Contributions of sulfur compounds to truffle Contributions of sulfur compounds to truffle aroma aroma

Changrong Ou, Xiaofen Du, Juan He, Jack Czarnecki, Michael QianMichael Qian

Oregon State UniversityOregon State UniversityCorvallis, OR 97331Corvallis, OR 97331

USAUSAEmail: michael.qian@oregonstate.eduEmail: michael.qian@oregonstate.edu

TruffleTruffle

• Truffles are fungi, like mushrooms, but grow under ground

•• Truffle is the fungal fruiting body of fungiTruffle is the fungal fruiting body of fungi

•• They grow slowly underground for months and are only fully They grow slowly underground for months and are only fully fragrant for a week or so, as they ripen near the end of their fragrant for a week or so, as they ripen near the end of their maturation processmaturation process

•• There are hundred truffle species, only a few (mostly in genus There are hundred truffle species, only a few (mostly in genus TuberTuber) are highly prized for human consumption) are highly prized for human consumption

•• Size and shape varySize and shape vary

Truffles form a symbiotic relationship with their Truffles form a symbiotic relationship with their environmentenvironment•• Truffle fungi grow symbiotically with the roots of certain treesTruffle fungi grow symbiotically with the roots of certain trees

–– oak, elm, chestnut, pine and willow.oak, elm, chestnut, pine and willow.

•• The tree provides the fungus with carbohydrates produced The tree provides the fungus with carbohydrates produced through photosynthesis through photosynthesis

•• in turn, fungus acts as an expanded fine root system for the in turn, fungus acts as an expanded fine root system for the tree, absorbing water and mineral nutrients through its very fintree, absorbing water and mineral nutrients through its very fine e root system root system

Culinary Treasures

Black Truffle (Tuber melanosporum) Black Truffle (Tuber melanosporum)

•• Black truffle (Black truffle (Tuber melanosporumTuber melanosporum) grows exclusively with oak ) grows exclusively with oak treetree

•• France accounts for 45%, Spain 35%, Italy 20%France accounts for 45%, Spain 35%, Italy 20%

•• Black truffles sell between$130Black truffles sell between$130––$380 per pound$380 per pound

White Truffle (Tuber magnatum) White Truffle (Tuber magnatum)

•• The White truffle (The White truffle (Tuber magnatumTuber magnatum) ) comes from Northern and Central comes from Northern and Central Italy. Most famously, around Alba of Italy. Most famously, around Alba of Italy. Italy.

•• Growing symbiotically with oak, Growing symbiotically with oak, hazel, poplar and beech hazel, poplar and beech

•• Harvest from October and NovemberHarvest from October and November

The The Tuber magnatumTuber magnatum truffles sell $2,200truffles sell $2,200-- $1,000 /lb $1,000 /lb

The record price paid for a single white truffle was $330,000 The record price paid for a single white truffle was $330,000 (3.3(3.3 lb)lb)

Oregon TruffleOregon Truffle

•• White truffle varieties:White truffle varieties:–– Tuber oregonenseTuber oregonense–– ripens in December through Februaryripens in December through February

–– Tuber gibbosumTuber gibbosum–– harvest in May and Juneharvest in May and June

•• Black truffle Black truffle –– Leucangium carthusianumLeucangium carthusianum–– has a distinctively has a distinctively fruity aromafruity aroma

Habitat of Oregon TruffleHabitat of Oregon Truffle

•• All three of OregonAll three of Oregon’’s s commerciallycommercially--harvested truffle harvested truffle species grow in young Douglas species grow in young Douglas fir stands at low elevations. fir stands at low elevations.

•• These stands span the region These stands span the region from northern California to from northern California to southern British Columbia, west southern British Columbia, west of the Cascades Mountain of the Cascades Mountain Range. Range.

Habitat of Oregon TruffleHabitat of Oregon Truffle

•• White truffles are found most White truffles are found most abundantly in former pasture or abundantly in former pasture or agricultural land that has been agricultural land that has been planted with young Douglas fir. planted with young Douglas fir.

•• Black truffles are widely distributed Black truffles are widely distributed in plantations near streams, but also in plantations near streams, but also on reforested hillsides.on reforested hillsides.

••

••The distribution of the three truffle The distribution of the three truffle species overlaps considerablyspecies overlaps considerably

•• Roughly 100,000 acres of forest are suitable for white and blacRoughly 100,000 acres of forest are suitable for white and black k truffles in Oregontruffles in Oregon

•• Less than 2% of this acreage is being harvested for trufflesLess than 2% of this acreage is being harvested for truffles

Female Pig Has Been Historically Used for Truffle Female Pig Has Been Historically Used for Truffle HuntingHunting

sulfides, and androstenol from truffle are thought be responsible

Pigs do eat truffles!

Trained Dog Works BetterTrained Dog Works Better

Aroma compounds in TruffleAroma compounds in Truffle

DMS DMTS

2,4-dithiapentane DMDS

1,2,4-trithiolane Methanethiol

Methyl(methylthio)methyl disulfide Tris(methylthio)methane

(methylsulfinyl)(methylthio)methane 2,2’-dithiodiethanol

Benzothiazole Diethanol sulfide

2-methylthioacetic acid Diethyl trisulfide

3-methylthiopropional 1-methylthiopentane

Gioacchini et al., 2008, RCM, 22:3146

Experiment 1Experiment 1-- Truffle HuntingTruffle Hunting

No truffle hunting animals were used

Young Douglas fir forest in Oregon in May 2008

Looking for animal Looking for animal activities on the groundactivities on the ground

HS-SPME-GC-Olfactometry-MS

• 1 g sliced truffle

• HS-SPME– 2 cm Carboxen/DVB/PDMS– 45C/1 hr

• GC-O-MS– ZB-Wax, 30 m X 0.25 nm X 0.25 μ– HP-5, 60 m X 0.32 nm X 0.25 μ

GCGC--O analysis of white truffle (ZBO analysis of white truffle (ZB--WAX column)WAX column)

Compounds Descriptors Inten. Identi. BasisH2S truffle, petroleum 9 RI, MS,PFPDacetaldehyde green 5 RI, MSMeSH/DMS sulfuric 7 RI, PFPD3-methylbutanal malty 6 RI, MS

ethyl isobutyrate fruity 8 RI, aroma

ethyl 2-methylbutyrate fruity, floral 6 RI, aroma

hexanal green, grassy 5 RI, MS

2-methylpropanol fruity, apple 7 RI, MS

DMDS rotten egg 5 RI, MS

t-2-pentenal fresh, green 5 RI, MS3-methylbutanol floral 7 RI, MS

GCGC--O analysis of white truffle (ZBO analysis of white truffle (ZB--WAX columnWAX column

Compounds Descriptors Inten. Identi. Basist-β-ocimene green, rosy 7 MS. aroma3-octenone mushroom 8 MS. aroma1-octen-3-one mushroom 10 MS. aroma

? floral, frangrant 10dimethyl trisulfide sulfurous 9 RIL. aromanonanal fresh, green 7 MS. aroma3-octanol mushroom 12 MS. aromamethional cooked potato 11 RIL. aroma1-octen-3-ol mushroom 13 MS. aroma

GCGC--O analysis of white truffle (ZBO analysis of white truffle (ZB--WAX columnWAX column

Compounds Descriptors Inten. Identi. Basis2-undecanone cooked, fatty 7 MS. aromaEthyl 3-(methylthio)propanoate rotten egg 8phenylacetaldehyde berry, fruity 5 MS. aroma? rotten, egg 73-methylbutanoic acid cheesy 5 MS. aromamethionol cooked potato 7 MS. aroma? mushroom, earthy 6hexanoic acid cheesy, sour 6 MS. aroma

GCGC--O analysis of black truffle (ZBO analysis of black truffle (ZB--WAX column)WAX column)

Compounds Descriptors Inten. Identi. Basis

H2S truffle, petroleum 6 RI, aroma

acetaldehyde fruity 5 RI,MS. aroma

MeSH sulfur 10 MS,RI

methyl isobutyrate fruity, apple 7 MS. aroma

EtSH/DMS rotten egg 11 MS,RI

methyl 2-methylbutyrate fruity, pineapple 9 MS. aroma

MeSAc rotten egg 8 RI, Aroma

isobutyl isobutyrate floral, sweet 8 MS, aroma

DMDS rotten egg 5 MS,RI

? coffee, nutty 10 MS. aroma

GCGC--O analysis of black truffle (ZBO analysis of black truffle (ZB--WAX column)WAX column)

Compounds Descriptors Inten. Identi. Basis

3-octenone mushroom 8 MS. aroma

1-octen-3-one mushroom 8 aroma

? floral, frangrant 9Dimethyl trisulfide sulfurous 9 RIL. aroma

methional cooked potato 9 RIL. aromaethyl 3-(methylthio)propanoate

Rotten eggs 7 MS. aroma

? mushroom, earthy 10methionol cooked 6 MS. aroma

5 10 15 20 25

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GCGC--PFPD of White and Black TrufflePFPD of White and Black Truffle

MeSH

MeSAC

DMDS

DMTS

Methional Methionol

Black

Truffle Aroma Changes QuicklyTruffle Aroma Changes Quickly

•• Aroma develops only at the Aroma develops only at the final stage of ripeningfinal stage of ripening

•• Aroma degrades quicklyAroma degrades quickly

•• Aroma cannot be easily Aroma cannot be easily preservedpreserved

•• Truffle oilTruffle oil–– Natural and/or synthetic Natural and/or synthetic

aroma in olive oilaroma in olive oil

MeSH

DMS DES

DMDS

DMSODMTS

MethionalMethionol

MeSH

DMDS

White Truffle

MeSHDMS

DES

DMDS DEDSDMSO

DMTS

MethionalMethionol

MeSAc

Et 3-(Me-thio)propanoate

ConclusionConclusion

•• Volatile sulfur compounds are primarily responsible for the Volatile sulfur compounds are primarily responsible for the characteristic aroma of white truffle aromacharacteristic aroma of white truffle aroma

•• In addition to sulfur compounds found in white truffle, In addition to sulfur compounds found in white truffle, methylthio acetate and ethyl 3methylthio acetate and ethyl 3--(methylthio)propanoate also (methylthio)propanoate also contribute to black truffle aromacontribute to black truffle aroma

•• Esters provide additional fruity aroma to Oregon black truffleEsters provide additional fruity aroma to Oregon black truffle