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Characterization of the Potent Odorants Contributing to the Characteristic Aroma of Matcha by Gas Chromatography-Olfactometry Techniques Ryoko Baba, Yohei Amano, Yoshiyuki Wada, and Kenji Kumazawa J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b00421 • Publication Date (Web): 25 Mar 2017 Downloaded from http://pubs.acs.org on March 29, 2017
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Journal of Agricultural and Food Chemistry
Characterization of the Potent Odorants Contributing to the Characteristic Aroma of Matcha
by
Gas
Chromatography-Olfactometry Techniques
Ryoko Baba, Yohei Amano, Yoshiyuki Wada, and Kenji Kumazawa Ogawa & Company, Ltd., 15-7 Chidori Urayasushi, Chiba 279-0032, Japan
To whom correspondence should be addressed. Fax: +81-47-305-1423 E-mail:
[email protected] 1
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ABSTRACT
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The odorants contributing to the characteristic aroma of Matcha were investigated
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by analysis of the headspace samples and the volatile fractions prepared by a
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combination of solvent extraction and the SAFE techniques using three Matcha powders
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of different grades (high, medium, and low). Gas chromatography-olfactometry of the
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headspace samples (GCO-H) and the aroma extract dilution analysis (AEDA) applied to
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the volatile fractions revealed 16 (FD factor ≥1) and 39 (FD factor ≥43) odor-active
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peaks, respectively. Among them, 14 and 37 of the odorants, most of which were newly
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detected in Matcha, were identified or tentatively identified by GC-MS and GC-O,
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respectively. By comparing the perceived odorants of three Matcha powders, it was
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revealed that eight compounds with sweet, green, metallic and floral notes showed high
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flavor dilution (FD) factors irrespective of the grades. In addition, some odorants were
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suggested to influence the characteristic aroma of each grade. Furthermore,
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trans-4,5-epoxy-(E)-2-decenal, one of the potent odorants of Matcha, was revealed to
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exist
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trans-4,5-epoxy-(E)-2-decenal is formed by a non-enzymatic reaction in Matcha,
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different from that in black tea, and that the unique manufacturing process of Matcha
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has a close connection with its formation.
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KEYWORDS:
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4,5-epoxy-(E)-2-decenal
as
a
racemic
Matcha,
mixture
green
in
Matcha.
tea,
aroma,
This
result
flavor,
21
2
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suggested
AEDA,
that
GCO-H,
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Journal of Agricultural and Food Chemistry
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INTRODUCTION
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Matcha is finely powdered green tea which is used in a Japanese traditional
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ceremony (Sado). Although Matcha was once mainly for drinking in Sado, suspended in
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a small amount of hot water, its characteristic flavor is getting popular all over the world,
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and being used for a lot of confectioneries such as cookies, chocolate, and ice cream. In
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addition, Matcha is also known as a healthy food utilizing the whole nutrition of the tea
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leaves.
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Matcha belongs to the steamed green tea, the same as Sen-cha, the most common
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green tea in Japan, leaves of which are immediately steamed after being plucked to
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inactivate the endogenous enzymes. However, it is different from Sen-cha in the raw
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materials and manufacturing process. The tea leaves for Matcha, which are called
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tencha, are sun-shaded for a few weeks before being plucked. In addition, the
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manufacturing process of Matcha is traditional and unique, in which the leaves are dried
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without rolling and ground in a stone mill. Therefore, Matcha has a unique green aroma
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with some sweet and roasted odors, totally different from Sen-cha, which has a fresh
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green aroma. Especially for high-quality Matcha, its refined and rich sweet aroma is
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highly palatable and attracts many people.
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Although it seems to be important to investigate the aroma of Matcha, there are
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very few reports about its odorants, compared to black tea and Sen-cha. This might be
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due to the fact that the aroma of Matcha is so delicate and easily changeable that it is
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difficult to analyze, in addition Matcha is difficult to handle because of its behavior as a
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fine powder. Therefore, the odorants of Matcha and the connection between their
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formation mechanism and its unique manufacturing process have not been clarified. 3
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In this study, the odorants contributing to the aroma of the three grades of Matcha
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were investigated by a gentle method of extraction and concentration to obtain a
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genuine aroma extract of Matcha. In addition, the connection between the formation of
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the aroma of Matcha and its manufacturing process was investigated from the point of
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view of the formation mechanism of trans-4,5-epoxy-(E)-2-decenal, one of the
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important odorants of Matcha.
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MATERIALS AND METHODS
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Materials. Matcha samples: Matcha products (high, medium, and low grade
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based on the market price) were purchased from Aiya Co., Ltd. (Aichi, Japan). The
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quality of high grade one was as high as an award-winning Matcha at a tea fair. All of
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these products were stored at -20 ˚C until needed.
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Chemicals. The following compounds were synthesized according to the procedures:
(Z)-1,5-octadien-3-one;1
(Z,Z)-3,6-nonadienal;2
2-acetyl-2-thiazoline;4
cis-
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literature
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3-methyl-2,4-nonanedione;3
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trans-4,5-epoxy-(E)-2-decenal;5
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Compounds 2, 5, 6, 8-13, 15, 17, 20, 21, 23, 26, 28-30, 34-37, 39 (Table 1), Ⅱ, Ⅳ, Ⅵ,
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Ⅶ, and Ⅷ (Table 2) were purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo,
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Japan); compounds 1, 4, 18, 32, 38 (Table 1), Ⅰ, and Ⅴ (Table 2) were purchased
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from Sigma-Aldrich Japan (Tokyo, Japan); and compound 31 (Table 1) was purchased
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from Wako Pure Chemical Industries (Osaka, Japan).
and
trans-4,5-epoxy-(E,Z)-2,7-decadienal.6
and
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Isolation of the Volatiles from Matcha. Matcha powder (8 g) was added to 80
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mL of diethyl ether that contained water (at a final concentration of 5 %) and 0.1 % 4
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2-octanol in methylene chloride (20 µL) as the internal standard solution. The mixture
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was stirred at room temperature for 2 hours, and filtered after the centrifugation (3000
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rpm) at 5 ˚C for 15 min, and dried over anhydrous sodium sulfate, and distilled under
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reduced pressure (
