substantial variation in percent lipid, mostly in triglyceride in the light muscle, the overall fatty acid fluctuations, especially in monoethylenic fatty acid, are less extravagant than those observed in herring (Ackman and Eaton, 1965; Acknlan et al.) 1967a; Drozdowski and Ackman, 1969). The gross fatty acid compositions (Tables 4 and 5), and supplementary details (Table 6), are those typical of 111arine fish fatty acids and in fact in our experience could be taken as guides for the composition of oils or lipids of many Canadian species not as yet examined provided due allo,vance was made for the proportions of triglycerides and phospholipids. This viewpoint is treated in detail elsewhere (Ackman, 1972). The details of monoethylenic fatty acids given in Table 6 show that these also consist of mixtures of isonlers resembling those of fats in other fatty species of fish such as herring which have long been accepted as human foodstuffs (Ackman and Castell, 1966). The high proportion of the "009" isomer in the C20 and C22 nlonoethylenic acids is perhaps of interest and supports the view that these fall fish have formed these acids by chain extension from the 18 :1w9. It is more obvious in these fish than in spring fish. The calorie content will vary with the total fat fronl about 125 calories/l00 g meat for spring mackerel to about 250 for fillets from fall fish. Protein, vitamin, and mineral content data is given elsewhere (Mannan et al., 1961; Stansby and Hall, 1967; Taarland et al.) 1958). At present fish roe and livers are not eaten widely in Canada although esteemed in Europe and elsewhere. It it expected that pressure to utilize more of limited fish landings will in future lead to promotion of selected organs which are now discarded, fronl appropriate fish and shellfish species. These might be served as prepared products similar to those at present imported from Japan or Europe and marketed in Canada mostly in specialty shops. The principal fatty acids of these organs given in Table 7 COlTIplement the data recorded in Tables 1 and 2.
Acknowledgements The authors thank l\fr. R. Legendre for preparation of the French abstract. J. Inst. Can. Technol. Aliment. Vol. 4, No 4, 1971
4.19 17.07 6.95 2.33 20.71 2.04 2.20 3.80 0.56 10.64 2.97 1.09 17.43
1.64 19.49 3.69 4.07 18.42 1.46 0.69 2.49 1.31 14.18 1.72 2.35 22.49
1.58 15.73 4.47 6.35 30.09 1.16 0.48 4.34 0.94 10.36 2.82 1.83 13.11
4.49 16.06 5.94 2.70 16.64 1.41 1.30 2.66 0.89' 16.88 1.57 1.88 18.80
References Ackman, R. G. 1972. Marine lipids and fatty acids as components of the human diet. in Recent Advances in Human Nutrition, edt M. A. Crowford (SUbmitted for publication). Ackman, R. G. and Castell, J. D. 1966. Isomeric monoethylenic fatty acids in herring oil. Lipids 1 :34l. Ackman, R. G. and Cornlier, M C. 1967. a-Tocopherol in some Atlantic fish and shellfish with particular reference to liveholding without food. J. Fish. Res. Bd. Canada 24:537. Ackman, R. G. and Eaton, C. A. 1966. Some commercial Atlantic herring oils; fatty acid composition. J. Fish. Res. Bd. Canada 23:991. Ackman, R. G., Eaton, C. A. and Ke, P. J. 1967a. Canadian marine oils of low iodine value: Fatty acid composition of oils from Newfoundland turbot (Greenland halibut), certain Atlantic herring, and a sablefish. J. Fish. Res. Bd. Canada 24:2563. Ackman, R. G., Eaton, C. A., Sipos, J. C., Hooper, S. N. and Castell, J. D. 1970. Lipids and fatty acids of two species of North Atlantic krill (Meganyctiphanes norvegica and Thysanoessa inermis) and their role in the aquatic food web. J. Fish. Res. Board Canada 27 :513. Ackman, R. G. and Hooper, S. N. 1970. Analyses of fatty acids from Newfoundland copepods and sea water with remarks on the occurrence of arachidic acid. Lipids 5 :417. Ackman, R. G., Sipos, J. C. and Jangaard, P. M. 1967b. A quantitation problem in the open-tubular gas chromatography of fatty acid esters from cod liver lipids. Lipids 2:25l. Anon, 1970. Annual Statistical Review of Canadian Fisheries, Vol. 2, 1954-1969. Economics Branch, Fisheries Service, Department of Fisheries and Forestry, Ottawa, 132 pages. Bligh, E. G. and Dyer, W. J. 1959. A rapid method of total lipid extraction and purification. Can. J. Biochem. Physiol. 37 :91l. DrOZdowski, B. and Ackman, R. G. 1969. Isopropyl alcohol extraction of oil and lipids in the production of fish protein concentrate from herring. J. Amer. Oil Chem. Soc. 46:371. Dubravic, M. F. and Nawar, W. W. 1969. Effects of high-energy radiation on the lipids of fish. J. Agr. Food Chem. 17:639. Fraser, D. I., Mannan, A. and Dyer, W. J. 1961. Proximate composition of Canadian Atlantic fish. III. Sectional difference in the flesh of a species of Chondrostei, one of Chimaerae, and some miscellaneous teleosts. J. Fish. Res. Bd. Canada 18 :893-905. Gruger, E. H., Jr., Nelson, R. W. and Stansby, M. F. 1964. Fatty acid composition of oils from 21 species of marine fish, freshwater fish and shellfish. J. Amer. Oil Chem. Soc. 41 :662. Hoy, D. L. and Clark, G. M. 1967. Atlantic mackerel fishery, 18041965. U.S. Dept. Int., Bur. Comm. Fish., Fishery Leaflet 603, 9 pages. Karrick, N. L. and Thurston, C. E. 1964. Proximate composition of silver salmon. J. Agr. Food Chem. 12:282-284. MacKay, K. T. 1967. An ecological stUdy of mackerel Scomber scombrus (Linnaeus) in the coastal waters of Canada. Fish. Res. Bd. Canada, Tech. Rep. No. 31, 127 pages. Mannan, A., Fraser, D. I. and Dyer, W. J. 1961. Proximate composition of Canadian Atlantic fish. II. Mackerel, tuna and swordfish. J. Fish. Res. Bd. Canada 18: 495-499. Montefredini, A. and Testa, C. 1964. Fatty acid composition of mackerel, shad and sardine oils. Atti Soc. Ita!. Sci. Vet. 18: 546549. Ploquin, J., Souroudjieva, B. and Sparfel, L. 1969. Rev. Franc. Corps Gras. 16: 78l. ROUbal, W. T. 1963. Tuna Fatty Acids: II. Investigation of the composition of raw and processed domestic tuna. J. Amer. Oil Chem. Soc. 40: 215-218. Stansby, M. E. and Hall, A. S. 1967. Chemical composition of commercially important fish of the United States. Fishery Industrial Research 3: (4): 29-46. Taarland T., Mathieson, E., Ovsthus, O. and Braekkan, O. R. 1958. Nutritional values and vitamins of Norvegian fish and fishproducts. Tidsskrift for Hermetikindustri 54: 405-412. Ueda, T. 1967. Fatty acid composition of oils from 33 species of marine fish. J. Shimonoseki Univ. Fish. 16 (1): 1. Received June 7, 1971
174
Abstract The light and dark muscle of Atlantic spring mackerel differed sharply in lipid content, the dark muscle showing about 12% in spring males and 9% in females as against values of 2-3% for light flesh from both sexes. Fall mackerel had nearly twice as much fat in the dark muscle and three times as much in the light muscle. The fatty acid compositions of the total lipids of different muscle samples from three lots of fish and of triglycerides and phospholipids from muscles of another lot of fish are compared.
Resume Le muscle clair et Ie muscle fonge du maquereau de l'atlantique printanier different considerablement en contenu lipide. Le muscle fon<;;e a montre- environ 12% pour les males et 9% pour les femelles en ,comparison de 2-3% !pour Ie muscle clair des deux sexes. Le maquereau d'automne a montn~ presque 2 fois autant de gras dans Ie muscle fon<;;e et 3 fois autant dans Ie muscle clair. Les compositions en acides gras des lipides totaux de differents echantillons provenant de trois lots de poissons et des triglycerides et phospholipides provenant d'un autre lot sont comparees.
Introduction The Atlantic mackerel (Scornber scombrus), and related species caught in other parts of the world, are highly esteemed as food fish. In the Atlantic provinces landings were 29,268,000 lbs in 1969, of which at least 10 million pounds were sold round or dressed in fresh or frozen form for human consumption, with a distinctly lesser amount being put up in brine and/or vinegar, canned, or lotherwise preserved (Anon, 1970). The muscle lipids of mackerel are of special interest as both light and dark meats are eaten, whereas in SOllIe other fatty species with distinctly different muscle type the dark muscle may not be utilized for human food (e.g., tuna; Roubal, 1963). This study was undertaken to indicate the proportions of major lipids and of their fatty acids in the two types of muscle, and to compare spring and fall mackerel in these and other respects.
Experimental Mackerel destined for this study were obtained from the gillnet and trap fisheries in the area immediately outside Halifax harbour. Those landed on June 10, 1965, were immediately frozen and kept at -40 0 until April, 1966, when they were thawed and examined. Fish landed on June 11, August 31 and October 3, 1966, ,vere analysed within a few hours of landing. The muscle was freed of skin and coarse bones and dissected carefully into light and dark meats, with the belly flaps being examined separately from the other white meat. These samples, the livers, and the gonads (spring fish lonly) were extracted by the method of Bligh and Dyer (3). The recovered lipids, except for the October, 1966 sample, were saponified and unsaponifiable material removed by American Oil Chemists' Official Method Ca-6b-53. The 169
fatty acids were th'en recovered and converted to methyl esters by refluxing for five minutes with 7% boron trifluoride in methanol. 'Vater was added and the esters were extracted into petroleum ether. This extract was washed once with water, once with sodium bicarbonate solution, once with saturated sodium sulphate solution, and dried over sodium sulphate prior to recovery of the esters. In the case of the October, 1966 sample the recovered lipid was fractionated on a styrene-divinylbenzene copolymer bead column as described elsewhere (Drozdowski and Ackman, 1969). The phospholipids and triglycerides were recovered quantitatively for fatty acid analyses. These were subjected to transesterification in a centrifuge tube (Teflon-lined screw cap) and the esters recovered by the same procedure as used for esterification. Some additional samples of fish collected in conjunction with these studies were measured, the muscle extracted for total lipid, and in some cases the IV (iodine values) determined on the total lipid. Most samples of methyl esters were analysed for fatty acid composition by gas-liquid chromatography on polar packed columns (EGSS-X and EGSS-Y) as described elsewhere (Ackman and Eaton, 1966). An additional analysis of the fall, 1966 samples was carried out on an open-tubular GLC column coated with butanediol-succinate polyester (Fig. 1) as described elsewhere (Ackman et al., 1967b; Ackman et al, 1970). Parts of all ester samples were hydrogenated and the resulting saturated esters used to verify accurate determination of unsaturated acids by chain lengths and to determine minor saturated components. Two decimal places are given in the results solely to show the relative proportions of these; accuracy would normally be within + 5% for major components with larger potential errors for lesser components.
Results and Discussion The mackerel is an interesting migratory species. The ,vestern Atlantic population, in part, winters along the eastern coast of the United States and spawns in coastal waters off New England in the spring. Another portion of the population migrates along the Atlantic coast of Nova Scotia to the Gulf of St. Lawrence, an important spawning and summer feeding ground. The fishery can be broadly broken down into three phases:- the spring northbound migration, usually of sexually maturing fish; a summer fishery in the Gulf of St. Lawrence; and the fall southbound migration. Further details of the biology and economic importance of these two groups of mackerel ,viII be found in recent publications (Hoy and Clark, 1967; MacKay, 1967). The fish studied were of common market size (Table 1) and several years of age (compare MacKay, 1967). The lipid contents of muscles and organs (Table Can. Inst. Food Techno!. J. Vol. 4, No.4, 1971
MACKEREL TRIGLYCERIDE METHYL ESTERS
16:0
I
21:S?
@\--
I
-5,
18:0
1
[eo
'0
90
1
/00
22:1
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~
"" 13+11
w9
n
/
20:1 18:2w6 I 18:3w3
",,7
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",9
"
(f)
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wll 20;0 \
W
a:: a:: 101
W 0
tv7
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\
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I
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120
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16:0
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161
S
Z 0 0-
0
22:S "" 3
22:S ",6
22:4",6
18:1
W (f)
!60
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22:6"" 3
s
14:0
200
HYDROGENATED METHYL ESTERS
w a:: 19.0
22:0
210
-5, 120
130
1
I
40
TI ME (Min. ) Figure 1
Open-tubular gas chromatographic analyses of fresh methyl esters from mackerel dark flesh triglycerides (A, continued on A') and the same sample after hydrogenation (B). Butanediol-succinate coated stainless steel .column 50 m in length x 0.25 mm I.D. operated in Perkin-Elmer Model 226 at 170· and 40 psig helium. Attenuation changes (marked x), and retention times are noted below baselines.
male fish, then the dark muscle is also higher in fat in the fall fish. The belly flap is in all cases remarkably high in total lipid, a characteristic also notable in coho salmon (Karrick and Thurston, 1964), or herring (Fraser et al., 1961). December, 1958, mackerel had 37.2% lipid in the belly flap (Mannan et al., 1961). As indicated in Table 3 the light muscle contains 0.5% phospholipids, the dark muscle 1.6% or three times as much. These relative proportions of phospholipids are found in comparable muscles in other species including fish as lean as cod (Ackman, 1972; Ackman and Cormier, 1967). The proportion
2) clearly reflect the nutritional status of the fish. In fall fish, which have been feeding heavily, the lipid levels in the light muscle are distinctly higher than in spring fish, and if allowance is made for the definite lower levels in the spring female fish relative to the
Table 1. Sex, size, and other pertinent data for mackerel studied for lipids and fatty acids Date landed Sex No. Av. Length Av. Weight Av. Weight Av. Weight Av. Weight fish (cm) (g) eviscerated liver(g) gonads ~)
June 10, 1965 June 10, 1965 May 31, 1966 May 31, 1966 August 31, 1966 Oct. 3, 1966 Table 3.
M F M F F F
5 4 7 5 6 4
35.4 35.2 36.1 36.9 36.7 35.5
486.3 458.6 563.6 561.0 540.2 439.3
389.0 367.1 452.6 449.5 493.2 410.4
(~
5.1 10.0 7.4 15.2 9.3 6.8
65.0 51.1 69.1 61.1
Recoveries of triglycerides and phospholipids from October 3, 1966 mackerel lipids and calculated iodine values for methyl esters of fatty acid from lipids. Triglycerides Percent in lipid in tissue
Light flesh Dark flesh Liver
89.5 74.2 79.5
J. lnst. Can. Techno!. Aliment. Va!. 4, No 4. 1971
9.1 10.7 14.4
Ester iodine value 152.3 144.3 130.9
Phospholipids Percent in lipid in tissue 4.7 11.3 9.3
0.5 1.6 1.7
Ester iodine value 242.9 208.1 242.1
170
OOO ...... "!<"!<
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of phospholipid to muscle should be approximately constant and the balance of the lipids indicated in Table 2 should be mostly triglycerides. Unpublished observations for mackerel from the Fish Inspection Laboratory, Halifax, indicate that fat contents for whole fish of about 8% in "spring" fish can rise in the course of three or four weeks to about 22% for "fall" fish with a maximum of 25.5% for 39 cm fish taken south of Halifax in November, 1965. Comparable figures (for fillets only) of Norwegian mackerel are:- spring, 5.4%, fall, 20.2% (Taarland, 1958). The methyl ester IV offer a rough guide to fatty acid compositions (Table 2) when considered from the view point of the typical high IV fatty acids of phospholipids blended into greater or lesser proportions of triglyceride fatty acids. The detailed aspects of overall fatty acid compositions are presented in Table 4 and 5. In Table 6 are given some additional details revealed by open-tubular GLC (Fig. 1). In 1965 spring male and female fish could clearly be differentiated in overall aspects of fatty acid composition (Table 2). In 1966 spring fish this was less obvious, and muscle fat IV were higher than in 1965 fish for both sexes. Lipid IV of both lots of fall (1966) spent (presumed to be female) fish differed a little from spring (female) fish for the muscle lipids, especially in the belly flap overall composition. This was principally due to the total monoethylenic acids decreasing in the belly flap from 50.8-53.7% (spring) female to 43.4% (fall) as shown in Tables 4 and 5, with a concurrent rise in polyunsaturated acids. Overall, the lower IV of the dark flesh lipid for spring male (1965) fish compared to female fish is reflected in the former Table 6.
Additional details of fatty acid information from open-tubular GLC of fall 1966 (October) mackerel lipids which were not included in Table 5.
Fatty Acid"+ C') C"l t- <>1 C')C'lt-CO
dm""';d
4, 8, 12-TMTD Pristanic Phytanic I 14 I 15 AI 15 1 16 I 17 AI 17 I 18 16:1 w 9 w7
w5 18:1 w 11 and 9
w7 w5
.....o
20:1 w 11 w9
w7 w5
22:1 w 13 and 11 w9
w7
Light Flesh TG PL
Dark Flesh TG PL
TG
0.05 0.04 0.03 0.04 0.31 0.16 0.13 0.32 0.15 0.14 0.96 4.27 0.26 17.40 6.01 0.48 0.46 4.50 0.83 0.11 4.08 1.38 0.16
0.06 0.02 0.13 trace 0.14 0.03 0.09 0.20 0.12 0.25 0.86 3.99 0.23 12.55 3.11 0.78 0.70 6.38 0.75 0.06 10.18 2.13 0.19
0.12 trace trace trace 0.03 0.02 0.08 0.20 0.08 0.20 0.60 2.72 0.10 30.45 7.76 0.64 0.59 5.41 0.54 0.05 2.82 0.99 0.05
trace 0.04 0.07 0.10 0.08 0.01 0.06 0.21 0.06 0.10 0.24 1.26 0.27 5.51 3.51 0.21 0.10 1.33 0.13 trace 0.81 0.15 0.06
0.03 0.06 0.13 0.13 0.06 0.01 0.06 0.26 0.13 0.22 0.27 0.99 0.14 8.67 5.05 0.68 0.19 2.80 0.34 0.11 1.16 0.29 0.08
Liver PL 0.01 0.01 0.02 0.01 0.04 0.01 0.07 0.47 0.24 0.21 0.65 0.82 0.22 10.03 3.51 0.17 0.08 1.38 0.13 0.05 0.32 0.08 0.04
" Shorthand notation for chain length, number of double bonds anteiso and position relative to methyl group - I = iso, AI + 4 8 12-TMTD 4,8,12-trimethyltridecanoic acid p~i~tanic = 2,6,10,14-tetramethylpentadecanoic acid phytanic 3,7,11,15-tetramethylhexadecanoic acid
= =
171
=
Can. lnst. Food Technol. J. Vol. 4, No.4, 1971
Table 4.
Fatty acid composition (Weight %) derived from total lipids of portions of spring mackerel. Spring 1965
Fatty Acid ~ 12:0 14:0 AI 15 I 15:0 I 16 16:0 I AI 17 17:0 18:0 19:0 20:0 Total 14:1 15:1 16:1 17:1 18:1 19:1 20:1 22:1 24:1 Total 16:2(J)6 & 4 16:3 w4 & 3 16:4 w 1 18:2 w6 18:3 w6 18:3w 3 18:4 w3 20:2 w6 20:3 w 6 20:3 w3 20:4 w6 20:4w 3 20:5 w3 21:5· ? 22:5w 6 22:5 w 3 22:6 w3 Total
+
+
~Shorthand
Light Flesh
Male Dark Flesh
Belly
0.16 6.05 0.48 0.60 0.10 17.07 0.35 0.40 3.15, 0.15 0.26 28.77 5.53 0.58 15.57 0.10 10.53 14.48 1.66 48.45 0.81 0.41 0.22 1.59 0.16 0.91 1.41 0.34 0.13 0.10 0.35 0.61 4.62 0.55 0.42 1.34 8.83 22.80
Spring 1966 Belly Flap
Light Flesh
Female Dark Flesh
Belly
Flap
Light Flesh
Male Dark Flesh
0.10 5.39 0.41 0.55 0.17 15.27 0.46 0.76 3.56 0.19 0.19 27.05
0.24 7.28 0.60 0.80 0.18 13.84 0.70 0.59 2.54 0.07 0.07 26.91
5.92 0.19 0.35 0.23 19.64 0.23 0.31 3.63 trace trace 30.50
0.14 5.81 0.58 0.72 0.25 15.88 0.54 0.52 2.95 0.19 0.13 27.71
0.12 6.00 0.42 0.54 0.11 14.51 0.44 0.51 2.38 0.12 0.09 25.24
0.15 4.94 0.25 0.46 0.12 16.02 0.23 0.29 3.53 0.09 0.05 26.13
0.19 5.67 0.33 0.48 0.14 16.34 0.54 0.49 3.18 0.09 0.05 27.50
0.36 6.13 0.52 0.75 0.23 13.72 0.42 0.47 2.65 0.11 0.04 25.40
4.59 0.41 13.68 0.06 9.84 14.39 1.73 44.70 0.64 0.44 0.27 1.72 0.17 1.05 2.05 0.33 0.17 0.13 0.43 0.66 6.44 0.40 0.29 1.27 11.82 28.28
6.09 0.64 17.39 0.06 12.15 15.74 1.60 53.67 0.86 0.51 0.34 1.83 0.14 1.25 2.52 0.27 0.10 0.08 0.27 0.51 4.86 0.18 0.11 0.85 4.72 19.40
7.09 0.23 14.05 0.07 6.42 10.89 1.50 40.25 0.31 0.27 0.23 0.89 trace 0.27 1.13 0.23 trace trace 0.53 0.53 7.66 0.58 0.28 1.24 15.10 29.25
5.86 0.51 12.75 0.08 8.50 12.96 1.60 42.26 1.07 0.42 0.38 1.33 0.21 0.90 1.38 0.37 0.21 0.19 0.62 0.67 7.26 0.61 0.64 2.90 10.85 30.01
6.15 0.55 15.52 0.12 10.33 14.20 1.27 47.38 0.79 0.47 0.36 1.75 0.20 1.30 2.54 0.41 0.20 0.12 0.62 0.78 7.06 0.46 0.25 1.38 7.92 27.37
5.41 0.40 13.38 0.05 9.13 12.23 1.14 41.74 0.67 0.21 0.33 1.81 0.20 0.90 1.74 0.47 0.11 0.21 0.61 0.70 7.58 0.52 0.39 1.60 14.08 32.13
5.93 0.35 15.34 0.14 8.43 13.04 1.72 44.95 0.88 0.31 0.56 1.47 0.21 0.58 1.28 0.34 0.07 0.09 0.60 0.64 7.16 0.44 0.20 1.33 11.43 27.59
7.03 0.56 17.78 0.13 9.92 14.23 1.19 50.84 0.99 0.30 0.43 1.67 0.28 1.01 2.18 0.29 0.17 0.18 0.41 0.51 7.35 0.36 0.20 0.97 6.43 23.73
Belly
Flap
Light Flesh
Female Dark Flesh
0.12 6.06 0.22 0.51 0.12 15.69 0.49 0.73 3.57 0.17 0.16 27.85
0.05 6.18 0.49 0.60 0.12 15.24 0.27 0.71 2.83 0.09 0.22 26.80
0.15, 5.05 0.41 0.49 0.10 16.63 0.53 0.36 3.04 0.13 0.12 27.01
5.87 0.33 14.77 0.10 10.28 14.81 1.68 47.84 0.60 0.47 0.13 1.64 0.19 1.18 1.98 0.38 0.26 0.17 0.54 0.80 4.80 0.28 0.82 1.39 8.66 24.29
6.42 0.42 16.91 0.u4 10.65 15.04 1.92 51.40 0.70 0.55 0.07 2.02 0.21 1.39 2.30
4.44 0.40 13.97 0.10 9.18 13.35 1.61 43.05 0.80 0.33 0.43 2.08 0.31 1.16 1.91 0.36 0.09 0.13 0.45 0.49 6.04 0.30 0.43 1.06 13.57 29.94
O.lt)
0.04 0.19 0.39 0.68 5.05 0.25 0.23 1.26 6.29 21.80
----
notation for chain length, number of double bonds and position relative to methyl group -
having 47.8% monoethylenic acids in the dark flesh as against 44.7% in the latter. As there is little difference in total saturated acids the affected balance must be in the polyunsaturated acids, especially the 22 :6w3. The 1966 spring and fall (August) flesh samples differ only a little in details of the saturated acids but the totals are lower in fall fish for all three muscle samples (Tables 4 and 5). The total monoethylenic fatty acids also differ little except in the belly flap, where they are lower in fall fish. However there are interesting differences as 18:1 is lower in the spring fish samples, a factor offset by higher 20:1 and especially 22 :1. The decrease in relative proportions of the latter acids in the fall suggests deposition of fatty acids typical of small crustaceans such as copepods or euphausiids, where these two acids are of minor ilUportance (Ackman et al., 1970). These animals are kno"rn to be a principal food for mackerel in the Gulf of St. Lawrence (MacKay, 1967). Fatty acids from the triglycerides of October (1966) fish confirmed the J. lnst. Can. Techno!. Aliment. Vol. 4, No 4, 1971
I
=
iso, AI
--~
Flap
= anteiso.
results for August fish. As suggested by. the similar IV, the polyunsaturated fatty acids differed but little in spring and fall (fenlale) 1966 light and dark muscle. Essentially the proportions of 20 :5w3 and 22 :6w3 and their relationship to the minor polyunsaturated fatty acids are also typical of the euphausiid crustacean fats (Ackman et al., 1970) although 22 :6w3 is 1/2 20 :5w3 in one species of small copepods potentially included in the diet (Ackman and Hooper, 1970). The percentage of unsaponifiable nlaterials in the muscle lipid varied inversely with the total lipid. Although the composition was not investigated, occasionally thin films crystallized in a pattern similar to that of cholesterol. Small proportions of hydrocarbons are also known to occur (Dubravic and Na,var, 1969). A tocopherol level of 310 p,g/g lipid, typical of many marine oils, has been recorded for mackerel lipid (Ackman and Cormier, 1967). Analysis of fall (1959) Atlantic mackerel fillets containing 12.9% oil (Gruger et al., 1964) differed especially from the Table 5 data in 16:0 (28.2%), 172
Table 5.
Fatty
Fatty acid composition (Weight %) derived from total lipids of portions of fall 1966 (August) mackerel and of principal lipids of portions of fall 1966 (October) mackerel. The latter were analysed on open-tubular GLC column.
acid~
12:0 14:0 I and AI 15 15:0 I 16 16:0 I and AI 17 17:0 18:0 19:0 20:0 Total 14:1 15:1 16:1 17:1 18:1 19:1 20:1 22:1 24:1 Total 16:2 16:3 16:4 18:2w6
3w 6
3 w3 4 w3 20:2 w6
3w6
3 w3 4 w6 4 w3 20:5.w3 21:5 ? 22:4 w6 22:5 w 6 5w3 22:6 w3 Total ~Shorthand
Fall 1966 August Light Flesh Dark Flesh Belly Flap 0.16 5.09 0.17 0.50 0.05 18.40 0.28 0.74 3.41 0.07 0.21 29.08
0.10 5.23 0.15 0.37 0.07 18.72 0.21 0.69 3.56 0.12 0.10 29.32 0.05
0.22 5.51 0.37 0.67 0.07 17.80 0.44 0.59 3.36 0.08 0.17 29.28
6.00 0.16 20.77 0.07 5.36 7.06 0.67 40.09 0.66 0.33 0.09 1.73 0.09 1.18 1.97 0.43 0.12 0.14 0.59 0.99 8.04 0.28
5.45 0.07 19.52 0.16 6.70 9.50 1.04 42.49 0.19 0.10 0.07 1.94 0.27 1.21 2.03 0.53 0.12 0.03
6.52 0.23 21.55 0.05 6.75 7.18 1.09 43.37 0.51 0.32 0.16 2.44 0.10 1.15 2.55 0.44
0.24 1.02 13.00 30.90
0.6D
0.90 7.04 0.19 0.02 0.27 0.94 11.75 28.20
0.11 0.58 0.77 7.44 0.30 0.26 1.19 9.00 27.32
Flesh
TG
PL
TG
PL
0.19 4.96 0.47 0.87 0.13 15.07 0.48 0.88 3.89 0.23 0.16 27.33 0.05 trace 5.49 0.34 23.89 0.11 5.90 5.62 0.98 42.38 0.47 0.12 0.13 1.41 0.08 1.30 2.15 0.39 0.07 0.11 0.40 0.69 7.65 0.34 0.10 0.12 1.38 13.38 30.29
trace 0.50 0.09 0.22 0.06 20.42 0.27 0.53 7.40 0.08 0.04 29.61 0.03
0.06 4.18 0.17 0.63 0.09 16.92 0.32 0.75 3.04 0.10 0.14 26.40 0.02
1.77 0.14 9.23 0.11 1.56 1.02 0.45 14.31 0.22 0.08 0.04 1.56 0.10 0.51 0.23 0.38 0.10 0.22 1.71 0.74 10.66 0.60 0.10 0.98 1.57 36.28 56.08
5.08 0.35 16.44 0.11 7.89 12.50 2.11 44.50 0.73 0.13 0.24 1.65 0.13 1.45 2.38 0.54 0.18 0.27 0.42 0.83 6.63 0.26 0.08 0.42 1.53 11.15 29.02
0.04 0.94 0.07 0.31 0.06 14.65 0.39 0.89 13.15 0.26 0.16 30.92 0.04 0.03 1.40 0.10 14.40 0.18 3.44 1.53 0.22 21.34 0.20 0.04 0.07 2.97 0.04 1.16 0.30 0.53 0.19 0.29 1.04 1.71 7.25 0.15 0.10 0.43 1.75 29.54 47.76
notation for chain length, number of double bonds and position relative to methyl group -
20:1 (3.1 %) and 22:1 (2.8%). Possibly some material listed as 20:4 should be included in 22 :1. Mackerel oil cold pressed from fillets of fish caught off Massachusetts is comparable, insofar as detail for fatty acid composition is given, to the spring 1966 oils (Dubravik and Nawar, 1969) . .A.\driatic mackerel seem to have broadly the same composition as Atlantic fish (Montefredini and Testa, 1964). Fatty acids obtained in France by hydrolysis of mackerel (presumed to be Sco1'nber 8oombru8) flesh had an iodine value of 251.5 but the fatty acid analysis does not agree with any well-known analysis reported for triglyceride-based fats of marine teleost fishes (Ploquin et al., 1969). The oil from Soomber japoniou8 has been analysed (Ueda, 1967) and bears some resemblance to the fall (1966) analyses of Atlantic fish. It had an IV of 143.3, but 18.1 at 23.9% apparently to some extent replaced 20:1 and 22 :1. These were possibly about 4.5% each; the details are obscured for 20 :1. Mackerel which were netted at Jeddore Harbour, N.S., on September 30, 1969, were relatively small, 173
Fall 1966 October Dark Flesh
Light
Liver
I
==
TG
PL
1.16 0.05 0.22 0.08 15.27 0.28 0.40 4.40 0.03 0.04 21.93 0.01
0.52 0.05 0.28 0.07 16.33 0.71 0.43 6.62 0.11 0.10 25.22 0.01
3.42 0.50 39.55 0.20 6.59 3.86 0.95 55.08 0.74 0.03 0.02 1.6H 0.08 0.71 0.93 0.20 0.15 0.36 0.57 1.06 4.86 0.39 0.45 0.34 1.89 8.53 23.00
1.69 0.18 13.71 0.10 1.64 0.44 0.08 17.85, 0.30 0.02 0.01 0.78 0.04 0.47 0.20 0.16 0.06 0.20 2.17 1.39 12.08 0.15 0.28 0.49 3.81 34.32 56.93
iso, AI
=
anteiso.
averaging 26.6 cm in length and 191 g in weight (six fish). The headed, eviscerated bodies weighed an average of 136 g and yielded 8.6% total lipid. The average weight of livers was 3.2 g with a lipid yield of 8.9%. These small fish ("tinker mackerel") probably had spent the summer in that vicinity. Two sizes of mackerel were represented in a catch in Long Harbour, Placentia Bay, Newfoundland, landed on July 29, 1970. Six larger fish, including both ripe and spent fish of both sexes, were an average of 34.2 cm in length and 425 g in weight. Three smaller fish appeared to be immature and averaged 30.2 Clll in length as against 305.3 g in weight. The dark flesh of the large fish contained 11.1 % lipid of IV 133.5, that of the small fish 14.6% lipid of Iv'" 148.2. The corresponding light flesh samples had lipid contents of 4.6% and 7.2%. These samples represent additional years, locations and sizes of fish, but do not appear to differ materially in either lipid content or triglyceride fatty acid composition from the 1965-1966 fish from Nova Scotia which had been examined in detail. Can. Inst. Food Techno!. J. Vol. 4, No.4, 1971
Table 7.
14:0 16:0 16:1 18:0 18:1 18:2 w6 18:4w3 20:1 20:4 w6 20:5 w3 22:1 22:5 w3 22:6 w3
Principal or nutritionally important fatty acids of mackerel livers and gonads (as percent of total fatty acids) Spring 1965 Male Female Liver C'onad Liver Gonad
Spring 1966 Male Female Gonad Gonad Liver Liver
2.12 11.63 5.03 6.81 17.54 2.66 2.06 8.80 0.82 10.35 7.57 2.31 10.45
1.37 11.99 3.15 7.93 22.63 1.01 0.99 6.23 0.70 11.28 10.49 3.51 9.59
1.43 20.01 2.46 4.48 15.78 1.52 0.59 2.24 1.51 13.08 1.28 2.14 28.16
1.92 17.56 4.13 5.51 28.46 1.50 0.76 4.33 1.20 8.91 3.21 1.23 14.63
It is possible to conclude that although commercial sized mackerel show substantial variation in percent lipid, mostly in triglyceride in the light muscle, the overall fatty acid fluctuations, especially in monoethylenic fatty acid, are less extravagant than those observed in herring (Ackman and Eaton, 1965; Acknlan et al.) 1967a; Drozdowski and Ackman, 1969). The gross fatty acid compositions (Tables 4 and 5), and supplementary details (Table 6), are those typical of 111arine fish fatty acids and in fact in our experience could be taken as guides for the composition of oils or lipids of many Canadian species not as yet examined provided due allo,vance was made for the proportions of triglycerides and phospholipids. This viewpoint is treated in detail elsewhere (Ackman, 1972). The details of monoethylenic fatty acids given in Table 6 show that these also consist of mixtures of isonlers resembling those of fats in other fatty species of fish such as herring which have long been accepted as human foodstuffs (Ackman and Castell, 1966). The high proportion of the "009" isomer in the C20 and C22 nlonoethylenic acids is perhaps of interest and supports the view that these fall fish have formed these acids by chain extension from the 18 :1w9. It is more obvious in these fish than in spring fish. The calorie content will vary with the total fat fronl about 125 calories/l00 g meat for spring mackerel to about 250 for fillets from fall fish. Protein, vitamin, and mineral content data is given elsewhere (Mannan et al., 1961; Stansby and Hall, 1967; Taarland et al.) 1958). At present fish roe and livers are not eaten widely in Canada although esteemed in Europe and elsewhere. It it expected that pressure to utilize more of limited fish landings will in future lead to promotion of selected organs which are now discarded, fronl appropriate fish and shellfish species. These might be served as prepared products similar to those at present imported from Japan or Europe and marketed in Canada mostly in specialty shops. The principal fatty acids of these organs given in Table 7 COlTIplement the data recorded in Tables 1 and 2.
Acknowledgements The authors thank l\fr. R. Legendre for preparation of the French abstract. J. Inst. Can. Technol. Aliment. Vol. 4, No 4, 1971
4.19 17.07 6.95 2.33 20.71 2.04 2.20 3.80 0.56 10.64 2.97 1.09 17.43
1.64 19.49 3.69 4.07 18.42 1.46 0.69 2.49 1.31 14.18 1.72 2.35 22.49
1.58 15.73 4.47 6.35 30.09 1.16 0.48 4.34 0.94 10.36 2.82 1.83 13.11
4.49 16.06 5.94 2.70 16.64 1.41 1.30 2.66 0.89' 16.88 1.57 1.88 18.80
References Ackman, R. G. 1972. Marine lipids and fatty acids as components of the human diet. in Recent Advances in Human Nutrition, edt M. A. Crowford (SUbmitted for publication). Ackman, R. G. and Castell, J. D. 1966. Isomeric monoethylenic fatty acids in herring oil. Lipids 1 :34l. Ackman, R. G. and Cornlier, M C. 1967. a-Tocopherol in some Atlantic fish and shellfish with particular reference to liveholding without food. J. Fish. Res. Bd. Canada 24:537. Ackman, R. G. and Eaton, C. A. 1966. Some commercial Atlantic herring oils; fatty acid composition. J. Fish. Res. Bd. Canada 23:991. Ackman, R. G., Eaton, C. A. and Ke, P. J. 1967a. Canadian marine oils of low iodine value: Fatty acid composition of oils from Newfoundland turbot (Greenland halibut), certain Atlantic herring, and a sablefish. J. Fish. Res. Bd. Canada 24:2563. Ackman, R. G., Eaton, C. A., Sipos, J. C., Hooper, S. N. and Castell, J. D. 1970. Lipids and fatty acids of two species of North Atlantic krill (Meganyctiphanes norvegica and Thysanoessa inermis) and their role in the aquatic food web. J. Fish. Res. Board Canada 27 :513. Ackman, R. G. and Hooper, S. N. 1970. Analyses of fatty acids from Newfoundland copepods and sea water with remarks on the occurrence of arachidic acid. Lipids 5 :417. Ackman, R. G., Sipos, J. C. and Jangaard, P. M. 1967b. A quantitation problem in the open-tubular gas chromatography of fatty acid esters from cod liver lipids. Lipids 2:25l. Anon, 1970. Annual Statistical Review of Canadian Fisheries, Vol. 2, 1954-1969. Economics Branch, Fisheries Service, Department of Fisheries and Forestry, Ottawa, 132 pages. Bligh, E. G. and Dyer, W. J. 1959. A rapid method of total lipid extraction and purification. Can. J. Biochem. Physiol. 37 :91l. DrOZdowski, B. and Ackman, R. G. 1969. Isopropyl alcohol extraction of oil and lipids in the production of fish protein concentrate from herring. J. Amer. Oil Chem. Soc. 46:371. Dubravic, M. F. and Nawar, W. W. 1969. Effects of high-energy radiation on the lipids of fish. J. Agr. Food Chem. 17:639. Fraser, D. I., Mannan, A. and Dyer, W. J. 1961. Proximate composition of Canadian Atlantic fish. III. Sectional difference in the flesh of a species of Chondrostei, one of Chimaerae, and some miscellaneous teleosts. J. Fish. Res. Bd. Canada 18 :893-905. Gruger, E. H., Jr., Nelson, R. W. and Stansby, M. F. 1964. Fatty acid composition of oils from 21 species of marine fish, freshwater fish and shellfish. J. Amer. Oil Chem. Soc. 41 :662. Hoy, D. L. and Clark, G. M. 1967. Atlantic mackerel fishery, 18041965. U.S. Dept. Int., Bur. Comm. Fish., Fishery Leaflet 603, 9 pages. Karrick, N. L. and Thurston, C. E. 1964. Proximate composition of silver salmon. J. Agr. Food Chem. 12:282-284. MacKay, K. T. 1967. An ecological stUdy of mackerel Scomber scombrus (Linnaeus) in the coastal waters of Canada. Fish. Res. Bd. Canada, Tech. Rep. No. 31, 127 pages. Mannan, A., Fraser, D. I. and Dyer, W. J. 1961. Proximate composition of Canadian Atlantic fish. II. Mackerel, tuna and swordfish. J. Fish. Res. Bd. Canada 18: 495-499. Montefredini, A. and Testa, C. 1964. Fatty acid composition of mackerel, shad and sardine oils. Atti Soc. Ita!. Sci. Vet. 18: 546549. Ploquin, J., Souroudjieva, B. and Sparfel, L. 1969. Rev. Franc. Corps Gras. 16: 78l. ROUbal, W. T. 1963. Tuna Fatty Acids: II. Investigation of the composition of raw and processed domestic tuna. J. Amer. Oil Chem. Soc. 40: 215-218. Stansby, M. E. and Hall, A. S. 1967. Chemical composition of commercially important fish of the United States. Fishery Industrial Research 3: (4): 29-46. Taarland T., Mathieson, E., Ovsthus, O. and Braekkan, O. R. 1958. Nutritional values and vitamins of Norvegian fish and fishproducts. Tidsskrift for Hermetikindustri 54: 405-412. Ueda, T. 1967. Fatty acid composition of oils from 33 species of marine fish. J. Shimonoseki Univ. Fish. 16 (1): 1. Received June 7, 1971
174