Characterization of the Potent Odorants Contributing to the

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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 is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

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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 (