Food Sci. Biotechnol. 20(3): 775-782 (2011)

DOI 10.1007/s10068-011-0108-4

Volatile Distribution in Garlic (Allium sativum L.) by Solid Phase

Microextraction (SPME) with Different Processing Conditions

Na Young Kim, Min Hee Park, Eun Yeong Jang, and JaeHwan Lee

Received: 25 January 2011 / Revised: 6 April 2011 / Accepted: 6 April 2011 / Published Online: 30 June 2011

© KoSFoST and Springer 2011

Abstract Treatments of autoclaving, high temperature

aging (aged-black garlic), crushing, and roasting at 100,

150, and 200oC were applied to alter the volatile profiles of

garlic (Allium sativum L.). Headspace volatiles in samples

were analyzed by a solid phase microextraction (SPME)-

GC/MS. Total peak areas of crushed-raw garlic were the

highest and those of aged-black garlic clove were the

lowest. Crushing effects were clearly observed in raw

garlic, aged-black garlic, and roasted garlic at 200oC for 60

min. Sulfur-containing volatiles including diallyl disulfide

and diallyl trisulfide were major volatiles. Generally, peak

areas of diallyl disulfide decreased when garlic received

autoclaving and roasting treatment while diallyl trisulfide

and allyl methyl trisulfide increased during heat treatment

compared to raw garlic. Roasting at 200oC for 60 min

caused the formation of pyrazines greatly in garlic. Principal

component analysis (PCA) for the volatile profiles by

SPME-GC/MS could discriminate types of processed

garlic successfully.

Keywords: garlic, headspace volatiles, processing effect,

solid phase microextraction

Introduction

Garlic (Allium sativum L.) is one of the oldest and

referenced herbs as food and medicinal ingredients (1).

Antibiotic, anti-yeast, cardioprotective, antihypertensive,

cancer chemopreventive, and cholesterol-lowering properties

are some representative biological activities reported in

garlic (2-5). Biological activities in garlic may be associated

with sulfur-containing compounds, which are responsible

for the characteristic pungent odor of garlic and garlic oil

(6,7).

Profiles of volatile and non-volatile compounds in garlic

are reviewed by many researchers including Lanzotti (8)

and Corzo-Martínez et al. (9). Fresh garlic contains alliin

(S-3-(2-propenylsulfinyl)-L-alanine)-, a derivative of cysteine.

When fresh garlic is crushed, allinase can convert alliin to

allicin (2-propene-1-sulfinothioic acid S-2-propenyl ester),

which is associated with the characteristic odor of crushed

fresh garlic. Garlic oil extracted by steam distillation (SD)

or simultaneous distillation and extraction (SDE) mainly

consists of allyl disulfide (4,5-dithia-1,7-octadiene) and

allyl trisulfide. Major volatiles of raw and heated garlic are

reported as sulfur-containing compounds including dimethyl

disulfide, 2-propen-1-ol, methyl-2-propenyl disulfide,

dimethyl trisulfide, diallyl disulfide, methyl-2-propenyl

trisulfide, and di-2-propenyl trisulfide (8,10,11).

Due to the garlic’s pungent odor, various cooking

treatments have applied to enhance its sensory attributes or

nutritional and medicinal properties. Some processing

methods including cooking in soaked water, roasting,

fermentation, steaming, hydrostatic pressure treatment, or

autoclaving have been applied to modify the off-odor of

garlic (12-14). A processing method, so-called ‘aging’ at

low temperature or in the presence of alcohol, has been

introduced to make aged garlic products in Asian markets

since 1950s’ (15,16). Aged garlic is made through soaking

sliced garlic cloves in 15-25% ethanol for several months

at ambient temperature and the extract of aged garlic also

possessed diverse bioactivity including immunomodulatory

activity and antioxidant activity (17,18). Recently, garlic

Na Young Kim, Min Hee Park, Eun Yeong Jang, JaeHwan Lee ( )Department of Food Science and Technology, Seoul National University ofScience and Technology, Seoul 139-743, KoreaTel: +82-2-970-6739; Fax: +82-2-971-5892E-mail: jhlee@seoultech.ac.kr

Na Young KimSeoul Metropolitan Government Research Institute of Public Health andEnvironment, Gwacheon, Gyeonggi 427-805, Korea

RESEARCH ARTICLE

776 Kim et al.

with black color is made through aging the garlic bulbs in

controlled moisture contents (70-80% relative humidity) at

70oC temperature. This process can be called as ‘high

temperature aging’ comparing to the traditional low

temperature aging with alcohol. In this process, garlic

bulbs without removing outer skin are treated at relatively

high temperature in the absence of alcohol for 2 weeks to

1 month duration, which is shorter period than traditional

aging process of about 20 months. The color of the aged

garlic cloves from high temperature aging process turns

from white to black or dark brown. Nutritional constituents

and sensory properties in aged-black garlic change greatly

(19). Pouch types of foods made of extracts of aged-black

garlic have been introduced in the markets and this

beverages gain popularity as healthy foods among consumers

who do not like strong and pungent odor in raw garlic.

Solid phase microextraction (SPME) is a solvent free

method for extracting and concentrating headspace

volatiles and has been successfully applied to diverse types

of foods. SPME has been used to analyze volatiles from

garlic (11) and garlic oil (20). Lee et al. (11) compared SD,

SDE, solid-phase trapping solvent extraction, and SPME as

the extraction methods for garlic volatiles and suggested

SPME could be an efficient tool to analyze volatiles of

garlic. Calvo-Gómez et al. (20) analyzed headspace volatiles

of garlic oil made by hydrodistillation using 8 different

types of SPME fibers. A total of 47 volatiles were

separated depending on the types of SPME fiber.

Although diverse treatments including high temperature

aging and roasting have adapted to treat garlic, studies on

the changes of volatile profiles in garlic from different

processing condition using SPME are rare in the literature.

The objective of this study was to analyze the distribution

of headspace volatiles in garlic treated with autoclaving,

high temperature aging (aged-black garlic), crushing, and

roasting by SPME-GC with a mass selective detector

(MS).

Materials and Methods

Materials Garlic bulbs were purchased from a local

grocery market in Seoul, Korea. Teflon-coated rubber

septa, a fiber assembly holder, 75 µm carboxen/

polydimethylsiloxane (CAR/PDMS) SPME fiber, and

aluminum caps were purchased from Supelco, Inc.

(Bellefonte, PA, USA). Standard volatile compounds and

n-paraffin were purchased from Sigma-Aldrich (St. Louis,

MO, USA).

Sample preparation Garlic bulbs have several layers of

white and papery coverings and 1 garlic bulb contains

several wedge-shaped cloves covered with inner layers.

Four different processing methods were applied to garlic

including autoclaving, high temperature aging, crushing,

and roasting.

Autoclaving treatment: Raw garlic bulbs without

removing outer layers were autoclaved at 121oC for 15 min

using an autoclave machine (Model SJ-220A100; Sejong

Scientific Co., Ltd., Bucheon, Korea).

High temperature aging treatment: For the aged-black

garlic samples, raw garlic bulbs without removing outer

layers were put in a cooker (Model BJC-062HT; Bubang

Techron, Seoul, Korea) and stored for 14 days at the mode

of ‘heating’ without opening the door. The temperature in

the cooker was maintained at 72±2.5oC.

Roasting treatment: Raw cloves of garlic with layers were

roasted using a coffee roaster (Model CBR-101; Genesis

Co., Ltd., Ansan, Korea) at 100, 150, and 200oC for 30 and

60 min, respectively.

Crushing treatment: Outer layers of raw garlic cloves,

autoclaved garlic cloves, aged-black garlic cloves, and

roasted garlic cloves were peeled out and then samples

were crushed using a mortar and a pestle to simulate the

effects of chewing on the headspace volatiles in the mouth.

Tested samples in this study were raw garlic clove, raw-

crushed garlic, autoclaved garlic clove, autoclaved-crushed

garlic, aged-black garlic clove, aged-black-crushed garlic,

roasted garlic clove, and roasted-crushed garlic, which

were designated as GC, CG, AGC, ACG, BGC, BCG,

RGC, and RCG, respectively. Roasted garlic at 100°C for

30 min expressed as RGC100/30.

Analysis of volatiles by SPME Analysis conditions of

SPME for volatile compounds were modified from Calvo-

Gomeza et al. (20) and Lee et al. (21). Two g of each garlic

sample was put in a 10-mL bottle and air-tightly sealed

with a Teflon-coated rubber septum and an aluminum cap.

Sample bottles were placed in the dark for 1 h at room

temperature and headspace volatiles of each garlic sample

were isolated using a 75 µm CAR/PDMS solid phase at

30oC for 30 min in a circulating water bath (RW-0525G;

Lab Camp, Bucheon, Korea). The isolated volatile

compounds were determined using GC/MS. Solid phase of

SPME was exposed in an injector for 3 min. All samples

from each treatment were prepared triplicate.

GC condition Analysis conditions of SPME for volatile

compounds were adapted from Lee et al. (21). Volatiles

attached in the 75 µm CAR/PDMS solid phase were

separated and identified using a Hewlett-Packard 6890 GC

equipped with a 5971A mass selective detector (Agilent

Technology, Palo Alto, CA, USA) and a DB-5ms column

(30 m×0.25 mm i.d., 0.25 mm film thickness, Agilent J &

W, Folsom, CA, USA). All mass spectra were obtained at

70 eV and 220oC ion source temperature. The identification

Volatiles in Processed Garlic by SPME 777

of compounds was made by a combination of NIST Mass

Spectra, linear retention indices (RI) of n-paraffin as

external references, and GC retention times of some

standard compounds. Helium was carrier gas at 1.0 mL/

min and the oven temperature was held at 40oC for 2 min

and increased from 40 to 160oC at 6oC/min and from 160

to 220oC at a rate of 10oC/min.

Statistical analysis Results of total peak areas and

selected major volatiles were statistically analyzed by

analysis of variance (ANOVA) and Duncan’s multiple

range test using commercially available software package

SPSS software program (SPSS Inc., Chicago, IL, USA). A

p value <0.05 was considered significant. Principal

component analysis (PCA) for volatiles in garlic by SPME

was conducted using covariance matrix with no rotation

and SPSS software program.

Results and Discussion

Distribution of volatiles in raw, autoclaved, aged-black,

and roasted garlic samples Changes of total ion counts

in garlic treated with different processing conditions are

shown in Fig. 1. Raw-crushed samples (CG) and aged-

black garlic cloves (BGC) showed the highest and lowest

total ion counts among tested samples (Fig. 1). Aged-

black-crushed garlic (BCG) had 11 times more total ion

counts than uncrushed samples (BGC). The lowest total

ion counts in BGC could be due to the presence of layers

in cloves, which may prevent the release of compounds

from the garlic cloves into the headspace. Generally, garlic

roasted at 150oC for 30 and 60 min had less total volatiles

compared to raw garlic and roasted garlic at 100oC. Much

variation was observed in total volatiles of garlic samples

among autoclaving, high temperature aging, roasting, and

crushing treatments. Calvo-Gomeza et al. (20) compared

commercially available 8 types of SPME solid phases for

the headspace volatiles of garlic oil and reported that solid

phase of 75 µm CAR/PDMS detected the maximum

number of volatiles compared to other SPME solid phases.

Although 75 µm CAR/PDMS could not detect all volatiles,

our study adapted 75 µm CAR/PDMS for the volatile

analysis based on the reports of Calvo-Gomeza et al. (20).

Major volatiles in garlic with raw, autoclaving, and high

temperature aging treatments are shown in Table 1.

Number of volatiles identified in GC, CG, AGC, ACG,

BGC, and BCG were 21, 18, 21, 20, 12, and 17,

respectively. Out of 21 volatiles in GC and CG, 17 sulfur-

containing compounds consisted more than 88.5% of total

ion counts. Most volatiles in raw garlic are diallyl

disulfides (46.14% of total volatiles in GC and 40.88% of

total volatiles in CG), 3-vinyl-1,2-dithiacyclohex-5-ene,

3-vinyl-1,2-dithiacyclohex-4-ene, and diallyl trisulfide

(5.99% of total volatiles in GC and 9.32% of total volatiles

in CG). 2-Propen-1-ol and 2-methyl- 3,4-dihydro-2H-

thiopyran, which were detected in GC, were not observed

in CG.

Dimethyl disulfide, which was not observed in raw

garlic samples (GC and CG), was observed in autoclaved

samples (AGC and ACG), indicating thermal reaction may

cause the formation of this compound. Yu et al. (27) and

Calvo-Gomez et al. (20) reported the detection of dimethyl

disulfide in garlic essential oil prepared from water or

solvent extraction. The boiling point of dimethyl disulfide

is 109-110oC and higher temperature may increase the

Fig. 1. Changes of total peak areas in garlic treated with different processing conditions. Different letters on the bar are significant atp<0.05.

778 Kim et al.

volatility of dimethyl disulfide. In raw garlic, dimethyl

disulfide may not have enough high volatility to be

detected by SPME fiber. Major volatiles in AGC and ACG

are in the order of diallyl disulfides (35.53% of total

volatiles in AGC and 31.23% of total volatiles in ACG),

diallyl trisulfide (17.31% of total volatiles in AGC and

22.07% of total volatiles in ACG), and allyl methyl

trisulfide. The contents of diallyl trisulfide were the most

increased volatile in autoclaved samples compared to those

in raw samples. Diallyl trisulfide, diallyl disulfide, and allyl

methyl trisulfide were reported as major sulfur-containing

volatiles in steamed garlic for 15 min and autoclaved garlic

for 5 min (22).

Distributions and number of volatiles in BGC were

substantially different from those of BCG. Allyl sulfides

consisted 58.3% of total volatiles in BGC and 10.8% of

total volatile in BCG. 3,4-Dimethylthiophene, 2-methyl-5-

ethylpyrazine, and 1,5-dithiocane, which were not detected

in BGC were found in BCG. 3,4-Dimethylthiophene and 2-

methyl-5-ethylpyrazine may be already formed and present

inside in the matrix of BGC during high temperature aging

process, which were liberated into the headspace when the

structure of matrix was crushed. Due to the temperature

over 72, enzymatic reactions for the formation of color and

volatiles may be inhibited during high temperature aging

process. Dark color can be developed from non-enzymatic

reactions including Maillard browning reaction and

caramelization (19). In low temperature aging process,

diallyl sulfide, diallyl disulfide, diallyl trisulfide, and

dithiin have been found in aged garlic through the activity

of allinase. In case of conditions of low enzyme activity, S-

allyl cysteine and S-allyl mercaptocysteine were main

sulfur-containing non-volatiles in aged garlic (23).

Major volatiles identified from roasted garlic samples

are shown in Table 2. The number of volatiles in roasted

garlic samples was greatly influenced by the roasting time,

roasting temperature, and crushing process. All the 100

roasted garlic samples, RGC150/30, and RCG150/30 had

Table 1. Effects of autoclaving, high temperature aging, and crushing process on the distribution of major volatiles in garlic

RI1) CompoundTotal volatiles (×108 ion counts)

GC2) CG AGC ACG BGC BCG

- Sulfur dioxide 0.55±0.18c3) 0.48±0.02bc 0.16±0.00a 0.13±0.03a 0.08±0.01a 0.35±0.02b

574 2-Propen-1-ol 0.15±0.02bc 0.09±0.06ab 0.12±0.02bc 0.03±0.05a 0.01±0.00a 0.20±0.00b

600 Allyl mercaptan 1.27±0.03bc 2.10±0.74c 1.43±0.50ab 1.06±0.02b 0.07±0.03a 0.53±0.00ab

697 Allyl methyl sulfide 0.28±0.01ab 0.12±0.17a 0.24±0.04ab 0.21±0.01ab 0.37±0.02b 0.86±0.01c

744 Dimethyl disulfide ND5) ND 0.04±0.01a 0.03±0.00a 0.04±0.01a 0.26±0.10b

856 Allyl sulfide(diallyl sulfide) 1.50±0.51a 1.58±0.26a 1.96±0.25a 1.50±0.24a 1.85±0.08a 5.44±0.10b

888 2-Methyl-3,4-dihydro-2H-thiopyran 0.20±0.28a 0.34±0.21a 0.24±0.18a 0.29±0.04a ND 0.81±0.05a

909 3,4-Dimethylthiophene 0.71±0.07c 0.78±0.00c 0.27±0.04b 0.19±0.04b 0.01±0.00a 0.08±0.00a

918 Allyl methyl disulfide 2.15±0.20d 1.33±0.10c 1.24±0.26c 0.82±0.11b 0.14±0.02a 2.00±0.03d

944 1,3-Dithiane 0.62±0.00c 0.36±0.03b 0.57±0.10c 0.36±0.05b 0.02±0.01a ND

980 Phenylethyl butyrate 1.22±0.13a 2.79±0.62b 3.30±0.97b 3.59±0.31b ND ND

989 Dimethyl trisulfide ND ND ND ND 0.01±0.00 ND

1,010 2-Methyl-5-ethylpyrazine ND ND ND ND ND 0.59±0.03

1,098 Diallyl disulfide 23.50±2.66d 23.51±1.73d 18.70±0.64c 13.60±1.29b 0.49±0.06a 12.89±0.34b

1,104 1,5-Dithiocane ND ND ND ND ND 10.40±0.39

1,160 Allyl methyl trisulfide 0.90±0.13b 0.99±0.51b 3.56±0.35c 2.89±0.42c ND 3.54±0.12d

1,176 1-Methyl-3-pyrrolin-2-one 0.51±0.11b 0.23±0.01a 0.45±0.02b 0.31±0.07a ND ND

1,183 O-Methyl 2-acetylhydrazinecarbothioate ND ND ND ND 0.06±0.00a 6.54±0.18b

1,191 1,3,5-Trithiane 0.24±0.05ab 0.55±0.34b 1.24±0.24c 1.07±0.10c ND ND

1,201 2,4-Dimethylthiazole 0.47±0.00b 0.44±0.00a ND ND ND ND

1,220 3-Vinyl-1,2-dithiacyclohex-4-ene 5.13±1.78b 6.86±1.97b 2.04±0.60a 1.49±0.14a ND 0.85±0.02a

1,250 3-Vinyl-1,2-dithiacyclohex-5-ene 6.21±1.71c 6.43±1.07c 2.70±0.12b 2.19±0.33b ND 2.50±0.06b

1,328 Diallyl trisulfide 3.05±0.27b 5.36±1.96b 9.11±1.20c 9.61±0.28c 0.03±0.00a 4.04±0.03b

1,355 1-Methylimidazole-2-thiol 1.53±0.01a 2.05±1.14a 2.08±0.13a 1.82±0.06a ND ND

1,432 5-Methyl-1,2,3,4-tetrathia-cyclohexane 0.48±0.04a 1.55±0.84ab 2.64±1.03b 1.96±0.33b ND 2.57±0.04b

1,535 1-Hydoxy-4-methyl-2,6-di-tert-butylbenzene 0.26±0.06b ND 0.54±0.12c 0.43±0.11c 0.04±0.04a 0.18±0.00ab

1)Linear retention indices (RI) were determined using n-paraffin as external references.2)GC, raw garlic clove; CG, raw-crushed garlic; AGC, autoclaved garlic clove; ACG, autoclaved-crushed garlic; BGC, aged black garlic clove,and BCG, aged-crushed black garlic

3)Mean±SD (n=3); ND, not detected; Different letters are significant at p<0.05 among the same row.

Volatiles in Processed garlic by SPME 779

Tab

le 2

. D

istr

ibu

tion

of

majo

r v

ola

tile

s d

ete

cte

d i

n g

arli

c w

ith

roasti

ng a

nd

cru

sh

ing t

reatm

en

ts

RI1)

Com

pound

Tota

l vola

tile

s (×

108 i

on c

ounts

)

RG

C100/

302)

RC

G100/

30

RG

C100/

60

RC

G100/

60

RG

C150/

30

RC

G150/

30

RG

C150/

60

RC

G150/

60

RG

C200/

30

RC

G200/

30

RG

C200/

60

RC

G200/

60

-S

ulf

ur

dio

xid

e0.

3±0.

00.

2±0.

00.

2±0.

10.

3±0.

00.

1±0.

10.

2±0.

00.

2±0.

00.

2±0.

00.

2±0.

00.

3±0.

10.

3±0.

00.

4±0.

0

574

2-P

ropen

-1-o

l0.

1±0.

00.

1±0.

00.

15±0.

020.

1±0.

10.

3±0.

00.

2±0.

00.

5±0.

10.

3±0.

10.

3±0.

00.

4±0.

10.

8±0.

70.

3±0.

0

600

All

yl

mer

capta

n1.

1±0.

0b3)

1.0±

0.4a

b1.

0±0.

3ab

1.1±

0.0b

0.6±

0.2a

b0.

5±0.

3a0.

87±0.

17ab

0.8±

0.2a

b1.

0±0.

3ab

0.8±

0.2a

bN

D0.

7±0.

1ab

697

All

yl

met

hyl

sulf

ide

0.2±

0.0a

0.3±

0.0a

b0.

3±0.

0ab

0.2±

0.0a

0.3±

0.1a

0.3±

0.0a

b1.

1±0.

5d0.

6±0.

1bc

0.7±

0.0c

0.7±0.

1c1.

1±0.

0d0.

7±0.

1e

744

Dim

ethyl

dis

ulf

ide

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

0.2±

0.0

772

3-M

ethyl-

thio

phen

eN

DN

DN

DN

DN

DN

DN

DN

DN

DN

DN

D0.

2±0.

0

844

2-M

ethylp

yra

zine

ND

ND

ND

ND

ND

ND

ND

ND

ND

0.3±

0.3a

0.1±

0.0b

.0.

1±0.

0b

856

All

yl

sulf

ide(

dia

llyl

sulf

ide)

2.4±

0.4a

2.7±

0.1a

b2.

8±0.

2abc

2.4±

0.1a

2.2±

0.3a

2.8±

0.1a

bc4.

1±1.

7cd

3.8±

0.5b

cd4.

2±1.

1d4.

2±0.

9d4.

9±0.

6d9.

2±0.

2e

888

2-M

ethyl-

3,4

-dih

ydro

- 2H

-thio

pyra

n0.

4±0.

00.

4±0.

00.

4±0.

10.

2±0.

20.

3±0.

00.

4±0.

00.

1±0.

10.

1±0.

10.

1±0.

10.

1±0.

10.

1±0.

10.

1±0.

0

909

3,4

-Dim

ethylt

hio

phen

e0.

3±0.

00.

2±0.

00.

2±0.

00.

1±0.

00.

1±0.

10.

2±0.

00.

1±0.

00.

1±0.

010.

1±0.

00.

1±0.

00.

1±0.

10.

1±0.

0

918

All

yl

met

hyl

dis

ulf

ide

1.2±

0.3a

b1.

2±0.

1ab

0.9±

0.6a

b0.

6±0.

1a0.

9±0.

2ab

0.9±

0.1a

b3.

7±1.

4e1.

8±0.

2bc

2.5±

0.2c

d2.

1±0.

4cd

2.5±

0.6c

d3.

0±0.0

de

944

1,3

-Dit

hia

ne

0.4±

0.1

0.2±

0.1

0.4±

0.0

0.2±

0.0

0.3±

0.1

0.4±

0.0

0.4±

0.0

0.3±

0.0

0.3±

0.0

0.3±

0.0

ND

ND

980

Phen

yle

thyl

buty

rate

2.8±

2.5

2.9±

1.0

3.3±

1.0

4.1±

0.1

0.7±

1.3

1.6±

0.4

1.4±

1.9

2.7±

0.4

3.2±

1.1

1.8±

1.6

ND

ND

1,0

14

2-M

ethyl-

3-e

thylp

yra

zine

ND

ND

ND

ND

ND

ND

ND

ND

ND

0.3±

0.3a

0.7±

0.1b

1.0±

0.1c

1,0

98

Dia

llyl

dis

ulf

ide

14.9

±5.

4bc

15.8

±2.

0bc

16.3

±0.

8c11

.4±1.

5abc

10.6

±1.

3ab

13.5

±1.

2bc

12.0

±2.

8abc

12.3

±0.

4abc

12.5

±2.

9abc

12.3

±1.

8abc

7.8

±1.

3a12

.2±0.

0abc

1,1

04

1,5

-Dit

hio

cane

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

2.6±

0.1

1,1

60

All

yl

met

hyl

tris

ulf

ide

3.8±

0.5a

b2.

9±0.

4a3.

6±0.

6ab

2.3±

0.1a

2.4±

0.6a

2.3±

0.4a

6.5±

0.4c

d4.

6±0.

3abc

5.6±

0.5b

cd3.

4±3.

0ab

2.2

±0.

4a7.

9±0.8

d

1,1

76

1-M

ethyl-

3-p

yrr

oli

n-2

-one

0.5±

0.1

0.4±

0.0

0.4±

0.0

0.2±

0.0

0.3±

0.3

0.4±

0.0

0.6±

0.2

0.5±

0.0

0.5±

0.1

0.3±

0.3

ND

ND

1,1

84

2,4

-Dim

ethyl-

6,7

-dih

ydro

-5H

-cy

clopen

ta[D

]pyri

mid

ine

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

6.8±

0.5

1,1

91

1,3

,5-T

rith

iane

1.5±

0.1

0.9±

0.3

1.2±

0.0

1.3±

0.0

0.7±

0.1

0.7±

0.1

1.0±

0.0

1.1±

0.1

1.1±

0.2

1.0±

0.2

0.6±

0.0

ND

1,2

12

2,5

-Dim

ethyl-

3-i

sobuty

lpyra

zine

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

0.2±

0.1

1,2

20

3-V

inyl-

1,2

-dit

hia

cycl

ohex

-4-e

ne

2.6±

0.2

2.2±

0.5

2.7±

0.1

1.8±

0.1

1.0±

0.4

1.0±

0.3

1.1±

0.2

1.5±

0.3

1.4±

0.5

1.2±

0.3

0.4±

0.1

0.8±

0.2

1,2

50

3-V

inyl-

1,2

-dit

hia

cycl

ohex

-5-e

ne

3.8±

1.3

3.4±

0.5

3.7±

0.1

2.5±

0.0

1.6±

0.5

1.6±

0.3

2.2±

0.3

2.4±

0.3

2.3±

0.6

2.1±

0.4

1.0±

0.1

2.4±

0.6

1,3

28

Dia

llyl

tris

ulf

ide

13.4

±0.

1e13

.5±1.

5e12

.4±2.

6de

10.9

±0.

0cde

6.4±

2.3a

bc6.

2±1.

8abc

8.1±

0.8b

cd6.

7±5.

4abc

9.8±

2.3b

cde

7.9±

1.6b

cd2.

6±0.

7a5.

4±0.

6ab

1,3

55

1-M

ethyli

mid

azole

-2-t

hio

l2.

3±0.

11.

9±0.

41.

8±0.

11.

4±0.

10.

7±0.

10.

7±0.

2N

D0.

4±0.

3N

D0.

2±0.

3N

DN

D

1,3

55

5-M

ethyl-

4,7

-dit

hia

dec

a-1,9

-die

ne

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

0.9±

0.3

1,4

32

5-M

ethyl-

1,2

,3,4

-tet

rath

ia-c

ycl

ohex

ane

2.9±

0.1

2.0±

0.9

2.4±

0.1

2.5±

0.1

1.3±

0.4

1.3±

0.3

2.0±

0.2

2.2±

0.3

2.2±

0.6

1.9±

0.5

0.8±

0.2

1.3±

0.3

1,5

35

1-H

ydox

y-4-

met

hyl-

2,6-

di-tert-

buty

lben

zene

0.8±

0.1

0.5±

0.1

0.5±

0.0

0.4±

0.1

0.4±

0.1

0.4±

0.1

0.8±

0.4

0.5±

0.1

0.6±

0.1

0.5±

0.1

0.4±

0.0

0.3±

0.1

1) L

inea

r re

tenti

on i

ndic

es (

RI)

wer

e det

erm

ined

usi

ng n

-par

affi

n a

s ex

tern

al r

efer

ence

s.2) R

oas

ted g

arli

c cl

ove

and r

oas

ted-c

rush

ed g

arli

c at

100oC

for

30 m

in w

ere

expre

ssed

as

RG

C100/3

0 a

nd R

CG

100/3

0, re

spec

tivel

y.

3) M

ean±

SD

(n=

3);

ND

, not

det

ecte

d;

Dif

fere

nt

lett

ers

are

signif

ican

t at

p<

0.0

5 a

mong t

he

sam

e ro

w i

n t

he

sele

cted

vola

tile

s.

780 Kim et al.

21 volatiles. However, the number of volatiles in RGC150/

60, RCG150/60, RGC200/30, RCG200/60, RGC200/60,

and RCG200/60 was 19, 20, 18, 20, 17, and 23,

respectively. Like other garlic samples, diallyl disulfide

was the most detected volatile. Due to the input of thermal

energy, pyrazines including 2-methylpyrazines, 2-methyl-

3-ethylpyrazine, and 2,5-dimethyl-3-isobutylpyrazine were

observed in garlic samples roasted at 200oC for 60 min.

However, these pyrazines were not observed in 100 and

150oC roasted garlic samples and even in RGC200/30, and

RCG200/30. The contents of diallyl trisulfide were high in

garlic roasted at 100oC and tended to decrease in samples

roasted at 150 and 200oC, which implies formation and

decomposition of diallyl trisulfide are depending on the

thermal energy. Considering the contents of diallyl

trisulfide in raw and autoclaved garlic, diallyl trisulfide

seems to be formed in garlic treated with around 100-120oC thermal energy but decomposed at higher temperature

like 150 and 200oC in garlic.

Maillard reaction has been regarded as major mechanisms

for the formation of pyrazines and pyridine in potato chips

(24) and in roasted sesame seed oil (25). 2-Methylpyrazine

was detected from Maillard reaction of glutathione and

reducing sugars such as glucose or fructose (26).

Six volatiles including dimethyl disulfide, 3-methyl-

thiophene, 1,5-dithiocane, 2,4-dimethyl-6,7-dihydro-5h-

cyclopenta[D]pyrimidine, 2,5-dimethyl-3-isobutylpyrazine,

and 5-methyl-4,7-dithiadeca-1,9-diene were found additionally

in RCG200/60, which implies these compounds may be

located inside of garlic matrix and crushing process helps

to release these volatiles to the headspace.

Volatiles of 1,3-dithiane, phenethyl butyrate, and 1-

methyl-3-pyrroin-2-one, which were detected in 100 and

150oC roasted samples, were not observed in RGC200/60,

and RCG200/60. 1,3-Dithiane and phenethyl butyrate were

found in raw and autoclaved samples implying these

compounds may be heat-labile and/or be changed into

other volatile or non-volatile forms.

Peak areas of 2-propen-ol and allyl methyl sulfide

started to increased in garlic roasted at 150oC and 3-vinyl-

1,2-dithiacyclohex-4-ene and diallyl trisulfide were

decreased from 150oC roasted samples.

Changes of relative contents of diallyl disulfide, diallyl

trisulfide, and allyl methyl trisulfides to the total sulfur-

containing compounds in garlic with different processing

conditions are shown in Fig. 2. Diallyl disulfide is the most

abundant sulfur-containing compound in garlic ranging

from 48% in GC to 18% in BGC. Relative contents of

diallyl disulfide in raw garlic clove (GC) were significantly

higher than those of other garlic samples and diallyl

trisulfide and allyl methyl trisulfide in GC were significantly

lower than other samples (p<0.05). Application of thermal

energy changed the profiles of sulfur-containing compounds

greatly. Generally, relative contents of diallyl disulfide

decreased in aged-black and roasted garlic and those of

diallyl trisulfide and allyl methyl trisulfide increased. Allyl

methyl trisulfide was not found in BGC, which may be due

to the inhibiting effects of layers in aged-black garlic clove.

Some sulfur-containing volatiles including 3-vinyl-1,2-

dithiacyclohex-5-ene and 3-vinyl-1,2-dithiacyclohex-4-ene

decreased upon autoclaving or roasting process.

Number of identified volatiles in this study was relatively

Fig. 2. Relative contents (%) of diallyl disulfide, diallyl trisulfide, and allyl methyl trisulfides to total sulfur-containing compoundsin garlic treated with different processing conditions. Different letters are significant at p<0.05 among the same volatiles; ND, not

detected

Volatiles in Processed Garlic by SPME 781

small compared to that of volatiles from previous reports.

Because SPME method just isolates and concentrates the

headspace volatiles adsorbed on the solid phase, number

and types of volatiles from SPME method are limited

compared to those from solvent extraction and purge and

trap methods.

Many volatiles identified in this study were already

reported in the previous reports of garlic (4,11,26). Woo et

al. (4) heated garlic bulb at 100, 110, 120, and 130oC and

extracted the volatiles using SDE and reported that the

major volatiles of raw and heated garlic were dimethyl

disulfide, 2-propen-1-ol, allyl methyl disulfide, dimethyl

trisulfide, diallyl disulfide, allyl methyl trisulfide, and

diallyl trisulfide. Lee et al. (11) reported that allyl methyl

sulfide, allyl sulfide, diallyl disulfide, and 1,3-dithiane

were representative volatiles from garlic samples using 50/

30 µm divinyl benzene/carboxen/polydimethylsiloxane

(DVB/CAR/PDMS) SPME fiber. Yu et al. (27) identified

allyl methyl trisulfide, diallyl disulfide, diallyl trisulfide,

dimethyl disulfide,1,3-dithiane, aniline, 2,4 dimethylfurna,

and 2-propen-1-ol using essential oils from raw crushed

garlic treated with diverse extraction methods including

steam distillation, water distillation, and SDE. Difference

in the number and profiles of detected volatiles may be due

to the volatile analysis and garlic processing methods.

PCA analysis of volatiles in garlic treated with diverse

processing PCA was conducted to determine the relation

among volatile distribution and garlic samples received

different processing. Loading and score plots of PCA for

volatiles in garlic samples are shown in Fig. 3. The first

principal component (PC1) and second principal component

(PC2) expressed 38.07 and 20.24% of the volatile variability

among headspace volatiles in diversely processed garlic,

respectively. Volatiles that are positively correlated to PC1

are pyrazines, allyl methyl disulfide, allyl methyl trisulfide,

and allyl sulfide and negatively correlated volatiles to PC1

are diallyl disulfide and allyl mercaptan (Fig. 3A). According

to the scoring plot, PCA clearly distinguished garlic

samples with different processing methods using volatile

profiles (Fig. 3B). Raw garlic clove and raw-crushed garlic

were grouped together and located negatively to PC1 score

while garlic roasted at 200oC for 60 min and aged-black

garlic samples were located positively. Samples autoclaved

and roasted at 100 and 150oC were grouped together (Fig.

3B). As roasting temperature increased from 100 to 200oC,

the PCA plot extended from the left side (negative value of

PC1 score) through the middle to the right side (positive

value). Loading and score plots of PCA showed that diallyl

disulfide and allyl mercaptan were more related with raw

garlic samples (CG and GC), while diallyl trisulfide and

pyrazines were more correlated with autoclaved and

roasted-crushed garlic at 200oC for 60 min, respectively.

PCA approaches using headspace volatiles are useful

techniques for differentiating foods prepared differently

(28). Park et al. (25) used PCA technique for the analysis

of headspace volatiles to discriminate sesame oil prepared

from sesame seeds roasted with different condition. PCA

using headspace volatiles can be a useful tool to

discriminate garlic prepared from different processing.

In conclusion, headspace volatiles in garlic samples

treated with autoclaving, high temperature aging, roasting,

and crushing process were analyzed by SPME-GC/MS and

volatile data were processed with PCA. Sulfur-containing

compounds including diallyl disulfide, allyl mercaptan,

allyl sulfide, and diallyl trisulfide were major volatiles in

garlic samples. Generally, diallyl disulfide decreased and

diallyl trisulfide increased upon receiving thermal energy

and pyrazines appeared in garlic roasted at 200oC for 60

min and aged-black garlic samples. PCA showed that

roasted or aged-black garlic could be differentiated from

raw garlic using profiles of headspace volatiles. This is the

first report comparing the distribution of volatiles using

SPME method from garlic and crushed garlic samples

prepared by diverse processing such as autoclaving, high

Fig. 3. Loading (A) and score (B) plots of PCA for theheadspace volatiles in garlic treated with different processingconditions by SPME-GC/MS.

782 Kim et al.

temperature aging, and roasting. Further studies are needed

to correlate among the changes of sensory attributes and

volatile profiles in diversely processed garlic.

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