蒸し芋のにおい特性

誌名誌名 日本食品保蔵科学会誌

ISSNISSN 13441213

巻/号巻/号 342

掲載ページ掲載ページ p. 65-70

発行年月発行年月 2008年3月

農林水産省 農林水産技術会議事務局筑波産学連携支援センターTsukuba Business-Academia Cooperation Support Center, Agriculture, Forestry and Fisheries Research CouncilSecretariat

( 9 ) Food Preservation Science VOL. 34 NO. 2 2008 CArticleJ 65

Aroma Characteristics of Steamed Sweet Potato -Comparison with Apple Juice Aroma Characteristics-

TAMAKI Kazuhiko*l ~ ， TAMAKI Takeshi*2 and MATSUO YUkO*3

* 1 Department of Food Science & Technology， Universi砂 ofCalifornia， Davis， CA 95616， USA

* 2 Akikusa Gakuen Junior College， 1789， 1zumi-cho， Tokorozawa-shi， Saitama 359-J J 12， Japan

* 3 Kanagawa University of Human Services， 1-10-1， Heisei-cho， Yokosuko-shi， Kanagawa 238-8522 Japan

In this study， the aroma characteristics of steamed sweet potato were compared with those of apple

juice and the difference was clarified by sensory evaluation and odor sensor and electroencephalographic

analyses. Although apple juice aroma was evaluated to be pleasant by all seven subjects. the same

tendency was not observed for all the subjects on the electroencephalogram. Three subjects were

relaxed by apple juice aroma， however no changes in α1 and α2 wave power were observed for the

remaining four subjects. It was concluded that apple juice aroma elicits no unpleasant mood. On the

other hand， by smelling steamed sweet potato aroma， a wave power was markedly decreased and a

sense of tension [was enhancedJ. A significant difference between apple juice aroma and steamed

sweet potato aroma was observed on the basis of the changes in α wave power. It was clarified that

steamed sweet potato aroma is di任erentfrom apple juice aroma， and is not as pleasant as apple juice

aroma.

(Received Sep. 3， 2007 ; Accepted Nov. 28， 2007)

Key words steamed sweet poωω aroma， apple juice aroma， sensory evaluation， odor sensor analysis，

electroencephalo g raph y，αwave power

蒸し芋のにおい， りんご、ジ、ユースのにおい，官能評価，においセンサ一分析，脳波検査， α波

パワー量

Sweet potato (Jpomoea batatas (1)). belongs to the

family ConvolvulaceaeD• It originated in Central

America and was introduced into Southeast Asia

from South America and then to Ryukyu Islands by

way of China. Thereafter， it was introduced to the

southern islands of ]apan and finally to the main

island. [Because it can easily be cultivated]， it was

the staple diet for starving people during World

War 11. However， its status as a staple diet ended

after ] apan became prosperous.

Sweet potato contains starch， vitamin C， and

dietary fiber. Even if heated. vitamin C in sweet

potato is not degraded easily. Thus， sweet potato is

an ideal nutrition of source. Recently， sweet potato

varieties having high s-carotene or anthocyanin

content have been developed2). We have been

studying them in the hope of utilizing them as a

potato as probiotic functional food. it is steamed at

the initial stage of preparation. It is important to

elucidate the aroma characteristics of steamed sweet

potato to enable its use as a probiotic functional

food. Various studies have been conducted to

identify and quantify volatile organic compounds in

baked sweet potat05H)， but there are few studies of

the aroma of steamed sweet potato.

Interestingly， an interview conducted in our

laboratory showed that the aroma of apple juice is

preferred over other drinks. It is important to

improve the aroma of functional food with probiotic

property for such food to be highly acceptable in

the market. Therefore， in this study. the aroma of

apple juice was compared with that of steamed

sweet potato.

Preference testing is often used to evaluate the

probiotic functional food3).'). degree of product acceptance in the market. In this

Sweet potato aroma is not pleasant and study. electroencephalography (EEG) was used to

improvements must be made for the use of sweet express the degree of preference numerically.

potato to produce processed food. To use sweet Recently， the analysis of brain waves has been used

S Corresponding author， E-mail: kaztamaki@hotmail.com

66 Food Preservation Science VOL. 34 NO.2 2008 ( 10 )

to evaluate human response to aroma. Studies have

shown that aroma influences brain waves either

positively or negatively. For instance certain smells

may relax or excite. EEG is used to study brain

activity in response to an external stimulus. The

brain wave often measured by EEG is the “α

wave". It has a specific freQuency range of 8 -13 Hz.

An increased αwave activity in the brain is a sign

of relaxation. In our experiment， the subjects were

exposed to either apple juice or steamed sweet

potato， and brain wave activity was measured and

analyzed by EEG. Sensory evaluation and odor

sensor analysis were performed as well.

What effect does aroma have on brain function?

Electrophysiological studies8l.9l have indicated that an

increase inαwave power is closely related to a

person's preference for certain aroma. When a

pleasant aroma is presented， αwave power

increases. The extent of increase is considerably

dependent on the subject's preference. Pleasant

aroma also increases the amplitude of the P300

component of event-related potentials and shortens

the latency of P300. In this study， the relationship

between psychologic data and electrophysiological

data is described.

Materials and Methods

1 . Sweet potato

The sweet potato cultivar “Benihayato"， which

was cultivated in Kagoshima， ]apan and harvested

in October 2004， was used in this study. The raw

tuber of this cultivar contains 8 mg of β-carotene per

100 g wet weight.

2. Preparation of steamed sweet potato

One kilogram of sweet potato was heated at 60-

650

C for 3.5 h and then steamed at 100t for 1 h

using boiling water.

3. Samples for measurement

Steamed sweet potatoes were kept at [30-350

CJ

and used for the experiment. Apple juice Dole

(produced by Yukijirushi Co.， LtdJ was also used.

4. Conditions for measurement

( 1 ) Sensory Evaluation

Seven subjects (]apanese female aged 20 -35

years) were selected using a difference test with

the following compounds at the indicated

concentratlOns :β-phenylethyl alcohol 1O-40%(w/w)，

methyl cyclopentenolone 10-4.5% (w / w)， isovaleric

acid 10-5.0% (w/w) ， r-undecalactone 10-45% (w/w)，

and skatole 10-5.0% (w/w) (all from Daiichi Yakuhin

Kogyo Co.， Ltd.， ]apan). The seven subjects were

asked to evaluate their preference for steamed

sweet potato， apple juice， and distilled water based

on a 7 -point scale 1 indicates very unpleasant

aroma and 7， very pleasant aroma. The subjects

were asked to have at least a 1-min rest period

between evaluations of samples: evaluation was

conducted twice each day for two consecutive days.

Next， using the s巴mantic differential (SD)

method，lOl aroma Quality was evaluated in terms of

“heavy to light，" “heated to fresh，" and “weak to

strong." After the subjects had familiarized

themselves with the samples， they were instructed

to rate each sample in terms of heavy to light

aroma on a 7-point scale : -3， very heavy aroma ;

-2， fairly heavy aroma -1， moderately heavy

aroma ， 0， intermediate + 1， moderately light

aroma ; + 2， fairly light aroma; and + 3， very light

aroma. Then， the subjects were instructed to rate

each sample in terms of heated to fresh aroma also

on a 7・pointscale -3， very heated aroma -2，

fairly heated aroma， -1， moderately heated

aroma ， 0， intermediate + 1， moderately fresh

aroma ; + 2， fairly fresh aroma; and + 3. very fresh

aroma. Lastly， they were instructed to rate each

sample in terms of weak to strong aroma on the 7-

point scale : -3， very weak aroma ; -2， fairly weak

aroma ， - 1， moderately weak aroma ， 0，

intermediate + 1， moderately strong aroma + 2，

fairly strong aroma; and + 3. very strong aroma.

They were asked to have at least a 1-min rest

period between stimuli， evaluation was conducted

twice on di任erent days. All the tests were

conducted for two consecutive days.

( 2 ) Sensor analysis

A Fox 4，000 electronic sensor eQuipped with an

ACU 500 humidifier was used. This instrument is

eQuipped with 18 metal oxide sensors inside three

chambers. Each chamber contains six metal oxide

sensors (p， flat-plate sensor; T， tubular sensor; SY，

non-doped tin oxide sensor; a temperature sensor;

and a relative humidity sensor). To provide a

constant flux of vector gas (humidified synthetic

air) through the electronic sensor， a humidifier (air

conditioning unit， model 1997， Alpha-M.O.SJ was used.

Analytical parameters Ci.e. sample Quantity， headspace

generation time， temperature， flow rate， and

injection time) were determined. The sensors were

carefully monitored to ensure that they return to

the baseline during the preliminary trials. The

( 11 ) CArticleJ Steamed Sweet Potato Aroma 67

optimum time was found to be 5 min after sample

injection. The data collection time was 120 sec.

Carrier gas flow was set to 150me/min and relative

humidity was regulated at 20%.

Although the electronic sensor is equipped with

very fairly moderatelymoderately fairly very ntermediately

heavy l-----i : 全一十一-@ . llight*

heated l-----f :全一ー←一一一一←h : Ifresh"

18 sensors. only the results of a limited number of unpleasant

metal oxide sensors were chosen for further pleasant"

analysis. after eliminating sensors with high

multicollinearity by stepwise regression analysis.

SPSS version 11. 0 was used for data processing

( 3 ) EEG analysis

Subjects recruited for EEG analysis were

]apanese females. aged 20 -35 years old. Each

subject was asked to sit on a chair. relax. and close

her eyes while the EEG system with a ten-twenty

electrode system was being set. A laboratory

assistant held the first sample approximately 5 cm

from the subject's nose and the subject was given

2 min to smell the sample. Next. the subject was

given distilled water to smell for 1 min and

thereafter asked to remain seated for 10 -15 sec.

Then. the subject was asked to smell the second

sample for 2 min. These procedures were repeated

twice each day for two days. The samples were

presented in random order to the subjects. The

electroencephalogram was recorded with a Neurofax

EEG-1518 (NIHON KODEN). EEG was reviewed

with a time constant of 0.03 sec and a Hi Cut

Filter of 60 Hz. EEG of 5.3-60 Hz frequency was

analyzed with 512-point FFT. and power value was

measured. Peak frequency.αI wave power (8 -10

Hz). and α2 wave power (10-13 Hz) were measured

for 5 sec each after the subject was presented a

sample. with an EEG analysis program ( NIHON

KODEN (QP-220 A) after eliminating artifacts.

Distilled water was used as control and t-test of the

results was ca1culated.

Results and Discussion

( 1 ) Sensory evaluation

Fig. 1 shows the results of the evaluation of

steamed sweet potato and apple juice using the SD

method. The t-test was performed for comparison

between the data of steamed sweet potato and

those of apple jUlce. A significant di任erencein the

factor“heavy to light" was observed at the 5 %

level. Next. a significant difference in the factor

“heated to fresh" was observed at the 1 % level.

From these results. it is thought that steamed

sweet potato has a heavy and heated (cooked) aroma.

weak strong"

Fig. 1 Aroma characteristics of steamed sweet potato and apple juice. measured by SD method

Oーベコ applejuice .→・ steamedsweet potato * significant at 5 % level

* * significant at 1 % level

while apple juice has a light and fresh aroma. The

standard deviation. which indicates of variation

among subjects. was small. In addition. a significant

di妊'erence in the factor “weak to strong" was

observed at the 1 % level. From this result. it is

thought that steamed sweet potato has a weak

aroma. while apple juice has a strong aroma. The

standard deviation was also small.

The result of the pleasantness test is also shown

in Fig. 1. A significant difference in the factor

“unpleasant to pleasant" was observed at the 5 %

level. The standard deviation was likewise small.

From this result. it was concluded that apple juice

aroma is more pleasant than steamed sweet potato

aro町la.

Apple juice aroma mainly originates from a

mixture of esters. aldehydes. and a1cohols. Among

ester compounds. ethyl acetate. butyl acetate. and

hexyl acetate are present in large amounts. (E)ー2-

Hexenal. an aldehyde. is present in large amounts

as welllll. A1cohols such as butanol and hexanol are

also present in large amountsll). These aromatic

compounds are responsible for the fruity and

fragrant aromas. On the other hand. the heavy

aroma of steamed sweet potato is due to terpenes.

ionone. s-damascenone. benzaldehyde. and

phenylacetaldehyde6H21. When Satsuma mandarin is

heated. an 0任flavoris generated. which resembles

the heavy aroma of steamed sweet potato and is

called imo-shu. ARAKI and SAKAKIBARA reported that

this heavy aroma is due to the large amount ofβ-

damascenonel1l. It is clear that aromatic compounds

in apple juice are different from those in steamed

sweet potato.

concentrations of volatile organic compounds in the

samples are di妊erent， there is a fixed correlation

between sensory aroma strength and

rate. When the aroma qualities

different， there is no

sensory aroma strength

response rate.Thus， from the fact that the sensory

aroma strength of steamed sweet potato is less than

that of apple juice， it cannot be concluded that the

sensor response rate of the former is lower than

that of the latter. However. it is clear that there is

a marked difference in the amount of volatiles

between steamed sweet potato and apple juice.

( 3) EEG analysis

Organoleptic values and changes in

electroencephalogram for the seven subjects

shown in Table 1. The upper panel shows

results of sensory evaluation and the lower

shows those ofα1 and α2 wave power measurements.

A cross (↑) represents significance at the 10% level

and an asterisk (*) represents significance at the

5 % level. Apple JUlce aroma was pleasant while

steamed sweet potato aroma was unpleasant

distilled water without aroma was between pleasant

and unpleasant. There were some di妊erences in

organoleptic values among the subjects.

When apple juice was presented to the subjects，

no significant change in α1

observed. On the other hand，

( 2) Odor sensor analysis

Fig. 2 shows the response patterns of the 18

sensors to the volatile organic compounds

steamed sweet potato and apple juice. The response

of most of the sensors to steamed sweet

potato were clearly lower than those to apple juice.

There is an exponential linear relationship between

sensor response rate and the concentrations of

volatile organic compounds. However， there is no

direct relationship between sensor response rate and

sensory aroma strength. When the aroma qualities

of the samples are the same and only the

2008

m

( 12 )

sensor

of the

correctlOn

and

NO.2 VOL. 34 Food Preservation Science 68

sensor

the

are

the

one

are

response

samples

between

SY/gCN

SY/gCT

SY/LG

P3012

P4012

rates

P40/l

Fig.2 Response patterns of 18 sensors to volatile organic

compounds in steamed sweet potato and apple juice

power was

m

wave

mcrease 4-steamed…t potato I 1-.-apple juice

αz an

Results of sensory evaluation and changes in a-wave power spectrum Table 1

subject G subject F subject E subject D subject C subject B subject A Evaluation

ヲ'pnvRU4aqtunL1A

a a a pleasant

a W a

s s

in termedia te W a w w w a w

s s s s

w s

unpleasant

s a s a s a s a s a s a s a

αI α2 α1 α』* mcrease

α2

αl a， αi a， α2 。1α2 a， αl α2 a， no change

α2 α2 a2 α2 α2

a，

*

decrease

a，

a， s and w indicate apple juice， steamed sweet potato. and distilled water samples，respectively * : significant at 5 % level (control=H，Q)

↑: significant at 10% level (control=H，Q)

The electroencephalogram indicates change in P 3

The upper panel shows the results of sensory evaluation and the lower panel shows the changes in a， and a， wave powers

α2 αl α2 α1 α2

( 13 ) CArticleJ Steamed Sweet Potato Aroma 69

wave power was observed for one subject. a tension. EEG analysis revealed that the tendency for

decrease in α2 wave power was observed for two

subjects， and no change inα2 wave power was

observed for four subjects. Further analysis was

conducted for the subject whose α2 wave power

was increased. When the subject smel1ed the control

sample，αwave power was barely observed. Thus，

it was surmised that stress was relieved by

smelling apple juice， which e任ectivelyincreased α

wave power. In two subjects whose α2 wave power

was decreased by sm巴llingapple juice， no significant

chang巴 IIIα1 wave power was observed. Thus， it

seems that the appearance of the fast component of

the αwave was suppressed.

From the above results， it was hypothesized that

the three subjects described above became relaxed

by smel1ing apple juice. Although apple juice aroma

was evaluated to be pleasant by al1 the subjects in

the sensory evaluation， the same tendency was not

observed in the electroencephalograms of al1 the

subjects.

When steamed sweet potato aroma was presented

to the subjects， an increase in al wave power was

observed for three subjects， a decrease inα1 wave

power was observed for three subjects， and no

change inα1 wave power was observed for one

subject (Table 1). When apple juice was presented，

no chang巴 IIIα1 wave power was observed. In

contrast. when steamed sweet potato was presented，

changes inα1 wave power were observed. This is

the key di妊erencebetween apple juice aroma and

steamed sweet potato aroma. From the finding that

α1 wave power increased significantly for three

subjects， whose α1 wave frequency did not change

significantly， it was thought thatα1 wave power

itself increased for three subjects.

In general， an increase inα1 wave power means

an increase in consciousness level or relaxation.

When a person is in a relaxed state.αwave

frequency decreases. As no change in αwave

frequency was observed in this experiment. it

appears that a relaxed state was not achieved;

instead consciousness level increased. For one of the

three subjects whose α1 wave power decreased after

smel1ing steamed sweet potato，α2 wave power a

also decreased. Thus it was clear that αwave

power completely was decreased and a sense of

tension developed. Although the change in αwave

power depends on each subject. it seems that

steamed sweet potato aroma induces a sense of

marked change is more clearly observed for

unpleasant aroma than for pleasant aroma.

The effects of apple juice aroma and steamed

sweet potato aroma on mental activity were studied

from the changes in the electroencephalogram. It

was clarified that apple juice aroma had less impact

on the electroencephalogram than steamed sweet

potato aroma. In general， EEG results may react

more sensitively to unpleasant aroma than to

pleasant aroma.

From the above results， steamed sweet potato

aroma was confirmed to be less pleasant than apple

JUlce aroma.

Acknowledgement We deeply thank Mr. Hitoshi

Iwasaki of NIHON KODEN CORPORATION and

Mr. Koichi Yoshida of Primetech Corporation for

their technical contributions.

References

1) KOBA Y ASHI， M.: Satsumaimo no kita michi in

Japanese p.20 Kokonshoin Publishers (1984)

2) SAKAMOTO， S.， MARUMINE， S.， IOE， Y.， Y AMAKA W A，

0.， KUKIMURA， H.， YOSIDA， T. and T ABUCHI， S.:

‘Benihayato' A New Sweet Potato Cultivar

Registered， Bulletin 01 即時ushu National

Agricultural Experiment Station， 24 (3)， 255 -277

(1987)

3) Committee on Diet Nutrition and Cancer

(National Academy Press. Washington D. c.)

(1982)

4) KISHIOA， A.: JP 2051579 C

5) SUN， ]. B.. SEVERSON， R. F.， SEVERSN. W. S. and

KAYS， S. ].: Quantitative technique for measuring

volatile components of baked sweet potatoes，

HortScience， 28 (11)， 1110-1113 (1993)

6) PURCELL， A. E.， LATER， D. W. and LEE， M. L.:

Analysis of the volatile constituents of baked

“Jewel" sweet potatoes， J. Agric Food Chem， 28 : ，

939-941 (1980)

7) HORVAT， R. ].， ARRENOALE. R. F.， DULL， G. G.，

CHAPMAN. G. W. and KAYS， S. J. Volatile

constituents and sugars of three diverse cultivars

of sweet potatoes [lpomoea batatas (L.) Lam.J， J

Food Sci.. 56 (3)， 714-716 (1991)

8) KOGA， Y.: Stress and aromatherapy， Fragrance

Journal， 86， 25-28 (1987)

9) KOGA， Y. and T AKEUCHI， H.: The e妊ect of

fragrance to brain function， Fragrance Journal， 17

70 Food Preservation Science VOL. 34 NO.2 2008 ( 14 )

( 9 )， 20~27 (1989)

10) SATO， S.: Kannou Kensa Nyumon in ]apanese

]USE Press (1978)

11) WILLAERT， G. A.， DIRINCK， P. ].， DE PORTER， H. L.

and SCHAMP， N. N.: Objective measurement of

aroma quality of golden delicious apples as a

function of controlled.atmosphere storage time，よ

Agric. Food Chem.， 31， 809~813 (1983)

12) T AMAKI， K.， EHARA K.， T AMAKI， T. and Y AMAZAKI

T.: Determination of aroma changes in sweet

potato CIpomoea batatas (L.) Lam) during sweet

potato juice production， Food Preservation Science，

33， 51 ~61 (2007)

蒸し芋のにおい特性

一りんごのにおいと比較してー

玉城和彦判 ・玉城 武叫・松尾祐子叫

* 1 カリフォルニア大学デーピス校

(カリフォルニア州デーピス95616)

* 2 秋草学園短期大学

(干359-1112埼玉県所沢市泉町1789)

* 3 神奈川県立保健福祉大学

(〒238-8522神奈川県横須賀市平成町 1-10-1)

甘藷を高付加価値化するため，原料処理過程の蒸し芋

のにおい特性について検討した。よいにおいをもっ市販

のりんごジ、ユースのにおいを対照とし， 蒸し芋のにおい

特性の違いを官能試験により調べた結果， 蒸し芋のにお

いは弱く，重くてフレ ッシュさに欠け，りんごより快く

ないことが明らかになった。

次に18種のセンサーを用いて抵抗値の変化率を計測し

たところ，蒸し芋はりんごに比べてかなりのセンサーに

ついてその変化率が小さかった。このことは前者が後者

に比べ，揮発性成分の含量が少ないことを意味している。

次にりんごと蒸し芋のにおいをかいだとき，脳波上に

どのような違いがあらわれるか蒸留水を対照として 7人

の被験者について調べた。りんごのにおいをかいだとき，

a， (8 ~10 Hzのα波)パワー量に変化はみられなかっ

たが，的 (1O~13 Hzのα波)パワー量は変化がみられ

た人と変化がみられない人に分かれた。解析の結果 7

人のうち 3人はりんごのにおいにより，リラ ックス状態

を示す脳波の変化がみられたが，残りの 4人については，

αh のパワー量とも変化がみられず， りんごの香りによ

る脳波の変化はみられなかった。一方蒸し芋の臭いをか

いだとき， α1パワー量に変化がみられた人と変化がみら

れない人に分かれ， りんごとは明確に脳波の変化に違い

がみられた。解析の結果蒸し芋のにおいは緊張感を与え

る「α波の減少J傾向がみられた。りんごと蒸し芋のに

おいが精神活動にどのような影響を与えるか調べたとこ

ろ， りんごは脳波にそれほど影響を与えないけれども，

蒸し芋は脳波に与える影響が大きいことがわかった。以

上の結果から，蒸し芋のにおいはりんごのにおいとはそ

の特性が明らかに異なり，りんごのに比べにおいが

pleasantで、はないことが明らかになった。

(平成19年9月3日受付，平成19年11月28日受理)