Journal of the Science of Food and Agriculture J Sci Food Agric 83:535–541 (online: 2003)DOI: 10.1002/jsfa.1397

Effect of industrial processing on deserttruffles Terfezia claveryi Chatin and Picoajuniperi Vittadini): proximate compositionand fatty acidsM Antonia Murcia,1∗ Magdalena Martınez-Tome,1 Ana Vera,1 Asuncion Morte,2

Almudena Gutierrez,2 Mario Honrubia2 and Antonia M Jimenez1

1Department of Food Science, Veterinary Faculty, Campus de Espinardo, University of Murcia, Apartado de Correos 4021, E-30008Murcia, Spain2Department of Vegetable Biology, Biology Faculty, Campus de Espinardo, University of Murcia, Apartado de Correos 4021, E-30008Murcia, Spain

Abstract: Our objectives were to investigate the proximate composition of two desert truffles (Terfeziaclaveryi Chatin and Picoa juniperi Vittadini) and to determine the effects of freezing and canning onproximate composition. The moisture content of T claveryi and P juniperi was 730.9 g kg−1 and 637.8 g kg−1

respectively; ash was 42.5 g kg−1 and 82.1 g kg−1 respectively; protein was 159.5 g kg−1 and 225.4 g kg−1

respectively; lipids were 69.5 g kg−1 and 199.4 g kg−1 respectively; fibre was 83.2 g kg−1 and 130.4 g kg−1

respectively; and carbohydrates were 645.5 g kg−1 and 366.6 g kg−1 respectively. The fatty acids compositionshowed high quantities of linoleic acid 18:2 (45.4% in T claveryi and 53.0% in P juniperi), the rest of thefatty acids in decreasing order were 16:0 > 18:1 > 18:3 > 18 : 0 + 22 : 0 > 20 : 0 + 24 : 0 > 14 : 0 + 22 : 1 >

15 : 0 + 16 : 1 + 17 : 0 + 21 : 0 in T claveryi and 18 : 1 > 16 : 0 > 18 : 0 + 18 : 3 + 16 : 1 + 20 : 0+22:1 > 14:0 +24:0 > 15:0 + 17:0 + 22:0 in the P juniperi. Little loss of ash, protein and lipids was observed as a result ofindustrial processing (p < 0.05). 2003 Society of Chemical Industry

Keywords: desert truffles; protein; fatty acid; lipid; fibre; ash; moisture; freezing; canning

INTRODUCTIONDesert truffles are a complex family of mycorrhizalhypogeous fungi, mainly containing species of thegenera Balsamia, Picoa, Terfezia, Tirmania and Tuber,whose geographical distribution is limited to arid andsemi-arid areas,1 particularly in the Middle East andNorth Africa,2,3 southern Europe4 (Spain, France,Italy and Greece), and other Mediterranean borderingcountries (Libya,3 Tunisia, Syria), as well as in Iran,Iraq and Kuwait.5 The regions where desert trufflesgrow have a mean temperature of 17 to 24.1 ◦C and127 to 360 mm of average annual rainfall.6,7

Desert truffles are of considerable interest for eco-logical reasons, because of the low water input requiredfor cultivation and as an alternative agricultural cropin arid and semi-arid areas, and are of commercialinterest because of the prices fetched on the openmarket.

Four species of desert truffle are common aroundthe world: Terfezia boudieri Chatin, Terfezia claveryi

Chatin, Terfezia leonis Tulasne, and Terfezia metaxasiChatin.8,9 They are edible fungi and are particularlyappreciated in Arab countries and in MediterraneanBasin countries as a whole.

The edible portion of desert truffles have a sizeranging from that of a walnut to a large apple, witha chocolate colour.5 Although Terfezia provide largequantities of a rich and much appreciated vegetable inthe cuisine of some countries, particularly during earlyspring when other vegetables are still in the fields, littleinformation is available regarding their compositionand nutritional status. In countries of the Middle Eastand North Africa, desert truffles are usually used incooked dishes and have long been used by Arabs ofthe desert as substitutes for meat in their diet; theirpreparation and cooking are similar to those of meat.Gray10 devoted special attention to the use of trufflesand recorded all known facts about their dietary usesand the extent of their contribution to the diet of somecommunities.

∗ Correspondence to: M Antonia Murcia, Department of Food Science, Veterinary Faculty, Campus de Espinardo, University of Murcia,Apartado de Correos 4021, E-30008 Murcia, SpainE-mail: mamurcia@um.esContract/grant sponsor: Ministerio de Educacion y Cultura; contract/grant number: IFD97-1746(Received 8 May 2001; revised version received 7 October 2002; accepted 16 January 2003)

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Studies show that truffles are rich in proteins,amino acids, minerals and carbohydrates.2,3,11 Theproximate composition of T boudieri has been studied3

and the results show that the protein is of highquality, since it contains nine essential amino acids,representing about 6% of the dry weight; truffles,then, could be considered a good source of protein.The nutritional value of truffles is ranked sixthimmediately after Agaricus bisporus (FAO/WHO).12

On the other hand, large segments of the population indeveloping countries suffer from protein malnutrition.Hence, research efforts are being directed to this areato identify and evaluate underexploited sources asalternative protein crops for these countries.13

There has been much recent interest in the potentialrole of dietary fibre in human nutrition. Fibre helpsto maintain the health of the gastrointestinal tractbecause it speeds up the transit of bowel contents,increases faecal bulk and frequency and protects thebody from colon cancer, diverticular diseases andirritable bowel syndrome. Finally, it lowers the levelof cholesterol in the blood, thus protecting againstcoronary disease.14

Little attention has been paid to the storage oftruffles, which may be spoiled by fungi and bacteriaeven at 2 ◦C, making storage extremely difficult.15,16

The occurrence of high numbers of bacteria and fungion truffles is to be expected due to their richnessin carbohydrates and other nutrients, including aminoacids, lipids, proteins and minerals.2,3,11,15,17,18 Dryingand/or freezing, on the other hand, might reduce thespoiling process. Therefore, keeping truffles dry and/orat low temperatures could increase their storage time.

However, although the consumption of frozen andcanned products is widely accepted, the nutritionalquality of these foodstuffs is increasingly coming underthe spotlight. Consumers are better informed aboutnutrition and are more sophisticated in their choiceof foods, looking for those that are wholesome andnutritious.19

The objectives of this research were to obtaininformation on the proximate composition, in termsof proteins, lipids, fatty acids, fibre and carbohydratesof the two truffle species T claveryi and P juniperito determine the effects of freezing and canning onproximate composition, and to determine the effect ofindustrial processing.

MATERIALS AND METHODSMaterialsSamples of two different species of desert truffle,T claveryi Chatin and P juniperi Vittadini, werecollected during March–April, 2000, from thesoutheastern part of Spain (Zarzadilla de Totana,Lorca, Murcia).

The truffles were harvested, transferred to a truckwithin 20 min, and later transported to the processingplant at a temperature of 0–5 ◦C. Trucks used to

transport truffles from the field complied with the EClegislation concerning refrigerated trucks.

Industrial processOnce in the processing plant, the samples were placedin pre-chilling chambers at 0–2 ◦C with a relativehumidity of 90–95 % for an average time of 24 h. Thesamples were passed through shakers to remove anydebris.

The truffles were washed several times in water(18 ◦C), containing decreasing concentrations ofchlorine, to eliminate foreign bodies (stones, insects,etc). The samples were cut into pieces and, from thispoint, the industrial processing was divided into twobatches: one for freezing and the other for canning.

Freezing treatmentA shower tunnel, approximately 10 m length, throughwhich the samples were conveyed at 2.15 m min−1,was used for blanching. The samples were blanchedin water at a water temperature of 94 ± 2 ◦C for 90 sand at a volume flowrate of 15 000 ml min−1.

The samples were placed on a wickerwork platformand showered with cold (5–10 ◦C) water (3.5 m)before being cooled by air injection. Later, the sampleswere frozen in individual pieces in a fluid bed tunnel(individual quick-frozen model Agacigoscandia) whichwas programmed to hold them for 4 min at −30 ◦C.The speed was 1.05 m min−1. The exit temperatureof the truffles was below −20 ◦C. They were thencalibrated for size and packed into plastic bags beforebeing placed in cardboard boxes. The boxes werestored at −20 ◦C (model Slos Freeze 26 B).

Canning treatmentThe truffles were placed in glass jars, which were thenfilled with hot (85 ◦C) filling medium (20 g l−1 NaClin water). The jars were closed and then heated at121 ◦C for 30 min before being cooled in water.

Sample preparationAll the samples came from the same harvesting andwere taken on the same day they were processed. Thesamples were sent from the processing plant to ourlaboratory in adequate conditions. A representativenumber of samples from the composite lots was usedfor analysis. The samples of truffles (raw, frozen andcanned) were freeze-dried in an FTSSYSTEMS

(GIRALT). Subsequently, freeze-dried samples wereground to a fine powder with a Moulinex model 505.

The Certified Reference Material used for controlanalysis was the Standard Reference Material appleleaf powder SRM 1515 from the National Institute ofStandards and Technology (NIST), for constituentelements as nitrogen (total) in concentration of2.25 ± 0.19 wt%.

Proximate analysisAsh and protein contentAsh was determined according to the AOAC methodOfficial Methods of Analysis ref 942.05.20 For the

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Proximate composition of desert truffles

determination of proteins we followed the AOACmethod21 using a Carlo Erba model AE 1108elemental analyser with a Porapack QS (25 cm)gas chromatography (GC) column and a ThermicConductivity Detector. Standard sample materials(EDTA, nicotinic acid, tryptophan and lysine, HCl)were place in a tared standard tin capsule forcalibration and performance testing. Helium at1.94 × 10−3 l s−1 was used as carrier gas; the reactortemperature was 1020 ◦C. The chromatographic oventemperature was 65 ◦C and the filament temperaturewas 190 ◦C. Samples weighing 1 mg were processedin these conditions, using V2O5, WO3 and MgO asadditives. The range was from 0.01 to 100%, witha standard deviation of 0.001%. The results of thenitrogen content were multiplied by 6.25 to obtain theprotein percentage.22

Analysis of dietary fibreThe fibre content was determined according to theAACC method.23

Analysis of lipidsThe gravimetric determination of the total lipidscontent was carried out according to the method ofBligh and Dyer.24

Determination of total lipids as fatty acid methyl estersThe procedure for determining fatty acid meltylesters (FAMEs) was carried out according to Murciaet al.25 A 2 ml volume of sulphuric acid/methanol wasadded to each residue obtained for total lipids andthe tubes were flushed under nitrogen and heatedfor 1 h at 100 ◦C. The tubes were then cooled,and 3 ml of hexane and 5 ml of water were addedto each, followed by mixing and centrifuging. Thehexane layer (3 ml) was transferred by pipettingto a clean vial and the solvent evaporated undernitrogen. The residues were dissolved in 100 µl ofhexane for methyl ester analysis by GC. A stainless-steel column (2 m × 2 mm id) GP 10% sp2330,on Chromasorb W/AW 100/120 (Teknokroma) wasused in a Shimadzu GC Mini 3 (PF) (ShimadzuCorporation) chromatograph equipped with a flameionization detector. The GC oven was operated at140 to 195 ◦C with a nitrogen carrier gas flow rateof 5 × 10−4 l s−1. The FAMEs were identified byreference to the retention times obtained for fatty

acid standards from SUPELCO (ref FAME Mix C8-C24 and FAME Mix GLC-90) using the previouslymentioned conditions. The results were quantified asthe percentage of area under each peak.

Additionally, 3 ml methylated lipid extracts werechromatographed in a Hewlett-Packard HP-5972GC/MS for confirmation of the identity of the fattyacid, which yielded a very small peak. A stainless-steel column (30 m × 0.250 mm id) packed with 5%phenyl methyl silicon was used. The measure meantconditions were the same as for GC previouslymentioned.

Statistical analysisAll experiments were carried out in quadruplicate.The results were analysed using Statistical Packagefor Social Sciences Windows 9.0, and the analysisof variance (ANOVA) procedure. The method beingused to discriminate among the means was Fisher’sleast significant difference (LSD) multiple range test.

RESULTS AND DISCUSSIONThe proximate compositions of T claveryi Chatin andP juniperi Vittadini in the fresh and processed forms(frozen and canned) are presented in Table 1.

Moisture contentThe moisture content in raw truffles was 637.8 g kg−1

in P juniperi, and 730.9 g kg−1 in T claveryi, whichis in accordance with that obtained by otherauthors for T boudieri (777.0 g kg−1),3 T claveryiChatin Gibaah (754.4 g kg−1),6 Tirmania nivea(752.7 g kg−1),6 T claveryi Chatin (780.0 g kg−1).26

The moisture content of the samples increased withindustrial processing (frozen and canned) in the sam-ples studied. For the frozen process the statisticalanalysis shows no significant variations (p < 0.05),with the moisture content increasing by 2% and1% in T claveryi and P juniperi respectively. How-ever, significant variations were observed in theincrease in the canning process (3% and 18% forT claveryi and P juniperi respectively). The literaturealso points to increasing humidity values duringthe industrial process in vegetables (broccoli, carrot,spinach, asparagus),27,28 with the moisture contentof the canned samples increasing by 5%. One pos-sible explanation for the increased moisture content

Table 1. Proximate composition (g kg−1 dry matter) of trufflea

Moisture Ash Crude protein Lipid Fibre Carbohydrateb

T claveryi Raw 730.9 ± 2.6 42.5 ± 3.2 159.5 ± 0.04 69.5 ± 2.2 83.2 ± 1.3 645.5 ± 0.3Freezing 747.8 ± 1.3 34.8 ± 0.15 150.6 ± 0.64 65.6 ± 2.9 78.5 ± 0.9 670.4 ± 0.5Canning 752.1 ± 0.3 37.7 ± 0.05 148.6 ± 1.7 62.1 ± 2.6 92.2 ± 1.5 659.8 ± 0.4

P juniperi Raw 637.8 ± 0.2 82.1 ± 1.4 225.4 ± 3.8 199.4 ± 0.4 130.4 ± 0.8 366.6 ± 0.4Freezing 644.1 ± 0.1 73.8 ± 0.3 222.0 ± 0.75 195.0 ± 0.7 132.2 ± 1.6 377.5 ± 0.6Canning 753.0 ± 1.2 77.2 ± 0.1 221.2 ± 2.8 189.8 ± 0.4 171.2 ± 1.2 341.6 ± 0.8

a Data are mean values of four experiments plus/minus standard deviation.b Carbohydrates calculated by difference.

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may be mechanical damage during handling, whichcauses the hyphae to fracture and parts of the surfaceto be less extensively matted, thus encouraging waterretention.29

Ash contentThe data of Table 1, referring to the ash content ofraw truffles, agree with those described for differentfresh truffle varieties by Sawaya et al6 (T claveryi andTirmania nivea) and Bokhary and Parvez26 (T claveryiAscocarp). This ash content decreased during thefreezing process by 19% and 11% in T claveryi andP juniperi respectively, which is also in accordancewith data obtained by Collins et al27 and Murciaet al28 (carrots, asparagus, spinach and broccoli, theash content of which decreased by to 50% as a result ofthe freezing process). However, only a slight decreasein the ash content was observed in the canned product,with decreases of 11% and 5.8% in T claveryi andP juniperi respectively, due to the addition of salt(NaCl) during canning, as reported by us for othervegetables such as spinach25 and broccoli.28

Protein contentTable 1 shows that the protein content of rawtruffles was 159.5 g kg−1 for T claveryi and washigher for P juniperi at 225.4 g kg−1; these findingsare in agreement with the 171.9 g kg−1 (dry matter)of T boudieri,3 the 195.9 g kg−1 (dry weight basis)of T claveryi Chatin Kholeissi6 and the 160 g kg−1

(dry weight) of T claveryi Chatin.26 The freezingprocess reduces these levels by 5.6% and 1.3% inT claveryi and P juniperi respectively; for the canningprocess the decrease was 6.9% and 1.7% in T claveryiand P juniperi respectively. Neither processed truffleshowed significant differences (p < 0.05) in proteinloss during industrial processing.

Data on the effect of industrial processing on theprotein levels from other vegetables are in accor-dance with these findings, which showed no significantdifferences (p < 0.05) in protein loss between bothindustrial processing studied (canned and frozen)thus, in canned kidney beans,30 a loss of 3.4% wasobserved; in canned peas31 it was 7%; in frozen andcanned spinach25 it was 20%; in broccoli28 it was31% and 32% for frozen and canned varieties respec-tively. These losses in raw proteins are probably dueto denaturation and solubility during the industrialprocess.25,28

Lipid contentThe lipid content of raw truffles was 69.5 g kg−1 (drymatter) in T claveryi; this is similar to that described byother authors3 in T boudieri, where the lipid contentwas 64.0 g kg−1 (dry matter). The lipid content indry weight of P juniperi was higher (199.4 g kg−1).These data are much higher than those obtained forother truffle species.3,6 There are no available data onP juniperi in the literature. There was a significant loss(p < 0.05) of approximately 10% and 5% (T claveryiand P juniperi respectively) in the lipid content of the T

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538 J Sci Food Agric 83:535–541 (online: 2003)

Proximate composition of desert truffles

canned product. However, in the freezing process,statistical analysis showed no significant variations(p < 0.05), with losses of 5% in T claveryi and 2%in P juniperi. The physical actions of processing, suchas washing, blanching in boiling water or freezing,cause injuries in the hyphae that were held together ina mat, and this causes cellular fluids to leak out. Thusthe surfaces were less matted, resulting in increasedpermeability and, therefore, compounds exuded fromthe fractured hyphae.29

Fatty acid compositionThe fatty acid composition of both T claveryi andP juniperi are recorded in Table 2. The data indicatethe content of fatty acid as a percentage of totalfatty acids. There was a high quantity of 18:2(45.4% in T claveryi and 53.0% in P juniperi);the rest of the fatty acids were, in decreasingorder, 16:0 > 18:1 > 18:3 > 18:0 + 22:0 >

20:0 + 24:0 > 14:0 + 22:1 > 15:0 + 16:1 +17:0 + 21:0 in T claveryi and 18:1 > 16:0 > 18:0+ 18:3 + 16:1 + 20:0 + 22:1 > 14:0 + 24:0 >

15:0 + 17:0 + 22:0 in P juniperi. A comparison withthe fatty acid composition obtained by other authorsis shown in Table 3, where the wide variability andlevels of fatty acids can be observed, depending onthe botanical species. Our results are similar to thefindings reported by Bokhary et al,18 although theydetected an unknown peak (5.3%) like a longer chainfatty acid. We obtained a signal representing 3.9%of the total as 24:0 fatty acid and this was verifiedby GC–Mass spectrometry. A comparison of thedata for fresh and processed samples showed slightbut not significant (p < 0.05) decreases in some fattyacids.

The ratios of unsaturated/saturated fatty acids(UFA/SFA), polyunsaturated/monounsaturated fattyacids (PUFA/MUFA) and linoleic/oleic acids (L/O)were calculated as indicators of nutritional andtechnological interest (Table 4).

The UFA/SFA ratio showed values greater thanunity for raw T claveryi, and no significant variations(p < 0.05) were detected with industrial processing.However, a higher UFA/SFA ratio of around 5.0increased slightly in processed samples in P juniperi.

Table 4. Ratios UFA/SFA, PUFA/MUFA and L/O of T claveryi and

P juniperi

UFA/SFA PUFA/MUFA L/O

T claveryi Raw 1.6 5.0 6.6Frozen 1.7 5.3 7.0Canned 1.8 6.9 10.0

P juniperi Raw 5.0 1.9 2.2Frozen 5.4 2.0 2.3Canned 5.5 1.9 2.2

The PUFA/MUFA ratio reached a value of 5.0 in rawT claveryi and 1.9 in raw P juniperi. The PUFA/MUFAratio showed the highest levels in frozen and cannedsamples of T claveryi. However, in P juniperi no signifi-cant variations (p < 0.05) were observed after process-ing samples. The L/O ratio reached values of 6.6 and2.2 in raw T claveryi and P juniperi respectively, sinceoleic acid is present in high proportions in P juniperi;the L/O ratio showed the highest levels in frozen andcanned samples of T claveryi. However, no significantvariations (p < 0.05) were observed for the L/O ratioin P juniperi after processing.

The consumption of vegetables has been recom-mended as a part of dietary programs to increasePUFA/SFA the ratio in order to reduce serum choles-terol and, indirectly, to prevent the development ofatherosclerosis.32–34 Some authors have also demon-strated the ability of various edible fungi to reduceblood serum cholesterol.35 This is also mentionedin the nutritional objectives of FAO/OMS36 scientists.However, the higher proportion of PUFAs makes lipidrancidity the main factor limiting storage life; PUFAsare ideal substrates for free-radical reactions, leadingto lipid peroxidation. Such lipid alteration gives riseto unpleasant odours and tastes, with the concomi-tant loss of organoleptic quality in food, leading toconsumer rejection.37 Because a high dietary intakeof PUFAs might overwhelm the normal antioxidantdefences of the organism and increase the need fordietary antioxidants,38–40 OMS41 suggests that PUFAintake should not be excessive. This could indicatethat the fatty acid composition of P juniperi is veryadequate nutritionally.

Table 3. Fatty acid composition of raw truffles obtained by other authors

Fatty acids compositiona

Variety Reference C14:0 C15:0 C16:0 C16:1 C17:0 C18:0 C18:1 C18:2 C18:3 C19:0 C20:0 C21:0 C22:0 C22:1 C24:0

Terfezia 9 4 2 16 7 18 7 5 3 — 11 5 1 1 8 —Terfezia 11 ND 0.64 12.28 1.05 0.35 3.0 16.38 22.14 ND ND 1.32 ND 0.33 0.2 —Tirmania nivea 11 ND ND 9.95 ND ND 4.86 10.76 4.13 1.56 ND ND ND ND ND —Tirmania pinoyi 11 1.88 ND ND 2.72 7.71 7.9 3.75 ND 4.94 8.06 2.09 1.65 0.15 2.07 —Tuber texense 1 0.2 — 11.4 — 0.2 3.4 45.9 38.0 — — 0.2 — — — —P juniperi ∗ 1.2 0.4 8.0 2.5 0.9 2.2 23.5 53.3 2.1 — 2.1 ND 0.8 2.0 1.5T claveryi ∗ 2.1 1.3 17.0 1.4 1.4 4.5 6.9 45.4 5.8 — 3.7 0.4 4.0 1.9 3.9

ND: not detected.∗ Results obtained in present paper.a Relative peak area (methyl esters).

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Fibre contentTable 1 shows the dietary fibre content of rawtruffles (83.2 g kg−1 dry matter for T claveryi and130.4 g kg−1dry matter for P juniperi). These resultsare in accordance with those obtained by otherauthors6 for T claveryi (70.2 g kg−1) and Tirmanianivea (130.2 g kg−1).

Freezing did not affect the dietary fibre content,although increases of 10% and 30% in T claveryi andP juniperi respectively were observed in the cannedproducts. These data are in accordance with the resultsobtained by other authors for canned kidney beans30

(at 121 ◦C heat treatment). This fact was apparentlydue to the effect of overheating on increasing theresistant amount of starch in the fibre residues.42

Carbohydrate contentThe carbohydrate data were obtained by differ-ence. The carbohydrate content was 645.5 g kg−1

in T claveryi and 366.6 g kg−1 dry weight basis inP juniperi. These results are in accordance withthose obtained by Ahmed et al3 with 597 g kg−1 inT boudieri.

In conclusion, epidemiological studies have revealed50–60 g to be the recommended daily intake ofprotein to provide good health and reduce the risk ofsome diseases.43 The protein content, which averaged20% of dry weight in truffles, is significantly higherthan in most vegetables and other fungi. One 250 gserving of desert truffles can contribute 23–27% of therecommended daily intake of protein. Desert truffles,which grow wild in desert regions, could be cultivatedeasily in several the developing countries of Africaand the Near East, making them important sources ofprotein for human consumption.

Also, the National Cancer Institute recommendsthat the daily diet contain between 25 and 35 g ofdietary fibre,43 values that are much higher than theaverage level actually consumed. Accordingly, oneserving of 250 g of truffles could contribute 16–22%of the recommended daily intake of fibre.

Our results showed good levels of fibre and MUFAand little changes in the proximate composition oftruffles during industrial processing (freezing andcanning). As a consequence, the consumption of thisprocessed food is recommended . The crop of trufflesis suitable in countries where there is water shortageand there is a limited availability of other vegetables.

ACKNOWLEDGEMENTSThis work was funded by the FEDER project,Ministerio de Educacion y Cultura (Spain), IFD97-1746. The authors thank Producciones de Molina, SL,Molina de Segura, Murcia, Spain, for the industrialprocessing (frozen and canned) of truffle samples.

REFERENCES1 Ackerman LGJ, Van Wyk PJ and du Plassis LM, Some aspects

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