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Volatile organic compounds in Tuber magnatum specimens from
Greece detected by SPME-GC-MS
Nefeli Sofia Sotiropoulou1, Vassileios Daskalopoulos2, Elias Polemis2, Georgios I. Zervakis2, Petros Tarantilis1
Introduction
Methods
Outcome
Several species of the genus Tuber (“true truffles”) are widely recognized for their excellent organoleptic characteristics.
Among them, the most popular and highly prized species is Tuber magnatum Picco, often referred to as “white truffle” or
“Piedmont truffle”. Until rather recently, T. magnatum was found to occur in north Italy only, but during the past 20-25 years it
became evident that its distribution also extends to the Balkan Peninsula. Since 2013 its existence was confirmed in Greece as
well, with Mt. Olympus being its southernmost limit in the country. Nowadays, significant quantities of high-quality white
truffles are collected and traded in Greece; therefore, this particular activity is of commercial importance. The aim of this work
is to assess the major volatile organic compounds (VOCs) that contribute to the characteristic aroma of T. magnatum
specimens collected from various regions of Greece.
Fresh samples of T. magnatum were collected from several regions of Greece through collaboration with local truffle hunters
(Fig. 1,2). Within 4-7 days from the date of collection, samples were processed, first by examining their maturity status with
the aid of a microscope (i.e., they were considered mature when they contained at least 80% mature asci), and then by
obtaining 1 g per sample from the gleba of mature ascocarps to determine their VOCs (Fig. 3,4). The VOCs of 14 T. magnatum
samples were trapped by solid phase microextraction (SPME) using a SPME fiber assembly
Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) (Fig. 5) [1]. Qualitative and quantitative (%) analysis of VOCs
was accomplished by gas chromatography combined with mass spectrometry (GC-MS) (Fig. 6).
References
According to our results, 13 VOCs were identified in total; they belong to the groups of sulfur compounds, ketones, alcohols, aldehydes, and hydrocarbons (Table 1). The maximum and
minimum number of compounds detected in truffle samples were ten and four, respectively. The most abundant VOC existing in all T. magnatum samples was bis(methylthio)methane,
ranging from 70.9% to 87.7% (average 80.1%); this sulfur compound with alliaceous (garlic) flavor is widely prescribed as the key component of white truffles aroma, and contributes
substantially to their unique gastronomic value. Bis(methylthio)methane is also found in cheese, shiitake mushrooms and lobsters. Moreover, dimethyl sulfide (sulfury, onion, corn and
cabbage flavors) and 2-acetyl-5-methylfuran (nutty and hay-coumarin flavors) were also detected in all truffle samples, but in lower relative percentages, i.e., 4.63-17.7% and 0.34-3.59%,
respectively. These VOCs (Fig. 7) are considered as the major compounds that contribute to the unique aroma of white truffles and were also found in specimens of T. magnatum
originating from other Balkan countries and Italy [2-4]. The other 10 compounds were not present in all samples, and in most cases they were detected at low percentages.
Table 1. Relative percentages (average of 3 replicates / sample) of identified volatile organic compounds of Tuber magnatum from various regions of Greece, extracted by SPME (green fonts are used for the compounds found in all samples examined).
Acknowledgements
No Compound Retention
time (min)
Region
Kozani Pieria Komotini Grevena
Tub275 (%)
Tub276 (%)
Tub288 (%)
Tub290 (%)
Tub291 (%)
Tub340 (%)
Tub299 (%)
Tub301(%)
Tub302 (%)
Tub331 (%)
Tub333 (%)
Tub355 (%)
Tub356 (%)
Tub357 (%)
1Dimethyl sulphide 1.73 5.24 15.22 8.47 12.93 8.67 5.88 8.66 12.20 5.55 10.41 10.58 17.66 5.37 4.63
22-Butanone 2.01 8.10 10.42 3.74 7.94 4.60 3.40 8.84
31,2-Ethanodiole 2.03 3.53 2.35
43-Methyl-butanal 2.42 2.77 1.31 2.51 3.02
5Pentanal 2.82 0.76
6Dimethyl disulfide 3.51 0.91 1.54 0.91 1.41 1.17
7Hexanal 4.62 0.47 0.36
8Bis(methylthio)methane 7.87 79.22 79.55 78.04 84.57 77.96 85.23 85.23 70.88 87.72 79.08 82.66 71.97 85.11 74.12
92-Acetyl-5-methylfuran 13.51 1.49 0.97 0.94 1.16 1.02 0.43 0.49 3.59 0.39 0.34 0.40 1.49 0.34 2.71
10
1
-Methoxy-3-methyl-
benzene
15.39 6.61 2.13 2.14 3.60 1.50 0.30 0.38 0.35 0.84 0.83 7.54 3.33 5.95
11 3,4-Dimethyl-3-hexen-2-one 16.02 0.89 1.34 4.02 0.80 0.67 7.32 0.50 0.53 1.34 1.05 1.09
12 Benzeneacetaldehyde 16.75 0.31
13 2-Methylthio acetic acid 25.00 0.62 3.57 3.63 2.17 1.76 2.45 0.93 1.40
Fig. 1. Sampling regions on the geomorphological map of Greece
Grevena
Kozani
Komotini
Pieria
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Fig. 7. VOCs of T. magnatum,
(A) Bis(methylthio)methane, (B) Dimethyl
sulfide and (C) 2-Acetyl-5-methylfuran.
This research project was supported by the Hellenic Foundation
for Research and Innovation (H.F.R.I.)under the “2nd Call for
H.F.R.I. Research Projects to support Post-Doctoral Researchers”
(Project Number: 1057).
We are thankful to the truffle collector
P. Kladopoulou for providing
specimens and photos for this work.
Conclusions
Bis (methylthio) methane was the main volatile compound in the fresh T. magnatum samples studied, while dimethyl sulfide was also detected
in all specimens at considerable amounts. In addition, the geographic origin of the examined T. magnatum samples did not appear to have a
significant impact on the amount of these major compounds, and differentiations were noted for some of the minor VOCs only. The results
also demonstrate that the VOC’s profile of fresh T. magnatum collected in Greece is similar to those obtained from different regions of Italy and
Slovenia, in most cases both quantitatively and qualitatively [2-5]. In conclusion, the SPME-GC-MS method has been successfully used for the
analysis of VOCs of Greek white truffles with the same efficiency as in previous studies dealing with material of other origins [2,4-8].
Fig. 2. Ascoma of sample Tub 290 from Kozani region
(scale bar 1cm)
Fig. 4. Triplicate of sample was
placed and sealed with butyl-
Teflon septum caps
Fig. 5. Extraction of VOCs of
samples using SPME holder for
manual sampling
Fig. 3. Mature asci and
ascospores of sample Tub 340
from Pieria region (scale bar
50μm)
Fig. 6. SPME/GC-MS chromatogram of VOCs of T. magnatum (Tub 275 from
Kozani, the number of peaks correspond to compounds of Table 1).
Time (min)
Relative abundance
1Agricultural University of Athens, Laboratory of General Chemistry, Iera Odos 75, 11855 Athens, Greece; 2Agricultural University of Athens, Laboratory of General and Agricultural Microbiology, Iera Odos 75, 11855 Athens
