volatile compounds of experimental liver pâté from pigs fed conjugated linoleic acid in...

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Research ArticleReceived: 31 October 2008 Revised: 28 April 2009 Accepted: 1 June 2009 Published online in Wiley Interscience: 21 July 2009

(www.interscience.wiley.com) DOI 10.1002/jsfa.3697

Volatile compounds of experimental liver patefrom pigs fed conjugated linoleic acidin combination with monounsaturated fattyacidsDiana Martin,∗ Teresa Antequera, Elena Muriel, Trinidad Perez-Palaciosand Jorge Ruiz

Abstract

BACKGROUND: Feeding conjugated linoleic acid (CLA) to pigs leads to CLA-enriched meat products, which are of current interestowing to the potential health properties of CLA. However, dietary CLA increases the ratio of saturated to monounsaturatedfatty acids (MUFA) in pig tissues. Combining CLA with high MUFA levels in pig diets may counteract this effect. Owing to themodification of fatty acid composition, variation in the volatile profile of derived meat products might be expected. The aim ofthe present work was to study the volatile profile, and its change during storage, of experimental liver pate manufactured frompigs fed different levels of CLA and MUFA.

RESULTS: Regardless of the CLA or MUFA level, 98 compounds were identified. Lower area units were observed for mostbranched aldehydes, ketones and alcohols and some furans, sulfur compounds and nitrogen compounds with increasing CLAand MUFA contents. Levels of nonanal, propan-2-one, dodecane, 2-pentylfuran and ethylbenzene were higher in CLA pates.The effect of experimental diets on the change in volatiles during storage was not significant.

CONCLUSION: Supplementation of pig diets with CLA isomers in combination with low or high MUFA levels seems to have asignificant effect on the volatile profile of pork liver pate.c© 2009 Society of Chemical Industry

Keywords: conjugated linoleic acid; monounsaturated fatty acids; volatile compounds; liver pate

INTRODUCTIONConjugated linoleic acid (CLA) has shown beneficial implica-tions for different pathologies in experimental animals, suchas anticarcinogenic effects, decrease in body fat mass, de-crease in serum cholesterol level and improvement in insulinsensitivity and immune function.1 As a consequence, the pro-duction of CLA-enriched foodstuffs is currently attracting muchinterest.2

Feeding animals with CLA has been proposed as an inter-esting approach for obtaining CLA-enriched meat and meatproducts, since the subsequent accumulation of CLA in animaltissues has been demonstrated.2 – 4 However, CLA feeding alsohas an effect on the fatty acid composition of animal tissuesby increasing the saturated fatty acid (SFA) content and de-creasing the monounsaturated fatty acid (MUFA) content.2,3,5

The resulting increase in SFA/MUFA ratio could have nega-tive health implications.6 Nevertheless, including high levelsof MUFA in pig diets when using dietary CLA has been sug-gested as a strategy for counteracting the decrease in MUFAcaused by CLA.3,5 On the other hand, some evidence of an-tioxidant activity of CLA isomers has been found,7 but thiseffect still remains inconclusive and needs to be examined morecarefully.

Liver pate is a popular meat product in European countries suchas France, Spain and Germany.8 – 10 Liver and its mixture with meatand/or fat are the typical ingredients of liver pate. Liver, pork andfat from CLA-fed pigs have been shown to accumulate CLA.3,4

Therefore these CLA-enriched raw materials could be used for themanufacture of CLA-enriched meat products. No previous studieson dietary CLA and liver pate have been found in the scientificliterature.

The preparation of liver pate involves the mixing and mincingof the raw materials and the subsequent application of hightemperatures. As a consequence of the thermal treatment andmincing of the ingredients, oxidative reactions are enhanced inliver pate, which in turn lead to the typical flavour and odourattributes of the product.11,12 The fat content and the fatty acidcomposition of this fat are among the main characteristics thatcontribute to the flavour and odour of meat products.13,14 Since

∗ Correspondence to: Diana Martin, Tecnologia de Alimentos, Facultad deVeterinaria, Universidad de Extremadura, Avda Universidad s/n, E-10071Caceres, Spain. E-mail: [email protected]

Tecnologia de Alimentos, Facultad de Veterinaria, Universidad de Extremadura,Avda Universidad s/n, E-10071 Caceres, Spain

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Volatile compounds of liver pate from pigs fed CLA and MUFA www.soci.org

dietary CLA leads to modification of the fatty acid profile of animaltissues, the greater the modification of the fatty acid compositioncaused by CLA is, the higher will be the expected variation in thevolatile profile of the manufactured meat product. However, veryfew studies regarding CLA and volatile compounds in meat prod-ucts have been found in the scientific literature. Only one studyhas been carried out on fresh pork from CLA-fed pigs,15 while allother studies have been performed on poultry.16 – 18 Furthermore,the combination of dietary CLA with different MUFA levels in pigdiets and its effect on the volatile profile of meat products havenot been studied previously and would also be of interest.

Therefore the aim of the present work was to study the volatileprofile, and its change during storage, of experimental liver patemanufactured with raw materials from pigs fed different levels ofCLA and MUFA.

MATERIALS AND METHODSAll animals were cared for in accordance with the University ofExtremadura Animal Care and Welfare Committee regulations.

Animals and feedingThree levels (0, 10 and 20 g kg−1, i.e. 0, 1 and 2%) ofcommercial enriched CLA oil supplementation (CLA-60, containingapproximately 560 g kg−1 CLA isomers: 280 g kg−1 cis-9,trans-11and 280 g kg−1 trans-10,cis-12; BASF, Dortmund, Germany) andtwo levels of MUFA (low, 190 g kg−1, and high, 390 g kg−1) werecombined for pig feeding (Table 1). All diets were formulated toprovide similar protein and energy levels, fulfilling the nutritionalneeds of female pigs at the considered ages as recommended bythe National Research Council.19

Table 1. Ingredients, chemical composition and fatty acid composition of experimental treatments for pig feeding

Low-MUFA feed High-MUFA feed

0% CLA 1% CLA 2% CLA 0% CLA 1% CLA 2% CLA

Ingredients (g kg−1)

Barley 533 533 533 533 533 533

Wheat 150 150 150 150 150 150

Bran 80 80 80 80 80 80

Soybean meal 44% 160 160 160 160 160 160

Palm oil 16 11 6 10 5 0

Soy olein 4 4 4 0 0 0

Olive olein 0 0 0 30 30 30

Hydrogenated palm stearin 30 25 20 10 5 0

CLA 0 10 20 0 10 20

Carbonate 12 12 12 12 12 12

Phosphate 4 4 4 4 4 4

Salt 4 4 4 4 4 4

L-Lysine 50 1.7 1.7 1.7 1.7 1.7 1.7

L-Threonine 0.3 0.3 0.3 0.3 0.3 0.3

Coline 75 0.4 0.4 0.4 0.4 0.4 0.4

Vitamin and mineral premix 5 5 5 5 5 5

Chemical composition (g kg−1)

Dry matter 892 896 894 893 895 896

Ash 49 51 50 51 56 53

Crude fibre 42 43 41 47 43 46

Crude fat 77 69 73 72 71 68

Crude protein 164 160 158 167 165 158

Nitrogen-free extract 628 641 640 624 627 638

Energy (kcal kg−1) 3238.8 3240.8 3242.8 3257.8 3259.8 3261.8

Fatty acid composition (g kg−1)

C14 : 0 8 6 5 5 3 3

C16 : 0 353 304 256 254 197 150

C16 : 1 1 1 1 5 4 4

C18 : 0 228 201 166 114 76 46

C18 : 1n-9 181 180 187 378 379 378

C18 : 2n-6 199 202 198 206 222 225

C18 : 3n-3 18 17 16 18 21 21

cis-9,trans-11-CLA 0 39 80 0 43 79

trans-10,cis-12-CLA 0 37 79 0 42 81

SFA 597 520 435 388 284 206

MUFA 188 186 192 389 388 387

PUFAa 215 219 215 224 244 247

a Excluding CLA isomers.

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www.soci.org D Martin et al.

The experiment was conducted using 288 finishing gilts(Large White × Landrace × Large White ). Pigs weighing

70 kg and aged about 140 days were randomly allotted tothe six different feeding treatments in four replicates of eachtreatment (12 pigs per replicate). Pigs were housed in groups(12 pigs per pen) in an environmentally controlled experimentalgrower/finisher shed and had ad libitum access to feed (single-space dry feeders) and water (nipple drinkers) until reaching107 kg final average weight. After fattening (53 days), pigs wereslaughtered at a local slaughterhouse by electrical stunning andexsanguination.

Sampling procedureRepresentative samples of mixed diets were taken before thebeginning of the trial in order to determine their chemical andfatty acid compositions. Eight animals from each treatment wererandomly selected for sampling. The whole loin and liver fromslaughtered animals were taken within 10 min after bleeding.Loins were kept at 4 ◦C for 24 h. Loins and livers were vacuumpackaged and frozen at −80 ◦C until required.

Manufacture of experimental liver pateThe liver pates were produced in the meat pilot plant at the De-partment of Food Science of the University of Extremadura, Spain.Six different experimental batches of pate were manufacturedaccording to the six dietary treatments of pigs. For the manu-facture of each experimental pate a composite mixture of theliver and meat from the eight selected pigs from each treatmentwas prepared by cutting the samples into small cubes (1.5 cm3).The same formula was used for all pates: 320 g kg−1 liver, 320 gkg−1 loin, 320 g kg−1 water, 20 g kg−1 sodium caseinate and 20 gkg−1 sodium chloride. Moreover, sodium di- and triphosphates(0.5 g kg−1), sodium ascorbate (0.05 g kg−1) and sodium nitrite(0.03 g kg−1), all generously provided by ANVISA (Madrid, Spain),were also added. All ingredients were minced in a vacuum cutter(Stephan, Hameln, Germany) preheated to 60 ◦C. After adding theingredients, the cutter temperature fell to 40–45 ◦C. The ingre-dients were minced until the temperature reached 65 ◦C (∼3.5min). Each group of experimental pates was manufactured intriplicate following the described process. The batter from eachreplicate was distributed and packed in four glass containers (50 gper container), which were then autoclaved at 115 ◦C for 30 min.The containers were allowed to cool to room temperature (∼1h) and then stored in the dark in a control heater at 25 ◦C. Twocontainers from each replicate of each type of pate were sampledat day 0 and day 200 of storage at 25 ◦C and frozen at −80 ◦C untilanalysis.

Volatile compoundsVolatile compounds of experimental pates were determinedby headspace solid phase microextraction (HS-SPME; Su-pelco Co., Bellefonte, PA, USA) using a fibre coated withcarboxen/poly(Divinylbenzene/carboxen/polydimethylsiloxane(50/30 µm)).20 A portion of pate (0.5 g) was weighed intoa 4 mL screw-capped vial and 1.5 mL of saturated sodiumchloride solution was added. Extractions were performed in athermostatted water bath at 40 ◦C for 30 min under stirring.Before extraction, samples were equilibrated for 10 min at thetemperature used for extraction. Prior to analysis the SPMEfibre was preconditioned at 250 ◦C for 60 min in the gas

chromatograph injection port. Analyses were performed usingan Agilent 6890 gas chromatograph coupled to an Agilent 5973mass-selective detector (Agilent, Avondale, PA, USA). Analyteswere separated using a 5% Phenyl-Methyl Silicone (HP-5) bondedphase fused silica capillary column (50 m × 0.32 mm i.d., filmthickness 1.05 µm; Hewlett-Packard, Palo Alto, CA, USA) operatedat 45 kPa of column head pressure, resulting in a flow rate of1.3 mL min−1 at 40 ◦C. Volatiles were desorbed into the gaschromatograph by placing the SPME fibre in the injection portfor 30 min. The injection port was operated in splitless mode.The column temperature was held at 40 ◦C for 10 min, raised to200 ◦C at a rate of 5 ◦C min−1 and then to 250 ◦C at a rate of20 ◦C min−1 and finally held at 250 ◦C for 5 min. The transferline to the mass spectrometer was held at 280 ◦C. Mass spectrawere obtained by electronic impact at 70 eV with a multipliervoltage of 1756 V and data collection at a rate of 1 scan s−1

over the m/z range 30–300. n-Alkanes (Sigma R-8769, Steinhein,Germany) were analysed under the same conditions to calculatethe retention indices (RIs) of the volatiles. Compounds wereidentified by comparison of their mass spectra and RIs with thoseof commercial reference compounds (Sigma-Aldrich, Steinhein,Germany), by comparison of their mass spectra and RIs withthose described on the web at http://webbook.nist.gov/, and bycomparison of their mass spectra with those contained in theWiley library. Results from the volatile analysis are given in areaunits (AU).

Statistical analysisThe data structure consisted of the volatile compounds ofexperimental liver pates from pigs fed the six different treatments.The experimental unit was each individual canned liver pate fromeach treatment. Statistical analyses were performed by meansof the general linear model procedure of the SPSS Version15.0 statistical package (SPSS Inc., Chicago, IL, USA). The effectof CLA and MUFA contents of the diets and their interactionon the volatile profile was evaluated by two-way analysis ofvariance (ANOVA). Differences were considered significant atP ≤ 0.05. When the effect of any of the factors was significant,differences between groups were analysed by Tukey’s post hoctest.

RESULTS AND DISCUSSIONVolatile profile of liver patesThe volatile compounds detected in experimental pates as affectedby dietary CLA, MUFA or CLA × MUFA interaction are shownin Table 2. A total of 98 compounds were identified in patesby HS-SPME coupled to gas chromatography/mass spectrometry(GC/MS). Compounds were assigned to 11 volatile classes: acids(two compounds, 2.7% of total AU), alcohols (five compounds,9.9% of total AU), aldehydes (18 compounds, 41.4% of totalAU), aliphatic hydrocarbons (11 compounds, 6.8% of total AU),aromatic hydrocarbons (five compounds, 4.9% of total AU), esters(two compounds, 1.4% of total AU), furans (nine compounds, 5.1%of total AU), ketones (21 compounds, 13.2% of total AU), nitrogencompounds (11 compounds, 3.3% of total AU), sulfur compounds(11 compounds, 8.7% of total AU) and terpenes (three compounds,1.9% of total AU). Most of the volatiles detected in the presentwork have been reported as volatile components of cooked pork,oxidised liver, canned liver sausage and liver pate.21 – 23

Aldehydes were the major group of volatile compounds in theexperimental pates. Lower AU were observed for most branched

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Table 2. Volatile profile (AU ×104) of liver pate from pigs fed different levels of CLA and MUFAa

Low MUFA High MUFA Pb

Compound 0% CLA 1% CLA 2% CLA 0% CLA 1% CLA 2% CLA SEM C M C × M Reliabilityc

Acids

2-Methyl butanoic acid 825.9a 490.5ab 887.9a 886.3a 339.6b 354.1b 58.2 0.002 0.026 0.033 B

2-Ethyl hexanoic acid 3551.5 1714.7 2925.8 2838.5 1791.0 893.2 366.5 0.217 0.227 0.491 B

Total acids 4377.4 2205.2 3813.7 3724.8 2130.6 1247.3 394.4 0.132 0.173 0.366

Alcohols

Hexan-1-ol 1650.9abc 1095.9bc 904.8bc 2760.8a 1981.8ab 660.3c 175.9 <0.001 0.025 0.055 A

Oct-1-en-3-ol 3153.5ab 2198.4bc 2334.4bc 4298.3a 2651.6abc 1364.5c 213.1 <0.001 0.518 0.034 A

2-Ethylhexan-1-ol 620.1a 196.7ab NDb 376.0ab 274.0ab NDb 96.2 0.001 0.631 0.473 A

4-Methylphenol 2424.9a 1720.6ab 1933.1ab 2081.1ab 1700.1ab 1218.8b 98.5 0.005 0.036 0.240 B

2,6-Dimethylcyclohexan-1-ol

4122.6ab 4272.4ab 4516.0ab 4241.1ab 5087.9a 3310.7b 174.3 0.163 0.782 0.048 B

Total alcohols 11972.0a 9484ab 9688.3ab 13757.3a 11695.4ab 6554.3b 545.1 0.001 0.772 0.042

Aldehydes

2-Methylpropanal 1539.5a 991.4abc 1280.4abc 1351.1ab 695.1bc 562.4c 90.2 0.004 0.010 0.308 B

3-Methylbutanal 16847.2a 9371.3bc 12877.3ab 14856.4ab 5226.0c 5384.0c 938.4 <0.001 0.001 0.188 A

2-Methylbutanal 390.4a 238.2ab 313.1a 355.8a 113.3b 104.1b 24.9 <0.001 0.001 0.143 A

Pentanal 88.8a 83.2ab 71.9ab 63.8ab 74.8ab 41.3b 4.7 0.075 0.017 0.540 A

2-Methylbut-2-enal 320.2a 224.5ab 249.1ab 322.3a 188.8ab 121.8b 19.1 0.004 0.099 0.249 B

Hexanal 8425.0 10685.6 8978.0 7795.4 10114.9 5655.6 596.2 0.089 0.196 0.538 A

Heptanal 44.5 45.0 48.3 33.2 47.5 35.8 4.5 0.311 0.076 0.277 A

(E)-Hept-2-enal NDb 368.4a 213.8a 365.4a 272.2a NDb 68.0 <0.001 0.550 <0.001 A

Benzaldehyde 4583.3ab 3934.0ab 4862.7ab 6156.0a 3729.0ab 3214.2b 325.1 0.045 0.858 0.054 A

Octanal 46.7 56.3 54.7 40.0 63.8 44.3 5.6 0.038 0.536 0.335 A

2-Ethylhex-2-enal 489.9a 412.6ab 404.9ab 454.7ab 338.7b 413.4ab 50.3 0.025 0.232 0.485 B

2-Phenylacetaldehyde 3315.5 3292.1 3554.0 3434.8 3213.8 2877.2 125.2 0.762 0.259 0.202 B

(E)-Oct-2-enal 486.9 751.9 650.3 712.5 753.7 392.5 32.4 0.032 0.889 0.053 A

Nonanal 5913.9ab 8142.4ab 7933.2ab 4807.3b 8481.1a 6815.4ab 215.0 0.003 0.351 0.593 B

Decanal 39.5 43.1 42.8 19.8 46.5 44.0 3.5 0.113 0.425 0.267 B

Dodecanal 8.2ab 4.0b 3.5b 10.8a 4.3b 3.3b 0.4 <0.001 0.450 0.586 B

Tetradecanal 3.1 2.6 2.4 3.8 2.3 2.3 0.2 0.039 0.778 0.459 B

Octadecanal 4161.1c 8100.6ab 11495.8a 8105.9ab 6149.5bc 7583.1bc 394.3 0.001 0.348 <0.001 C

Total aldehydes 46703.7ab 46747.2ab 53036.2a 48889.0a 39515.3ab 33294.7b 1525.6 0.314 0.005 0.010

Aliphatic hydrocarbons

2-Methylpentane 895.6a 608.4ab 388.2c 610.7ab 1044.9a 294.6c 45.7 <0.001 0.821 0.005 B

3-Methylpentane 761.5ab 678.2ab 445.5b 641.7ab 1047.8a 304.5b 98.0 0.001 0.708 0.061 B

Heptane 909.9 572.6 417.8 779.0 885.1 426.0 85.3 0.072 0.663 0.427 A

Oct-2-ene 4.2ab 4.7ab 3.6b NDc 5.6a 5.1ab 0.9 <0.001 0.136 <0.001 C

Decane 930.3 1213.2 982.1 ND 1291.1 1207.7 75.4 0.117 0.126 0.448 A

Undecane 2418.6 2536.1 2058.0 ND 2850.5 2138.3 543.0 0.081 0.448 0.651 B

Dodecane 863.6bc 1392.8a 1049.7abc 599.0c 1416.7a 1265.8ab 68.1 <0.001 0.935 0.160 C

2-Methyldodecane 449.8 1008.3 551.0 343.8 543.4 586.9 70.9 0.093 0.196 0.284 B

Tetradecane 363.3 301.8 360.3 295.8 372.9 223.1 19.6 0.549 0.246 0.069 B

Pentadecane 452.0a 431.8a 469.7a 388.2a 370.2a 224.5b 18.1 0.065 <0.001 0.007 B

Hexadecane 90.3 77.8 114.0 123.9 84.6 83.0 6.8 0.280 0.816 0.152 B

Total aliphatichydrocarbons

8139.1ab 8825.7ab 6839.9b 3782.1c 9912.8a 6759.5b 459.1 <0.001 0.031 0.001

Aromatic hydrocarbons

Methylcyclopentane 1542.2 855.2 666.8 1359.2 1420.9 1035.6 148.2 0.375 0.440 0.571 B

Toluene 806.2 738.4 775.7 865.9 807.5 432.7 49.6 0.131 0.452 0.140 B

Ethylbenzene NDc 630.0ab 862.5a NDc 553.6b 464.8b 55.4 <0.001 0.008 0.011 B

1,3-Xylene 2154.4ab 2208.0ab 2729.2a 2020.9ab 2011.5ab 1598.8b 99.8 0.937 0.010 0.051 B

Styrene 845.6 876.9 983.8 670.0 825.4 711.7 47.7 0.666 0.094 0.650 A

Total aromatichydrocarbons

5348.4 5308.5 6018.0 4916.0 5618.9 4243.6 244.9 0.439 0.090 0.059

Esters

Ethyl acetate 391.1 286.2 161.8 401.0 256.5 194.5 30.1 0.011 0.939 0.901 B

[(E)-Hex-3-enyl]butanoate

1034.2 2828.3 1281.0 502.9 1223.8 712.2 243.2 0.098 0.064 0.597 C


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Table 2. (Continued)

Total esters 1425.3 3114.5 1442.8 903.9 1480.3 906.7 224.6 0.400 0.193 0.991

Furans

2-Methylfuran 18.6 11.2 16.9 20.8 9.5 6.9 1.8 0.059 0.356 0.359 C

2-ethylfuran 65.2 55.6 75.7 83.0 63.4 46.3 4.1 0.239 0.867 0.039 B

Dihydro-2-methyl-2(3H)-furanone

629.0 571.7 460.7 550.9 429.8 425.6 27.4 0.122 0.137 0.726 B

Furan-2-carbaldehyde 55.3a 44.6ab 45.6ab 59.8a 41.8ab 28.5b 2.5 0.001 0.216 0.100 B

2-Furylmethanol 118.5ab 96.5b 111.0ab 129.6a 98.6ab 52.9c 5.1 <0.001 0.022 <0.001 B

2-Pentylfuran 2824.1 3355.9 3468.4 2968.1 3891.5 3772.3 137.2 0.045 0.218 0.828 B

5-Hexyloxolan-2-one 299.6 183.2 300.1 277.0 123.3 173.5 20.4 0.025 0.071 0.496 C

Unidentifiedbenzofuranone

1369.6a 941.2ab 1024.2ab 1211.6a 1112.2a 534.5b 65.6 0.002 0.140 0.050 C

Dihydro-5-(2-octenyl)-2(3H)-furanone

82.3 125.6 92.9 119.4 76.4 94.7 8.4 0.925 0.854 0.203 B

Total furans 5462.2 5385.5 5595.5 5420.2 5846.5 5135.2 174.2 0.790 0.986 0.363

Ketones

Acetone 1809.5 1516.2 3212.6 1772.4 1803.9 4081.2 300.4 0.009 0.501 0.793 B

Butane-2,3-dione 1171.9a 806.9ab 776.7ab 801.7ab 705.7b 510.7b 50.1 0.006 0.005 0.397 C

1-Hydroxypropan-2-one 218.2b 126.6b 138.5b 737.5a 93.3b 57.8b 49.8 <0.001 0.049 0.001 B

Pentan-2-one 501.1a 303.7abc 339.4ab 259.3bc 207.0bc 95.6c 30.4 0.025 <0.001 0.292 A

Pentane-2,3-dione 247.1a 131.4b 149.0ab 183.0ab 98.7b 86.8b 13.3 <0.001 0.017 0.791 B

4-Hydroxybutan-2-one 83.0 67.0 52.1 63.8 81.2 42.6 5.4 0.065 0.646 0.413 B

Hexan-2-one 312.1ab 258.9ab 247.1ab 433.7a 248.8ab 154.7b 22.0 0.004 0.867 0.084 B

Heptan-3-one 11.9a 8.3ab 12.9a 7.7ab 5.8ab NDb 1.1 0.187 <0.001 0.022 B

Heptan-2-one 1737.5 1992.5 2094.9 1792.6 1800.8 1333.2 92.0 0.693 0.104 0.177 A

6-Methylheptan-2-one 503.6 729.5 597.5 657.2 777.3 383.8 52.6 0.130 0.969 0.328 B

Octane-2,3-dione 867.8 1254.5 1278.4 774.2 1458.9 853.6 86.8 0.049 0.536 0.276 B

6-Methylhept-5-en-2-one

2299.8 2845.9 2661.3 2165.4 2973.2 1874.1 151.7 0.122 0.390 0.409 B

Unidentifiedcyclohexanone

1179.9ab 1284.3ab 1929.0a 1008.7ab 1157.0ab 620.5b 127.6 0.819 0.031 0.070 C

Unidentifiedcyclohexanone

855.3ab 823.5ab 689.4ab 1001.3a 619.0ab 366.3b 58.8 0.029 0.257 0.267 C

1-Phenylethanone 42.1 40.0 36.4 49.9 43.5 31.3 1.9 0.029 0.569 0.336 B

Nonan-2-one 614.6 841.6 599.0 765.8 895.0 503.9 45.5 0.016 0.667 0.491 A

Decan-2-one 308.3 389.8 350.5 405.1 481.8 353.8 23.4 0.266 0.180 0.654 B

3,3-Dimethyloctan-2,7-dione

660.8ab 659.4ab 713.7ab 645.3ab 850.9a 514.6b 30.6 0.115 0.890 0.025 C

Undecan-2-one 97.5 118.7 142.7 92.5 140.0 107.2 11.2 0.516 0.794 0.573 B

6,10-Dimethylundeca-5,9-en-2-one

367.4a 307.0a 209.3ab NDb 268.8a 190.1ab 26.8 0.120 0.005 0.012 B

Tridecan-2-one 71.0 89.8 89.7 55.9 108.7 77.1 5.4 0.026 0.775 0.320 C

Total ketones 13960.4 14595.5 16320.1 13673.0 14819.3 12238.9 637.9 0.168 0.060 0.179

Nitrogen compounds

Pentanenitrile 303.7a 171.5ab 145.3ab 188.5ab 124.1b 103.4b 19.1 0.017 0.047 0.624 B

Pyrazine 61.6b 70.3ab 65.3b 98.0a 46.0b 41.6b 4.0 0.002 0.504 <0.001 B

Pyridine 402.5 512.0 525.5 298.6 343.3 339.2 42.1 0.700 0.085 0.922 B

1H-Pyrrole 146.7 90.5 120.1 182.4 107.4 77.7 11.6 0.022 0.876 0.349 B

2-Methylpyrazine 95.4ab 93.9b 94.9ab 129.9a 66.9bc 57.4c 5.0 <0.001 0.148 <0.001 C

Hexanenitrile 671.8ab 858.5ab 947.3a 414.1bc 517.5ab NDc 70.9 0.196 <0.001 0.006 B

2,6-Dimethylpyrazine 351.4ab 550.0a 604.8a 568.1a 506.8a NDb 50.1 0.079 0.127 0.003 B

Unidentified pyrrol 1219.2a 657.6b 716.4ab 1108.4ab 755.2ab NDc 73.8 <0.001 0.026 0.008 B

2-Phenylacetonitrile 174.8ab 146.9ab 282.5a NDb 186.7ab NDb 32.5 0.331 0.004 0.028 B

1,4-Dimethylbenzene-2-nitro

807.8 746.0 923.8 823.0 872.7 739.2 52.2 0.988 0.902 0.565 C

3-Methyl-1H-indole 24.9a 15.2bc 19.1b 14.8c 10.3d 14.2cd 0.9 <0.001 <0.001 0.017 B

Total nitrogencompounds

4259.8a 3912.4ab 4445.0a 3825.8ab 3536.9ab 1372.7b 246.4 0.400 0.006 0.002

Sulfur compounds

Methanethiol 548.1 650.3 854.0 349.4 947.9 366.0 108.4 0.494 0.572 0.405 B

Thiophene 28.8a 20.0a 22.1a 18.3a 19.9a NDb 1.5 <0.001 <0.001 0.004 B

(continued overleaf )


21

01


Table 2. (Continued)

Low MUFA High MUFA Pb

Compound 0% CLA 1% CLA 2% CLA 0% CLA 1% CLA 2% CLA SEM C M C × M Reliabilityc

1,3-Thiazole 78.6a 50.6bc 61.2abc 72.5ab 55.9abc 36.1c 3.3 <0.001 0.097 0.060 B

2-Methylthiophene 782.7ab 614.0abc 841.0a 497.7bc 780.4ab 380.0c 40.1 0.505 0.004 0.001 B

3-Methylthiophene 266.4a 233.8ab 227.1ab 181.4ab 208.5ab 96.2b 15.7 0.126 0.007 0.293 B

3-Methylsulfanylpropanal 4446.9ab 4234.9ab 3617.6b 5382.3a 4041.8ab 2796.0b 203.9 0.001 0.937 0.111 B

Methylsulfanylbenzene 602.9 504.7 627.9 491.0 676.6 399.8 32.2 0.489 0.373 0.015 B

1-(1,3-Thiazol-2-yl)ethanone

1627.8 1484.5 1610.5 1672.3 1707.1 1284.7 62.2 0.396 0.875 0.199 B

2-Methylpentane-2-thiol 42.0 41.6 50.8 31.2 50.1 24.9 2.9 0.315 0.089 0.036 C

5-Methylthiophene-2-carbaldehyde

768.4 552.5 829.8 883.0 702.3 330.9 63.7 0.250 0.522 0.061 B

Benzothiophene 750.5 1188.5 1120.8 849.9 899.5 603.6 67.3 0.277 0.103 0.219 B

Total sulfur compounds 9943.1a 9575.4a 9862.8a 10429.0a 10090.0a 6318.2b 368.3 0.044 0.186 0.002

Terpenes

1-Methyl-4-prop-1-en-2-yl-cyclohexene

2295.3 2620.3 3247.2 555.5 1762.3 1710.4 375.4 0.505 0.079 0.888 B

1,8,8-Trimethyl-7-oxabicyclo[2.2.2]octane

48.0 63.9 82.9 64.7 49.5 34.2 7.0 0.990 0.287 0.200 B

2,6-Dimethyloct-7-en-2-ol 954.5 823.4 821.9 933.8 876.8 528.0 84.8 0.619 0.736 0.804 B

Total terpenes 3297.8 3507.6 4152 1554 2688.6 2272.6 372.2 0.403 0.076 0.777

Total volatile compounds 114889.2ab 112661.5ab 121214.3a 110875.1ab107334.6ab 80343.7b 3701.7 0.538 0.009 0.027

a Values followed by different letters within the same row are significantly different (P ≤ 0.05). ND, not detected.b C, CLA; M, MUFA.c Reliability of identification: A, mass spectrum and RI identical with reference compound; B, mass spectrum and RI from literature in accordance; C,tentative identification by mass spectrum.

aldehydes in CLA pates, whereas the AU of most unbranchedaldehydes in pates were not affected by dietary CLA supplementa-tion. The main source of branched aldehydes in meat products isthe Strecker degradation of amino acids, such as 2-methylbutanalfrom the degradation of isoleucine or 3-methylbutanal from thedegradation of leucine.24 According to our results, the yield ofStrecker aldehydes in experimental pates was reduced by CLAsupplementation of pig diets. This result is of interest, takinginto account that 3-methylbutanal was the compound with thehighest AU in 0% CLA pates (14.0% of total AU of volatiles,regardless of dietary MUFA level), whereas for 1 and 2% CLA patesit represented only 6.6 and 8.7% respectively. The contributionof 3-methylbutanal to the overall flavour of meat products hasbeen described in ham, sausage and bacon.25 – 27 Estevez et al.23

also found important amounts of Strecker aldehydes in liver pate.3-Methylbutanal has been associated with nutty, cheesy and saltynotes in Parma ham26 and with almond-like and toasted flavourin other dry-cured products.28 Thus CLA-containing pates mightshow lower flavour notes associated with Strecker aldehydes,especially 3-methylbutanal. No previous studies regarding thedecrease in Maillard products in meat products as consequenceof dietary CLA have been found in the scientific literature.

Unbranched aldehydes are considered the most importantbreakdown products of lipid oxidation in meat and meat products.The AU of pentanal, hexanal, heptanal and decanal in experi-mental pates were not influenced by the CLA level of the dietarytreatments, whereas the AU of nonanal increased significantlywith dietary CLA supplementation (P < 0.05). A higher presence ofoctadecanal in CLA pates was also observed (P < 0.05). Neverthe-less, this is a high-molecular-weight aldehyde whose importance

to flavour development is only due to the fact that it can act as aprecursor of lower-molecular-weight alkanals and alkenals.29

During lipid oxidation, unsaturated fatty acids are oxidisedto specific lipid hydroperoxides that, in turn, decompose tospecific aldehydes.30 Thus nonanal might result mainly from theoxidation of n-9 MUFA such as C18 : 1n-9 via 10-hydroperoxy-8-ene. Therefore the higher the C18 : 1n-9 content is, the higherwill be the expected content of oxidation products such asnonanal from this fatty acid. However, the raw materials usedfor the manufacture of the experimental pates in the present workshowed a lower proportion of C18 : 1n-9 due to dietary CLA.4 Thusthe lower content of C18 : 1n-9 in CLA pates was not in agreementwith the higher AU of nonanal in pates due to dietary CLA, sincea lower nonanal AU would be expected. Therefore the oxidationof C18 : 1 n-9 did not seem to be the only origin of nonanal in thepresent work.

In meat products such as pates the thermal degradation offatty acids, both SFA and unsaturated fatty acids, determines thegeneration of a large number of volatile compounds.24 Accordingto the mechanism of degradation of SFA proposed by MacLeod andAmes,31 nonanal could derive from the degradation of a diversityof monohydroperoxides of C10 –C24 SFA. The raw materials usedfor the manufacture of the experimental pates in the present workshowed a higher proportion of SFA due to dietary CLA, with C16 : 0and C18 : 0 being the major SFA in the raw materials.4 Thereforethe thermal degradation of these two SFA (via 8-hydroperoxyand 10-hydroperoxy respectively) could be proposed as anotherpotential source of nonanal in pates. Nonanal flavour has beendescribed as having fatty, citrus and green notes.


21

02


The raw materials used for the manufacture of the experimentalpates in the present work showed a higher proportion of C18 : 2n-6 in the neutral lipid (NL) and polar lipid (PL) fractions of liverand the PL fraction of loin due to dietary CLA.4 Enrichment ofpig diets in unsaturated fatty acids, especially C18 : 2n-6, hasbeen found to lead to higher concentrations of several aldehydesin lean meat and cooked pork, such as deca-2,4-dienal, non-2-enal and hexanal, suggesting a higher trend to oxidation andrancidity perception of these meats.32,33 Previous studies have alsofound an increasing trend in the AU of most volatile compoundsof lipid oxidation, especially aldehydes, due to dietary CLA infresh Longissimus dorsi of CLA-fed pigs.15 Du et al.16 also founda proportional increase in aldehydes in meat from CLA-fed henscompared with control hens during 7 days of storage. Thesefindings were not in agreement with those in the present studyon CLA-enriched pates, since most aldehydes that were expectedto derive from lipid oxidation, especially those from oxidation ofC18 : 2n-6, did not show a significant influence of dietary CLA. Theuse of nitrites in the pate formulation could be one of the reasonsfor the lack of relevant differences in the AU of aldehydes fromlipid oxidation between untreated and CLA-treated pates. ThusRamarathnam et al.34 reported a lower concentration of carbonylcompounds in cured pork treated with nitrites compared withuncured pork. In addition, Guillard et al.35 found the strongesteffect of nitrites on decreasing the AU of volatiles for hexanal andoct-1-en-3-ol.

However, although it might be masked by nitrites, the protectiveeffect against lipid oxidation attributed to CLA7 should not bediscarded. In agreement with this, lower susceptibility to oxidationwas found for the raw materials used in the manufacture of the liverpates due to dietary CLA,4 and it was also reflected in lower levelsof thiobarbituric acid-reactive substances (TBARS) in CLA pates(Martin D et al., unpublished). On the other hand, if lipid oxidationand the yield of derived carbonyls were influenced by dietaryCLA, it might also explain the lower yield of Strecker compoundsderived from carbonyls observed in CLA pates in the presentwork.36 In fact, the formation of these compounds has also beendescribed in model systems containing oxidised phospholipidsand amino acids.37

After aldehydes, ketones were the second most abundantgroup of volatiles identified in the experimental pates. Ketonesin cooked meat products can be formed both by autoxidationor degradation of lipids and by Maillard reactions.30 Similarlyto branched aldehydes, the CLA enrichment of pig diets led tomanufactured pates with significantly lower AU for many ketones.Most of these affected ketones are likely generated through lipidoxidation, pointing out a protective effect of dietary CLA on thegeneration of ketones from lipid oxidation. On the other hand,the AU of one of the major ketones, acetone, was the only onethat tended to be higher owing to dietary CLA (P = 0.009, nosignificant differences by Tukey’s test), which suggests a differentorigin of acetone from that of the other ketones. The higherAU of acetone due to dietary CLA has been also observed indry-cured loin from CLA-fed pigs38 and in meat from CLA-fedhens.16,18

Alcohols were the third major group of volatile compoundsfound in the experimental pates. Significantly lower AU of mostalcohols due to dietary CLA were observed. Alcohols are generatedmainly as reaction products from lipid oxidation. The compoundoct-1-en-3-ol is an important volatile frequently found in meatproducts and is associated with the autoxidation of arachidonicacid (C20 : 4n-6) via 12-hydroperoxide.39 C20 : 4n-6 was one of the

major fatty acids in the lipid fractions of the raw materials usedfor the manufacture of the pates, especially in the lipid fractions ofliver.4 The proportion of C20 : 4n-6 in the raw materials was loweras a consequence of CLA supplementation of pig diets.4 This lowerproportion of C20 : 4 n-6 is in agreement with the lower derivedoxidation products in manufactured pates, such as oct-1-en-3-ol(P < 0.05).

The higher the temperature of the thermal treatment is, thegreater will be the formation of heterocyclic compounds throughMaillard reactions in cooked meat products,39 including nitrogencompounds (pyrazines, pyridines and pyrrols), sulfur compounds(thiazoles and thiophenes) and furans. Sulfur compounds at lowlevels are known for contributing to the pleasant meaty aroma ofmeat and meat products.40 Moreover, interactions of aldehydeswith other volatile compounds, Maillard products and volatileprecursors such as amino acids are likely pathways of formationof sulfur compounds such as thiophenes and thiazoles.36,40 In thepresent work, regardless of the MUFA level of the treatments, patesfrom CLA-fed pigs showed lower AU for thiophene, 1,3-thiazoleand 3-methylsulfanylpropanal (P < 0.05).

Aliphatic hydrocarbons have been found to derive from lipidoxidation or lipid degradation.40 The AU of 2-methylpentane and3-methylpentane were lower as a result of CLA supplementation(P < 0.05). In contrast, the AU of dodecane was higher for CLApates (P < 0.05). According to MacLeod and Ames,31 the thermaldegradation of SFA might also lead to the formation of aliphatichydrocarbons. As reported previously,4 the SFA content of the rawmaterials of the liver pates was higher owing to dietary CLA. Thethermal degradation of these SFA might explain the higher contentof derived hydrocarbons in CLA pates. Specifically, according tothe mechanism described by MacLeod and Ames,31 dodecanemight derive from C16 : 0 degradation via 4-hydroperoxy or C18 : 0degradation via 6-hydroperoxy.

Furans are well-known Maillard reaction and lipid oxidationproducts. The AU of several furans in the experimental pates wereaffected by CLA treatment. For example, furan-2-carbaldehyde,2-furanmethanol, 5-hexyloxolan-2-one and an unidentified ben-zofuranone were lower owing to CLA supplementation (P < 0.05),similarly to other Maillard products such as branched aldehydesand sulfur compounds in the experimental pates. In contrast, 2-pentylfuran was the only furan whose AU was higher owing todietary CLA (P < 0.05). This compound has been found in cookedpork as an autoxidation product of C18 : 2n-6.39 The conjugateddiene radical generated by the cleavage of 9-hydroxy linoleicacid may react with oxygen to produce vinyl hydroperoxide,which then undergoes cyclisation via the alkoxy radical to yield 2-pentylfuran.15 As reported previously, the proportion of C18 : 2n-6in the raw materials used for pate manufacture was higher owingto CLA supplementation.4 Therefore the higher C18 : 2n-6 contentwould be in agreement with the higher level of its derived oxida-tion compound, 2-pentylfuran. Curiously, as reported previously,other typical volatiles such as deca-2,4-dienal, non-2-enal andhexanal derived from C18 : 2n-6 oxidation were not detected oraffected by dietary CLA in the liver pates. The autoxidation of con-jugated forms of C18 : 2n-6 cannot be discarded as a contributorto 2-pentylfuran levels. Some CLA isomers have been reported tobe rapidly decomposed to furan fatty acids when heated in air.41

The subsequent cleavage and formation of 2-pentylfuran fromthe furan fatty acids formed from CLA might be proposed as alikely origin of 2-pentylfuran from oxidation of CLA. In agreementwith the observations in the present work, Pastorelli et al.15 alsofound higher levels of 2-pentylfuran in fresh loin from CLA-fed


21

03


pigs. 2-Pentylfuran has been related to green bean and butterodour.

Regarding aromatic hydrocarbons, the most remarkable resultwas the effect of the assayed treatments on the AU of ethylbenzene(P(CLA) < 0.001, P(MUFA) = 0.008 and P(CLA × MUFA) = 0.011).This volatile was present only in those pates manufactured fromCLA-fed pigs. A similar result was observed in the fresh loin usedfor pate manufacture (to be published elsewhere), since the AU ofethylbenzene was significantly higher with dietary CLA.

Dietary CLA affected the AU of several nitrogen compounds inthe experimental pates. For example, the AU of pentanenitrile,pyrazine, 1H-pyrrole, 2-methylpyrazine, 3-methyl-1H-indole andone unidentified pyrrol were lower for CLA treatments (P < 0.05).As reported previously, many nitrogen compounds are associatedwith Maillard reactions, and the lower level of nitrogen compoundsdue to dietary CLA is in agreement with the generally lower amountof volatile compounds derived from Maillard reactions found inCLA-containing pates. Most nitrogen compounds are associatedwith roasted meat flavour.21

Volatile acids, terpenes and esters were minor volatilecompounds found in the experimental pates. The AU of 2-methylbutanoic acid was conditioned by CLA (P = 0.002) andMUFA (P = 0.026) levels as well as their interaction (P = 0.033).The AU of ethyl acetate was lower owing to dietary CLA (P < 0.05),while terpenes were not affected by any of the assayed treatments.

Similarly to the effect of dietary CLA, MUFA supplementationof the pig diets also led to lower detection of a large number ofvolatile compounds in the experimental pates, especially thoserelated to Maillard reactions, i.e. branched aldehydes, ketones,nitrogen compounds and sulfur compounds. Thus, regardless ofthe CLA level, high-MUFA diets showed significant lower AU oftotal volatiles (P = 0.009). On the other hand, the combinationof CLA × MUFA levels also led to different AU of many volatilecompounds in the manufactured pates.

Changes in main volatile compounds of pates during storageOnce the application of high temperatures takes place in thermallytreated meat products, the autoxidation of lipids and off-flavourgeneration are the main causes of changes in the volatile profileduring subsequent storage of the final product.39 No previousstudies on the evolution of the volatile profile of liver pate duringstorage have been found in the scientific literature.

No qualitative differences in the profile of volatiles were foundin the experimental pates after 200 days of storage. The changesin total AU of the main groups of volatile compounds in themanufactured pates after 200 days of storage are shown in Fig. 1.In general, the total AU of alcohols and nitrogen compoundsincreased (P < 0.001) while those of aldehydes, furans and sulfurcompounds decreased (P < 0.001) at day 200. The total AU ofaliphatic hydrocarbons, aromatic hydrocarbons and ketones didnot change during storage.

Dietary CLA did not affect the change in total AU of anygroup of volatile compounds during storage. In contrast, theMUFA level of the treatments had a significant effect on thetotal AU of alcohols (P = 0.001), aldehydes (P = 0.045), aliphatichydrocarbons (P = 0.016), aromatic hydrocarbons (P = 0.022)and sulfur compounds (P = 0.004) after 200 days of storage of thepates. A CLA × MUFA interaction effect on the change in total AUof aldehydes (P = 0.023), aromatic hydrocarbons (P = 0.044) andsulfur compounds (P < 0.001) was also observed.

The specific volatile compounds that changed significantlyduring storage of the pates are detailed in Table 3. The increase

in total alcohols seemed to be mainly determined by thesignificant increase (P < 0.001) in the AU of 2-ethylhexan-1-oland 2,6-dimethylcyclohexanol.

The decrease in the total AU of aldehydes after 200 days ofstorage was due to the significant decrease in both branchedand unbranched aldehydes (Table 3). The decrease in the AU ofbranched aldehydes was less marked for dietary CLA and high-MUFA treatments. This would result from the lower initial valuesof branched aldehydes in the manufactured pates at day 0 dueto dietary CLA and MUFA level. Thus, the lower the initial AUof volatiles was, the lower was the decrease during storage. Thedecrease in the AU of unbranched aldehydes was independent ofthe CLA and MUFA levels in the pig diets.

Curiously, the major aldehyde, hexanal, did not change duringstorage of the experimental pates (P(t) = 0.317), regardless ofthe dietary treatment. This is of interest, taking into account thathexanal is considered as a marker volatile of lipid oxidation.42

Therefore the small decrease in most aldehydes during storage,and particularly the lack of change in the AU of hexanal, wouldindicate that no relevant lipid oxidation of the manufacturedpates took place during storage, regardless of the dietarytreatment.

As reported previously, the use of nitrites in the formulationof pates might be one of the main factors controlling lipidoxidation and the subsequent production of derived volatilecompounds in experimental pates. In accordance with this, theTBARS of liver pates determined at the beginning of the assay alsoremained unaffected during storage (Martin D, et al., unpublished).Moreover, the antioxidant effect attributed to Maillard-derivedvolatiles43 might also contribute to the control of lipid oxidation.In contrast, the antioxidant effect proposed for CLA isomers, whichhas been pointed out previously in dry-cured loin44 and in theoxidative stability of fresh liver,4 was not evidenced in the changesin volatile profile of the liver pates, since CLA treatment did nothave a significant effect on the changes in the main volatilesderived from lipid oxidation. It could be that the low levels of lipidoxidation due to nitrites or generated antioxidant volatiles made itimpossible to observe any antioxidant effect of CLA on the volatilechanges.

The decrease in the total AU of furans after 200 days of storagewas mainly due to the significant decreases in 2-ethylfuran (P =0.023), furan-2-carbaldehyde (P < 0.001) and 2-pentylfuran (P <

0.001). Although 2-furylmethanol (P = 0.009), 5-hexyloxolan-2-none (P = 0.008) and an unidentified benzofuranone (P < 0.001)increased during storage, these increases did not significantlyinfluence the total AU of furans. In accordance with theobservations in Fig. 1, dietary CLA and MUFA supplementationdid not influence the overall decrease in furans. The total AUof nitrogen compounds increased after 200 days of storageowing to the increase in most nitrogen compounds, without asignificant effect of dietary CLA or MUFA level on the extentof increase. The total AU of sulfur compounds decreased owingto the decreases in 1,3-thiazole (P = 0.008), 3-methylthiophene(P < 0.001), methylsulfanylbenzene (P < 0.001), 2-methylpentan-2-thiol (P < 0.001) and benzothiophene (P < 0.001). In the caseof CLA supplementation and low-MUFA diets the decrease inbenzothiophene was more marked, and it was not even detectedin 1% CLA/low-MUFA and 2% CLA/low-MUFA pates after 200 daysof storage. The decrease in 3-methylthiophene was also moremarked for low-MUFA diets.


21

04


0

5000

10000

15000

20000

25000ar

ea c

ount

s x

10-4

Low MUFA High MUFA

*** ***

******

***

*

Total alcohols 0 days 200 days

p(t)=0.000

0

10000

20000

30000

40000

50000

60000

70000

area

cou

nts

x 10

-4

******

****** *

Low MUFA High MUFA

*

Total aldehydes 0 days 200 days

p(t)=0.000 p(t x CLA x MUFA)=0.023

0

2000

4000

6000

8000

10000

12000

14000

area

cou

nts

x 10

-4

0% CLA 1% CLA 2% CLA 0% CLA 1% CLA 2% CLA 0% CLA 1% CLA 2% CLA 0% CLA 1% CLA 2% CLA

Low MUFA High MUFA

**

*

Total aliphatic hydrocarbons 0 days

p(t)=0.276 p(t x MUFA)=0.016

0

1000

2000

3000

4000

5000

6000

7000

8000

area

cou

nts

x 10

-4

Low MUFA High MUFA

**

Total aromatic hydrocarbons 0 days 200 days

p(t)=0.700

0

1000

2000

3000

4000

5000

6000

7000

8000

area

cou

nts

x 10

-4

Low MUFA High MUFA

***

Total furans0 days

0

5000

10000

15000

20000

25000

area

cou

nts

x 10

-4

Low MUFA High MUFA

Total ketones

p(t)=0.602 p(t x CLA)=0.293

0

1000

2000

3000

4000

5000

6000

7000

8000

area

cou

nts

x 10

-4

Low MUFA High MUFA

***

***

*

Total nitrogen compounds 0 days 200 days

p(t)=0.000 p(t x CLA)=0.919

0

2000

4000

6000

8000

10000

12000

14000

area

cou

nts

x 10

-4

Low MUFA High MUFA

* * ***

*

**

Total sulfur compounds 0 days 200 days

p(t x CLA x MUFA)=0.144p(t x MUFA)=0.001p(t x CLA)=0.350 p(t x MUFA)=0.045p(t x CLA)=0.855

p(t x CLA)=0.002 p(t x CLA x MUFA)=0.153

200 days

p(t x CLA x MUFA)=0.044p(t x MUFA)=0.022p(t x CLA)=0.857

p(t x CLA x MUFA)=0.573

200 days 0 days 200 days

p(t x CLA x MUFA)=0.743p(t x MUFA)=0.482

p(t x CLA x MUFA)=0.104p(t x MUFA)=0.413 p(t x CLA x MUFA)=0.000p(t x MUFA)=0.004p(t x CLA)=0.071p(t)=0.000

0% CLA 1% CLA 2% CLA0% CLA 1% CLA 2% CLA0% CLA 1% CLA 2% CLA0% CLA 1% CLA 2% CLA



p(t x MUFA)=0.889p(t x CLA)=0.608p(t)=0.000

Figure 1. Changes in main families of volatile compounds during storage of liver pate from pigs fed different levels of CLA and MUFA. Asterisks indicatethat values at day 0 and day 200 within the same treatment are significantly different at ∗P ≤ 0.05, ∗∗P ≤ 0.01 or ∗∗∗P ≤ 0.001.

CONCLUSIONSThe results of this study reveal that supplementation of pig dietswith CLA isomers in combination with low or high MUFA levelsseems to have a significant effect on the volatile profile of porkliver pate. This would be of interest from the sensory point of view,since different flavour notes might be perceived in CLA-containingpates. The change in the volatile profile of pates during storage wasnot markedly affected by dietary treatments. The hypothesis of a

protective effect of CLA on the generation of volatile compoundsshould not be rejected.

ACKNOWLEDGEMENTSThis research was supported by the Ministerio de Educacion yCiencia, Spain (AGL 2003-03538). CLA was generously provided byBASF. The valuable cooperation of Dr Clemente Lopez-Bote and


21

05


Tab

le3

.V

ola

tile

com

po

un

ds

(AU

×104

)ofl

iver

pat

efr

om

pig

sfe

dd

iffer

entl

evel

so

fCLA

and

MU

FAth

atch

ang

edd

uri

ng

sto

rag

ea

Low

MU

FAH

igh

MU

FA

0%C

LA1%

CLA

2%C

LA0%

CLA

1%C

LA2%

CLA

Pb

Day

0D

ay20

0D

ay0

Day

200

Day

0D

ay20

0D

ay0

Day

200

Day

0D

ay20

0D

ay0

Day

200

tt×

Ct×

Mt×

C×

M

Alc

ohol

s

2-Et

hyl

hex

an-1

-ol

620.

149

48.1

∗∗∗

196.

750

63.6

∗∗∗

ND

5419

.5∗∗

∗37

6.0

5827

.2∗∗

∗27

4.0

5423

.2∗∗

∗N

D51

53.4

∗∗∗<

0.00

10.

787

0.11

40.

339

2,6-

Dim

eth

ylcy

clo

hex

an-1

-ol

4122

.063

52.0

4272

.449

15.0

4516

.052

29.4

4241

.154

65.7

5087

.957

31.1

3310

.755

19.6

∗∗∗<

0.00

10.

318

0.78

70.

243

Ald

ehyd

es

2-M

eth

ylp

rop

anal

1539

.560

5.2∗

991.

469

2.1

1280

.483

9.9∗∗

∗13

51.1

861.

8∗69

5.1

693.

856

2.4

789.

6<

0.00

10.

004

0.00

40.

627

3-M

eth

ylb

uta

nal

1684

7.2

3345

.5∗∗

∗93

71.3

2073

.6∗∗

∗12

877.

325

23.3

∗∗∗ 14

856.

433

08.4

∗∗∗

5226

.020

91.0

∗∗∗

5384

.021

59.5

∗∗∗<

0.00

1<

0.00

10.

001

0.23

6

2-M

eth

ylb

uta

nal

390.

411

7.9∗∗

238.

212

5.4∗

313.

115

5.4∗∗

∗35

5.8

194.

6∗11

3.3

93.0

104.

111

0.7

<0.

001

0.00

20.

001

0.71

0

2-M

eth

ylb

ut-

2-en

al32

0.2

122.

7∗∗∗

224.

512

9.1∗∗

249.

112

8.8∗∗

∗32

2.3

160.

618

8.8

115.

012

1.8

157.

1<

0.00

10.

006

0.03

70.

194

Hep

tan

al44

.525

.945

.030

.3∗

48.3

30.7

∗∗33

.220

.4∗

47.5

29.7

∗∗∗

35.8

33.3

<0.

001

0.44

60.

179

0.24

0

(E)-

Hep

t-2-

enal

ND

344.

6∗∗∗

368.

443

6.4

213.

829

0.3

365.

437

2.9

272.

235

6.8

ND

363.

5∗∗∗

0.01

80.

875

0.83

40.

479

2-Ph

enyl

acet

ald

ehyd

e33

15.5

2284

.5∗∗

3292

.120

33.1

∗∗∗

3554

.024

37.7

∗∗34

34.8

2757

.332

13.8

1753

.5∗∗

∗28

77.2

2188

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21

06


Dra Elena Gonzalez as well as the collaboration of I+DAgropecuaria in designing the experimental diets, sampling andpig management are also acknowledged. Diana Martin thanks theMinisterio de Educacion y Ciencia for funding her research.

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volatile compounds of experimental liver pâté from pigs fed conjugated linoleic acid in...

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