Meat Science 77 (2007) 246–256www.elsevier.com/locate/meatsci

Extensive feeding versus oleic acid and tocopherol enriched mixed diets for the production of Iberian dry-cured hams: EVect on chemical

composition, oxidative status and sensory traits

S. Ventanas, J. Ventanas, J. Tovar, C. García, M. Estévez ¤

Food Technology Department, Faculty of Veterinary, University of Extremadura, Campus Universitario, 10071 Cáceres, Spain

Received 16 June 2006; received in revised form 25 February 2007; accepted 9 March 2007

Abstract

The present study aimed to analyse the chemical composition and oxidative status of Iberian dry-cured hams from pigs fed diVerentWnishing diets: extensive feeding on acorns and pasture in a “Montanera” traditional system (MON), fed in conWnement with a mixed dietcontaining high-oleic sunXower oil (115 g/kg of diet) and supplemented with 250 mg/kg �-tocopherol (HOVE), and fed in conWnementcontrol mixed diet (CON) without added tocopherol and oleic acid fat. Muscles from MON dry-cured hams contained signiWcantly(p < 0.05) higher amounts of intramuscular fat (IMF) than those from HOVE and CON hams. The feeding background aVected thetocopherol levels in dry-cured hams as those from MON and HOVE pigs had signiWcantly higher levels of �-tocopherol than those fromCON pigs whereas the extensive feeding provided muscles from MON pigs with signiWcantly higher levels of �-tocopherol than the exper-imental diets did to CON and HOVE pigs. The HOVE diet signiWcantly increased the levels of oleic acid in Iberian dry-cured hams withthese levels being similar to the oleic acid levels found in MON hams and signiWcantly higher than those in CON hams. Compared to dry-cured hams from CON pigs, those from MON and HOVE pigs exhibited a higher oxidative stability as a likely result of a most favourablefatty acid composition and the presence of higher tocopherol levels. The principal component analysis (PCA) successfully discriminatedbetween dry-cured hams from pigs fed diVerent Wnishing diets.© 2007 Elsevier Ltd. All rights reserved.

Keywords: Iberian ham; Extensive feeding; Tocopherol; Oleic acid; Intramuscular fat; Oxidation; Sensory features

1. Introduction

The Iberian ham is a Spanish high-priced dry-curedproduct obtained from Iberian pigs and subjected to a longripening process (above 30 months). Apart from the tradi-tional ripening procedure, the extraordinary sensory fea-tures of this product are mainly due to the geneticbackground of the animals and the traditional outdoorfeeding for Iberian pigs (Ventanas, Ventanas, Ruiz, & Est-évez, 2005). The extensive feeding involves the intake ofnatural resources from ever-green oak forests, mainlyacorns and pasture, during autumn months until slaughter

* Corresponding author. Tel.: +34 927257122; fax: +34 927257110.E-mail address: mariovet@unex.es (M. Estévez).

0309-1740/$ - see front matter © 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.meatsci.2007.03.010

in winter time (López-Bote, 1998). This feeding strategyaVects the chemical composition and oxidative stability ofIberian pigs’ tissues and the sensory quality of the Iberiandry-cured products (Ventanas et al., 2005). Acorns providehigh-levels of MUFA (mainly oleic acid) and �-tocopherolto Iberian pigs whereas the grass is a recognised source ofn¡3 fatty acids (mainly linolenic acid) and �-tocopherol(Daza, Rey, Ruiz, & López-Bote, 2005; Rey, Daza, López-Carrasco, & López-Bote, 2006). Tocopherols are lipidsoluble antioxidants which are accumulated in cellularmembranes where the initiation of oxidative processes inmuscle foods takes place. The protective role of tocopherolsagainst lipid oxidation in Iberian dry-cured ham is mani-fested by a reduction of the generation of lipid oxidationproducts during ripening and improving some particular

S. Ventanas et al. / Meat Science 77 (2007) 246–256 247

sensory characteristics such as Xavour and odour intensity(Cava, 1999; Ruiz & López-Bote, 2002). According to Wnd-ings by Ruiz, Ventanas, Cava, Andrés, and García (2000),the high-levels of intramuscular fat and oleic acid in Iberianhams are responsible for certain texture and appearancetraits which inXuence consumer’s acceptability such oili-ness, brightness, juiciness and marbling.

Unfortunately, the traditional extensive feeding regimeis not always feasible because the availability of the naturalresources is largely inXuenced by environmental factors andtherefore, is limited up to one pig per hectare. In fact, onlyhalf a million hams amongst the 2.6 million Iberian dry-cured hams produced per year are derived from free-rangereared Iberian pigs. Therefore, it was necessary to developalternative feeding systems which generally involve usingmixed diets (López-Bote, 1998). In order to minimise costs,conventional mixed diets in semi-intensive conditions wereused at the beginning which led to products with a consid-erably higher oxidative instability and lower nutritionaland sensory quality (García et al., 1996; Timón, Martín,Petrón, Jurado, & García, 2001). The high-levels of linoleicacid in the green hams increased the incidence of ‘Xoppymeats’ and were responsible for the development ofunpleasant Xavour notes during the ripening process (Ven-tanas et al., 2005). Consequently, great eVorts have beenmade in the last 10 years to improve the characteristics ofthe mixed diets in order to enhance the oxidative stabilityof the product and improve its nutritional and technologi-cal quality (Ruiz & López-Bote, 2002). Nowadays, Iberianpigs which cannot be fed outdoors, are raised in conWne-ment and fed on oleic acid-enriched diets supplementedwith �-tocopherol up to 200 mg/kg in order to imitate thefavourable eVects of the traditional extensive feeding sys-tem on Iberian dry-cured hams’ quality (Daza et al., 2005;Isabel et al., 2003; Rey et al., 2004). However, dry-curedhams from free-range reared Iberian pigs are much moreappreciated than those from pigs fed in conWnement andthe price of the former is twice as much as the price of thelatter (35–50D/kg versus 15–20D/kg).

Findings by Daza et al. (2005) and Ventanas, Estévez,Tejeda, and Ruiz (2006) conWrmed that muscles fromIberian pigs subjected to dietary supplementation with200 mg/kg �-tocopherol contain similar levels of such anti-oxidant than those from free-range reared Iberian pigs.Also recently, Isabel et al. (2003) and Ruiz et al. (2005)reported the positive eVect of feeding on MUFA-enricheddiets on the levels of oleic acid in muscles from industrialgenotype and Iberian pigs, respectively. However, no com-parative study has been deliberately carried out to evaluatethe eVect of both feeding systems (traditional extensive ver-sus mixed diets) on the chemical composition and oxidativestability of Iberian dry-cured hams. Likewise, the eVect ofsuch feeding systems on relevant sensory features in Iberiandry-cured hams is currently poorly understood.

The present study was carried out to evaluate the eVectsof the aforementioned feeding systems on the chemicalcomposition and oxidative stability of Iberian dry-cured

hams and their implications on technological, nutritionaland sensory aspects.

2. Material and methods

2.1. Animals and sampling

This study was carried out with 30 Iberian pigs with aninitial live weight of 80 kg. Pigs were divided into threebatches (nD10) according to the type of feeding during theWnish-fattening period. The trial was carried out simulta-neously for all groups of animals. The fattening period forHOVE and CON pigs lasted 60 days while MON pigs werefattened for 90 days in order to reach the same weight atslaughter as it is generally known that feed conversion andthe average daily gain are lower in pigs fed outdoors.

MON pigs were free-range reared and exclusively fed onacorns and grass according to the traditional ‘Montanera’feeding system. Each pig had an approximate space of 5 haand the averaged temperature from November to Februarywas 8 °C. According to estimations made on Iberian pigswith free access to the feeds, the average daily intake ofacorns and grass is around 6 kg and 2 kg, respectively (Reyet al., 2006). The energy level provided by the acorns to thepigs is around 4.7 Mcal/kg (Nieto, Rivera, García, & Aguil-era, 2002).

HOVE pigs were reared indoors and fed on a mixed dietcontaining high-oleic sunXower oil (57.5 g/kg of diet) andsupplemented with 250 ppm of vitamin E (all-rac-�-toc-opheryl acetate). The composition of the HOVE diet was asfollows (mg/kg of diet): barley 48£104, wheat 15£ 104,wheat bran 15£104, soybean meal 8.5£104, beet pulp5£104, sunXower high-oleic 5.75£ 104, calcium carbonate9£103, calcium phosphate 7£ 103, sodium chloride 4£ 103,vitamin/mineral mix 5£ 103, mix vit E 250.

Finally, CON pigs were reared indoors and fed on a con-trol mixed diet without added tocopherol and oleic acid fat.The control diet contained (mg/kg of diet): barley 15£ 104,wheat 50£ 104, corn 20£ 104, soybean meal 11.1£ 104, lard1.2£ 104, calcium carbonate 8£103, calcium phosphate1.1£ 104, sodium chloride 4£ 103 and vitamin/mineral mix5£103.

Mixed diets and water were supplied to Iberian pigsad libitum and the estimated average daily intake per Ibe-rian pig was around 4.5 kg of mixed diet. Both mixed dietswere isocaloric and provided around 3.3 Mcal/kg to thepigs.

Animals from the three batches were slaughtered byelectrical stunning and exsanguinated at the same slaugh-terhouse at a live weight of around 140 kg. Pigs fed onmixed diets (HOVE and CON) and MON pigs were slaugh-tered one month part. No diVerences were observedbetween batches for carcass yield (80% in average). Sam-pling of hams was carried out within the hour followingslaughter. Hams were removed from the carcasses and keptunder refrigeration (24 h) before being subjected to the rip-ening process following the procedure described by García

248 S. Ventanas et al. / Meat Science 77 (2007) 246–256

et al. (1996). No diVerences were found between green hamsfrom diVerent batches for weight (11 kg in average), neitherfor subcutaneous fat thickness (6 cm in average). After theripening process, Iberian hams showed an average ripeningloss of 30% and no diVerences were observed in this regardbetween batches. Muscles biceps femoris were dissectedfrom dry-cured hams and sliced for physico-chemical andsensory analyses.

2.2. Analytical methods

2.2.1. Chemical analysis of dietsProximate composition of diets was carried out accord-

ing to the following AOAC procedures (AOAC, 2000):nitrogen content by the Kjeldahl method (976.05), crudeprotein (954.01), crude fat (920.39), crude Wbre (962.09) andash (942.05).

2.2.2. Chemical composition and fatty acid analysis ofdry-cured ham

Moisture and protein were determined in dry-curedhams using oYcial methods (AOAC, 2000). Intramusculartotal lipids were extracted from the muscles and feeds andquantiWed according to the method described by Bligh andDyer (1959). Total chlorides were quantiWed according tothe Carpentier–Vohlard oYcial method (ISO 1443).

For the analysis of the fatty acid proWles of the bicepsfemoris muscles from dry-cured hams and of diets (HOVEand CON mixed diets, acorn and grass), fatty acid methylesters (FAMEs) were prepared by acidic transesteriWcationin the presence of sulphuric acid (5% sulphuric acid inmethanol) (Sandler & Karo, 1992). FAMEs were analysedby gas chromatography using a Hewlett–Packard HP-5890A gas chromatograph, equipped with a Xame ionisa-tion detector (FID). Separation was carried out on a poly-ethylene glycol-TPA modiWed fused silica semi-capillarycolumn (30 m long, 0.53 mm id, 1 �m Wlm thickness) main-tained at 225 °C. Injector and detector temperatures were230 °C. Carrier gas was nitrogen at a Xow rate of1.8 mL min¡1. Individual FAMES were identiWed by com-paring their retention times with those of standards of allfatty acids analysed supplied by Sigma Aldrich (Steintein,Germany). Results are expressed as percentage of the totalfatty acids analysed.

2.2.3. Tocopherol quantiWcationFor the determination of �- and �-tocopherol, 0.8 g mus-

cle was homogenised in 6 mL 0.054 M dibasic sodium phos-phate buVer adjusted to pH 7.0 with HCl. After mixing withabsolute ethanol and hexane and centrifugation (2000 rpm,5 min at 4 °C), the upper layer containing tocopherol wasevaporated to dryness and subsequently dissolved in etha-nol prior to analysis by reverse phase HPLC (HP 1050, witha UVD, HPIB 10 detector)(Hewlett–Packard, Waldbronn,Germany). Separation was made on a Lichrocart PR 18endcapped column (250£ 4 mm i.d., 5�m particle size)(Merck Darmstad, Germany), the mobile phase was metha-

nol:water (97:3 v/v) at a Xow rate of 2 mL min¡1, and peakswere registered at 292 nm (Rey, López-Bote, Soares, & Isa-bel, 1997). For quantiWcation purposes, standard curveswere prepared using chemicals (�- and �-tocopherol) sup-plied by Sigma–Aldrich (Steinheim, Germany).

2.2.4. Thiobarbituric acid-reactive substances (TBARS)TBARS were evaluated using the method of Salih,

Smith, Price, and Dawson (1987). Ham (2.5 g) were dis-pensed in cone plastic tubes and homogenised with 7.5 mLperchloric acid (3.86%) and 0.25 mL BHT (4.2% in ethanol).While homogenisation, the plastic tubes were immersed inan ice bath to minimise the development of oxidative reac-tions during extraction of TBARS. The slurry was Wlteredand centrifuged (2000 rpm for 5 min) and 2 mL aliquotswere mixed with 2 mL thiobarbituric acid (0.02 M) in testtubes. The test tubes were placed in a hot water bath (90 °C)for 30 min together with the tubes from the standard curve.After cooling, the absorbance was measured at 532 nm. Thestandard curve was prepared using a 1,1,3,3-tetraethoxy-propane (TEP) solution (0.2268 g) in 3.86% perchloric acid.

2.2.5. Protein carbonyls quantiWcationProtein carbonyls (ButterWeld & Stadtman, 1997), were

quantiWed both in dry-cured ham following the methoddescribed by Oliver, Ahn, Moerman, Goldstein, and Stadt-man (1987). Homogenates (1 g of sample in 10 ml of 0.15 MKCL buVer) were divided into two equal aliquots of 0.1 mL.Then, proteins were precipitated in both aliquots by 10%TCA (1 mL) and centrifuged for 5 min at 5000 rpm. Onepellet was treated with 1 mL 2 N HCL (protein concentra-tion measurement) and the other with an equal volume of0.2% (w/v) 2,4-dinitrophenylhydrazine (DNPH) in 2 NHCL (carbonyl concentration measurement). Both sampleswere incubated for 1 h at room temperature. After this time,samples were precipitated with 10% TCA (0.8 mL) andwashed twice with 1 mL ethanol:ethyl acetate (1:1, v/v). Thepellets were then dissolved in 2 mL 6 M guanidine HCLwith 20 mM sodium phosphate buVer pH 6.5, stirred andcentrifuged for 2 min at 5000 rpm to remove insolublefragments. Protein concentration was calculated fromabsorption at 280 using BSA as standard. The amount ofcarbonyls was expressed as nmol of carbonyl per mg ofprotein using the adsorption coeYcient 21.0 nM¡1 cm¡1 at370 nm for protein hydrazones.

2.3. Volatile aldehydes analysis

The SPME Wbre, coated with a carboxen–poly(dim-ethylxilosane) (CAR/PDMS) (70 �m thickness), was pre-conditioned prior analysis at 220 °C during 30 min. TheHeadspace (HS) sampling was performed as follows: 1 g ofminced ham was placed in 2.5 mL vials and the SPME Wbrewas exposed to the headspace of the minced ham while thesample equilibrated during 30 min immersed in water at37 °C. Analyses were performed on a HP5890GC series IIgas chromatograph (Hewlett–Packard, USA) coupled to a

S. Ventanas et al. / Meat Science 77 (2007) 246–256 249

mass-selective detector (Agilent model 5973). Volatiles wereseparated using a 5% phenyl-95% dimethyl polysiloxanecolumn (Restek, USA) (30 m£0.25 mm id., 1.0 mm Wlmthickness). The carrier gas was Helium at 18.5 psi, resultingin a Xow of 1.6 mL min¡1 at 40 °C. The SPME Wbre was des-orbed and maintained in the injection port at 220 °C duringthe whole chromatography run. The injector port was inthe splitless mode. The temperature program was isother-mal for 10 min at 40 °C and then raised at the rate of7 °C min¡1 to 250 °C, and held for 5 min. The GC/MS trans-fer line temperature was 270 °C. The mass spectrometeroperated in the electron impact mode with an electronenergy of 70 eV, a multiplier voltage of 1650 V and collect-ing data at a rate of 1 scan s¡1 over a range of m/z 40–300.Six saturated aldehydes (pentanal, hexanal, heptanal, oct-anal, nonanal, decanal and undecanal) were identiWed bycomparing their linear retention indexes (LRI) with thosefrom standard compounds (Sigma–Aldrich, Steinheim,Germany). Results from the volatiles analysis are providedin area units (AU).

2.4. Sensory analysis

The samples were assessed by a trained panel of 12 mem-bers using a descriptive analysis method previously devel-oped by García et al., 1996 using the FIZZ (version 1.01)program. A 10 cm unstructured scale was used, theextremes being “very low” and “very high”. Threeextremely thin slices (1–1–5 mm) from the muscle bicepsfemoris from Iberian dry-cured ham were obtained using aknife and were immediately presented on a glass plate tothe assessors. All sessions were done at room temperaturein a six-booth sensory panel room equipped with whiteXuorescent lighting. The whole panel participated in eachsession, with the panellist order being randomised. Threehams from each group were successively evaluated in eachsession and the sample order was also randomised.

2.5. Statistical analysis

The results from the experiments (nD10 within eachbatch) were used as variables and analysed using an Analy-sis of Variance (ANOVA) (SPSS, 1997) in order to comparephysico-chemical parameters between hams from pigs feddiVerent Wnishing diets. Tukey’s tests were used whenANOVA found signiWcant diVerences between treatments.Pearson correlations were calculated between physico-chemical parameters and sensory traits. A principal compo-nent analysis (PCA) was also applied to variables. Statisti-cal signiWcance was predetermined at 0.05.

3. Results and discussion

3.1. Chemical composition of diets

Proximate composition and fatty acid proWles of pastureand acorns and CON and HOVE mixed diets are shown in

Table 1. The pasture contained the highest crude protein(21.75% DM), crude Wbre (20.2% DM) and ash (13.47%DM), whereas the acorns showed the highest content ofnitrogen-free extractives (NFE) (80.73% DM) and the low-est of protein (8.05% DM). HOVE mixed diet had higherlevels of fat than the control diet (8.29 versus 3.55% DM),but similar than those found in acorns (7.18% DM).

Regarding the fatty acid proWles of the feeds, the pasturehad a relatively high-proportion of PUFA (70.97%), partic-ularly of �-3 fatty acids, whereas the CON diet had higherlevels of SFA and PUFA (25.05% versus 11.06 % and42.62% versus 21.62%, respectively) and lower in MUFA(and 32.32% versus 67.32%) compared to the HOVE mixeddiet. As intended, HOVE mixed diet and acorns had a simi-lar fatty acid proWle, showing the highest level of MUFAand a relative low-proportion of PUFA. These results areconsistent with those obtained by Cava (1999) and Dazaet al. (2005).

3.2. Composition of muscles from dry-cured hams

The chemical composition of biceps femoris musclesfrom pigs fed diVerent Wnishing diets is shown in Table 2.The range of moisture (from 42.9 to 49.9 g/100 g muscle)and IMF (from 5.5 to 9.5 g/100 g muscle) values obtained inthe present study is similar to that reported by otherauthors in Iberian dry-cured ham (Carrapiso & García,2003; Cava, 1999; Ruiz et al., 2000). The feeding back-ground signiWcantly aVected the proximate composition ofthe muscles since those from MON pigs contained lessmoisture than muscles from CON pigs whereas those fromHOVE pigs showed intermediate values. Samples fromCON pigs contained signiWcantly higher amounts of pro-tein than those from MON and HOVE pigs. The IMF con-tent followed an opposite behaviour and muscles fromMON pigs contained signiWcantly higher amounts of IMFthan those fed with mixed diets (CON and HOVE pigs). Inagreement with these results, Petrón, Muriel, Timón, Mar-tín, and Antequera (2004) reported that muscles bicepsfemoris from dry-cured hams from Iberian pigs fed on

Table 1Proximate composition and fatty acid proWle of mixed diets (HOVE andCON), grass and acorns

SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA:polyunsaturated fatty acids.

a DM, dry matter.b NFE, nitrogen-free extractives.

HOVE CON Pasture Acorns

Dry matter 90.54 88.66 10.76 53.9Ash (% DM)a 4.62 3.95 13.47 2.17Crude protein (% DM) 16.95 16.72 21.75 8.05Crude Wbre (% DM) 5.69 3.29 20.2 1.87Fat (% DM) 8.29 3.55 3.07 7.18NFE (% DM)b 64.45 72.49 46.52 80.73� SFA 11.06 25.05 21.68 12.09� MUFA 67.32 32.32 7.35 66.88� PUFA 21.62 42.62 70.97 21.04

250 S. Ventanas et al. / Meat Science 77 (2007) 246–256

acorns and pasture contained signiWcantly higher intramus-cular lipids than those from dry-cured hams from pigs fedon conventional mixed diets. The high-levels of IMF inmuscles and meat products from Iberian pigs have beengenerally attributed to the breed-dependant ability to syn-thesise and accumulate large amount of lipids in their tis-sues (Ventanas et al., 2005) and, according to resultsobtained in the present study, the IMF content in muscles isalso aVected by the Wnishing diets given to Iberian pigs.According to Goerl, Eilert, Mandigo, Chen, and Miller(1995) a low-ratio protein/caloriWc value in diets leads tohigh-fat deposition in porcine tissues. Therefore, the intakeof acorns during the Wnishing phase of fattening wouldexplain the higher levels of IMF in free-range reared Ibe-rian pigs since acorns provide a high-caloriWc value withhigh-fat and carbohydrates levels and relatively low-pro-tein contents.

The present study reports, for the Wrst time, tocopherollevels in Iberian dry-cured hams (Table 2). The feedingbackground aVected the levels of �-tocopherol in musclesfrom dry-cured hams because muscles from MON andHOVE pigs contained signiWcantly higher levels than thosefrom CON pigs. These results were expected as the tocoph-erol levels in porcine tissues reXect the tocopherol concen-tration of the diets (Ruiz & López-Bote, 2002). In goodagreement with the present results Daza et al. (2005) andVentanas et al. (2006) reported that raw muscles from Ibe-rian pigs fed diets supplemented with �-tocopherol up to200 mg/kg contained similar �-tocopherol levels to thosefrom pigs fed on natural resources (acorns and pasture).Muscles from MON pigs had signiWcantly higher levels of�-tocopherol than muscles from CON and HOVE pigs(Table 2). Acorns have been highlighted as importantsources of �-tocopherol for extensively reared pigs and thepresence of such tocopherol isomer in pig muscles is almostrestricted to tissues from pigs fed acornst (Cantos et al.,2003; López-Bote, 1998) which is in agreement with resultsobtained in the present work.

The large diVerences reported in the present studyregarding the chemical composition of dry-cured musclesfrom the experimental batches are consistent with the het-erogeneity observed in the raw material (fresh muscle bicepsfemoris) (data not shown).

No signiWcant diVerences were found between batchesfor the total amount of chlorides regardless of the heteroge-neity of the raw material. No diVerences were foundbetween green hams for the depth of the subcutaneous fatwhich is largely inXuential on salt absorption patterns.Additionally, in order to obtain products with similar saltcontent, the producers adjust the time during which thehams are kept in the salting chambers depending on thefeeding background since it is generally recognised thatIberian hams from pigs fed outdoors contain higher IMFthan those fed on mixed diets.

3.3. Fatty acid composition of muscles from dry-cured hams

The feeding background signiWcantly aVected the fattyacid proWles of the m. biceps femoris from pigs fed diVerentWnishing diets (Table 3). As expected, the fatty acid proWlesof the muscles from dry-cured hams reXected the fatty acidcomposition of the feeds given to the pigs, and therefore,samples from MON and HOVE pigs had signiWcantlyhigher levels of oleic acid and total MUFA than the CONcounterparts. In contrast, muscles from CON Iberian hamshad signiWcantly higher levels of certain SFA (stearic acid),linoleic acid and total PUFA than those from MON andHOVE Iberian hams. Consistently, muscles from MON pigsreXected the high-levels of oleic acid from the acorns withwhich MON pigs were fed. Cava (1999) reported similarresults comparing the fatty acid proWles of Iberian dry-curedhams from free-range reared Iberian pigs and Iberian pigsfed on conventional mixed diets. According to our results,using oleic acid-enriched mixed diets was a successful strat-egy to increase the proportion of such fatty acid in Iberiandry-cured hams up to the levels generally found in dry-curedhams from Iberian pigs fed on acorns. The modiWcation ofthe fatty acid composition of dry-cured hams through die-tary means has been recently studied by Ruiz et al. (2005)who fed Iberian pigs on elevated MUFA levels leading toproducts with equivalent MUFA levels to those found in thepresent study. Furthermore, Daza et al. (2005) and Ventanaset al. (2006) eYciently increased the MUFA levels in musclesfrom Iberian pigs using oleic acid-enriched mixed diets.

Besides the eVect of the fatty acid composition on cer-tain sensory features, the diVerent fat composition of dry-

Table 2Chemical composition (means § standard deviation) of muscle biceps femoris in dry-cured hams from pigs fed diVerent Wnishing diets

A Statistical signiWcance.B g/100 g muscle.C �g/g muscle.

a,b,c Means with diVerent superscript diVer signiWcantly.

MON HOVE CON PA

MoistureB 42.99c § 1.71 47.89b § 1.79 49.93a § 1.59 0.000IMFB 9.51a § 1.48 7.08b § 1.41 5.47b § 1.66 0.000ProteinB 32.96b § 1.89 34.53b § 1.32 36.93a § 1.43 0.000ChlorideB 3.74 § 1.62 3.11 § 0.94 3.01 § 0.86 0.818�-TocopherolC 6.36a § 2.03 6.73a § 1.32 2.09b § 0.73 0.000�-TocopherolC 1.50a § 0.41 0.10b § 0.04 0.14b § 0.07 0.000

S. Ventanas et al. / Meat Science 77 (2007) 246–256 251

cured hams could have further eVects with nutritionalimpact. Dietary fatty acids are believed to inXuence thecholesterol levels in blood through the modiWcation of theconcentration of certain lipoproteins (Okuyama & Ikem-oto, 1999). SFA show proatherogenic eVects as theyincrease the levels of low-density lipoproteins (LDL)whereas unsaturated fatty acids show overall antiathero-genic eVects (Mattson & Grundy, 1985). MUFA show thestrongest antiatherogenic eVects since they reduce the lev-els of LDL without modifying or even increasing the levelsof high-density lipoproteins (HDL). Considering theseaspects, the fatty acid composition of the hams from MONpigs are associated with better nutritional aspects com-pared to those produced with tissues from pigs fed withmixed diets. From a nutritional point of view, considerableattention has been recently paid to the relative proportionbetween n¡ 6 and n¡ 3 fatty acids. Diets with inappropri-ate n¡ 6/n¡ 3 ratios have been highlighted as risk factorsin certain cancers and coronary heart diseases and, there-fore, it is recommended to keep this ratio below 4 (Enser,2001; Wood & Enser, 1997). The n¡ 6/n¡ 3 ratio was sig-niWcantly lower in muscles from MON dry-cured hamsthan in those from HOVE and CON dry-cured hamsmainly derived from the higher percentages of n¡ 3 fattyacid in the former. According to Muriel, Ruiz, Ventanas,and Antequera (2002) free-range rearing and feeding pigson pasture increase the levels of long chain n¡ 3 fatty acidsin porcine muscles which is in agreement with the presentresults. The dry-cured hams from free-range reared Iberian

pigs would contribute to increase the n¡ 6/n¡ 3 ratio inthe diet to a lesser extent than dry-cured hams from Ibe-rian pigs fed on mixed diets.

3.4. Oxidative status of muscles from dry-cured hams

Lipid oxidative reactions take place during ripening ofdry-cured hams (Andrés, Cava, Ventanas, Muriel, & Ruiz,2004) leading to the degradation of fatty acids and the sub-sequent generation of secondary lipid oxidation productssuch as TBARS and lipid-derived volatiles. No signiWcantdiVerences were found between batches for TBARS num-bers (Table 4). However, the headspace from CON dry-cured hams contained signiWcantly higher amounts of cer-tain saturated aldehydes such as hexanal and heptanal thanthat from HOVE and MON dry-cured hams. The suscepti-bility of muscle to lipid oxidation depends upon the balancebetween antioxidant and prooxidant factors (Frankel,1984). The fatty acid composition and the tocopherol levelsin porcine muscles are considered to decisively inXuence theintensity of the oxidative reactions and their adverse eVectsduring the ripening of hams (Cava, 1999). In this sense, thehigher levels of PUFA in CON dry-cured hams wouldexplain the higher oxidative instability of these hams com-pared to those from HOVE and MON batches. Moreover,the presence of high-levels of �-tocopherol in samples fromMON and HOVE pigs likely inhibited the generation of thelipid-derived volatiles. Muscles from MON pigs containedadditional levels of �-tocopherol derived from acorns which

Table 3Fatty acid proWle (means § standard deviation) of muscle biceps femoris in dry-cured hams from pigs fed diVerent Wnishing dietsA

SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids.A Results are expressed as means in percent.B Statistical signiWcance.

a,b,c Means with diVerent superscript diVer signiWcantly.

MON HOVE CON PB

C12:0 0.07b § 0.01 0.09a § 0.01 0.07b § 0.01 0.002C14:0 1.15b § 0.10 1.31a § 0.10 1.21ab § 0.14 0.043C16:0 22.68§ 0.85 23.05§ 0.83 22.48 § 0.89 0.377C17:0 0.17c § 0.02 0.21b § 0.04 0.25a § 0.04 0.000C18:0 9.72b § 0.56 9.90b § 0.54 10.91a § 1.05 0.006C20:0 0.18b § 0.02 0.24a § 0.02 0.24a § 0.04 0.000� SFA 33.97§ 1.27 34.79§ 1.04 35.17 § 1.77 0.197C16:1 (n ¡ 7) 3.86 § 0.42 4.33§ 0.46 3.96 § 0.76 0.193C17:1 (n ¡ 7) 0.20b § 0.03 0.25a § 0.03 0.26a § 0.04 0.003C 18:1 (n ¡ 9) 49.57a § 1.17 48.74a § 2.11 46.34b § 2.02 0.003C20:1 (n ¡ 7) 0.97a § 0.09 0.88ab § 0.09 0.84b § 0.09 0.010� MUFA 54.60a § 1.16 54.21a § 2.28 51.39b § 2.52 0.006C18:2 (n ¡ 6) 8.33b § 0.62 8.37b § 1.55 9.88a § 1.43 0.025C18:3 (n ¡ 6) 0.10b § 0.03 0.11ab § 0.03 0.14a § 0.02 0.007C18:3 (n ¡ 3) 0.42 § 0.05 0.32§ 0.05 0.37 § 0.04 0.001C20:2 (n ¡ 6) 0.33 § 0.05 0.30§ 0.03 0.34 § 0.04 0.077C20:3 (n ¡ 6) 0.19b § 0.04 0.20b § 0.05 0.30a § 0.07 0.000C20:4 (n ¡ 6) 1.88ab § 0.31 1.64b § 0.62 2.36a § 0.58 0.024C20:5 (n ¡ 3) 0.19a § 0.03 0.05b § 0.01 0.05b § 0.02 0.000� PUFA 11.43b § 0.94 11.00b § 2.29 13.44a § 2.10 0.024n ¡ 6 10.83b § 0.90 10.62b § 2.24 13.02a § 2.08 0.019n ¡ 3 0.60a § 0.07 0.38b § 0.06 0.42b § 0.04 0.000n ¡ 6/n¡ 3 18.06b § 1.51 28.20a § 3.51 31.24a § 4.92 0.000

252 S. Ventanas et al. / Meat Science 77 (2007) 246–256

probably enhanced the oxidative stability of such samples.Recently, Estévez, Ventanas, and Cava (2007) isolated phe-nolic compounds from tissues of free-range reared Iberianpigs which could have been accumulated as a result of theintake of natural resources. In fact, a large variety of poly-phenols have been described as components of the acornswith which Iberian pigs are usually fed (Cantos et al., 2003).There is no evidence, however, that these substances actu-ally contribute to enhance the oxidative stability of porcinetissues.

Though the positive eVect of lipid oxidation on thedevelopment of desirable aroma characteristics in dry-cured ham has been reported (Carrapiso, Jurado, Timón, &García, 2002) the development of oxidative reactions inIberian pig products has been generally associated with lossof quality including aroma, colour and texture deteriora-tion and generation of toxic compounds (Cava, 1999; Pet-rón, García-Regueiro, Martín, Muriel, & Antequera, 2003).In fact, tocopherols have been described as successful inhib-itors of lipid oxidative reactions during ripening of Iberiandry-cured ham improving some particular sensory charac-teristics such as Xavour and odour intensity (Cava, 1999).The relatively high-level of tocopherols in the Iberian dry-cured hams from the present study veriWes that these sub-stances persist in hams after a long ripening process (above24 months). The persistence of these substances in cellularmembranes after Iberian ham processing would allow theprotection against lipid oxidation beyond the ripeningstage. In fact, Isabel et al. (1999) found that ham slices frompigs supplemented with tocopherol showed lower discol-ouration and lower weight losses than those from pigs fedon conventional diets when stored imitating the conditionsof marketing display. However, the hams from the afore-mentioned study were obtained from industrial genotypepigs and subjected to a considerably shorter ripening pro-cess (6–12 months).

The feeding background also aVected the oxidative sta-bility of the proteins from dry-cured hams since MON and

HOVE samples contained signiWcantly smaller amounts ofprotein carbonyls than the CON counterparts. Currently,the occurrence of protein oxidation in dry-cured products ismostly unknown although recent studies by Ventanas et al.(2005) contributed to understand the relationship betweenlipid and protein oxidation. In agreement with the afore-mentioned study, results from the present study suggestthat the occurrence of protein oxidation followed a similarpattern to the oxidative degradation of lipids and was likelyaVected by similar factors.

3.5. Relationship between chemical and sensory parameters

In order to establish relationships between chemicalparameters and oxidation indices and sensory traits, Pear-son correlations were calculated (Table 5). The IMF waslargely inXuential on most sensory properties of dry-curedhams as signiWcant correlations between IMF and mostappearance, texture and Xavour traits were found. In fact, apositive and signiWcant correlation was found betweenIMF and marbling (R2: 0.40; p < 0.01) which is in agreementwith results found by Ruiz et al. (2000). Additionally, theIMF showed positive and signiWcant correlation with oth-ers appearance traits such as the redness and the brightnessof lean and the fat oiliness. In agreement with resultsreported by Ruiz et al. (2000), both the IMF and the mois-ture were signiWcantly correlated with juiciness. Given thatjuiciness has been pointed out as the main trait inXuencingoverall quality of Iberian dry-cured ham it seems clear thatIMF content is crucial in determining the acceptability ofthe product by consumer (Ruiz, García, Muriel, Andrés, &Ventanas, 2002).

The positive and signiWcant correlations found betweenIMF and the intensity and persistence of Xavour suggestthe possibility that the IMF would have inXuenced the gen-eration and release of aroma volatiles, aVecting the aromaperception by consumers which is in agreement with resultsrecently reported by Carrapiso (2007).

Table 4Protein carbonyls, TBARS and volatile aldehydes (means § standard deviation) isolated from muscle biceps femoris in dry-cured hams from pigs feddiVerent Wnishing diets

A Statistical signiWcance.B nM carbonyls/mg protein.C mg MDA/kg muscle.D Results expressed as area units (AU £ 106).

a,b,c Means with diVerent superscript diVer signiWcantly.

MON HOVE CON PA

CarbonylsB 7.37b § 0.85 6.84b § 0.67 8.87a § 0.72 0.000TBARSC 0.36§ 0.13 0.34 § 0.09 0.33 § 0.19 0.847AldehydesD

Pentanal 47.12§ 16.55 50.52 § 26.71 66.44 § 18.20 0.137Hexanal 221.36b § 46.77 206.66b § 34.55 313.70a § 43.31 0.000Heptanal 8.83b § 1.70 11.31b § 3.34 17.07a § 5.92 0.002Octanal 5.66§ 1.68 5.91 § 2.19 7.41 § 1.79 0.143Nonanal 6.78§ 2.06 6.54 § 2.39 7.39 § 2.39 0.755Decanal 0.48§ 0.19 0.30 § 0.08 0.41 § 0.15 0.107Undecanal 0.37§ 0.17 0.25 § 0.07 0.30 § 0.11 0.217

S. Ventanas et al. / Meat Science 77 (2007) 246–256 253

The major fatty acids could have an inXuence on certainsensory features, with the stearic and oleic acids showingthe highest signiWcance, which is consistent with resultsreported by other authors (Ruiz et al., 2000; Wood et al.,2004). Stearic and oleic acids played opposite roles in cer-tain appearance traits since a positive signiWcant correla-tion was found between oleic acid and lean redness andbrightness and fat oiliness whereas a negative signiWcantcorrelation was found between such sensory traits and stea-ric acid. In the present study, PUFA such as linoleic acidsigniWcantly correlated as well with brightness and oilinessbut to a lesser extent than stearic and oleic acids which is inagreement with previous Wndings (Carrapiso et al., 2003).Fat consistency and appearance itself plays a signiWcantrole in consumer acceptability as Spanish consumers verymuch appreciate a soft and oily fat in Iberian dry-curedham (Ruiz et al., 2002). Ruiz et al. (2002) suggested that thepositive eVect of oiliness on Iberian dry-cured ham accept-ability is most likely due to a positive link between higheroleic acid contents and a desirable Xavour. In this sense,high-levels of oleic acid-derived volatiles such as heptanal,octanal and nonanal in dry-cured and cooked productsfrom Iberian pigs have been considered a plausible reXec-tion of the high-levels of such fatty acid in the tissues (Est-évez, Morcuende, Ventanas, & Cava, 2003, 2004; Martín,Timón, Petrón, Ventanas, & Antequera, 2000) and werehighlighted to contribute pleasing sweet or fruity aromanotes (Specht & Baltes, 1994). In agreement with that, posi-tive and signiWcant correlations were found between oleicacid and the persistence of the aroma although this couldbe an indirect relationship due to the positive relationshipbetween IMF and oleic acid.

SigniWcant correlations were found between the oxida-tion indices and certain sensory traits. Hexanal levels andTBARS, to a lesser extent, were negatively correlated withmost positive sensory features which is in agreement withthe documented association between lipid oxidation anddeterioration of colour, texture and Xavour of meat prod-ucts (Morrissey, Sheehy, Galvin, Kerry, & Buckley, 1998).Particularly remarkable are the signiWcant correlationsfound between protein carbonyls and most sensory traitsin dry-cured ham since very little information is availableregarding the occurrence of protein oxidation and theiradverse eVects in dry-cured products. A signiWcant positivecorrelation was found between protein carbonyls and ran-cidity suggesting the likely interactions between lipid andprotein oxidation processes which were previouslyreported by Viljanen, Kylli, Kivikari, and Heinonen(2004), Estévez and Cava (2004) and Ventanas et al. (2005).The signiWcant negative correlations found between pro-tein carbonyls and certain appearance (i.e., redness of lean)and texture features are consistent with previous reportsproposing plausible mechanisms by which the develop-ment of protein oxidation in meat products would aVectthe stability of myoglobin pigments leading to colour dete-rioration and would aVect meat texture through the estab-lishment of cross-linking between muscle proteins(Estévez, Ventanas, & Cava, 2005). Moreover, positive andsigniWcant correlations were detected between the proteinoxidation index and bitterness and sourness which couldbe explained by the fact that a large variety of acids andamino-containing molecules with taste potential have beenrecognised as protein oxidation products (Davies, Fu,Wang, & Dean, 1999).

Table 5Pearson’s correlation coeYcients (R2) between chemical parameters and oxidation indexes and sensory features of muscle biceps femoris in dry-curedhams from pigs fed diVerent Wnishing dietsa

Statistical signiWcance: (¤) p < 0.05; (¤¤) p < 0.01; (¤¤¤) p < 0.001.a n D 24 Iberian dry-cured hams for correlation coeYcients.

Sensory features Chemical composition Oxidation indexes

Moisture IMF Tocopherol C16:0 C18:0 C18:1 C18:2 Protein carbonyls TBARS Hexanal

AppearanceRedness ¡0.55¤¤ 0.47¤¤ 0.53¤¤ 0.03 ¡0.47¤¤ 0.44¤ ¡0.29 ¡0.46¤ 0.21 ¡0.44¤

Brightness ¡0.58¤¤ 0.54¤¤ 0.67¤¤¤ 0.24 ¡0.46¤ 0.44¤ ¡0.40¤ ¡0.48¤¤ ¡0.12 ¡0.56¤¤

Marbling ¡0.34 0.41¤ 0.12 0.20 ¡0.04 0.25 ¡0.35 0.07 ¡0.04 0.00Oiliness ¡0.66¤¤¤ 0.58¤¤¤ 0.77¤¤¤ 0.03 ¡0.57¤¤¤ 0.60¤¤¤ ¡0.43¤ ¡0.53¤¤ ¡0.04 ¡0.64¤¤¤

TextureHardness ¡0.35 0.24 ¡0.10 ¡0.05 0.01 0.14 ¡0.06 0.07 0.47¤¤ ¡0.18Juiciness ¡0.59¤¤ 0.59¤¤¤ 0.63¤¤¤ 0.12 ¡0.53¤¤ 0.57¤¤¤ ¡0.51 ¡0.44¤¤ 0.11 ¡0.62¤¤¤

TasteSaltiness ¡0.46¤¤ 0.33 ¡0.03 0.16 ¡0.08 0.08 ¡0.15 0.11 0.01 ¡0.17Sweetness 0.05 0.26 0.30 ¡0.28 ¡0.27 0.19 0.02 ¡0.45¤¤ ¡0.09 ¡0.17Bitterness 0.40¤ ¡0.52¤¤ ¡0.44¤ ¡0.20 0.40¤ ¡0.34¤ 0.28 0.64¤¤¤ 0.10 0.40¤¤

Sourness ¡0.05 ¡0.10 ¡0.26 ¡0.27 0.19 0.06 0.01 0.43¤¤ 0.01 0.43¤¤

FlavorIntensity ¡0.73¤¤¤ 0.57¤¤¤ 0.43¤ 0.10 ¡0.24 0.26 ¡0.22 ¡0.16 0.12 ¡0.46¤¤

Persistence ¡0.76¤¤¤ 0.52¤¤ 0.42¤ 0.04 ¡0.36¤ 0.45¤ ¡0.37¤ ¡0.07 0.11 ¡0.39Rancidity 0.16 ¡0.21 ¡0.36¤ ¡0.16 0.30 ¡0.17 0.12 0.63¤¤¤ 0.07 0.27

254 S. Ventanas et al. / Meat Science 77 (2007) 246–256

3.6. Principal component analysis

A PCA was performed using data obtained from thechemical and sensory characterisation of muscle bicepsfemoris from dry-cured hams in order to determine the rela-tionship between chemical and sensory parameters and todiscriminate between samples from pigs with diVerent feed-ing background. Fig. 1a shows the similarity map of themeasured parameters deWned by the two Wrst PrincipalComponents (PC#1 and PC#2, respectively) thataccounted for the 52.5% of the total variability. The relativeposition of the variables in the similarity map suggests closerelationships between certain parameters supporting theresults obtained from the Pearson correlations.

As expected, IMF was situated on the positive axis ofPC#1, far from the origin and close to the oleic acid andsensory features with which IMF has recognised relation-ships (brightness, oiliness and juiciness). Other set of rele-vant sensory features such as lean redness and Xavourintensity and persistence was situated in the right upperquadrant, far from the positive axis of PC#1 and the ori-gin and near to �-tocopherol. In the opposite location, thelipid and protein oxidation indices (hexanal and proteincarbonyls) were situated in the left upper quadrant, farfrom the negative axis of PC#1 and the origin and rela-tively near to rancidity, bitterness and sourness which is inagreement with the Pearson correlation coeYcients calcu-lated.

Fig. 1. Iberian dry-cured hams: projection of the samples (a) and physicochemical and sensory variables (b) onto the space deWned by the principal compo-nents (PC#1/PC#2). Sample groups: (�) MON; (�) HOVE; (�) CON.

a

b

S. Ventanas et al. / Meat Science 77 (2007) 246–256 255

The projection of the samples onto the PC space(Fig. 1b) showed that hams from MON pigs were situatedon the positive axis of PC#1, in the plane area correspond-ing to high-values of IMF, oleic acid and tocopherols.According to the PCA, dry-cured hams from free-rangereared Iberian pigs are mainly deWned by sensory featureswhich positively inXuence consumer’s acceptability such aslean redness, brightness, oiliness, marbling, juiciness andXavour intensity and persistence. On the contrary, hamsfrom pigs fed control diets were situated in the negativepositive axis of PC#1 within the plane area of the stearicand linoleic acids, the oxidation indexes and negative sen-sory features such as the rancidity and the bitterness. Sam-ples from HOVE pigs were situated in an intermediateposition in the negative axis of PC#2 and relatively close tothe origin. The relative proximity between samples fromMON and HOVE pigs suggest that using HOVE diets forfeeding Iberian pigs partially imitates the composition andquality traits of hams from MON pigs. However, accordingto the results obtained in the PCA, the variables computedin the model clearly discriminated between dry-cured hamsfrom pigs fed diVerent Wnishing diets. In fact, consumerpreference tests carried out with samples from the sameIberian-dry cured hams (data not shown) conWrmed thatpoint since non-trained subjects discriminated between Ibe-rian dry-cured hams from MON and HOVE pigs andshowed a clear preference for hams from MON pigs.

4. Conclusions

The feeding background inXuences the chemical compo-sition and oxidative status of the Iberian dry-cured hamsthrough the modiWcation of their fatty acid compositionand the incorporation of substances with antioxidant activ-ity. The purpose of improving the quality characteristics ofIberian dry-cured hams from pigs reared in conWnement byusing enhanced mixed diets was partially fulWlled. On onehand, the dietary supplementation with tocopherol in oleicacid-enriched diets is a successful strategy to increase thelevels of �-tocopherol and oleic acid in Iberian-dry-curedhams. On the other hand, the hams from pigs fed on thisenhanced diet do not attain the IMF levels of hams fromIberian pigs fed on acorns which could be considered a seri-ous drawback since this parameter inXuences essential sen-sory features of Iberian hams such as the fat oiliness thejuiciness and the Xavour.

Acknowledgements

Sonia Ventanas thanks the ‘Ministerio de Educación’ forthe ‘FPU’ grant and support. This study was supported bythe “Ministerio de Ciencia y Tecnología” project entitled:“Hacia el establecimiento de predictores de calidad en lamateria prima y en productos del cerdo ibérico medianteparámetros Wsico-químicos (ULTRAFAT)” (Project AGL2001-6932-01). The authors thank Ana Galaz for labora-tory support and Dr. Tejeda for tocopherol analyses.

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