J Sci Food Agric 1998, 77, 244È250

Lipid Composition and Palatability of CannedSardines. Inýuence of the Canning Process andStorage in Olive Oil for Five YearsBaltasar Ruiz-Roso,* Isabel Cuesta, Mercedes Perez, Elisa Borrego, LourdesPe� rez-Olleros and Gregorio Varela

Departamento de Nutricio� n, Facultad de Farmacia, Universidad Complutense, Madrid,Avda Complutense s/n, Madrid 28040, Spain

(Received 16 April 1996 ; revised version received 21 July 1997 ; accepted 22 October 1997)

Abstract : Lipid variations of canned sardines in olive oil, both quantitative andin fatty acid composition, have been studied during various stages of the canningprocess : raw sardines (RS), precooked sardines (PS), just canned sardines (CS)and sardines stored for 6 months (6MS), 12 months (12MS) and 5 years (5YS).The e†ect of maturation on the palatability of sardines has also been observed bymeans of triangle tests using a panel of 60 tasters. Our results show a signiÐcantloss of SFA in Ðsh during the canning process (C16 : 0, 273^ 6 g kg~1 of fat inRS and 169^ 11 g kg~1 of fat in CS) and a rise in MUFA (C18 : 1207 ^ 2 g kg~1 of fat in RS and 506 ^ 14 g kg~1 of fat in CS) ; PUFA showedalmost no variation. The maturation and canning processes both yielded similarqualitative modiÐcations. The palatability of the sardines was signiÐcantly higherafter 6 months of maturation than immediately after canning, and this qualitywas maintained, for at least 5 years of storage. 1998 SCI.(

J Sci Food Agric 77, 244È250 (1998)

Key words : canning ; fatty Ðsh ; olive oil ; sardine ; lipids ; palatability ; maturation

INTRODUCTION

According to data from the National Food Survey(ENNA-3 1995) Spain shares Ðrst place with Portugalin the Ðshing consumers ranking of EC countries, with adaily average intake of 76 g per day. Of this amount amajor part applies to fatty Ðsh (11 g per day), and inparticular to sardines (6É6 g per day). The role of fattyÐsh in the human diet is very important not onlybecause of its high quality proteins (Moreiras-Varelaand Ruiz-Roso 1986 ; Garcia-Arias et al 1992), but alsofor the PUFA content of its fat, particularly from then-3 family. For this reason fatty Ðsh consumption iswidely recommended for prevention and treatment ofcardiovascular disease (Kromhout et al 1985 ; Heroldand Kinsella 1986 ; Nestel 1986 ; Hearn et al 1987 ; Von

* To whom correspondence should be addressed.Contract/grant sponsor : Bernardo Alfageme SA.

Schacky 1987). However, epidemiological studies thattry to relate cardiovascular diseases (CVD) and fattyÐsh consumption have not taken into account that boththe industrial and culinary processes of these types offood can cause deep quantitative and qualitative alter-ations in fat content. Referring to this, the authorsrecently published a paper about the e†ects of deep-frying on fat intake (FI) quality, where we concludedthat FI could be markedly modiÐed by means of thisprocess (Varela and Ruiz-Roso 1992). This inÑuencecould also occur in other processes using fats such asfatty Ðsh canned in oil. In the current study we wouldlike to highlight the canning of sardines. This processconsists of two main phases : Ðrst, the open phase, inwhich the Ðsh is dried and fat is removed through theÑow of hot air ; and a second, closed phase, duringwhich the so-called coating-oil is added to the canswhich are then closed and sterilised. After this phase aninteresting, but not well known, maturation process

2441998 SCI. J Sci Food Agric 0022È5142/98/$17.50. Printed in Great Britain(

L ipid composition and palatability of canned sardines in olive oil 245

begins and continues until the cans reach the consumer.The changes in fatty acid composition through thecanning and maturation processes may also causechanges in the palatability of the canned Ðsh(Hellendoor et al 1969 ; Kramer 1986). Thus, the aim ofthe present study is to determine what the e†ects are ofthe canning and maturation processes on the fatty acidcomposition and on some organoleptic characteristicsof sardines canned in olive oil.

MATERIAL AND METHODS

Materials

Sardines (Sardina pilchardus) weighing roughly 93 g andwith an average length of 22 cm were used. They werecaught in Sada (Spain), during the month of July 1988,and refrigerated on a Ðshing boat at 3È4¡C for approx-imately 24 h. Then the Ðsh were canned in the canningfactory of Bernardo Alfagame SA (Vigo, Spain) with thesame machinery and under the same conditions that areusually employed. The treatment began by putting thesardines (nearly 120 kg) into a saturated NaCl solutionfor 6 h. After this, the anterior third, Ðn and viscerawere removed by hand, and up to 50% of the initialsample weight was lost. The remaining pieces werecanned using 105 ] 60 ] 20 mm cans (three per can).At this stage the Ðrst sample was taken to determine thelipid composition. Twenty cans were then randomlychosen. These are referred to as raw sardines (RS). TheÐsh cans were then steam cooked at 110¡C for 30 min ina continuous-system type Flash cooker, followed by adrying and degreasing process with the Ñow of hot airat 110¡C for 15 min.

Shortly after the precooking process a second sam-pling was taken : 20 randomly chosen cans (precookedsardines, PS). After precooking, 33 g of reÐned olive oil(Aceites Toledo ReÐneri� a Andaluza SA) were added toeach can by means of an automatic injection system.The fatty acid composition of this olive oil was asfollows (g kg~1 of fat) : C16 : 0 118, C16 : 1 5, C18 : 0 29,C18 : 1 773, C18 : 2 64, C18 : 3 5 and C20 : 1 6. Imme-diately after this the cans were made airtight by acontinuous-cycle machine. Once closed they were sub-mitted to a sterilisation procedure for 45 min at 115¡Cand 1É75 kg cm~2 of pressure, in a vertical steam auto-clave. Next, a shower system cooled and washed thecans. Again, 20 randomly chosen cans were sampled(just canned sardines, CS).

When the canning process Ðnished the product wasstored at room temperature for 6 months before beingreleased to the market. In these 6 months the matu-ration process takes place. After 6 months another sam-pling was done, using 20 randomly chosen cans, referredto as 6 months maturation sardines (6MS). Since thematuration process continues until the moment of con-

sumption we took another sample of 20 cans at 12months and at 5 years after being stored : 12 monthsmaturation sardines (12MS) and 5 years maturationsardines (5YS).

In an attempt to stop any further modiÐcation of Ðshcomposition, or interchange of substances between thefood and the coating oil, all the samples were imme-diately frozen at [ 40¡C once the sampling had beenperformed. After draining the coating liquids, the Ðshwere dried at 60¡C in vacuum and stored at [ 40¡C ina nitrogen atmosphere.

METHODS

Chemical analysis

The following determinations were carried out threetimes on all samples of sardines : water content byweight loss at 105¡C until constant weight ; total proteinwas determined by the Kjeldahl procedure (kjeltecautoanalyst Auto 1030, Tecator, Sweden) using a 6É25conversion factor (AOAC 1975) ; total lipid wasextracted from dried samples with petroleum ether at40È60¡C in a Soxtec System 1040 Tecator extractionUnit, with the ether extract gravimetrically evaluated ;and ash by incineration in a muffle furnace at 450È500¡C to constant weight (AOAC 1975). Fatty acidcontent was determined both in drained sardines and inthe coating oil.

Fatty acid analysis

Fish fat was extracted by a modiÐcation of the Blighand Dyer (1959) method and a modiÐcation of theFolch et al (1957) method to purify the fat extract. Thefatty acid analysis was carried out following the Met-calfe et al (1966) method, slightly modiÐed by Figueroa(1984) and Higon (1985). A Hewlett-Packard 5890-IIchromatograph with a Ñame ionisation detector andwith a steel-column packed supelcoport 2330 at 10% on100/200 Chromosorb W AW (2 m of length, 1/8 in id)was used. The carrier gas, nitrogen, at a Ñow of30 ml min~1, maintained Ñows of hydrogen at40 ml min~1 and air up to 240 ml min~1. The tem-perature of the column was maintained for 8 min at180¡C, then increased to 240¡C by 2¡C min~1, this tem-perature was maintained for 4 min. The temperature ofthe injector was 250¡C and the temperature of thedetector was 300¡C. The peak areas were measuredusing a Hewlett-Packard 7673 integrator. The fattyacids were identiÐed by comparing their relative andabsolute retention times with those of commercial stan-dards (Sigma, St Louis, USA) analysed under the sameexperimental conditions.

246 B Ruiz-Roso et al

Palatability tests

The sensory test was carried out by means of a panel oftasters. The Ðrst phase of the study was undertaken by agroup of 60 university students, neither selected nortrained. They completed a triangle test of di†erentiationand quality assessment with a hedonic scale from 0 to10 (Anzaldu� a-Morales 1994). With this method, eachtaster sat in an individual box and three complete,drained samples were given to them. Two of these werefrom the same maturation period and the third one wasfrom a di†erent period. The tasters were asked to iden-tify the di†erent samples and to assess them. The di†er-ence between just canned samples and samples with 12months of storage were identiÐed. Each taster dupli-cated the test during alternative days. From the tasterswho correctly identiÐed the di†erent samples on bothdays, seven were chosen to form the selected panel whocontinued with a second series of quality assessmentwith the same hedonic scale of the sensory attributes :appearance, texture and taste of sardines in variousmaturation stages : CS, 6MS, 12MS and 5YS.

To carry out the assessments at the same time, withthe selected sardine samples from the same productionlot, the maturation process was stopped after thecanning, with just canned sardines (CS), at 6 months ofstorage (6MS), at 12 months of storage (12MS) and at 5years of storage (5YS). Because of this the cans weredeep-frozen at [ 40¡C to inhibit Ñuid exchangebetween the Ðsh and the coating liquid.

Statistical analysis

Sardine samples were analysed in triplicate. The resultsare shown as mean values of triplicate samples andstandard deviation of mean. StudentÏs t-test was used tocompare means. The signiÐcance of the results wasestablished at P\ 0É05 level.

RESULTS AND DISCUSSION

After the precooking of sardines an important loss ofmoisture was observed (Table 1). This fact has alreadybeen referred to by other authors (Joshi and Saralaya1982 ; Gall et al 1983 ; Mustafa and Medeiros 1985 ;Moreiras-Varela and Ruiz-Roso 1986 ; Belmonte 1988).On the other hand, the sterilisation did not alter thewater content of the Ðsh, since precooking is an openprocess, but the sterilisation is done with the canalready closed, thereby limiting water loss of the Ðsh(Perez 1990).

In regard to the lipid content (Table 1) an importantfat loss took place during the precooking phase. Thefood passed from 406 ^ 8É8 in RS to 315 ^ 1É1 g kg~1

TABLE 1Determinations of water content, protein, fat and ash (g kg~1

dry matter) in raw or processed sardinesa

Sardines W ater Protein Fat Ash

RS 630^ 0É5 508^4É4 406^8É8 92^3É8PS 567^1É0 601^8É7 315^1É1 88^1É8CS 559^3É0 537^16É4 359^9É4 84^1É3

6MS 541^0É2 531^5É5 362^4É1 84^1É812MS 535^0É5 530^5É0 363^3É0 84^1É05YS 476^5É0 527^3É9 365^7É3 84 ^ 1É6

a Values are means^ standard deviations ; RS, raw sardines ;PS, precooked sardines ; CS, just canned sardines ; 6MS, 6months maturation sardines ; 5YS, 5 years maturation sard-ines.

in PS in dry matter ; reduction in water and fat contentis one of the goals of this canning phase (Meesemaeckerand Sohier 1956 ; Lema et al 1986 ; Beamonte 1988 ;Garci� a Arias 1989). However this fat loss did not havethe same e†ect on all of the sardine fatty acids (Tables 2and 3). The percentage of some, such as SFA andPUFA n-3, increased while MUFA and n-6 PUFA weremarkedly reduced. After the precooking, as we men-tioned above, the cans were Ðlled with coating oil, thenclosed and sterilised. Once the cans were cooled andwashed, a net incorporation of fat from the coating oilto the Ðsh during the sterilisation phase was observed,in accordance with Valls et al (1983) and Aubourg et al(1990). The Ðsh fat increased from 359^ 9É4 CS to315 ^ 1É1 g kg~1 PS, although it did not reach thecontent of the raw sardines (406 ^ 8É8 g kg~1). Someauthors (Seet and Duane Brown 1983 ; Garci� a Arias1989), have reported similar Ðndings. In addition, if wetake into account that, as previously mentioned, theprecooking produced an important reduction in thepercentage of MUFA, since they are abundant in oliveoil, their levels were likely to be higher in CS than inRS. n-3 PUFA and SFA were markedly less important.In relation to this, Garci� a Arias (1989) has alsoobserved that in preserved tuna the sterilisationenriches the Ðsh with the most abundant fatty acids ofthe coating oil. We veriÐed this fact as we observed thefatty acid modiÐcations of the coating oil. Thus, forinstance, the content in oleic acid changed from773 ^ 12 g kg~1 in the crude oil to 598 ^ 38 g kg~1 inthe coating oil of CS (Table 4), in agreement with theresults of Valls et al (1983), who reported an increase ofthe oleic acid content in canned olive oil sardines.

As to the storage, it produced some minor loses infood moisture. Water content decreased from 559^ 3 inCS to 541 ^ 0É2 g kg~1 in 6MS and 476 ^ 4É96 g kg~1in 5YS (Table 1). The passing of water from the Ðsh tothe coating oil is an e†ect already described by Garci� aArias (1989) in tuna. Sardine maturation did notproduce important modiÐcations in the total fat content

L ipid composition and palatability of canned sardines in olive oil 247

TABLE 2Fatty acids composition in raw, canned and stored sardines (g kg~1 of fat)a

Fatty acids RS PS CS 6MS 12MS 5Y S

C14 : 0 67^ 3 90 ^ 3 42 ^ 3 36 ^ 2 30 ^ 2 25 ^ 0É8C16 : 0 273^ 6 336 ^ 23 169 ^ 11 142 ^ 2 145 ^ 2 146 ^ 0É3C17 : 0 1^ 0É0 12 ^ 1 È È È ÈC18 : 0 35^ 1 27 ^ 2 32 ^ 2 34 ^ 1 32 ^ 2 32 ^ 0É03C19 : 0 39^ 2 21 ^ 2 È È È È

SFA 415 495 243 212 207 203

C16 : 1 53 ^ 1 65 ^ 7 34 ^ 2 29 ^ 2 34 ^ 3 39 ^ 0É06C18 : 1 n-9 207 ^ 2 109 ^ 6 506 ^ 14 555 ^ 5 523 ^ 15 481 ^ 0É2C20 : 1 n-9 35 ^ 13 40 ^ 6 14 ^ 6 8 ^ 3 È È

MUFA 295 214 554 592 557 520

C18 : 2 n-6 21 ^ 1 4 ^ 1 37 ^ 3 38 ^ 2 38 ^ 2 30 ^ 0É3C20 : 4 n-6 28 ^ 0É0 25 ^ 5 31 ^ 4 29 ^ 1 29 ^ 1 29 ^ 0É2PUFA n-6 49 29 68 67 67 68

C18 : 3 n-3 33 ^ 15 42 ^ 5 26 ^ 6 23 ^ 1 22 ^ 1 21 ^ 0É2C22 : 5 n-3 18 ^ 12 6 ^ 5 4 ^ 1 4 ^ 1 5 ^ 2 7 ^ 0É09C20 : 5 n-3 112 ^ 5 133 ^ 24 63 ^ 5 56 ^ 3 65 ^ 5 75 ^ 1É4C22 : 6 n-3 54 ^ 33 70 ^ 14 45 ^ 5 44 ^ 2 62 ^ 3 64 ^ 1É1PUFA n-3 217 251 138 127 154 167

a Abbreviations : RS, raw sardines ; PS precooking sardines ; CS, canned sardines ; 6MS, 6months maturation sardines ; 12MS, 12 months maturation sardines ; 5YS, 5 years maturationsardines.

(Table 1). These results are in accordance with theresults of other authors (Ramel et al 1971 ; Quaglia et al1976 ; Garci� a Miranda 1984 ; Garci� a Arias 1989), withdi†erent canning conditions.

During the can maturation the qualitative changescontinue occurring, although not in signiÐcant quan-tities from a nutritional point of view. Because of this,the SFA decreased from 243 g kg~1 of fat in CS to

TABLE 3Fatty acids composition in raw, canned and stored sardines (mg per 100 g of sardine)a

Fatty acids RS PS CS 6MS 12MS 5Y S

C14 : 0 1006 ^ 45 1228^ 41 665 ^ 47 598 ^ 33 506 ^ 34 478 ^ 15C16 : 0 4101 ^ 90 4583^ 314 2676 ^ 174 2359 ^ 33 2448 ^ 34 2792 ^ 6C17 : 0 15^ 0É0 164^ 14 È È È ÈC18 : 0 526 ^ 15 368^ 27 507 ^ 32 565 ^ 17 540 ^ 34 612 ^ 1C19 : 0 586 ^ 30 286^ 27 È È È È

SFA 6234 6629 3848 3522 3494 3882

C16 : 1 796 ^ 15 887^ 95 538 ^ 32 482 ^ 33 574 ^ 51 746 ^ 1C18 : 1 n-9 3110 ^ 30 1487^ 82 8011 ^ 222 9222 ^ 83 8828 ^ 253 9200 ^ 4C20 : 1 n-9 526 ^ 195 546^ 82 222 ^ 95 133 ^ 50 È È

MUFA 4432 2920 8771 9837 9402 9946

C18 : 2 n-6 315 ^ 15 55^ 14 586 ^ 47 631 ^ 33 641 ^ 34 574 ^ 6C20 : 4 n-6 421 ^ 0É0 341^ 68 491 ^ 63 482 ^ 17 490 ^ 17 555 ^ 4PUFA n-6 736 396 1077 1113 1131 1129

C18 : 3 n-3 496 ^ 225 573^ 68 412 ^ 95 382 ^ 17 371 ^ 17 402 ^ 2C22 : 5 n-3 270 ^ 180 82^ 68 63 ^ 16 66 ^ 17 84 ^ 34 134 ^ 2C20 : 5 n-3 1682 ^ 75 1814^ 327 997 ^ 79 930 ^ 50 1097 ^ 84 1434 ^ 27C22 : 6 n-3 811 ^ 496 955^ 191 712 ^ 79 7377 ^ 33 1047 ^ 51 1224 ^ 21PUFA n-3 3259 3424 2184 8755 2599 3194

a Abbreviations : RS, raw sardines ; PS precooking sardines ; CS, canned sardines ; 6MS, 6 months matu-ration sardines ; 12MS, 12 months maturation sardines ; 5YS, 5 years maturation sardines.

248 B Ruiz-Roso et al

TABLE 4Fatty acids composition in the raw and coating olive oil (g kg~1)a

Fatty acids RO OCS O6MS O12MS O5Y S

14 : 0 È 34^ 5 29^ 2 30 ^ 1 21 ^ 1É1C16 : 0 118 ^ 19 165 ^ 23 219^ 9 208 ^ 6 121 ^ 0É6C17 : 0 È È È È ÈC18 : 0 29^ 0É0 30 ^ 6 22^ 3 24 ^ 8 27 ^ 0É03C19 : 0 È È È È È

SFA 147 229 270 276 169

C16 : 1 5 ^ 0É0 35 ^ 3 22^ 3 30 ^ 2 35 ^ 0É23C18 : 1 n-9 773 ^ 12 598 ^ 38 534^ 3 533 ^ 3 598 ^ 0É3C20 : 1 n-9 6 ^ 1 12 ^ 4 16^ 1 16 ^ 1 È

MUFA 784 645 572 564 633

C18 : 2 n-6 64 ^ 9 41 ^ 2 39^ 1 37 ^ 1 39 ^ 0É3C20 : 4 n-6 È 25^ 5 12^ 3 20 ^ 2 24 ^ 0É04PUFA n-6 64 66 51 57 68

C18 : 3 n-3 5 ^ 1 19 ^ 7 22^ 1 21 ^ 1 16 ^ 0É04C22 : 5 n-3 È 2^ 1 2 ^ 0É0 2 ^ 1 4 ^ 0É2C20 : 5 n-3 È 40^ 9 50^ 1 55 ^ 2 52 ^ 0É06C22 : 6 n-3 È 18^ 4 22^ 2 22 ^ 1 32^ 1PUFA n-3 5 79 96 100 104

a Abbreviations : RO, raw oil ; OCS, oil of canned sardines ; O6MS, oil of 6 monthsmaturation sardines ; O12MS, oil of 12 months maturation sardines ; O5YS, oil of5 years maturation sardines.

203 g kg~1 in 5YS, the MUFA decreased from554 g kg~1 of fat in CS to 520 g kg~1 in 5YS, the n-6PUFA did not change and the n-3 PUFA increasedslightly (Tables 2 and 3). No important variations incoating oil were observed, although when these tookplace they had an opposite trend in respect to thosefound in the Ðsh, as Valls et al (1983) reported. There-fore, the precooking and sterilisation processes seem tobe where the larger lipid composition modiÐcationsoccurred with the canned sardines in olive oil, as Gal-lardo et al (1989) indicate.

Palatability

The triangle tests were performed by a panel of 60volunteers, neither selected nor trained, who carried outthe di†erentiation tests of canned sardines stored atroom temperature for 12 months (12MS) and justcanned sardines (CS) from the same production lot. Asa result, in 95% of the tests they were able to correctlydistinguish the just canned sardines from the ones with12 months maturation. Furthermore, the tasters alsoassessed the appearance, texture and taste signiÐcantlyhigher in the 12MS than the CS (Table 5). This outcomeindicates that the group of untrained people is able todetect sensory di†erences produced by the maturationprocess in canned sardines, and signiÐcantly they con-sider the modiÐcations as positive.

Afterwards, with a selected group of seven people, weattempted to Ðnd the optimal storage period for thispreserve, since, as quoted by Hellendoorn et al (1969)and Kramer (1986), a lengthy storage period may alterthe nutritional value and the sensory quality of thecanned foods. Di†erentiation and quality assessmenttests were performed, with maturation periods that weredi†erent but similarity designed to previous ones. Whenthese tests were performed, we found that when thetasters were given the CS and 6MS, a signiÐcantlyhigher quality value was given to the sardines stored forsix months because of their appearance, texture andtaste. The quality at 6 months was maintained withoutsigniÐcant di†erences as is shown in Table 5, in sardinesstored 12 months as well as sardines matured for 5years.

In summary, from the point of view of food lipids,canning the sardines in the olive oil produced slightquantitative modiÐcations with regards to the raw Ðsh,and very important qualitative changes in their fattyacids. There are important losses of SFA and there is anincrease in MUFA and n-6 PUFA and n-3 showedslight variations. The loses were restricted to theexchanges between the Ðsh and the coating oil. Thematuration process brought about only slight qualit-ative changes in fatty acids of canned sardines. The pal-atability of the canned sardines in olive oil, according tothe assessments of the tasters, was excellent. Gradingwas signiÐcantly higher at 6 months of maturation than

L ipid composition and palatability of canned sardines in olive oil 249

TABLE 5Sensorial testa

Maturation Number of tasters Number of Appearance T exture T astePeriods tests

Untrained panelCS 57 È 4É5 ^ 2É4 3É7 ^ 2É1 2É9 ^ 1É812MS 57 È 6É3 ^ 1É7* 6É7 ^ 1É9* 7É3 ^ 1É5*

T rained panelCS 7 14 4É9 ^ 3É7 4É5 ^ 3É2 3É3 ^ 3É46MS 7 14 7É3 ^ 2É2* 7É5 ^ 2É2* 7É4 ^ 3É7*12MS 7 14 7É3 ^ 2É6* 7É3 ^ 2É4* 7É5 ^ 2É5*5YS 7 14 7É6 ^ 2É0* 6É4 ^ 4É3* 7É3 ^ 4É6*

a Values are means^ standard deviations. CS, canned sardines ; 6MS, 6 months maturation sardines ;12MS, 12 months maturation sardines ; 5YS, 5 years maturation sardines ; * signiÐcantly di†erent(P\ 0É05) from canned sardines.

just canned, and this good sensory quality was main-tained for at least 5 years of storage.

ACKNOWLEDGEMENT

This work was supported in part by Bernardo AlfagemeSA.

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