Composition of n-3 oils from some great lakes freshwater fish

JOURNAL

OF FOODCOMPOSITlON

Composition

AND ANALYSIS

2, 13-2 1 (1989)

of n-3 Oils from Some Great Lakes Freshwater ~.KARAHADIANAND

Fish’

R.C. LINDSAY

Department of Food Science, University of Wisconsin-Madison,

Madison, Wisconsin 53706, U.S.A.

Received July 29, 1988, and in revised form February 3, 1989 Lipids from Salvelinus namaycush siscowet (siscowet lake trout), S. namaycush namaycush (lake trout), and S. fontinalus (brook trout) from the Great Lakes showed similar fatty acid profiles. The Salvelinus sp. oils contained about 4% eicosapentanenoic acid (EPA; C 20:5n3) and between 5.9 and 9.6% docosahexaenoic acid (DHA; C 22:6n3). Siscowet lake trout contained 36% fat (wet wt) and 3 1% of the lipid fraction was oleic acid while other trout contained from 7 to 10% fat of which 17-26% was oleic acid. Siscowet lake trout oil contained 26 ppm Aroclor I260 polychlorinated biphenyls (PCB), and only one-half to two-thirds of this was removed by steam deodorization. Alewife (Alosa pseudoharengus) oil contained 8.6% EPA (C 20:5n3) and 8.6% DHA (C 22:6n3). Oil rendered from Lake Michigan whitefish (Coregonus clupeqformis) offal contained 7.8% EPA (C 20:5n3) and 2.9% DHA (C 22:6n3) and less than 0. I % ppm of PCB. 0 1989 Academic Press, hc.

INTRODUCTION

Reports on the health benefits of long-chain n-3 fatty acids (Begin et al., 1985; Dyerberg et al., 1987; Kinsella, 1986; Kromhout et al., 1985; Lee et al., 1985; Phillipson et al., 1985) have stimulated interest in identifying new potential sources of n-3 oils. Marine fish oils are noted for high concentrations of n-3 fatty acids (Ackman, 1974; 1967; Gruger, 1967; Kinsella, 1987), and a variety of these are available on the world market (Barlow, 1988; Dreosti, 1967; Sand, 1967; Sone, 1967). Menhaden oil provides the largest supply of domestically produced fish oil (Bimbo, 1986), but its use in the U.S. food supply is currently pending approval by the Food and Drug Administration (Anonymous, 1987a; 1987b). Freshwater fish oils have not been utilized much even industrially except for Lake Michigan alewives (Alosa pseuduharengus). Although some freshwater fish, such as carp (Cyprianus curpio) (Kinsella, 1987) and catfish (Ictalurus punctatus) (Mustafa and Mederios, 1985), appear to contain limited concentrations of n-3 fatty acids, many freshwater fish have notable amounts of long-chain n-3 fatty acids (Ackman, 1967; Kinsella, 1987). Major supplies of marine fish oils around the world will probably provide most of the future needs, but small regional supplies could bring added economic benefits to local fisheries. Commercial fisheries of the Great Lakes have declined since early in the century because of depleted stocks and competition from sports fisheries (Francis et al., 1979). Generally, the commercial harvest is limited to those species which have little interest to the sports fishery, such as alewives, whitefish (Coregonus clupeaformis), and the siscowet lake trout (Salvelinus namaycush siscowet) that is found only in Lake Superior. Because of its fatty nature (to 48% wet wt; Thurston, 1962) and deep water I Research supported by the College of Agriculture and Life Sciences, University of Wisconsin-Madison, and the University of Wisconsin Sea Grant Institute under a grant from the National Sea Grant College Program, Federal Grant NA84A-D-0065, Project AS/A-g. 13

0889- 1575/89 $3.00 Copyright 0 1989 by Academic Press, inc. All rights of reproduction in any form reserved.

14

KARAHADIAN

AND LINDSAY

habitat (Becker, 1983) the siscowet lake trout is not prized as a sports fish. Fisheries managers have estimated that up to 2 million pounds of this fish could be harvested annually from Lake Superior (Becker, 1983). The alewife population of Lake Michigan is estimated at 1 billion kg, and currently only about 2% is harvested for fish oil and meal (Becker, 1983). The alewife harvest from Lake Michigan for oil and meal production has dropped from about 28 millions lb in 1975 to 18 million lb currently because of lower populations and their conservation as the forage base for salmon and lake trout in sports fisheries programs (Becker, 1983; Bishop and Vogel, 1975). Whitefish constitutes a significant commercial fishery in the Great Lakes, but processing facilities are not concentrated near alewife reduction facilities. As a result, disposal of offal poses a problem because municipal landfill sites are reluctant to accept fish cleaning wastes, and when they do, it is costly. Whitefish offal has been reported to contain about 15% lipid (Kinsella, 1987), and it is estimated that about 150,000 lb of oil could be recovered from whitefish processing annually. Microcontaminants, especially polychlorinated biphenyls (PCB) and DDT-derived compounds, have plagued the fisheries of the Great Lakes in modern times, but it has been claimed that these compounds can be removed from fish oils by conventional deodorization procedures (Addison and Ackman, 1974; Addison et al., 1978; Smith et al., 1968). Therefore, the purpose of this study was to determine the fatty acid composition of siscowet lake trout oil, and to compare these data to that from closely related species of lake trout found in the Great Lakes. Additionally, the n-3 compositions of lipids of alewives and whitefish offal were also determined, and the removal of PCB from siscowet oil by vacuum steam deodorizations was evaluated. MATERIALS

AND

METHODS

Samples Eight Lake Superior siscowet lake trout (S. namaycush siscowet) were obtained in April 1986 from a commercial fishery (Bodin Fisheries, Bayfield, WI), and the average length and weight were 73 cm (+3 cm) and 3.6 kg (+0.9 kg), respectively. Three Lake Superior lake trout (S. namaycush namuycush) which ranged in size from 1.3 to 3.7 kg each were also obtained. Lake Michigan brook trout (S. fontinalis) and lake trout (S. namaycush namaycush) samples (three each) from early summer capture (1986) were obtained from the Wisconsin Department of Natural Resources (DNR). Lake trout ranged from 3.7 to 6.3 kg each while brook trout ranged from 0.1 to 0.4 kg each. Two commercially dressed fresh whitefish (C. cfupeufirmis) (0.5 to 1.25 kg) were obtained from both Lake Superior (Bodin Fisheries) and Lake Michigan (Johnson Fisheries, Green Bay, WI) in the spring of 1987. Freshly captured Lake Michigan alewives were obtained from a commercial fisherman at Two Rivers, Wisconsin (September 1985). A composite ten-fish sample was used for the analysis. Whitefish offal was obtained from a commercial fish processing plant located on Lake Michigan (May 1987; Hickey Brothers, Bailey’s Harbor, WI). Preparation of Samples Whole trout and whitefish were filleted, skinned, and then minced with a grinder (5-mm plate; Hobart Mfg. Co., Kitchenaid Division, Troy, OH). Batches of fish

n-3

OILS

OF

FRESHWATER

FISH

15

minces and fatty tissues from whitefish offal were heat-rendered by first diluting the mince with water (1: l), acidifing with 1 Mphosphoric acid to pH 5.5, and then bringing the slurry to a boil for 10 min. After cooling to 45°C oil was recovered using a separatory funnel and then dried over a bed of celite/anhydrous sodium sulfate (50: 50, wt/wt; J. T. Baker Chemical Co., Jackson, TN/Amend Drug and Chemical Co., Irvington, NJ). Dried oils were held under vacuum (4 mm Hg) at 4°C prior to analysis to minimize oxidation. Steam Deodorization

of Siscowet Lake Trout Oil

Siscowet lake trout oils were steam-deodorized using an all-glass laboratory apparatus (Heide-Jensen, 1963; Karahadian, 1988). Oils were deodorized using a high temperature condition (2 10 f 5°C for 0.5 h) and a low temperature condition (100 + 5°C for 2 h) while a vacuum (4 mm Hg) was maintained and steam from aqueous 0.0 1 N acetic acid was generated. Chemical Anal.ysis Total lipids of fish were determined by the method of Bligh and Dyer ( 1956) and moisture was determined by the AOAC vacuum oven procedure (section 7.003; Horowitz, 1975). Polychlorinated biphenyls (PCB) were determined by the methods summarized by Johnson et al. (1976) and Griffitt and Craun ( 1974). Total fatty acid compositions of oils were determined by preparation of methyl esters according to the procedure of Metcalf and Schmitz (1966) using BF3-methanol (Applied Science, State College, PA). Methyl esters of the fatty acids were separated with a permanently bonded polyethylene glycol-fused silica capillary column (Supelcowax 10; Supelco, Inc., Bellefonte, PA). The column oven was temperature programmed from 50°C after holding for 1 min to 180°C at 30”C/min, and finally 2”C/ min from 180 to 250°C. Identification of fatty acid methyl esters was based upon published retention times and positions of eluting esters off of a Supelcowax 10 column (Anonymous, 1984). Peak areas were integrated on a Spectra Physics 4200 computing integrator (Spectra Physics, San Jose, CA) and concentrations of each ester were calculated as the percentage of the total area of the chromatogram. RESULTS

AND

DISCUSSION

The percentage compositions of fatty acids lipids from the Salvelinus sp. from the Great Lakes are summarized in Table I. The fatty acid profiles are somewhat similar among the fish, and the lipids contained about 4% eicosapentaenoic acid (EPA; C 20: 5n3) and from 5.9 to 9.6% docosahexaenoic acid (DHA; C 22:6n3). Total fatty acid compositions of siscowet oils extracted by solvents (Bligh and Dyer, 1956) were compared to those that were heat rendered, and it was observed that nearly identical profiles were present in each (data not shown). The most pronounced difference in fatty acid composition between the fish was observed for oleic acid (C 18: 1n9) in which the lipid of Lake Superior siscowets constituted 3 1% oleic acid compared to only 17 to 26% in the other Salvelinus sp. Genetics, environmental temperatures, and food sources are among the factors that influence the composition of fish lipids (Becker, 1983) and siscowets inhabit deepwater zones of Lake Superior where they forage on deepwater coregonids and sculpins (Eddy and Underhill, 1974). Brook trout from Lake Michigan showed the highest concentration of linoleic acid (C 18:

16

KARAHADIAN

AND TABLE

FATTY

ACID COMPOSITION

(5. Fatty

namavcush siscowet)

LINDSAY I

OF OILS FROM GREAT

(S.

namaycustl "amaycush)

LAKES TROUT

(5.

(Salve/inus

sp.)”

namavcustl "amavcush) wanb

acids

SD

c 21:5n3 c 22:5”6 c 22:5n3 c 2z:m3d c 24:1n9 Unknown

a Captured b Mean and ‘Not present d This peak e Percentage

in 1986. standard deviation calculated from three samples. in the sample or not calculated. may also contain a small amount of C 24:0. of total fatty acid = peak area/total peak area.

2n6; 5.9%, Table 1) and the lowest concentration of arachidonic acid (C 20:4n6; 1.9%, Table 1) among the samples and these fish preferentially feed on aquatic insects and crustaceans (Becker, 1983). The Great Lakes trout all contained at least 10% EPA (C 20:5n3) plus DHA (C 22: 6n3) in total lipids which indicated that all would provide good quality n-3 oils, The very fatty nature of siscowet lake trout compared to other Salvelinus sp. is indicated in the compositional data shown in Table 2. Lake Michigan lake trout are considered to be a fatty fish, but siscowet lake trout contain over three times the fat of these fish. Thus, siscowet lake trout provide an unusual local fish oil resource that potentially could be developed for high quality n-3 oil. Environmental contaminants currently associated with the Great Lakes and their accumulation in fishery products (Hicks et al., 1978; Hileman, 1988) pose possible problems in the utilization of siscowet oil for human consumption. The heat-rendered oil from the spring-harvested siscowet lake trout contained 26 ppm of Aroclor 1260 PCB (Table 3). Siscowet lake trout analyzed by the Wisconsin Department of Natural Resources in July of 1984 and 1985 contained an average of 1.2 ppm 1260 PCB in the edible tissue, and this concentration would be approximately equivalent to about 6.2 ppm in the rendered oil (L. Liebenstein, personal communication,

n-3

OILS

OF

FRESHWATER TABLE

2

COMPOSITIONAL ANALYSIS OF GREAT

Species

LAKES

Salvelinus sp.

% Composition a Moisture

Lipid (wet

Lake

17

FISH

b

weight)

Superior Siscowet Lake

Lake

lake

trout

36

45

7

71

trout

Michigan Lake

trout

Brook

11

65

4

74

trout

n Average of three fish; standard deviation less than 1.6 for each set. h Standard deviation less than 4.0 for each set.

1987). In 1984, the U.S. Food and Drug Administration imposed a maximum tolerance level of 2 ppm for PCB concentration in edible flesh (Code of Federal Regulations, 1986). Because of the tendency of these contaminants to accumulate in the lipid tissues, higher concentrations of PCB are found in larger, fattier fish than in smaller, leaner fish (Masnado, 1986). Addison and Ackman (1974) and Addison et al. (1978) have reported that processing marine oils containing PCB through degumming, alkali refining and bleaching steps did not destroy or lower the PCB content of the oils. However, they found that a process involving commercial hydrogenation and steam deodorization (250°C for 2.5 h and 7-10 mm Hg) removed all PCB from the fish oils (Addison and Ackman, 1974; Addison el al., 1978). Takeshita and Yoshida (1971) reported that deodorization of rice bran oil containing Arochlor 1254 PCB under similar conditions (230°C at 4 mm Hg for 60-90 min) was insufficient to remove the contaminants. High temperature steam deodorizations (>2OO”C) also have been shown to damage the nutri-

TABLE

1260PCB INSTEAM-DEODORIZEDSISCOWETLAKETROUT

CONCENTRATIONOFAROCHLOR

Oil

3

sample

Deodorization

Concentration

conditions

Control,

heat-rendered

Low-temperature High-temperature

(PPm)

none

deodorized deodorized

OILS”

26.0

100-C

for

2 h

21O’C

for

0.5

8.9 h

16.6

” Oil samples for all treatments were taken from a composite reservoir of oil extracted from eight fish.

18

KARAHADIAN

AND TABLE

LINDSAY 4

MAJORFATTYACID COMPOSITIONOFWHITEFISH(C clupeaformis) LIPIDSFROMTHEGREATLAKES

i-l.= “T 9.8 nr 25.3 3.4 3.4 4.2 6.0 3.1 17.7

’ Capture site not known (Kinsella, 1987). ’ Captured in the spring of 1987. Fatty acid values reported for body oils are from a composite two-fish sample. ’ Not reported.

tional quality of fish oils through induction of isomerization and polymerizations (Perula and Chang, 1988; Wijestundera et al., 1988). Vacuum deodorizations of siscowet lake trout oil at 210°C for 30 min removed less than half of the PCB (Table 3) and about two-thirds of the Aroclor 1260 PCB was removed under longer, low temperature vacuum deodorizations conditions ( 100°C for 2 h). The less rigorous processes employed here were chosen because most of the fishy flavors are removed under these conditions (Karahadian, 1988). Thus, additional studies appear to be needed to more clearly define deodorization conditions capable of removing PCB and other microcontaminants from fish oils without damaging the quality of n-3 fatty acids (Perula and Chang, 1988; Wijestundera et al., 1988). Fatty acid compositions of oils obtained from muscles of whitefish of the Great Lakes showed slight differences in the fatty acid composition depending upon capture site (Table 4). Whitefish feed on larvae and pupae of pelecypods, gastropods, and Diptera (Reckahan, 1970), and their dietary pattern may contribute to the difference between the fatty acid profiles of whitefish and lake trout (Table 1). Concentrations of EPA (C 205n3) plus DHA (C 22:6n3) in whitefish oils were higher than for lake trout species (Tables 1 and 4), and ranged from 16% to 18.2% of the total fatty acids. A literature report (Kinsella, 1987) indicates a higher level of DHA (C 22:6n3) in whitefish lipid ( 17.7%; Table 4) than was found for the Great Lakes whitefish, but the source of the fish was not reported. Since there is a strong commercial market for fresh whitefish, the lipid associated with the muscle likely would not be considered as an oil source. The fat content of whitefish offal has been reported at 15% (Kinsella, 1987), but offal from spring harvested (May) whitefish contained over 20% fat on a wet weight basis. Some differences were observed between the fatty acid composition of the offal and muscle (Table 4) and the DHA (C 22:6n3) concentration was considerably lower in the offal (2.9%).

n-3

OILS

OF

FRESHWATER TABLE

19

FISH

5

MAJOR FATTY ACID COMPOSITION OF ALEWIFE LIPID (A. aseudoharengus) FROM LAKE MICHIGAN % of Fatty

acid

total

Literaturea

lipid Lake

Michiganb

(body C 16:l

14.65

15.5

c 1a:1n9

18.15

24.1

C 18:2n6

3.72

1.8

C 18:3n3

3.56

c 20:lnllC

1.61

1.8 -d

C 20:4n6

2.42

3.6

C 20:5n3

8.22

C 22:11113~

0.43

8.6 -d

C 22:6n3

5.36

8.6

oil)

a Captured from the Great Lakes (Ackman, 1967). b Captured in September 1985. Fatty acid values reported reflect a composite IO-fish lipid sample. ‘Other isomers may be present. d Data not available.

Still, the lipids from whitefish offal contained 10.7% of EPA (C 20:5n3) plus DHA (C 22:6n3) which would be worthy of consideration for recovery. Analysis of oil from whitefish offal revealed that less than 0.1 ppm PCB was present, and this probably reflects the low concentrations of PCB found in the forage ofwhitefish (Becker, 1983). The lipid content of alewife has been reported to be as high as 19.8% of the muscle (wet wt; Sidwell, 198 l), but the sample of fall-caught alewives in the current study contained only 3.6% on a dressed fish basis. The major fatty acid profile of Lake Michigan alewife oil is presented in Table 5, and the oil contained 8.6% each of EPA (C 20:5n3) and DHA (C 22:6n3). Alewives inhabit a range of lake depths and their forage base varies, but they consume mostly zooplankton and deepwater amphipods (Morsel1 and Norden, 1968). Alewives accumulate PCB, and over 10 ppm have been encountered in Lake Michigan alewives (Hicks et al., 1978). Alewife oil is mostly used for non-food industrial purposes (Dyer, 1967), and the oil often contains over 100 ppm of PCB. Thus, utilization of Lake Michigan alewife oil as an n-3 source for human consumption will require efficient procedures for the removal of PCB and other environmental contaminants. In summary, the potential for utilizing high-fat siscowet lake trout from Lake Superior and alewife from Lake Michigan for high quality n-3 oils exists if PCB can be removed economically. However, lipids from whitefish offal could also provide a source of n-3 fish oil with limited concerns for PCB contaminants. Additional research is needed to define deodorization or other process conditions that are suitable for economic removal of PCB and other microcontaminants without damaging the nutritional quality of fish oils. ACKNOWLEDGMENTS The authors thank Dr. L. Leibenstein of the Wisconsin Department of Natural Resources for providing fish samples from Lake Michigan and historical data relating to PCB contents in selected fish. Additionally, appreciation is extended to V. Slama and S. Pritzel for assistance in sample preparation.

20

KARAHADIAN

AND LINDSAY

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n-3 OlLS OF FRESHWATER

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21

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PELURA, T. J., AND CHANG, S. S. ( 1988). The effect of deodorization time and temperature on the chemical, physical and sensory characteristics of menhaden oil. J. Amer. Oil. Chem. Sot. (abstract) 65,500. PHILLIPSON, B. E., ROTHCROCH, D. W., CONNOR, W. E., HARRIS, W. S., AND ILLINGWORTH, D. R. (1985). Reduction of plasma lipids, lipoproteins and apoproteins by dietary fish oils in patients with hypertriglyceridemia. N. Engl. J Med. 312,12 lo- 12 14. RECKAHAN, J. A. (1970). Ecology of young lake whitefish (Coregonus clupeafirmis) in South Bay, Manitoulin Island, Lake Huron. In Biology of Coregonid Fishes (C. C. Lindsey and C. S. Woods, Eds.), pp. 437-460. University of Manitoba Press, Winnipeg. SAND, G. (1967). Fish oil industry in Europe. In Fish Oils: Their Chemistry, Technology, Stability, Nutritional Properties, and Uses (M. E. Stansby, Ed.), pp. 405-42 1. AVI Publ. Co., Westport, CT. SIDWELL, V. A. (198 1). In Chemical and Nutritional Composition ofFinfishes. Whales, Crustaceans, Mollusks and their Products. NOAA Technical Memorandum, NMFS/SEC- 1 I. SMITH, K. P., POLEN, P. B., DEVRIES, D. M., AND COON, F. B. (1968). Removal of chlorinated pesticides from crude vegetable oils by simulated commercial processing procedures. J. Amer. Oil Chem. Sot. 45, 866-869.

SONE, H. ( 1967). Fish oil industry in Japan. In Fish Oils: Their Chemistry, Technology, Stability, Nutritional Properties, and Uses (M. E. Stansby, Ed.), pp. 422-421. AVI Publ. CO., Westport, CT. TAKESHITA, Y., AND YOSHIDA, H. (197 I). Rice bran oil contaminated with chlorobiphenyl. Chem. Abstr. 74,138847.

THURSTON, C. E. (1962). Physical characteristics and chemical composition of two subspecies of lake trout. J Fish Res. Board Canad. 19,39-44. WIJESTUNDERA, R. C., RATNAYAKE, W. M. N., AND ACKMAN, R. G. (1988). Some EPA artifacts in heated oils. J. Amer. Oil Chem. Sot. (abstract) 65,474.