Effects of Various Fat Sources, α-Tocopheryl Acetate, and Ascorbic AcidSupplements on Fatty Acid Composition and α-Tocopherol Content

in Raw and Vacuum-Packed, Cooked Dark Chicken Meat

R. Bou,*1 S. Grimpa,* F. Guardiola,* A. C. Barroeta,† and R. Codony*

*Nutrition and Food Science Department-CeRTA, Faculty of Pharmacy, University of Barcelona, Av. Joan XXIII s/n.,08028 Barcelona, Spain; and †Departament de Ciencia Animal i dels Aliments, Facultat de Veterinaria,

Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain

ABSTRACT A factorial design was used to study theeffects of dietary fat sources (beef tallow, fresh and oxi-dized sunflower oils, and linseed oil), α-tocopheryl ace-tate (0 and 225 mg/kg), and ascorbic acid (0 and 110 mg/kg) supplementation on fatty acid composition, as wellas on fat and α-tocopherol content in vacuum-packedraw and cooked meat stored at −20°C. Raw meat fattyacid composition was affected by dietary fat sources andtocopheryl acetate supplementation. After cooking, meatcomposition was only affected by dietary fat sources.Birds fed linseed oil yielded meat rich in n-3 fatty acids,especially linolenic acid, which provides about 20% of

Key words: chicken meat, nutritional value, fat source, tocopheryl acetate supplementation,ascorbic acid supplementation

2006 Poultry Science 85:1472–1481

INTRODUCTION

Various studies have attempted to enrich poultry meatand eggs in 20:5n-3 (eicosapentaenoic acid; EPA) and22:6n-3 (docosahexaenoic acid; DHA), because these fattyacids help prevent cardiovascular disease (Kinsella et al.,1990; Knapp, 1991; Hargis and van Elswyk, 1993). How-ever, meat rich in these fatty acids presents several prob-lems related to oxidation susceptibility and sensory char-acteristics (Hargis and van Elswyk, 1993; Wood and En-ser, 1997).

The precursor of EPA and DHA is the 18:3n-3 (linolenicacid; LNA). Some vegetable sources are rich in LNA andare thus useful for enriching chicken meat with this fattyacid, as well as with their derivatives, EPA and DHA(Ajuyah et al., 1993; Lopez-Ferrer et al., 1999). Other vege-table sources rich in 18:2n-6 (linoleic acid; LA), the n-6precursor of arachidonic acid, also play an important rolein human nutrition. In fact, adequate intakes for bothprecursors have been set (Food and Nutrition Board,

2006 Poultry Science Association Inc.Received November 28, 2005.Accepted March 13, 2006.1Corresponding author: ricard_bou@ub.edu

1472

the adequate intake for this fatty acid. Birds fed sunfloweror oxidized sunflower oil produced meat rich in n-6 fattyacids, whereas those fed beef tallow resulted in meat richin saturated and monounsaturated fatty acids. Raw andcooked dark chicken meat α-tocopherol content was onlyaffected by tocopherol supplementation. Supplementa-tion with α-tocopheryl acetate led to α-tocopherol–en-riched meat, which provides about 25% of the recom-mended dietary allowance. Moreover, this content in vac-uum-packed samples was not modified even after 7 moof storage at −20°C.

2005) and a LA:LNA ratio of 5:1 to 10:1 is recommendedfor human nutrition (Food and Agriculture Organizationand World Health Organization, 1994).

However, polyunsaturated fatty acids (PUFA) areprone to oxidation, and their oxidation products are ab-sorbed by the intestine, with deleterious effects (Chow,1992; Kubow, 1993; Grootveld et al., 1998; Cohn, 2002).Despite this, birds fed discarded frying fats and oils didnot show any detrimental effects (Mahungu et al., 1999;Billek, 2000). Nevertheless, meat from slightly growthdepressed chickens, resulting from oxidized oil consump-tion, showed changes in fatty acid composition and de-creased α-tocopherol content (Sheehy et al., 1993; Engberget al., 1996; Jensen et al., 1997). In addition, birds fedoxidized oils recorded higher susceptibility to oxidationin raw (Sheehy et al., 1993; Galvin et al., 1997; Jensen etal., 1997) and cooked (Galvin et al., 1997; Jensen et al.,1997) dark chicken meat.

Related to these factors, dietary α-tocopheryl acetate(α-TA) supplementation in chickens yielded meat withincreased oxidation stability and α-tocopherol content(Lin et al., 1989; Jensen et al., 1998; Surai and Sparks,2000) that could overcome the prooxidizing effects ofoxidized oils (Sheehy et al., 1993; Galvin et al., 1997).Therefore, α-TA supplementation prevents lipid oxida-tion and increases meat nutritional value.

INFLUENCE OF DIETARY FAT SOURCES AND SUPPLEMENTS ON CHICKEN MEAT 1473

On the other hand, ascorbic acid (ASC) is an essentialnutrient in poultry when birds are subjected to stress(Pardue and Thaxton, 1986). Indeed, ASC supplementa-tion is controversial, because, depending on the concen-tration, it can act either as an antioxidant or as a prooxi-dant in muscle foods (Decker and Xu, 1998). Furthermore,low concentrations of ASC in meat lead to prooxidanteffects by reducing free-transition metals such as Fe (III)or Cu (II) to lower valence states [i.e., Fe (II) and Cu (I)],whereby the catalyst is more active in decomposing lipidhydroperoxides to free radicals. In contrast, ASC at highconcentrations shows antioxidant effects due to its abilityto scavenge oxygen and lipid free radicals (Decker andXu, 1998; Frankel, 1998). Thus, because ASC and otherantioxidants can have synergistic effects, oxidation sus-ceptibility may be reduced as a result of ASC supplemen-tation. In accordance with this, Aydemir et al. (2000) re-ported increased glutathione peroxidase activity and low-ered oxidation in erythrocytes from chickens fed ASCsupplements. However, several authors reported no effecton α-tocopherol or oxidative stability in meat from chick-ens fed this supplement (King et al., 1995; Whitehead andKeller, 2003).

The aim of this study was to use a factorial design toassess the effects of different types of fat sources, α-TA,and ASC supplements and their interactions on bird pro-ductive responses, fatty acid composition, fat content,and α-tocopherol content either in raw or cooked darkchicken meat.

MATERIALS AND METHODS

Experimental Design

The experiment received prior approval from the Ani-mal Care and Use Committee of the Universitat Auto-noma de Barcelona. Birds were reared and slaughteredin compliance with national regulations.

A 4 × 2 × 2 factorial design was planned and conductedin triplicate to study the influence of various dietary fac-tors (4 types of fat sources and 2 levels of α-TA and ASCsupplementation) on BW, BW gain from 22 to 57 d, feedconversion ratio from 22 to 57 d, carcass yield, bonelessleg yield, fatty acid composition, fat content, and α-to-copherol content in either raw or cooked dark chickenmeat after various periods of storage at −20°C.

The effects of these dietary factors on TBA values, lipidhydroperoxide and cholesterol oxidation products con-tent, and sensory analysis have been discussed in previ-ous works (Bou et al., 2001; Grau et al., 2001a,b).

Dietary Treatments and Birds

Sixteen isocaloric dietary treatments were preparedfrom a basal diet (Table 1) by the combination of 4 fatsources [Caila i Pares, S.A., Barcelona, Spain; beef tallow(BT), sunflower oil (SO), oxidized sunflower oil (OSO),and linseed oil (LO)] added at 6%, 2 α-TA supplements(Rovimix E-50, Hoffmann-La Roche Ltd., Basel, Switzer-

Table 1. Ingredients and composition of the basal diet

Ingredients, %

Corn 30.0Corn germ meal 18.4Soybean meat, 44% CP 17.4Sorghum 10.0Sunflower meal 8.0Barley 5.8Rye 5.0Beef tallow 0.1Calcium carbonate 1.9Dicalcium phosphate 1.4Hydrated magnesium silicate 1.0Salt 0.3Sodium bicarbonate 0.1Trace mineral-vitamin mix1 0.5Calculated composition

DM 88.2CP 16.0Crude fat 4.1Crude fiber 5.1Ash 7.4Metabolizable energy, kcal/kg 2,750

1Did not include all-rac-α-tocopheryl acetate.

land; 0 or 225 mg/kg of feed), and 2 ASC supplements(Rovimix C, Hoffmann-La Roche Ltd.; 0 or 110 mg/kg offeed). Unrefined SO, of which the specific absorbances at232 (K232) and 270 nm (K270) were 2.87 and 0.25, respec-tively, was oxidized by heating it in a fryer for 12 hat 160°C and then leaving the oil in the fryer at roomtemperature for 6 d (K232 = 4.40; K270 = 0.83).

Two hundred forty female broiler chicks (Ross, 1 d old)were fed a control diet for 6 d. One-wk-old birds wererandomly placed in 48 pens (5 birds per pen). Dietarytreatments were randomly distributed; 3 pens were as-signed to each treatment, and broiler chickens were fedad libitum for 50 d.

Sample Preparation

Broiler chickens (57 d old) were leg-ringed and slaugh-tered according to commercial procedures (Avıcola MariaS.A. slaughterhouse, Begur, Spain). Carcasses were trans-ported to the processing plant (Cuit’s, Cassa de la Selva,Spain) and stored for 3 d at 4°C in a walk-in cooler. Legswith skin from each pen were divided into 2 groups. Onegroup of legs was hand-deboned, ground, and vacuum-packed in high-barrier multilayer bags and then storedat −20°C for various periods. The other group of 5 legswas hand-deboned, vacuum-packed in polyamide andpolyethylene bags and cooked at 80°C for 35 min in apressure cooker. Thereafter, cooked legs plus their exu-dates were ground, vacuum-packed in polyamide andpolyethylene bags, and stored at −20°C. The oxygen per-meability of all bags was 50 cm3�cm−2�bar�24 h (DIN stan-dard 53380; 23°C).

Reagents and Standards

Butylated hydroxytoluene, pyrogallol, and all-rac-α-to-copherol were obtained from Sigma (St. Louis, MO). The

BOU ET AL.1474

methanol and ethanol (96%) used in α-tocopherol analysiswere of HPLC grade. Extraction reagents for fatty acidand fat content determination were of American Chemi-cal Society grade.

Determination of α-Tocopherol

Two grams of a sample (legs with skin) were homoge-nized using a polytron homogenizer (model PT 2000,Kinematica, Lucerne, Switzerland) for 30 s at 19,800 rpmwith 5 mL of absolute ethanol containing 1% pyrogallol(wt/vol) and 0.012% butylated hydroxytoluene (wt/vol).Ten milliliters of 1.6 N of methanolic KOH was thenadded, and saponification was carried out at 70°C for 30min. Nonsaponifiables were then extracted with petro-leum ether and filtered through a 0.45-�m Teflon mem-brane. After solvent evaporation under a nitrogen streamat 30°C, the residue was redissolved in 96% ethanol. Chro-matographic separation of this solution was performedusing a liquid chromatograph (HP series 1100, Hewlett-Packard GmbH, Waldbronn, Germany ) equipped witha manual injector (model 7725i, Rheodyne, Cotati, CA)featuring a loop volume of 20 �L and a column (25 ×0.46 cm) packed with 5 �m − 80 A Extrasil ODS2 and aprecolumn (1 × 0.4 cm) packed with 5 �m − 100 A Kro-masil ODS (HPLC column and precolumn, Teknokroma,Sant Cugat del Valles, Spain). Sample compounds wereisocratically eluted with methanol and detected througha fluorescence detector (model 1046A, Hewlett-PackardGmbH; excitation and emission wavelengths of 288 and330 nm, respectively). Alpha-tocopherol content was de-termined by means of the recovery applied and an experi-mental calibration curve, using all-rac-α-tocopherol as anexternal standard, ranging from 0 to 50 �g/mL.

Fat Extraction and Fatty Acid Composition

Samples (1.5 g) of milled feed or meat (cooked or rawdark chicken meat plus skin) were weighed in 32 × 210-mm tubes, with 1.5 mL of 0.1% aqueous EDTA was imme-diately added. Subsequently, 20 mL of chloroform/meth-anol (2:1, vol/vol) was added, and the mixture was ho-mogenized for 40 s at 19,800 rpm using a polytron homog-enizer (model PT 2000, Kinematica). Extracts were filteredthrough filter paper (no. 1, Whatman plc, Middlesex, UK)into 50-mL screw-capped tubes, and the residues werereextracted twice with the same solvent: first with 7 mL(30 s at 19,800 rpm) and then with 5 mL (10 s at 19,800rpm). Ten milliliters of water was then added to thesetubes, and they were stoppered and shaken for 30 s beforebeing centrifuged for 20 min at 500 × g. The chloroformphase was filtered through anhydrous sodium sulfateusing Whatman filter paper, and then washed twice with5 mL of chloroform. The lipid extract obtained was con-centrated to 1 mL in a vacuum rotary evaporator at 35°C,and the rest of the solvent was removed in a light nitrogenstream, with the flask then stored in a vacuum desiccator(10 mm Hg overnight). Fatty acid methyl esters were

Table 2. Birds’ BW, BW gain, feed conversion ratio, and leg yield1

BW gain Feedfrom 22 conversion Leg

BW to 57 d ratio from yield3

(kg) (kg) 22 to 57 d2 (%)

Fat source4

BT 1,938 1,527 2.74 9.1SO 1,861 1,468 2.82 8.9OSO 1,852 1,483 2.90 8.8LO 1,833 1,398 2.83 9.0

α-TA5 supplementation0 mg/kg 1,874 1,463 2.80 9.0225 mg/kg 1,867 1,476 2.84 8.8

ASC6 supplementation0 mg/kg 1,885 1,459 2.82 9.0100 mg/kg 1,856 1,480 2.83 8.9

Global SEM 0.016 13 0.058 0.077

1Values in this table correspond to least-squares means obtained frommultifactor ANOVA (n = 48).

2Feed intake (kg)/BW (kg).3Boneless leg weight expressed on a BW basis.4BT = beef tallow; SO = sunflower oil; OSO = oxidized sunflower oil;

LO = linseed oil.5α-TA = α-tocopheryl acetate.6ASC = ascorbic acid.

prepared from the extracted lipid fraction and determinedfollowing the method described by Guardiola et al. (1994).

Statistical Analyses

To determine whether the dietary factors and their in-teractions affected water and fat content in raw andcooked meat and bird productive responses, a multifactorANOVA was carried out.

In addition, to determine whether the dietary factorsstudied affected raw and cooked fatty acid composition,a multifactor ANOVA was performed. Furthermore, forsubsets of each dietary factor (4 fat sources, 2 α-TA sup-plements, and 2 ASC supplements), various 1-way AN-OVA were carried out to study whether cooking affectedfatty acid composition.

A multifactor ANOVA was carried out to determinewhether the dietary factors and their interactions affectedα-tocopherol content in raw and cooked meat. Further-more, by taking each dietary factor into consideration, 1-way ANOVA was conducted to study whether cookingaffected meat α-tocopherol content at either storage time.In addition, by considering each dietary factor, 1-wayANOVA was carried out to study whether storage timeaffected both raw and cooked meat α-tocopherol content.

Interactions among more than 2 factors were ignoredand P ≤ 0.05 was considered significant. Least squaresmeans for the main factors with a significant effect wereseparated using Scheffe’s test.

RESULTS AND DISCUSSION

Bird Performance and CarcassCharacteristics

Chicken BW, BW gain, feed conversion ratio, and bone-less leg yield were not affected by any of the dietary

INFLUENCE OF DIETARY FAT SOURCES AND SUPPLEMENTS ON CHICKEN MEAT 1475

Table 3. Fatty acid composition (expressed as area normalization in a percentage) of the experimental feeds1

OxidizedBeef Sunflower sunflower Linseed

Fatty acid tallow oil oil oil

12:0 ND ND ND ND14:0 2.354 0.137 0.153 0.15516:0 21.711 8.835 9.478 8.98218:0 14.853 3.842 4.208 3.40220:0 0.298 0.345 0.347 0.20522:0 0.031 0.568 0.645 0.202SFA 39.247 13.729 14.832 12.94614:1n-5 ND ND ND ND16:1n-9 0.332 0.039 0.043 0.04416:1n-7 1.605 0.164 0.174 0.17518:1n-9 33.880 25.163 27.544 20.83018:1n-7 0.968 0.481 0.563 0.40320:1n-9 0.210 0.202 0.250 0.22022:1n-9 ND ND ND NDMUFA 37.036 26.049 28.574 21.73118:3n-3 1.188 0.792 1.703 35.18518:4n-3 0.012 ND ND 0.01820:4n-3 ND ND ND ND20:5n-3 ND ND ND ND22:5n-3 ND ND ND ND22:6n-3 ND ND ND NDPUFA n-3 1.199 0.792 1.703 35.20218:2n-6 22.450 59.387 54.804 30.07518:3n-6 ND ND ND ND20:2n-6 0.066 0.044 0.074 0.04620:3n-6 ND ND ND ND20:4n-6 ND ND ND ND22:4n-6 ND ND ND ND22:5n-6 ND ND ND NDPUFA n-6 22.516 59.431 54.878 30.121PUFA 23.715 60.223 56.581 65.323PUFA/SFA 0.604 4.387 3.815 5.046

1Values in this table correspond to means (n = 8). SFA = saturated fatty acids; MUFA = monounsaturatedfatty acids; PUFA = polyunsaturated fatty acids; ND = not detected.

factors (Table 2). Lopez-Ferrer et al. (1999) also did notfind any differences in final BW and carcass yield in birdsfed different vegetable oil sources. Moreover, the additionof OSO to the feed did not provoke detrimental effectson these parameters, which are only observed if oxidizedoils are fed at high doses, are extremely overheated, orboth (Billek, 2000).

Raw Meat Fatty Acid Composition

Feed fatty acid composition is shown in Table 3. Feedscontaining BT had the highest content of total saturatedfatty acids (SFA) and total monounsaturated fatty acids(MUFA), whereas feeds containing LO had the highestcontent of total n-3 PUFA. Feeds containing SO or OSOwere similar in having a high content of n-6 PUFA. Never-theless, feeds containing OSO had a lower content oftotal n-6 PUFA than those containing SO as a result ofLA oxidation.

Dietary fat sources affected raw dark chicken meat fattyacid composition (Table 4). Dark meat from birds fed BThad higher amounts of 16:0, 18:0, and 18:1n-9 than birdsfed other fat sources. However, birds fed LO yieldedmeat with a higher content of LNA and total n-3 PUFA,whereas those fed SO or OSO had a higher content ofLA and total n-6 PUFA. This meant that feed fatty acidcomposition had a great influence on chicken meat fatty

acid composition (Chanmugam et al., 1992; Hargis andvan Elswyk, 1993; Cherian et al., 1996; Wood and Enser,1997; Surai and Sparks, 2000; Bou et al., 2005a).

Based on feed fatty acid composition and its influenceon meat fatty acid composition, meat from birds fed OSOrecorded lower LA content than that of birds fed SO diets,because these reflected LA losses recorded in OSO dietsas a result of SO heating. Similar results were reportedin dark chicken meat from birds fed different oxidized oils(Sheehy et al., 1993; Jensen et al., 1997; Bou et al., 2005b).

However, ∆6-desaturase substrate preferences also ex-plain meat fatty acid composition. This enzyme couldexplain the differences observed in 18:3n-6. This fatty acidwas not found in feeds (Table 3), so the high amounts inLNA recorded in meat from birds fed LO would enhancethe synthesis of 18:4n-3 and explain the lowest 18:3n-6content recorded in this meat. Moreover, although birdsfed BT had a lower content in LA, they showed higher18:3n-6 levels than those fed LO (Table 4).

In relation to this, the high LA:LNA feed ratio couldalso explain the low formation of 22:5n-3 and 22:6n-3 inbirds fed SO, compared with those birds fed BT. There-fore, although meat from chickens fed BT recorded asimilar amount of LNA to those fed SO and lower thanthose fed OSO (Table 4), this meat had an increased con-tent in 22:5n-3 and 22:6n-3 compared with that of birdsfed SO and similar to that of birds fed OSO.

BOU ET AL.1476

Table 4. Fatty acid composition (expressed as area normalization in a percentage) in raw dark chicken meat with skin1

Ascorbic acidTocopheryl acetate supplementation

Added fat source (6%)

supplementation (mg/kg) (mg/kg)OxidizedBeef Sunflower sunflower Linseed

tallow oil oil oil 0 225 0 110 SEM

12:0 0.063a 0.030b 0.028b 0.030b 0.038 0.038 0.038 0.038 0.00114:0 1.752a 0.397b 0.398b 0.365b 0.738a 0.718b 0.735 0.724 0.00516:0 23.414a 16.166b 15.888b 14.546c 17.907a 17.079b 17.490 17.913 0.10518:0 8.379a 5.754b 5.619b 4.809c 6.112 6.151 6.150 6.074 0.03520:0 0.086bc 0.111a 0.094ab 0.071a 0.092 0.090 0.092 0.089 0.00322:0 0.017b 0.041a 0.043a 0.018b 0.029 0.031 0.030 0.029 0.001SFA 33.712a 22.469b 22.069b 19.839c 24.914a 24.106b 24.535 24.886 0.11814:1n-5 0.357a 0.073b 0.074b 0.075b 0.151a 0.138b 0.144 0.151 0.00216:1n-9 0.734a 0.493b 0.511b 0.533b 0.566 0.571 0.571 0.561 0.00716:1n-7 4.800a 2.343b 2.392b 2.539b 3.215a 2.818b 3.002 3.344 0.04318:1n-9 39.821a 30.886b 31.197b 29.202c 32.677 32.888 32.705 32.831 0.11018:1n-7 1.745a 0.993c 0.937d 1.067b 1.181 1.190 1.183 1.187 0.00420:1n-9 0.304a 0.207b 0.197b 0.197b 0.231 0.221 0.227 0.230 0.00222:1n-9 0.021a 0.017b 0.022a 0.021a 0.019 0.021 0.021 0.019 0.001MUFA 47.781a 35.013b 35.331b 33.634c 38.040 37.848 37.852 38.223 0.11918:3n-32 0.893c 0.633c 1.835b 23.607a 6.543 6.940 6.762 6.501 0.08518:4n-32 0.026bc 0.014c 0.037b 0.241a 0.083a 0.076b 0.082 0.078 0.00220:4n-3 0.011b 0.001b 0.014b 0.122a 0.040 0.034 0.037 0.040 0.00320:5n-32 0.023b 0.011b 0.035b 0.473a 0.131 0.140 0.135 0.132 0.00422:5n-32 0.085b 0.036c 0.090b 0.485a 0.173 0.175 0.176 0.170 0.00422:6n-32 0.048b 0.022c 0.043b 0.163a 0.069 0.068 0.070 0.066 0.002PUFA n-32 1.086c 0.717c 2.053b 25.091a 7.039 7.433 7.263 6.987 0.08918:2n-62 16.266d 39.773a 38.646b 20.788c 28.635 29.114 28.912 28.561 0.12618:3n-6 0.165c 0.321a 0.261b 0.066d 0.206 0.200 0.204 0.205 0.00620:2n-62 0.132b 0.229a 0.217a 0.119b 0.174 0.174 0.174 0.175 0.00220:3n-6 0.154b 0.245a 0.261a 0.145b 0.195 0.208 0.200 0.197 0.00420:4n-62 0.562b 0.914a 0.892a 0.296c 0.628b 0.706a 0.673 0.616 0.01222:4n-62 0.138c 0.265a 0.234b 0.037d 0.155b 0.183a 0.168 0.156 0.00322:5n-62 0.036c 0.084a 0.064b 0.009d 0.042b 0.055a 0.048 0.042 0.004PUFA n-62 17.452d 41.831a 40.575b 21.461c 30.034 30.642 30.379 29.952 0.130PUFA 18.539b 42.548a 42.628a 46.552a 37.074b 38.075a 37.642 36.939 0.176PUFA/SFA 0.551c 1.896b 1.934b 2.357a 1.632b 1.739a 1.685 1.634 0.018

a–dLeast squares means corresponding to a certain factor with different letters differ significantly (P ≤ 0.05).1Values in this table correspond to least squares means obtained from multifactor ANOVA (n = 48). SFA = saturated fatty acids; MUFA =

monounsaturated fatty acids; PUFA = polyunsaturated fatty acids.2Interaction between fat source and α-tocopheryl acetate supplementation.

Hence, these findings confirm that both feed fatty acidcomposition and biosynthetic pathways are involved inmeat fatty acid composition, with ∆6-desaturase actingas the rate-limiting enzyme.

Alpha-tocopheryl acetate supplementation caused anincrease in 20:4n-6, 22:4n-6, 22:5n-6, and total PUFA con-tent and PUFA:SFA ratio in raw chicken meat (Table 4).The increase of some PUFA has been previously reportedand has been attributed to tocopherol antioxidant activity(Ajuyah et al., 1993; Cherian et al., 1996; Surai and Sparks,2000). This effect may also explain the relative lower con-tent (area normalization as a percentage) in 16:0 and totalSFA for α-TA-supplemented treatments.

In addition, α-tocopherol activity could explain the sig-nificant interaction recorded between dietary fat sourceand α-TA supplementation for several PUFA (Tables 4and 5). Meat from birds receiving LO and 225 mg/kg ofα-TA had higher amounts of LNA and lower amountsof LA, whereas the opposite trend was observed in birdsfed SO and OSO (Table 5). These and other significant

interactions may be because α-tocopherol can be used toprotect LNA, which is more prone to oxidation than LA,in birds fed LO or BT. On the contrary, in birds fed SOand OSO, α-tocopherol may be used in protecting thehigh amount of LA and other very long chain n-6 PUFApresent in these meats.

In relation to ASC supplementation, ASC did not affectraw dark chicken meat fatty acid composition (Table 4).

Despite these effects on fatty acid composition, totalfat content of raw dark meat was not affected by dietaryfactors (Table 6). Likewise, no differences were reportedin total fat content of dark (Ajuyah et al., 1991) and white(Scaife et al., 1994) meat when comparing chickens feddifferent dietary fats.

Cooked Meat Fatty Acid Composition

Several mechanisms such as lipid oxidation; lipid diffu-sion, exchange, or both; and water losses occur duringcooking, and their various effects, depending on the culi-

INFLUENCE OF DIETARY FAT SOURCES AND SUPPLEMENTS ON CHICKEN MEAT 1477

Table 5. Influence of the significant interaction between dietary fat source and α-tocopheryl acetate (α-TA)supplementation on the composition of some selected fatty acids in raw dark chicken meat with skin1

Added fat and α-TA dose (mg/kg)

OxidizedBeef tallow Sunflower oil sunflower oil Linseed oil

Fatty acid P 0 225 0 225 0 225 0 225

18:2n-6 ≤0.004 16.042 16.489 39.503 40.096 37.494 39.798 21.503 20.073n-6 PUFA ≤0.002 17.201 17.702 41.493 42.236 39.237 41.913 22.206 20.71618:3n-3 ≤0.001 0.842 0.944 0.652 0.610 2.549 1.121 22.128 25.085n-3 PUFA ≤0.001 1.037 1.136 0.735 0.696 2.833 1.274 23.554 26.628

1Values in this table correspond to least squares means obtained from multifactor ANOVA (n = 48). PUFA =polyunsaturated fatty acids.

nary practices involved, can lead to relative increasesin some fatty acids (Kesava Rao et al. 1996; Rodriguez-Estrada et al., 1997; Duckett and Wagner, 1998; Dal Boscoet al., 2001; Echarte et al., 2003; Conchillo et al., 2004;Badiani et al., 2005).

Given that water and lipid content was not affectedduring the cooking of vacuum-packed dark chicken meat(Table 6), lipid oxidation thus explained the decreasedcontent of 22:5n-3 and 20:4n-6 in cooked meat from birdsfed BT (Tables 4 and 7). In addition, this decrease wasalso significant for the 20:4n-6 content in meat from birdsfed SO, whereas no differences were observed in meatfrom birds fed OSO or LO.

Moreover, the previously reported effects of dietary fatsources on raw dark meat fatty acid composition werestill present after cooking and showed similar results tothose reported in raw meat (Tables 4 and 7). Therefore,cooked meat from birds fed BT contained the highestamount of total SFA, oleic acid, and total MUFA, whereasmeat from birds fed LO had the highest content in LNAand other n-3 PUFA (Table 7). Meat from birds fed SOand OSO had a higher content in LA and total n-6 PUFAthan other meats. Therefore, chicken meat was rich inSFA and MUFA in cases where birds were fed BT, in n-3 PUFA when they were fed LO, or in n-6 PUFA whenthey were fed SO or OSO.

Consequently, 100-g edible portions from birds fed BTyielded 1.3% for LA and 0.8% for LNA in terms of ade-quate intakes (Table 8), whereas those from birds fed LOprovided 21.7% of the LNA adequate intake (Food andNutrition Board, 2005). Meats from birds fed SO andOSO provided 3.5 and 3.3% of the LA adequate intake,respectively (Table 8). However, the ratio n-3:n-6 in meatfrom birds fed BT was more favorable than that of SO orOSO diets.

Poultry meats rich in n-3 PUFA, most of them obtainedthrough the addition of marine oils to poultry diets, ledto an increased nutritional value, although this meat isprone to decreased oxidative stability and sensory prob-lems (Hargis and van Elswyk, 1993; Wood and Enser,1997). In fact, cooked dark chicken meat from our experi-mental birds showed such deficiencies (Bou et al., 2001;Grau et al., 2001a,b). Vacuum-packed meat from thosebirds fed LO showed the lowest oxidative stability overvarious storage periods at −20°C (Grau et al., 2001a,b),

as well as the highest scores for rancid aroma and flavorafter long-term frozen storage (Bou et al., 2001), whereasmeat from birds fed BT was less susceptible to oxidationand rancidity. Nevertheless, these works also showed thatthese meats are protected against oxidation and ranciditythrough α-TA supplementation (Bou et al., 2001; Grau etal., 2001a,b). Moreover, meats containing a high contentof very long chain PUFA, as a result of fish oil consump-tion, can also be efficiently protected against oxidationthrough dietary α-TA supplementation (Cherian et al.,1996; Surai and Sparks, 2000). Moreover, the appropriatebalance between dietary PUFA and α-TA supplementa-tion leads to dark chicken meat not only rich in thosePUFA, but also one accepted by consumers (Bou et al.,2004, 2005a).

In relation to α-TA supplementation, this α-TA supple-ment did not affect cooked dark chicken meat fatty acidcomposition. Most likely, its previously reported effectson fatty acid composition were not sufficiently strong toremain after cooking (Table 7).

Table 6. Water and fat content of raw and cooked dark chicken meatwith skin1

Raw Cooked Raw Cookedmeat meat meat meat

fat fat water water(%) (%) (%) (%)

Fat source2

BT 15.6 15.6 62.82 61.72SO 14.6 14.9 62.56 62.34OSO 15.5 15.7 61.97 62.89LO 14.3 15.0 63.49 63.96

α-TA3 supplementation0 mg/kg 15.1 15.1 62.90 62.85225 mg/kg 14.8 15.5 62.52 62.60

ASC4 supplementation0 mg/kg 14.8 15.1 62.86 62.70100 mg/kg 15.1 15.5 62.56 62.76

Global SEM 0.21 0.22 0.18 0.26

1Values in this table correspond to least squares means obtained frommultifactor ANOVA (n = 48 and n = 16 for fat and water contents,respectively).

2BT = beef tallow; SO = sunflower oil; OSO = oxidized sunflower oil;LO = linseed oil.

3α-TA = α-tocopheryl acetate.4ASC = ascorbic acid.

BOU ET AL.1478

Table 7. Fatty acid composition (expressed as area normalization in a percentage) in cooked dark chicken meatwith skin1

α-TA ASCsupplementation supplementation

Added fat source (6%)

(mg/kg) (mg/kg)OxidizedBeef Sunflower sunflower Linseed

tallow oil oil oil 0 225 0 110 SEM

SFA 33.879a 22.743b 22.207b 20.101c 24.898 24.513 24.807 24.695 0.155MUFA2 48.168a 33.640c 35.362b 32.716c 37.414 37.545 37.213 37.947 0.19218:3n-32 0.917c 0.642c 1.897b 24.131a 6.736 7.052 6.897 6.730 0.13020:5n-32 0.022b 0.011b 0.034b 0.474a 0.127 0.143 0.133 0.131 0.00522:5n-32 0.069b,x 0.034c 0.084b 0.479a 0.165 0.168 0.167 0.162 0.00422:6n-32 0.042b 0.019c 0.038b 0.167a 0.064 0.069 0.069 0.059 0.002PUFA n-32 1.086c 0.732c 2.111b 25.627a 7.215 7.554 7.388 7.208 0.13218:2n-62 15.928d 40.838a 38.555b 20.949c 29.154 29.031 29.260 29.818 0.20520:3n-6 0.147b 0.275a 0.241a 0.155b 0.206 0.203 0.203 0.208 0.00620:4n-6 0.449c,x 0.873a,x 0.772b 0.264d 0.577 0.599 0.586 0.579 0.01222:4n-62 0.126c 0.260a 0.208b 0.034d 0.163 0.161 0.156 0.156 0.00322:5n-62 0.032c 0.084a 0.058b 0.012d 0.046 0.047 0.045 0.049 0.001PUFA n-62 16.932d 42.914a 40.347b 21.587c 30.510 30.426 30.629 30.189 0.218PUFA2 18.017c 43.646b 42.458b 47.215a 37.726 37.980 38.017 37.397 0.280PUFA/SFA 0.533c 1.926b 1.914b 2.359a 1.659 1.708 1.675 1.678 0.025

a–dLeast squares means corresponding to a certain factor with different letters differing significantly (P ≤ 0.05).xIndicates significant differences between raw and cooked meat.1Values in this table correspond to least square means obtained from multifactor ANOVA (n = 48). α-TA =

α-tocopheryl acetate; ASC = ascorbic acid; SFA = saturated fatty acids; MUFA = monounsaturated fatty acids;PUFA = polyunsaturated fatty acids.

2Interaction between fat source and α-TA supplementation.

In addition, in accordance with what occurs in rawmeat, ASC supplementation did not affect cooked meatfatty acid composition (Table 7).

Similar to raw meat, none of the dietary factors affectedcooked dark chicken meat fat content (Table 6).

Raw Meat α-Tocopherol Content

Raw meat α-tocopherol content was not influenced bydietary fat sources after 0 or 7 mo of storage at −20°C,

Table 8. Nutrients provided by 100 g of edible portion (cooked dark meat) depending on dietary factors andcoverage of the human recommended daily dietary intakes1

α-TA3 ASC4

supplementation supplementationDietary fat source2 (mg/kg) (mg/kg)

Nutrient BT SO OSO LO 0 225 0 110

Linoleic acid (mg) 230 590 557 302 421 419 423 431Coverage5,6 (%) 1.3 3.5 3.3 1.8 2.5 2.5 2.5 2.5Linolenic acid (mg) 13 9 27 348 97 102 100 97Coverage6 (%) 0.8 0.6 1.7 21.8 6.1 6.4 6.2 6.1EPA + DHA (mg)7 0.9 0.4 1.0 9.3 2.7 3.1 2.9 2.7Coverage8 (%) 0.01 0.04 0.09 0.84 0.25 0.28 0.27 0.25α-tocopherol (mg) 1.83 2.22 1.96 1.75 0.16 3.72 1.94 1.94Coverage9 (%) 12.2 14.8 13.1 11.7 1.1 24.8 12.9 12.9

1Results are calculated by taking the fat content average found in cooked dark chicken meat.2BT = beef tallow; SO = sunflower oil; OSO = oxidized sunflower oil; LO = linseed oil.3α-TA = α-tocopheryl acetate.4ASC = ascorbic acid.5Coverage of the dietary recommendations for this nutrient in a percentage.6Adequate intake for men is 17 g/d for linoleic acid and 1.6 g/d for linolenic acid.7EPA = eicosapentaenoic acid; DHA = docosahexaenoic acid.8Recommended daily dietary intake for the sum of EPA and DHA is 0.65 g/d based on 2,000 kcal diet.9Recommended dietary allowances for men is 15 mg/d of α-tocopherol.

although significant differences (P = 0.045) were recordedafter 3.5 mo (Table 9).

Related to these previous results, meat from birds fedLO and OSO showed lower α-tocopherol content at 3.5mo of frozen storage, a trend also exhibited at 0 and 7mo (Table 9). Despite this, Scheffe’s test was unable todistinguish among the means at 3.5 mo of storage. Thus,there were no differences in α-tocopherol amounts be-tween meats from birds fed these fat sources similar towhat had been reported in meat from animals fed corn

INFLUENCE OF DIETARY FAT SOURCES AND SUPPLEMENTS ON CHICKEN MEAT 1479

Table 9. Effects of the dietary factors on α-tocopherol content of raw and cooked dark chicken meat stored fordifferent periods at −20°C (mg/100 g of edible portion)1

Raw (mo) Cooked (mo)

0 3.52 7 0 3.53 7

Fat source4

BT 2.52 2.67 2.46 1.60 1.98 1.92SO 2.35 2.65 2.41 2.15 2.34 2.17OSO 2.18 2.13 2.09 1.78 2.08 2.02LO 2.19 2.17 2.06 1.69 1.78 1.77

α-TA5 supplementation0 mg/kg 0.37b 0.37b 0.35b 0.16b,x 0.17b,x 0.15b,x

225 mg/kg 4.25a 4.44a 4.15a 3.44a,x 3.92a,x 3.79a

ASC6 supplementation0 mg/kg 2.29 2.34 2.27 1.76 2.08 1.99100 mg/kg 2.33 2.47 2.24 1.85 2.01 1.95

Global SEM 0.77 0.86 1.00 0.88 0.71 0.98

a–bLeast squares means in the same column for a certain factor with different letters differing significantly (P≤ 0.05).

xIndicates significant differences between raw and cooked meat.1Values in this table correspond to least squares means obtained from multifactor ANOVA (n = 48).2Fat source showed significant differences, although means cannot be separated by Scheffe’s test (P = 0.045).

Interaction between fat source and α-TA supplementation.3Interaction between fat source and α-TA supplementation.4BT = beef tallow; SO = sunflower oil; OSO = oxidized sunflower oil; LO = linseed oil.5α-TA = α-tocopheryl acetate.6ASC = ascorbic acid.

and tuna oils (Surai and Sparks, 2000), nor from animalsfed coconut, olive, linseed, or partially hydrogenated soy-bean oils (Lin et al., 1989). Nevertheless, other authorsreported higher α-tocopherol amounts in meat from birdsfed olive oil than in those meats from birds fed BT (O’Neillet al., 1998).

In addition, the trend involving meat from birds fedOSO compared with those fed SO has been reported tobe significant by other authors (Sheehy et al., 1993; Galvinet al., 1997). Related to these results, different authorshave explained the decrease of α-tocopherol content inmeat as stemming from lower feed α-tocopherol contentin oxidized oil treatments, among other factors (Sheehyet al., 1993; Engberg et al., 1996; Galvin et al., 1997; Bouet al., 2005b).

Raw meat α-tocopherol content increased as a resultof α-TA supplementation (Table 9), SO α-tocopherol pro-tects lipids against lipid oxidation as has been demon-strated by decreasing TBA values, lipid hydroperoxidecontent, and cholesterol oxidation products from samplesof the same experiment (Grau et al., 2001a,b). The onsetof lipid oxidation in meat originating from birds fed LOmay also explain the influence of the observed interactionbetween fat source and α-TA supplementation in darkchicken meat after 3.5 mo of storage at −20°C, as well asmeat α-tocopherol content (data not shown).

Moreover, the recorded α-tocopherol content for rawdark chicken meat with its skin from birds fed the α-TAsupplement is much higher than that from birds receivingα-TA supplements ranging from 160 to 200 mg/kg (Gal-vin et al., 1997; Morrissey et al., 1997; O’Neill et al., 1998;Surai and Sparks, 2000). This can be explained by thehigh content of α-tocopherol in adipose tissue (Cherian

et al., 1996; Surai and Sparks, 2000) and indicates its im-portant role when meat is not trimmed or consumed withits skin.

Ascorbic acid supplementation did not have any sig-nificant effects on meat α-tocopherol content for eachstorage period (Table 9). Similarly, King et al. (1995) re-ported that ASC supplementation has no effect on meatα-tocopherol content or on its TBA value. In this trial,however, ASC supplementation led to increased TBA val-ues in raw dark chicken meat (Grau et al., 2001a). Theseprior results could be explained by the fact that ASCat low concentrations has been described as acting as aprooxidant via its interaction with iron (Decker and Xu,1998; Grau et al., 2001a).

Storage at −20°C, even after 7 mo, did not provoke adecrease in the α-tocopherol content of vacuum-packedraw dark meat (Table 9). Given that α-tocopherol reduceslipid oxidation under different storage conditions (Jensenet al., 1998), this result agreed well with the nonsignificantdifferences in TBA values during storage time, even after7 mo at −20°C, recorded from the same experimental rawmeat samples (Grau et al., 2001a).

Cooked Meat α-Tocopherol Content

Cooked dark meat α-tocopherol content was not af-fected by dietary fat sources after 0, 3.5, and 7 mo ofstorage at −20°C (Table 9). Nevertheless, as was observedin raw meat, cooked meat α-tocopherol content frombirds fed OSO showed lower values than meat from birdsfed SO. Moreover, cooked meat from birds fed LO alsoshowed lower α-tocopherol amounts compared withother meats.

BOU ET AL.1480

In samples from the same experiment, TBA values werehigher, at either storage period, in cooked meats frombirds fed LO (Grau et al., 2001a), whereas rancidity scores,after 13 mo of frozen storage, were also higher in thismeat; no differences were observed among the rancidityscores of other meats (Bou et al., 2001). In addition, similarto raw meat, an interaction was observed between dietaryfat and α-TA supplementation for α-tocopherol contentin cooked meat after 3.5 mo of storage at −20°C.

Similar to its effect in raw meat, α-TA supplementationsignificantly increased α-tocopherol content in dark,cooked meat (Table 9). Cooked meat with increased α-tocopherol meant that 100-g edible portions provided24.8% of the recommended daily allowance (Table 8). Inaddition, in samples from the same experiment, cookedmeat fed 225 mg/kg of α-TA supplement improved ran-cid aroma and rancid flavor after long-term storage (Bouet al., 2001) and recorded lower TBA values (Grau et al.,2001a) than cooked dark chicken meat.

Ascorbic acid supplementation did not affect cookedmeat α-tocopherol content (Table 9). Ascorbic acid sup-plementation also did not affect oxidative stability (Grauet al., 2001a) or sensory scores (Bou et al., 2001) of cookeddark chicken meat from the studied experimental diets.These results are consistent with those reported by Kinget al. (1995), who reported that ASC supplementation didnot affect sensory scores.

Storage of vacuum-packed cooked dark meat kept at−20°C did not lead to decreased meat α-tocopherol con-tent (Table 9). This result was in agreement with thenonsignificant differences in TBA values during the fro-zen storage of these samples (Grau et al., 2001a).

A significant decrease in the α-tocopherol content wasobserved as a result of cooking (Table 9). Therefore, α-TA supplementation and cooking are the main factorsaffecting α-tocopherol content in meat. Indeed, the mainfactors responsible for promoting cooking-related lipidoxidation, and, consequently, the described loss of α-tocopherol, seem to be 1) protein denaturation, whichcan lead to the loss of antioxidant enzyme activity (e.g.,inactivation of catalase and glutathione peroxidase), orthe release of iron from metalloproteins (mainly myoglo-bin); 2) disruption of cell membranes, which brings PUFAand cholesterol into contact with prooxidants; and 3) ther-mal decomposition of hydroperoxides to prooxidant spe-cies, such as alkoxyl and hydroxyl radicals as a result ofcooking (Rhee et al., 1988; Decker and Xu, 1998; Frankel,1998; Morrissey et al., 1998; Grau et al., 2001a).

ACKNOWLEDGMENTS

This work was supported in part by research grantsfrom the Comissio Interdepartamental de Recerca i Inno-vacio Tecnologica (CIRIT) and Comision Interministerialde Ciencia y Tecnologıa (CICYT).

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