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Comparison of umami-taste active components in the pileus and stipe

of pine-mushrooms (Tricholoma matsutake Sing.) of different grades

In Hee Cho a, Hyung-Kyoon Choi b, Young-Suk Kim a,*

a Department of Food Science and Technology, Ewha Womans University, Seoul 120-750, Republic of Koreab College of Pharmacy, Chung-Ang University, Seoul 156-756, Republic of Korea

a r t i c l e i n f o

 Article history:Received 12 March 2009

Received in revised form 10 April 2009

Accepted 25 May 2009

Keywords:

Pine-mushroom (Tricholoma

matsutake Sing.)

Umami-taste

Free amino acids

50-Nucleotides

Equivalent umami concentration

a b s t r a c t

Umami-taste active components in pine-mushrooms (Tricholoma matsutake Sing.) were comparedaccording to different grades (first, second, third, and fourth) and parts (pileus and stipe). The contents

of umami-taste active free amino acids, such as aspartic acid and glutamic acid, decreased in the order

of second grade > third grade > fourth grade > first grade. Also, the contents of umami-taste active 50-

nucleotides were highest and lowest in pine-mushrooms of second and first grades, respectively. All

the contents of umami-taste active amino acids and 50-nucleotides were higher in the pileus than in

the stipe, irrespective of pine-mushroom grades. Equivalent umami concentration values of pine-mush-

rooms ranged from 13.26 (in the stipe of first grade) to 204.26 g (in the pileus of second grade) per 100 g.

All the quantitative data obtained in this study are highly consistent with our previously data on umami

sensory intensities of pine-mushrooms.

Ó 2009 Elsevier Ltd. All rights reserved.

1. Introduction

The characteristic flavour substances of mushrooms can be clas-

sified into non-volatile and volatile components (Maga, 1981). The

taste of edible mushrooms is primarily attributed to several water-

soluble substances, including 50-nucleotides, free amino acids, and

soluble carbohydrates (Altamura, Robbins, Andreotte, Long, & Has-

selstrom, 1967; Chen, 1986; Craske & Reuter, 1965; Hac, Long, &

Blish, 1949; Holts, 1971; Hommond & Nichols, 1975; Lin, 1988;

Mau, Chyau, Li, & Tseng, 1997; Tseng & Mau, 1999). Craske and

Reuter (1965) separated the amino acids present in an aqueous ex-

tract of  Boletus edulis, and demonstrated that the most intense

mushroom flavour was associated with highly basic amino acids.

Also, Altamura et al. (1967) found that a series of novel free amino

acids could be responsible for the characteristic flavour of  Agaricusbisporus. Moreover, non-protein nitrogenous components (e.g. pur-

ine base) that were present in fruit bodies could also contribute to

the overall mushroom flavour note (Hac et al., 1949). Therefore, it

was accepted that some amino acids and 50-nucleotides made

important contributions to the flavour of mushrooms.

The predominant flavour of mushrooms is the umami-taste,

also called the palatable taste or the perception of satisfaction,

which is related to an overall flavour perception induced or

enhanced by monosodium glutamate (MSG), glutamic acid, and

50-nucleotides (Bellisle, 1999; Yamaguchi, 1979). In particular,

the equivalent umami concentration (EUC) of mushrooms has of-

ten been calculated in order to understand their umami-like taste

characteristics (Chiang, Yen, & Mau, 2006; Mau, 2005; Tsai, Tsai, &

Mau, 2008; Tsai, Wu, Husang, & Mau, 2007). However, the profile

of taste components including those related to the umami-taste

in pine-mushrooms has not been reported although the taste com-

ponents of other mushrooms have been extensively studied

(Chang, Chao, Chen, & Mau, 2001; Lee, Jian, & Mau, 2009; Mau,

Lin, Ma, & Song, 2001; Mau, Wu, Wu, & Lin, 1998; Tseng & Mau,

1999; Yang, Lin, & Mau, 2001).

Our research group has conducted a series of studies on the fla-

vour characteristics of pine-mushrooms (Tricholoma matsutake

Sing.) (Cho, Choi, & Kim, 2006; Cho, Kim, Choi, & Kim, 2006; Cho,

Namgung, Choi, & Kim, 2008; Cho et al., 2007) and evaluated the

intensities of sensory taste attributes in pine-mushrooms accord-

ing to their grades (Cho et al., 2007). The intensities of most taste

attributes have been found to be either strongest or weakest in

pine-mushrooms of the highest grade, with the decreasing or

increasing, respectively, according to their grades. However, an

interesting finding was that the intensity of umami-taste was

strongest in pine-mushrooms of second grade (Cho et al., 2007).

The aims of the present study were to (1) profile the chemical

components related to the umami-like taste in pine-mushrooms

according to their grades, (2) assess their EUC values to elucidate

the synergistic effect of umami-taste components, and (3) under-

stand the correlation between their chemical compositions and

0308-8146/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.doi:10.1016/j.foodchem.2009.05.084

* Corresponding author. Tel.: +82 2 3277 3091; fax: +82 2 3277 4213.

E-mail address: yskim10@ewha.ac.kr (Y.-S. Kim).

Food Chemistry 118 (2010) 804–807

Contents lists available at ScienceDirect

Food Chemistry

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sensory attributes (especially focusing on the umami-taste attri-

bute) according to their grades.

2. Materials and methods

 2.1. Pine-mushroom

Pine-mushrooms of four grades cultivated in Inje-eup, Gang-

won-do, Republic of Korea, in 2006 were used in this study. Fresh

pine-mushrooms were wrapped in LLD-PE (low-level-density-

polyethylene) film and stored at À70 °C in a deep freezer until

use. Then they were thawed at 4 °C in a refrigerator for 3 h before

sliced using a cutter (model SFS-102, Shinomura, Sanjo, Niigata, Ja-

pan). Then the pine-mushrooms were freeze-dried for the analysis

of free amino acids and 50-nucleotides.

 2.2. Free amino acids assay

Free amino acids were extracted and analysed using EZ:faast-

free amino acid analysis kit (Phenomenex, Torrance, CA) combined

by gas chromatograph-flame ionisation detector (GC-FID) as de-

scribed by Elmore, Koutsidis, Dodson, Mottram, and Wedzicha(2005). Freeze-dried pine-mushroom powder (1 g) was extracted

with 15 ml of methanol at 75 °C for 25 min and cooled to room

temperature. Then 15 ml of water and 17 ml of chloroform were

added and this was centrifuged at 3000 rpm for 10 min. The super-

natant was used as an extract sample for EZ:faast analysis. The

preparation of a sample for GC-FID began with the addition of 

20 nmol of novaline internal standard, followed by a solid phase

extraction and then two derivatisation steps at room temperature.

The derivatised amino acids were extracted into isooctane/chloro-

form (100 ll) and analysed by an HP 6890 GC-FID (Hewlett–Pack-

ard, Palo Alto, CA).

An aliquot of the derivatised amino acid solution (2 ll) was

injected at 250 °C in split mode (1:15) onto a ZB AAA capillary

column (60 m length 0.25 mm i.d. 0.25 mm film thickness,Phenomenex). The oven temperature was held at 110 °C for

1 min, then increased to 320 °C at 32 °C/min, and then held at

320 °C for 2 min. The carrier gas was helium at a constant flow

rate of 1.5 ml/min. Each free amino acid was identified by

matching its retention time with that of EZ:faast standard in

GC chromatogram and quantified using its respective calibration

curve.

 2.3. 50-Nucleotides

50-Nucleotides were extracted and analysed as described by

Taylor, Hershey, Levine, Coy, and Olivelle (1981). Freeze-dried

pine-mushroom powder (500 mg) was extracted with 25 ml of 

deionised water. This suspension was heated to boil for 1 min,cooled, and then centrifuged at 3000 rpm for 15 min. The extrac-

tion was repeated twice. The combined supernatants were then

evaporated, and filtered using a 0.45 lm PVDF filter (26 mm, Phe-

nomenex) prior to HPLC analysis.

HPLC analysis was carried out using a HP series 1100 ultra per-

formance liquid chromatograph (UPLC) system equipped with a

G1311A quaternary pump, variable wavelength detector, and auto

sampler (Hewlett–Packard). 50-Nucleotides were separated by Sun-

fire C18 column (4.6 Â 250 mm, 5 ll) (Waters Co., Milford, MA)

using an isocratic mobile phase of 0.5 M potassium phosphate

(pH 4.0 with phosphoric acid) at a flow rate of 1 ml/min and UV

detection at 254 nm. Each 50-nucleotide was identified by match-

ing its retention time with that of an authentic standard in HPLC

chromatogram and quantified using its respective calibrationcurve.

 2.4. Equivalent umami concentration (EUC)

EUC (g MSG/100 g) is the concentration of MSG equivalent to

the umami intensity given by a mixture of MSG and 50-nucleotides

and is represented by the following addition equation (Yamaguchi,

Yoshikawa, Ikeda, & Ninomiya, 1971):

Y ¼ Raibi þ 1218ðRaibiÞðRa jb jÞ

where Y is the EUC of the mixture in terms of g MSG/100 g; ai is the

concentration (g/100 g) of each umami amino acid [aspartic acid

(Asp) or glutamic acid (Glu)]; a j is the concentration (g/100 g) of 

each 50-nucleotide [50-IMP, 50-GMP, 50-XMP, 50-AMP]; bi is the rela-

tive umami concentration (RUC) for each umami amino acid to MSG

(Glu, 1 and Asp, 0.077); b j is the RUC for each umami 50-nucleotide

to 50-IMP (50-IMP, 1; 50-GMP, 2.3; 50-XMP, 0.61 and 50-AMP, 0.18);

and 1218 is a synergistic constant based on the concentration (g/

100 g) used.

 2.5. Statistical analysis

Analysis of variance (ANOVA) was performed using the general

line model (GLM) procedure to determine significant differences inthe amounts of free amino acids and 50-nucleotides of pine-mush-

rooms according to their grades. Duncan0s multi-range test was

conducted when the samples exhibited a significance difference

between samples, with the level of significance set at P < 0.05. Both

ANOVA and Duncan0s multiple range test were performed with

SPSS (version 10.1, Chicago, IL).

3. Results and discussion

The quality of mushrooms depends on various factors such as

their aroma, taste, texture, and colour, with the aroma and taste

being the most important. Pine-mushrooms have been classified

according to their appearance by the Korean National Forestry

Cooperatives Federation (http://www.koreanforest.com), which isaffected mostly by their ripening stages and cultivating conditions.

Our previous studies demonstrated that the flavour characteristics

of pine-mushrooms vary distinctively with their grades, with the

intensities of most sensory flavour attributes being either strongest

or weakest in pine-mushrooms of the highest grade. A total of 15

sensory attributes, such as sweet, salty, sour, bitter, umami, piny,

floral, alcohol-like, meaty, moldy, wet soil-like, fishy, fermented,

metallic, and astringent properties, in pine-mushrooms, were de-

scribed by eight trained panelists. The intensities of sweet, piny,

floral, and meaty attributes were strongest in pine-mushrooms of 

the highest grade, whereas those of sour, bitter, alcohol-like, mol-

dy, wet soil-like, fermented, metallic, and astringent attributes

were highest in pine-mushrooms of the lowest grade, both ones

being decreased or increased according to their grades. However,it was noteworthy that the umami-taste was strongest in pine-

mushrooms of second grade (7.84), followed by third grade

(6.56), fourth grade (5.84), and first grade (5.00), respectively

(Cho et al., 2007).

As indicated in Table 1, 23 amino acids were identified in the

two parts of the four grades of pine-mushrooms, with ANOVA their

mean contents differed significantly with part and grade (P < 0.05).

Free amino acids were grouped according to Komata (1969) into

the following four classes of taste components: MSG-like, sweet,

bitter, and tasteless. Chen (1986) found that sweet components

(alanine, glycine, and threonine) and MSG-like components (aspar-

tic and glutamic acids) were taste-active amino acids in mush-

rooms. In the present study, the content of glutamic acid

decreased in the order of second grade > third grade > fourth gra-de > first grade. Also, the content of aspartic acid was highest in

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pine-mushrooms of second grade, followed by those of third, first,

and fourth grades. The contents of both aspartic and glutamic acids

were higher in the pileus than in the stipe, irrespective of the

grade. Moreover, as for the umami-taste, the total contents of 

aspartic and glutamic acids were highest and lowest in pine-mush-

rooms of second and first grades, respectively, which is consistentwith the sensory results in our previous study (Cho et al., 2007).

Yamaguchi et al. (1971) reported that four of the six 50-nucleo-

tides (50-AMP, 50-IMP, 50-GMP, and 50-XMP) normally detected in

mushrooms contribute to umami-taste. Table 1 lists the contents

of the 50-nucleotides (50-AMP, 50-CMP, 50-GMP, and 50-UMP) iden-

tified in the pileus and stipe of pine-mushrooms of the four grades.

The contents of 50-AMP and 50-GMP exhibiting umami-taste de-

creased in the order of second grade > third grade > fourth gra-

de > first grade. As for the umami-taste active free amino acids,

the contents of 50-AMP and 50-GMP were higher in the pileus than

in the stipe.

Yamaguchi et al. (1971) suggested that the combination of 

umami amino acids and umami 50-nucleotides would synergisti-

cally increase the umami-taste of mushrooms. The EUC value of 100% indicates that the umami intensity of mushrooms per 1 g

dry matter is equivalent to the umami intensity of 1 g of MSG; in

other words, 1 g MSG/g dry matter. The EUC values of pine-mush-

rooms varied widely, ranging from 204.26% in the pileus of second

grade mushrooms to 13.26% in the stipe of first grade mushrooms.

Mau (2005) grouped the EUC values into four levels: (1) >1000 g,

(2) 100–1000 g, (3) 10–100 g, and (4) <10 g per100 g ofdrymatter,corresponding to >10, 1–10, 0.1–1, and <0.1 g MSG/g, respectively.

Therefore, the EUC values of our tested pine-mushrooms were in

the second level. On the other hand, it was noteworthy that the

EUC values and umami sensory intensities exhibited the same pat-

terns in pine-mushrooms of different grades. Also, the EUC values

were higher in the pileus than in the stipe.

In conclusion, the total contents of umami-taste active free ami-

noacidsand5 0-nucleotides were highest and lowest in pine-mush-

rooms of second and first grades, respectively. Also, the EUC value,

which could express the synergistic effect between umami-taste

components, decreased in the order of second grade > third gra-

de > four grade > first grade. All of these results are highly consis-

tent with those of the sensory tests performed in our previous

study (Cho et al., 2007), showing that amino acids (e.g., asparticacid and glutamic acid) and 50-nucleotides (e.g., 50-AMP and 50-

 Table 1

Contents of free amino acids identified in pine-mushrooms of two different parts according to their four grades.

Content (mg/g dry weight)

In the pileus In the stipe

1st 2nd 3rd 4th 1st 2nd 3rd 4th

 Amino acids

Alanine 3.95 ± 0.36Aa 3.96 ± 0.11A 4.00 ± 0.48A 4.03 ± 0.26A 1.96 ± 0.15C 1.95 ± 0.24C 3.15 ± 0.37B 1.34 ± 0.09D

Glycine 0.96 ± 0.10B 1.09 ± 0.05A 0.87 ± 0.04C 0.83 ± 0.03C 0.58 ± 0.04D 0.64 ± 0.06D 0.81 ± 0.07C 0.34 ± 0.02EValine 1.08 ± 0.13AB 1.04 ± 0.03A 0.83 ± 0.06AB 0.57 ± 0.01B 0.53 ± 0.04B 0.55 ± 0.05B 0.70 ± 0.06AB 0.00 ± 0.00C

Leucine 1.70 ± 0.18B 1.84 ± 0.07A 1.50 ± 0.14C 0.99 ± 0.07E 0.86 ± 0.05F 0.95 ± 0.07EF 1.24 ± 0.10D 0.40 ± 0.01G

Isoleucine 0.00 ± 0.00D 0.69 ± 0.01A 0.58 ± 0.03B 0.38 ± 0.02C 0.36 ± 0.01C 0.35 ± 0.02C 0.00 ± 0.00D 0 .00 ± 0.00D

Proline 1.73 ± 0.19C 1.78 ± 0.07BC 1.62 ± 0.03C 2.05 ± 0.20A 1.68 ± 0.12C 1.86 ± 0.12B 0.00 ± 0.00E 1.25 ± 0.01D

Thioproline 0.00 ± 0.00B 0.45 ± 0.06A 0.00 ± 0.00B 0.00 ± 0.00B 0.00 ± 0.00B 0.00 ± 0.00B 0.00 ± 0.00B 0.00 ± 0.00B

Aspartic acid 3.28 ± 0.26C 5.45 ± 0.36A 3.84 ± 0.44B 3.22 ± 0.36D 0.78 ± 0 .08G 1.38 ± 0.08E 0.86 ± 0.14F 0.70 ± 0 .04H

Methionine 0.30 ± 0.06B 0.25 ± 0.02C 0.35 ± 0.01A 0.34 ± 0.00A 0.00 ± 0.00D 0.00 ± 0.00D 0.00 ± 0.00D 0.00 ± 0.00D

Hydroxyproline 0.41 ± 0.07C 0.29 ± 0.04F 0.48 ±.20AB 0.36 ± 0.01DE 0.34 ± 0.01E 0.49 ± 0.08A 0.46 ± 0.06B 0.38 ± 0.07D

Glutamic acid 4.42 ± 0.19F 8.60 ± 1 .03A 6.91 ± 1.02C 5.24 ± 0.21D 2.50 ± 0 .18H 7.48 ± 0.49B 5.01 ± 0.64E 3.40 ± 0 .24G

Phenylalanine 2.81 ± 0.35D 3.03 ± 0 .14C 3.60 ± 0 .80A 2.68 ± 0.10D 2.37 ± 0.13E 3.16 ± 0.30B 3.33 ± 0.40BC 1.93 ± 0.21F

Aminoadipic-acid 0.27 ± 0.02D 0.37 ± 0.06B 0.31 ± 0.04C 0.41 ± 0.03A 0.15 ± 0.00F 0.23 ± 0.00E 0.29 ± 0.04CD 0.00 ± 0.00G

Ornithine 9.49 ± 0.49G 12.60 ± 0.36F 21.95 ± 1.42B 15.68 ± 1.48D 15.00 ± 0.99D 26.82 ± 2.56A 20.66 ± 2.70C 13.63 ± 1.27E

Lysine 3.73 ± 0.12C 4.93 ± 0.19B 7.86 ± 2.49A 5.30 ± 0.43B 3.48 ± 0.05C 5.06 ± 0.98B 5.57 ± 0.74B 2.84 ± 0.23D

Histidine 2.98 ± 0.09E 4 .18 ± 0.16C 5.78 ± 1.75A 4.83 ± 0.30B 2.09 ± 0.14G 3.35 ± 0.55D 2.63 ± 0.20F 1.67 ± 0.13H

Tyrosine 3.44 ± 0.18E 4.17 ± 0.31D 7.20 ± 2.24A 4.55 ± 0.34CD 4.12 ± 0.52D 5.68 ± 0.60B 4.72 ± 0.24C 3.03 ± 0.08E

Hydroxyproline 0.00 ± 0 .00B 0.17 ± 0 .03A 0.00 ± 0 .00B 0.00 ± 0 .00B 0.00 ± 0 .00B 0.37 ± 0 .06B 0.00 ± 0 .00B 0.00 ± 0 .00B

Tryptophane 0.79 ± 0.09G 0.93 ± 0 .07F 1.17 ± 0.28D 1.49 ± 0.05B 1.21 ± 0.22D 1.62 ± 0.14A 1.03 ± 0.14E 1.40 ± 0 .11CCystathionine 0.57 ± 0.03AB 0.63 ± 0 .11A 0.50 ± 0 .22CD 0.61 ± 0 .06A 0.14 ± 0.00F 0.44 ± 0 .04D 0.34 ± 0.05E 0.00 ± 0 .00G

Umami-taste active amino acidsb 7.70 ± 0.23E 14.05 ± 0.70A 10.75 ± 0.73B 8.46 ± 0.29D 3.28 ± 0.13H 8.86 ± 0.29C 5.88 ± 0.39F 4.10 ± 0.14G

50-Nucleotides

50-AMPc 0.57 ± 0 .04B 0.67 ± 0.03A 0.65 ± 0.01A 0.65 ± 0.01A 0.14 ± 0 .01E 0.34 ± 0.01C 0.25 ± 0 .02D 0.22 ± 0 .01D

50-CMPd 0.76 ± 0 .03C 1.38 ± 0.05A 0.95 ± 0.03B 0.74 ± 0.03C 0.49 ± 0 .04E 0.58 ± 0.01D 0.59 ± 0 .02D 0.44 ± 0 .04E

50-GMPe 0.64 ± 0 .03B 0.80 ± 0.01A 0.79 ± 0.05A 0.69 ± 0.05B 0.16 ± 0 .01E 0.40 ± 0.01C 0.31 ± 0 .05D 0.29 ± 0 .05D

50-UMPf  0.51 ± 0 .01B 0.58 ± 0.05 0.56 ± 0.01AB 0.55 ± 0.02AB 0.17 ± 0 .01F 0.33 ± 0.04 C 0.27 ± 0 .03D 0.22 ± 0 .02E

Flavor 50-nucleotidesg 0.64 ± 0 .03B 0.80 ± 0.01A 0.79 ± 0.05A 0.69 ± 0.05B 0.16 ± 0 .01E 0.40 ± 0.01C 0.31 ± 0 .05D 0.29 ± 0 .05D

Equivalent umami concentration (EUC)h

EUC 90.59 ± 0.03D 204.26 ± 0.06A 164.63 ± 0 .04B 109.89 ± 0.11C 13.26 ± 0 .02G 85.32 ± 0.01D 44.87 ± 0 .06E 28.09 ± 0.01F

a Eachvalues are expressed asmean± SD (n = 3) aresignificant differences (P < 0.05) among pine-mushrooms using Ducan’smultiplecomparison test between thesamples

having the different letter in a row.b Umami-taste active amino acids, aspartic acid + glutamic acid.c 50-AMP, 50-adenosine monophosphate.d

50

-CMP, 50

-cytosine monophosphate.e 50-GMP, 50-guanosine monophosphate.f  50-UMP, 50-uridine monophosphate.

g Flavor 50-nucleotides, 50-GMP+ 50-IMP + 50-XMP.h Calculated based on theequation: Y ¼ Rai bi þ 1218ðRai biÞðRa jb jÞ (Yamaguchi, Yoshikawa, Ikeda, & Ninomiya, 1971) where Y istheEUCof the mixture intermsof g MSG/

100 g; ai is the concentration (g/100 g) of each umami amino acid [aspartic acid (Asp) or glutamic acid (Glu)]; a j is the concentration (g/100 g) of each 50-nucleotide [50-IMP,

50-GMP, 50-XMP, 50-AMP]; bi is the relative umami concentration (RUC) for each umami amino acid to MSG (Glu, 1 andAsp, 0.077); b j is the RUC foreach umami 50-nucleotide

to 5 0-IMP (50-IMP, 1; 50-GMP, 2.3; 50-XMP, 0.61 and 50-AMP, 0.18); and 1218 is a synergistic constant based on the concentration (g/100 g) used.

806 I.H. Cho et al./ Food Chemistry 118 (2010) 804–807 

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GMP) are key umami-taste components of pine-mushrooms. More-

over, the contents of umami-taste active free amino acids and 5 0-

nucleotides and the EUC values were higher in the pileus than in

the stipe in all four grades of pine-mushrooms.

 Acknowledgements

This study was supported by both the Korea Science and Engi-

neering Foundation (R01-2004-000-10276-0) and the Korea Re-

search Foundation (KRF-2005-908-C00064).

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