Fatty Acids and Lipid Classes of ThreeUnderutilized Species and Changes Due to Canning

MALCOLM B. HALE and THOMAS BROWN

Introduction

The coastal herrings are, in general,small, bony fishes of the familyClupeidae which regularly occur inlarge schools and have the highestpotential yield of any fishery resourcein the west-central Atlantic Ocean andGulf of Mexico. Houde (1976) esti­!J1ated that the resource in the easternGulf alone could probably support a500,000 metric ton (t) annual yield.Several species have been utilized tosome extent as bait fish and menhad­en have been fully exploited for fishmeal, but the untapped potential ofsmall herrings and related species forfood use is great.

The coastal herrings are not suit­able for the traditional fresh or frozenmarkets because of their small size,bony structure, and readily oxidizablefat content. Several species have agood potential as canned products,however, since the bones are softened

A BSTRA CT-Canned products were pre­pared from three underutilized species that areabundant in the Gulf of Mexico: Spanish sar­dine, Sardinella aurita; thread herring, Opis­thonerna oglinurn; and chub mackerel, Scorn­ber japonicus. Proximate chemical composi­tions, fatty acid profiles, and lipid class com­positions are reported for both raw andcanned products. Results indicate that heatprocessing in sealed cans has no significant ef­fect on the fatty acid profile or lipid class com­position. The use of vegetable oil as a packingmedium, however, has major effects on theproduct fatty acid profile. Linoleic acid(18:2w6) is greatly increased and the con­centrations of long-chain polyunsaturated fat­ty acids decreases.

April-May-June 1983,45(4-6)

during heat processing and sealedcans prevent lipid oxidation duringstorage.

In recent years, there has beenmuch interest in the effect of diet onthe risk of coronary heart disease(CHD). Several studies have demon­strated that the consumption of fishor fish oils lowers serum lipid levels inboth human subjects and experimen­tal animals. Von Lossonczy et a1.(1978) showed that both serum cho­lesterol and triglycerides (triacylgly­cerols) were reduced in healthyhuman subjects by ingestion of a con­trolled diet based on mackerel. Trus­well (1978) stated, "It is firmly estab­lished that plasma total cholesterol ispositively related to the risk of subse­quent CHD." In addition, eicosapen­taenoic acid (EPA, 20:5w3), a majorfatty acid in marine fish, also protectsagainst CHD by acting as a precursorfor a prostaglandin which slows therate of blood clotting (Rawls, 1981).

Coastal herrings and other under­utilized species from southeasternU.S. coastal waters have relativelyhigh contents of the highly unsatur­ated fatty acids (HUFA) containingfive or six double bonds. Processingor storage conditions, however, couldpotentially result in undesirablechanges to these labile compounds.

Malcolm B. Hale and Thomas Brown are withthe Charleston Laboratory, Southeast Fish­eries Center, National Marine Fisheries Ser­vice, NOAA, P.O. Box 12607, Charleston, SC29412'{)607. This paper is Contribution No.83-30C, Southeast Fisheries Center.

Although the effects of frozen storageon fatty acid composition of fish hasbeen widely studied and reported, theeffects of processing in general andcanning in particular are not wellknown. Dudek et a1. (1981) reportedfatty acid data on six seasonal sampleseach of Atlantic mackerel and sock­eye salmon. Their data indicated thatneither canning, broiling, baking, normicrowave cooking had a significanteffect on total polyunsaturated fattyacids (PUFA) or the five and sixdouble-bonded HUFA. Giddings andHill (1975) heat processed blue crabfor 10 minutes at 121 DC and foundthat PUFA losses were not excessiveand changes in lipid fractions wereslight.

In this paper we present fatty acid,lipid class, and proximate composi­tion data on some abundant but gen­erally unfamiliar species and indicatewhether nutritionally desirable poly­unsaturated fatty acids are affected bythe canning process.

Materials and Methods

The fish samples used for the pri­mary study were collected in May andJune 1982, from the vicinity of Pana­ma City, Fla. Spanish sardines, Sardi­nella aurita, and chub mackerel,Scomber japonicus, were harvestedby beach seine; thread herring, Opis­thonema oglinum, was harvested bypurse seine. Samples were frozen intoice blocks in polyethylene containersat the Southeast Fisheries Center'sPanama City Laboratory and latertransported to the SEFC Charleston

45

Table 1.-Size data for whole fish and proxlmale chemical compositions for dressed,H&G fish, both raw and canned.

Proximate composition (dressed, H&G)

Raw Canned Raw Canned Raw Canned

75.41 69.63 75.22 70.81 73.73 69.7720.09 24.52 2005 23.21 21.08 24.79

3.22 4.21 2.71 3.41 3.07 3.301.75 1.90 304 3.21 2.66 3.03

matic print-out of temperatures andcomputed Fo values at 2-minute inter­vals. Samples for chemical analysisconsisted of the drained solids con­tents from the individual cans forwhich the specified Fo values weredetermined.

Spanish sardines, harvested in Sep­tember 1981, from the vicinity of PortSt. Joe, Fla., were canned in an earlierprocessing study. The dressed fishwere heat processed to the normallevel (Fo = 12) in two groups: I) Witha 2 percent brine packing medium and2) with soybean oil as a packingmedium. Raw dressed samples anddrained solids from each cannedproduct were comminuted and ana­lyzed for proximate chemical compo­sitions and fatty acid profiles.

Protein, moisture, and ash contentswere determined by AOAC methods(AOAC, 1975) and the lipid contentwas determined by a chloroform­methanol extraction method (Smith etal., 1964).

Fatty acid methyl esters were pre­pared from extracted lipids by themethod of Metcalfe and Schmitz(1961) and were analyzed with a Hew­lett-Packard 5830A gas chromato­graph equipped with a 50 m flexiblefused silica capillary column coatedwith Carbowax 20-M. Separation wasisothermal at 210 0C with injector anddetector at 300 0c. The individual fat­ty acid esters were identified by meansof a computer program containingequivalent chain length (ECL) valuesof authentic standards and those ofesters of cod liver oil (Ackman and

78.8± 13.518.8 ± 0.77

Chub mackerel

108.4± 12.618.2± 0.56

Thread herring

Size data (whole fish)

Burgher, 1965).Lipid classes were quantified using

an automated system of thin layerchromatography (TLC) with flameionization detection (Iatroscan Lab­oratories, Tokyo, Japan) of the typedescribed by Sipos and Ackman(1978). Type S (II) chromarods werespotted with 10-20 JAg of lipid dis­solved in heptane:chloroform (1: 1 byvolume) and developed for 30 minutesin hexane:diethylether:acetic acid (85:15:0.02) to separate triglycerides, freefatty acids, sterols, and total polarlipids. Detector peaks were quantifiedwith a Hewlett-Packard 3390A re­porting integrator.

Results and Discussion

Length, weight, and proximatecomposition data for the lots of Span­ish sardine, thread herring, and chubmackerel used in this study are listedin Table 1. Both protein and lipidconcentrations increase during can­ning due to moisture losses. Relativeto other fish, these species rate high inprotein and moderate in fat content.

The major fatty acids, as deter­mined for raw and canned samples,are listed in Table 2 for Spanish sar­dine, Table 3 for thread herring, andTable 4 for chub mackerel. The 16:0and 22:6w3 fatty acids predominate inall three species. There are minor vari­ations in the analytical results for in­dividual fatty acids, but no definitepattern is apparent. The oxidation offish lipids normally results in a de­crease in the polyunsaturated fattyacids (PUFA) and particularly those

71.5± 23.816.9± 1.7

Spanish sardine

Moisture (%)Protein (%)Lipid (%)Ash (%)

Mean weight (g ± SO)Mean length (em ± SO)

Item

'Mention of trade names or commercial firmsdoes not imply endorsement by the NationalMarine Fisheries Service. NOAA.

Laboratory in Styrofoam 1 boxes. Onarrival, the plastic containers weresealed in Cryovac bags and stored at- 30 °C until processed (within 2weeks).

The individual fish were separatedfrom ice blocks in cold tap water afterpartial thawing in a chilled roomovernight. Length and weightmeasurements were made on a repre­sentative sample of each lot. A sub­sample of approximately 500 g wasdressed, comminuted in a food pro­cessor, sealed in plastic sample cupsand frozen for later analysis.

Fish for processing were washedafter removal of heads, tails, and vis­cera. The dressed fish were immersedin a 60 degree brine (15.8 percentNaCl) for 15 minutes, drained, lightlyrinsed, and refrigerated for 1-2 hoursbefore packing. The dressed threadherring and chub mackerel werepacked into 307 x 409 (No.2) cansand the Spanish sardines were cut intochunks and packed into 307 x 113(No. \12 tuna) cans. Needle-type cop­per-constantan thermocouples werecentered in several cans in each runusing Ecklund receptacles and con­nectors. The packed fish were steamprecooked to a temperature of about190 OF (88 0C). Free liquid wasdrained from the cans and a hot 2 per­cent brine was added. Lids were ap­plied to the cans and sealed with aRooney can sealer. Cans of each spe­cies were processed in two batches in aRDTI-3 steam retort (Dixie CannerEquipment Co.). One batch was pro­cessed to the normal sterilization level(Fo = about 12) and the second batchto an Fo value (total heat exposure)about 50 percent greater. The Fo valueis a measure of total heat exposure atthe center of the can, including heat­up, processing, and cool-down. An Fovalue of 12 indicates a degree of steri­lization equivalent to that obtainedduring 12 minutes at a constant 250°F(121°C). The thermocouples insidethe cans were connected to a data log­ger (Kaye Instrument Co.) for auto-

46 April-May-June 1983,45(4-6)

Table 2.--MaJor fally acids of rsw snd canned Spanish Tsble 3.-MsJor fslly sclds of raw and csnned thread Table 4.-Major fslly acids of raw and canned chubsardines, Sard/nelfa aurlta (weight percent composl- herring, Oplsthonema og/lnum (weight percent com- mackerel, Scomber japonicus (weight percent com-

tlon). position). position).

Sample form Sample form Sample form

Canned Canned Canned Canned Canned CannedFatty acid Raw (Fe ~ 13.3) (Fe = 17.7) Fatty acid Raw (Fe = 12.1) (Fe ~ 17.3) Fatty acid Raw (Fe = 13.3) (Fe - 18.8)

14:0 3.9 3.5 4.1 14:0 5.7 4.6 5.1 14:0 2.8 2.3 2.8

16:0 22.2 21.8 22.8 16:0 23.5 23.5 23.0 16:0 185 17.3 17.6

17:0 1.6 1.5 1.5 17:0 1.9 1.8 1.8 17:0 1.6 1.8 1.7

18:0 75 7.7 7.3 18:0 7.8 7.8 7.5 18:0 8.4 9.4 8.3

16:1 5.7 5.4 6.1 16:1 5.8 5.2 5.0 16:1 3.9 3.6 4.0

18:1 11.3 10.2 11.4 18:1 11.0 9.7 9.6 18:1 14.5 12.1 13.7

20:1 1.3 1.2 1.1 20:1 2.0 1.8 1.6 20:1 27 2.4 2.7

22:1 0.1 0.1 22:1 01 0.2 0.2 22:1 0.7 0.7 0.8

18:2w6 1.2 1.3 1.4 18:2w6 1.7 1.7 1.9 18:2w6 1.4 1.3 1.4

18:3w3 0.7 0.8 0.8 18:3w3 0.7 0.8 0.9 18:3w3 0.7 0.6 0.8

18:4w3 0.7 0.6 0.8 18:4w3 0.5 0.6 0.6 18:4w3 0.6 0.4 0.6

20:4w6 18 1.9 1.8 20:4w6 3.1 3.2 3.7 20:4w6 3.2 4.1 3.2

20:5w3 8.1 7.8 9.4 20:5w3 6.7 6.9 6.7 20:5w3 5.3 5.4 5.5

22:5w6 1.2 1.4 1.2 22:5w6 1.3 1.5 1.7 22:5w6 2.2 2.8 2.1

22:5w3 1.4 1.2 1.3 22:5w3 1.9 1.6 1.6 22:5w3 2.7 3.0 2.822:003 17.2 19.3 20.6 22:003 21.1 24.1 22.2

22:6w3 227 25.1 22.1Total saturated 43.2 42.0 41.3 Total saturated 34.8 342 33.9

Total saturated 37.7 37.3 390 Total monoenes 19.2 17.5 16.5 Total monoenes 22.5 19.0 22.2

Total monoenes 19.4 17.8 19.5 Total PUFA 37.6 40.5 422 Total PUFA 42.7 46.9 44.0

Total PUFA 42.9 44.9 41.6 Total HUFA 27.7 29.5 30.6 Total HUFA 31.3 35.3 326

Total HUFA 33.6 35.6 33.9

Table e.-Lipid class composition of raw and canned Table 7.-Lipld class composition of raw and cannedSpanish sardines. thread herring.

Table 5.-Effect of packing media on concentrations oftotal11plds and selected fally acids for canned Spanishsardines.

Sample form Sample formSample

Raw. headed Canned in Canned inItem and gutted 20/0 brine soybean oil

PercentTotal lipids 1.3 2.05 9.64

16:018:018:118:2w620:5w322:003

Fatty acids (% of total)25.18 25.38

8.09 8.489.71 11.741.06 1.324.86 4.29

29.46 25.50

13.815.04

21.4243.50

0.844.34

Canned Canned Canned CannedLipid class Raw (Fe = 13.3) (Fe = 17.7) Lipid class Raw (Fe = 12.1) (Fe = 17.3)

Percent of total Percent of totalTriglycerides 67 55 66 Triglycerides 61 65 61Free fany acids 7 7 5 Free fany acids 4 4 5Sterols 2 3 2 Sterols 2 3 4Polar lipids 22 35 26 Polar lipids 32 28 31Unidentified 2 Unidentified 1

Table a.-lipid class composition of raw and eannedchub mackerel.

Sample form

Lipid class RawCanned

(Fe ~ 13.3)Canned

(Fe = 18.8)

tern. Triglycerides predominate withpolar lipids a strong second. An ap­parent shift from triglycerides topolar lipids was indicated by analysesof two of the canned samples. Thisshift did not show up in the cor­responding samples canned at higher

with five or six double bonds(HUFA). However, neither docosa­hexaenoic acid (22:6w3) nor otherHUFA showed any consistent patternof change due to heat processing inthis study.

Shown in Table 5 is the effect thatpacking media can have on the fattyacid profiles of canned fish. Lipidcontent and selected fatty acids arelisted for the Spanish sardines har­vested in September 1981. Headedand gutted (H&G) fish were analyzedboth raw and as the drained solidsafter canning in either 2 percent brine

or in soybean oil. Fat content of theseSpanish sardines was low, and a sig­nificant amount of the soybean oilwas absorbed. Consequently, the fat­ty acid profJle showed a much higherlevel of l8:2w6 and much lower22:6w3, since soybean oil containsabout 65 percent 18:2 and no 22:6w3at all.

The lipid class compositions as de­termined by the automated TLC sys­tem, for Spanish sardine, thread her­ring, and chub mackerel appear inTables 6, 7, and 8, respectively. Allthe raw samples have a similar pat-

TriglyceridesFree fany acidsSterolsPolar lipidsUnidentified

6462

27

Percent of total51 65

6 54 2

40 28

April-May-June 1983.45(4-6) 47

Fo values, however, and was probablyan artifact.

Conclusions

Lipid characteristics of thesesamples of Spanish sardines, threadherring, and chub mackerel are fairlysimilar, with relatively high levels ofhighly unsaturated fatty acids and apredominance of triglycerides as alipid class. No significant changes inPUFA concentrations or lipid classdistributions due to heat processing insealed cans were demonstrated. Theuse of oil as a packing medium canhave great effects on the lipid contentand fatty acid proftle of the finalproduct. The positive medical benefitsof the highly unsaturated fatty acidscontained in marine lipids could bemore fully realized with a fish oilpacking medium rather than vege­table oils. The present food regula­tions would probably limit usage to

48

oil recovered from precooking of thesame species, however.

Acknowledgments

We thank Gloria Seaborn for per­forming the lipid class analyses, JimBonnet for the proximate composi­tion data, Rick Dufresne (PanamaCity) for collecting the fish, and JohnGoodwin for assistance in processingand sample preparation.

Literature Cited

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AOAC. 1975. Official methods of analysis ofthe Association of Official Anal. Chern.12th ed. Assoc. Off. Analytical Chern.,Wash. D.C.

Dudek, J. A., B. A. Behl, E. R. Elkins, Jr.,R. E. Hagen and H. B. Chin. 1981. Deter­mination of effects of processing and cook­ing on the nutrient composition of selectedseafoods. Natl. Food Processors Assoc.,

Wash., D.C.Giddings, G. G., and L. H. Hill. 1975. Pro­

cessing effects on the lipid fractions andprincipal fatty acids of blue crab(Callinectes sapidus) muscle. J. Food Sci.40: 1127-1129.

Houde, E. D. 1976. Abundance and potentialfor fisheries development of some sardine­like fishes in the eastern Gulf of Mexico.Proc. Gulf Caribb. Fish. Inst. 28:73-82.

Metcalfe, L. D., and A. A. Schmitz. 1961. Therapid preparation of fatty acid esters forgas chromatographic analysis. Anal.Chern. 33:363-364.

Rawls, R. 1981. Fatly acid source a factor inheart disease. Chern. & Eng. News 59(6):24 (Feb. 9).

Sipos, J. c., and R. G. Ackman. 1978. Auto­mated and rapid quantitative analysis oflipids with chromarods. J. Chromatogr.Sci. 16:443-447.

Smith, P., Jr., M. E. Ambrose, and G. M.Knobl, Jr. 1964. Improved rapid methodfor determining total lipids in fish meal.Commer. Fish. Rev. 26(7):1-5.

Truswell, A. S. 1978. Diet and plasma lipids­a reappraisal. Am. J. Clin. Nutr. 31:977­998.

Von Lossonczy, T. 0., A. Ruiter, H. C.Bronsgeest-Schoute, C. M. Van Gent, andR. J. J. Hermus. 1978. The effect of a fishdiet on serum lipids in healthy human sub­jects. Am. J. Clin. Nutr. 31:1340-1346.

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