JFS C: Food Chemistry

Changes in the Composition of Raw Tea Leaves

from the Korean Yabukida Plant during
C: Food Chemistry

High-Temperature Processing to Pan-Fried

Kamairi-Cha Green Tea
MENDEL FRIEDMAN, CAROL E. LEVIN, SUK-HYUN CHOI, SEUNG-UN LEE, AND NOBUYUKI KOZUKUE

ABSTRACT: To develop a better understanding of compositional changes occurring during the production of com-
mercial teas, we determined by high-performance liquid chromatography (HPLC) changes in ingredient levels
during each of several manufacturing steps used to produce Kamairi-cha, a premium green tea. Kamairi-cha uses
pan-frying instead of the usual blanching technique to inactivate the enzymes responsible for producing traditional
black tea. The resulting tea lacks the characteristic bitterness of green tea, producing a green tea that is described
as sweet tasting. The processing steps used to produce this pan-fried tea were as follows: 1st roasting, 1st rolling,
2nd roasting, 2nd rolling, 1st firing, and 2nd firing. The results show that during production at temperatures up to
300 ◦ C, raw leaves lost (in percent) 97.3 water, 94 two chlorophylls, 14.3 seven catechins, and 2.75 caffeine. A sepa-
rate analysis showed that the final product contained 21.67 mg/g dry wt of the biologically active amino acid thea-
nine. The results of this 1st report on changes in individual catechins and other tea ingredients in tea leaves during
pan-frying make it possible to select production conditions that maximize levels of beneficial tea ingredients. The
possible significance of the results for the human diet is discussed.
Keywords: catechin, Kamairi-cha, pan-fried, tea, theanine

Introduction pathogenic bacteria (Friedman and others 2006a; Friedman 2007;

T ea leaves produce organic compounds that may be involved

in the defense of the plants against invading phytopathogens
(Chiu 2006; Ho and others 2009). These secondary metabolites in-
Juneja and others 2007, 2009; Sirk and others 2008).
Most green teas produced from fresh tea leaves undergo steam
treatment, which results in teas with a characteristic bitter taste.
clude polyphenolic catechins present in green teas, oxidation prod- Because the rare Kamairi-cha green tea does not undergo the usual
ucts of catechins formed during fermentation called theaflavins steam treatment but is exposed to a high-temperature treatment
present in black teas, and the 3 methyl-xanthine alkaloids caffeine, called pan-frying in hot iron pans, the tea has a sweet taste and
theobromine, and theophylline that may be present in both tea cat- pleasant flavor. Processing conditions can have a dramatic effect
egories. Tea leaves also contain the biologically active amino acid on flavonoid content. Black tea, which is made from the same plant
theanine (Figure 1). Catechins, theaflavins, and theanine are re- but is processed differently, that is, fermented, has a distinctly dif-
ported to have numerous beneficial effects when consumed as part ferent flavonoid profile than green tea. Most of the catechin con-
of the human diet (Cui and others 2008; Miyagawa and others 2008; tent is converted into theaflavins during the fermentation process.
Owen and others 2008; Patel and others 2008; Bolling and others While still antioxidative, theaflavins may have different effects on
2009). health (Cooper and others 2005). Green teas that have been pas-
In the course of previous studies designed to determine the teurized for use in bottled tea drinks have been shown to have a
composition of commercial tea leaves, we developed improved ex- high rate of epimerization of catechins from the more abundant
traction and analysis methods that can be used to determine the cis (epi) form (Chen and others 2001) to the trans form. Epimer-
content of all these ingredients (Friedman and others 2005, 2006b). ized trans-catechins were found to have stronger superoxide scav-
In related studies, we found that catechin levels decrease during enging abilities (Guo and others 1999) and may possibly be more
storage of commercial teas (Friedman and others 2009) and ex- hypocholesterolemic (Ikeda and others 2003) than their cis coun-
plored inhibitory activities of tea catechins, theaflavins, and the terparts. It is apparent that tea processing can affect the quantity
amino acid theanine against human cancer cells (Friedman and and quality of health-giving constituents. It is therefore of inherent
others 2007) and of tea flavonoids and teas against foodborne interest to determine the fate of catechins and alkaloids during the
multiple steps used in the preparation of the specialty variety tea,
MS 20090056 Submitted 1/20/2009, Accepted 3/19/2009. Authors Friedman called green Kamairi-cha tea. This tea has a distinctively different
and Levin are with Western Regional Research Center, Agricultural Research taste than traditional green tea, although it is classified as a green
Service, U.S. Dept. of Agriculture, Albany, CA 94710, U.S.A. Author Choi tea because it has not been fermented.
is with Dept. of Food Service Industry, Seowon Univ., 361-742, Mochung-
dong, Heungduk-gu, Cheongju-city, Chungbuk, Korea. Authors Lee and Previous studies on Kamairi-cha green and other roasted teas
Kozukue are with Dept. of Food Service Industry, Uiduk Univ., 780-713, reported that (1) the degree of rolling during the manufacturing
Gangdong, Gyeongju, Gyongbuk, Korea. Direct inquiries to author Fried- process affects the catechin and amino acid content of Japanese
man (E-mail: Mendel.Friedman@ars.usda.gov).
Kamairi-cha tea (Kinugasa and others 1997); (2) the quality of

C406 JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 5, 2009 

C 2009 Institute of Food Technologists
R

doi: 10.1111/j.1750-3841.2009.01185.x
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Changes in the composition of raw tea leaves . . .

Japanese Kamairi-cha green tea is influenced by the distribution Maillard type reactions between amino acids and sugar degrada-
of heat in contact with tea leaves (Gejima and Nagata 2000); tion products (Kumazawa and Masuda 2002); (4) controlling the
(3) pan-frying of Japanese Kamairi-cha tea leaves produced 51 dis- roasting temperature can be used to mitigate acrylamide forma-
tinct and potent odor-active compounds formed by heat-induced tion in this tea (Mizukami and others 2008); (5) volatile extracts

C: Food Chemistry
OH OH Figure 1 ---
3' Structures of
2' OH OH
4' OH 7 catechins,
HO 7
8
O
H B 5' HO O
H OH OH
4 theaflavins,
2
A C 6' H OH alkaloids,
6 H 3
H 2 chlorophylls,
5 4 OH OH HO O and the amino
OH OH H OH
acid theanine
(-)-catechin (C) (-)-epicatechin (-)-epigallocatechin (EGC) evaluated in
this study.
HO OH
H OH H OH
HO O HO O OH
HO
OH OH O
O O H OH
H H O
OH OH OH OH
O O HO H OH
O
OH OH OH
(-)-catechin gallate (-)-epicatechin gallate OH (-)-gallocatechin gallate
OH
(CG) (ECG) (GCG)

OH
H OH OH
HO O OH OH

O OH HO OH
HO O OH
H O
OH OH O
OH HO O
O O OH
HO OH
OH OH
HO O OH
HO OH
theaflavin (TF)
(-)-epigallocatechin-3-gallate O
(EGCG) HO O OH
OH
HO OH
O
H OH OH
O OH
C H O
H C H R theaflavin-3,3'-digallate OH O
CH3 OH
(TF3,3'G) OH
H3C CH2 HO O OH

N N O
H Mg H O CH3 HO O
N N N OH
HN
H3C OH
CH3 O N N
H OH
H CH CH3
2 theaflavin-3-gallate
H theobromine
H2C (TF3G)
C CH3 O
C O O
O O O CH3 OH
H3C N OH OH
CH3 CH3 N

chlorophyll O N N O OH
HO
a: R=CH 3 CH3 O
b: R=CHO caffeine HO O
OH
OH O
O H O
H3C N OH
NH N OH
O
H2N N
O O N
OH
theanine CH3
OH
theophylline theaflavin-3'-gallate
(TF3'G)

Vol. 74, Nr. 5, 2009—JOURNAL OF FOOD SCIENCE C407

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Changes in the composition of raw tea leaves . . .

from roasted teas exhibited antioxidative properties (Yanagimoto sulting samples was analyzed in triplicate. The following steps were
and others 2003); (6) consumption of roasted tea was not asso- used to in the production of pan-fried Kamairi-cha green tea:
ciated with increasing incidence for stroke risk among Japanese
men and women (Tanabe and others 2008); and (7) consumers pre- 1. Tea leaves (3 kg) of the “Yabukida” plant (3-y-old plants) were
fer green teas prepared by “roasting” over those prepared by tra- harvested between 8 and 9 AM on April 23, 2007 at Bosung,
ditional methods (Lee and others 2008). Pan-fried teas are more Korea (Figure 2). Processing of selected leaves started at 5 PM
expensive than teas produced by steaming of the leaves and are of the same day.
C: Food Chemistry

largely unavailable in Western countries (Wikipedia Encyclopedia 2. Tea leaves (1.5 kg) were placed into a round iron pan (diameter,
2008). 1 m; bottom thickness, 3 cm; thickness of the rest of the pan,
The main objectives of the present study were (1) to describe 1 cm, shown in Figure 2B). The following conditions were then
multistep processes we used to prepare Kamairi-cha green tea by used to process the leaves:
pan-frying fresh tea leaves; (2) to determine changes in the levels
a. Pan-heating: the pan was heated up to 250 to 300 ◦ C by
of moisture, chlorophyll a and b, 7 catechins, and 3 alkaloids dur-
strong flue gases.
ing each of several steps used in the manufacture of pan-fried green
b. 1st roasting: the tea leaves were mixed (hand-rolled) for
tea from fresh tea leaves to the final product; and (3) to determine
5 min.
the theanine content of the final product.
c. Cooling: the tea leaves were cooled by a fan immediately af-
ter roasting.
Materials and Methods
d. 1st rolling: the leaves were machine-rolled for 5 min at
37 rotations/min.
Materials
e. 1st selection: badly shaped tea leaves were removed by
The following catechin and alkaloid standards with the in-
hand.
dicated purities were obtained from Sigma/Aldrich (St. Louis,
f. 2nd roasting: the temperature of the pan was adjusted to
Mo., U.S.A.): (–)-epigallocatechin from green tea (EGC) (≥95%),
100 ◦ C, and the tea leaves were then hand-mixed for 1 min.
(–)-catechin from green tea (C) (≥98%), (–)-epicatechin from green
g. 2nd cooling: the leaves were then immediately cooled by a
tea (EC) (≥98%), (–)-epigallocatechin gallate from green tea (EGCG)
fan.
(≥95%), (–)-gallocatechin gallate from green tea (GCG) (≥98%),
h. 2nd rolling: the leaves were machine-rolled for 4 to 5 min at
(–)-epicatechin gallate from green tea (ECG) (≥98%), (–)-catechin
37 rotations/min.
gallate from green tea (CG) (≥98%), caffeine (CAF) (≥98%), theo-
i. 1st firing: the leaves were dried in a rolling drum at 40 to
bromine (TB) (≥99%), and theophylline (TP) (≥99%). Theaflavin,
50 ◦ C for 4 h.
theaflavin-3-gallate, theaflavin-3’-gallate, and theaflavin-3,
j. 2nd firing: the leaves were dried in a rolling drum at 60 to
3’-digalllate (all [≥90%] were obtained from Wako, Osaka, Japan).
70 ◦ C for 2 h. This final step generates the desirable rich fla-
L-theanine was obtained from LKT Laboratories (St. Paul, Minn.,
vor in the processed leaves.
U.S.A). high-performance liquid chromatography (HPLC) solvents
were filtered through a 0.45-μM membrane (Millipore, Bedford,
Mass., U.S.A.) and degassed in an ultrasonic bath before use. Analysis of moisture content of tea leaves
The moisture content of the tea leaves following each processing
Manufacture of Kamairi-cha (pan-fried tea) step was determined by drying the samples in a vacuum oven at
Kamairi-cha tea was produced in a single batch. During various 70 ◦ C in the presence of P 2 O 5 for 12 h as described in the official
stages of the process, 50 g of sample were removed. Each of the re- AOAC method (AOAC 1965).

Figure 2 --- Harvesting of tea leaves.

(A) The complete view of a tea
garden at Bosung, Korea. (B) The iron
pan used for manufacture of
Kamairi-cha (Korean green tea).
(C) Hand rolling. (D) Cooling of leaves
by an electric fan immediately after
the rolling process.

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Changes in the composition of raw tea leaves . . .

Analysis of chlorophyll a and b content of tea leaves preceding processing steps using SigmaPlot 11 (Systat Software
The procedure was adapted from the official AOAC method Inc., San Jose, Calif., U.S.A.). One-way analysis of variance (ANOVA)
(AOAC 1965) and from a method we previously used with potato and Holm–Sidak multiple comparisons tests were used to deter-
sprouts (Kozukue and others 2001). Briefly, the leaves (approx- mine statistical significance at the 5% level.
imately 0.5 g) from each processing step and MgCO 3 (0.1 g)
were macerated in a glass mortar with 80% acetone/water (15 Results and Discussion
mL). The sample was then centrifuged at 15000 × g for 10 min
Moisture content

C: Food Chemistry
at 5 ◦ C. The resulting pellet was extracted 3 times with of
80% acetone (10 mL) and centrifuged. The extracts were com- Table 1 shows that the 1st roasting causes a 6% loss of water,
bined and adjusted with 80% acetone to a volume of 50 mL. whereas the 2nd roasting caused no significant loss of moisture.
This solution was used to analyze for 2 chlorophylls by vis- The low decrease in water content in these high-heat processes is
ible spectrophotometry with the aid of a Shimadzu UV Mini likely due to the short processing time. The 1st firing, designed to
1240 Spectrophotometer (Shimadzu Corp., Kyoto, Japan). Chloro- remove water and stabilize the tea against further fermentation, en-
phyll a absorbs at 665 nm and chlorophyll b at 645.2 nm. zymatic activity, and oxidation, then causes an 88% loss of water.
Concentration of individual chlorophylls was calculated as de- The 2nd firing removes an additional 7%. The overall loss was 98%
scribed elsewhere (Kozukue and others 2001). of the original water content.

Extraction of tea leaves for catechin and alkaloid Chlorophyll a and b content
analysis Because chlorophyll is reported to exhibit anticarcinogenic
For extraction with distilled water, each tea sample (approxi- properties (Castro and others 2008; Simonich and others 2008), it
mately 1.5 g) was placed into a 250 mL flask to which was added wa- was of interest to determine its fate during the processing steps
ter (100 mL) that was previously brought to the boiling point. The used to prepare the green tea. Table 2 shows that the chlorophyll
sample was then stirred slowly with a magnetic stirrer for 5 min, a and b content (in milligrams per gram dry wt) of the harvested
cooled, and centrifuged at 18000 × g for 5 min at 5 ◦ C. The super- tea leaves was 2.24 and 0.77, respectively. These values remained
natant was filtered through a 0.45 μM Millipore nylon filter before largely unchanged during the 2 roasting and 2 rolling steps. They
analysis. then decreased sharply to 0.56 and 0.17 during the 1st roasting and
to 0.13 and 0.04 during the 2nd firing, respectively. The final green
HPLC analysis of catechins and alkaloids in tea leaves
The method was adapted from our previous studies (Friedman Table 1 --- Moisture content of leaves during each of sev-
and others 2005, 2006b). HPLC was carried out on a Hitachi liq- eral stages of manufacturing of Kamairi-cha green tea.a
uid chromatograph model 665-II equipped with an autosampler Processing conditions Average ± SD
(model 655A-40, Hitachi, Ltd., Tokyo, Japan). The stainless steel col-
umn (250 × 4 mm i.d.) was packed with Inertsil ODS-3v (5 μM par- Raw tea leaf 75.54 ± 0.35
1st roastingA 71.10 ± 0.06b,c
ticle diameter) (GL Sciences, Tokyo, Japan). The column tempera-
1st rollingB 69.88 ± 0.65b
ture was maintained constant with a Shimadzu column oven CTO- 2nd roastingC 69.74 ± 0.44b
10vp (Shimadzu, Kyoto, Japan). The gradient system consisted of 2nd rollingD 68.82 ± 0.65b
a mixture of acetonitrile and 20 mm KH 2 PO 4 . The flow rate was 1 1st firingE 8.04 ± 0.24b,c
mL/min at a column temperature of 30 ◦ C. A Shimadzu photo diode 2nd firingF 2.35 ± 0.15b,c
array UV-VIS detector (model SPD-10Avp, Shimadzu) was set from Green teaG 2.04 ± 0.08c
200 to 700 nm. The tea extract (10 μL) was injected directly into the A
Pan roasted 250 to 300 ◦ C, 5 min.
B
column. Analyses, each in triplicate, were carried out with 3 sepa- Machine rolled, 5 min.
C
Pan roasted 100 ◦ C, 1 min.
rate extracts. D
Machine rolled, 4 to 5 min.
E
Drum-dried 40 to 50 ◦ C, 4 hr.
The initial composition of the mobile phase consisted of 7% ace- F
Drum-dried 60 to 70 ◦ C, 2 hr.
G
tonitrile (A) and 93% of 20 mm KH 2 PO 4 (B) (v/v) was maintained Cooled, finished product.
a
Listed values are expressed as average (mg/g dry weight) ± SD; n = 3.
for 6 min. Solvent A was then increased linearly to 10% in 20 min, Shading indicates significantly different than previous step.
15% in 25 min, 20% in 30 min, and 25% in 45 to 70 min. Program-
b
Significantlydifferent than the previous processing step (P < 0.001).
c
Significantly different than the starting material (raw leaves) (P < 0.001).
ming was then continued in the isocratic mode as follows: 40% B in
70.1 to 75 min and 7% A to 76.1 to 90.1 min.
Identification and quantification was accomplished by compar- Table 2 --- Changes in chlorophyll a and chlorophyll b con-
ing integrated chromatographic peak areas from the test samples tent during the manufacture of Kamairi-cha green tea.A
to peak areas of known amounts of standard compounds using the Processing
Hitachi Chromato-integrator model D-2500 (Hitachi Ltd., Tokyo, conditionsa Chlorophyll a (A) Chlorophyll b (B) (A) + (B)
Japan). Each peak was identified by comparing the retention times
Raw tea leaf 2.24 ± 0.40 0.77 ± 0.065 3.01
and absorption spectra of unknowns to those of standards. 1st roasting 2.15 ± 0.15 0.73 ± 0.06 2.88
1st rolling 1.80 ± 0.24 0.62 ± 0.07 2.42
HPLC analysis of theanine in tea leaves 2nd roasting 2.15 ± 0.08 0.65 ± 0.01 2.81
2nd rolling 2.14 ± 0.11 0.73 ± 0.08 2.97
Extraction of theanine from tea leaves with boiled water and 1st firing 0.56 ± 0.03b,c 0.17 ± 0.00b,c 0.73
analysis as DNP-theanine by HPLC was performed as described 2nd firing 0.13 ± 0.01c 0.04 ± 0.00c 0.17
previously (Friedman and others 2007). Green tea 0.14 ± 0.01c 0.04 ± 0.00c 0.18
A
Listed values are expressed as average (mg/g dry weight) ± SD; n = 3.
Statistical analysis Shading indicates significantly different than previous step.
a
See Table 1.
Statistical analyses were performed on the analyzed catechin, al- b
Significantly differentthan the previous processing step (P < 0.001).
kaloid, and chlorophyll concentration changes found during the c
Significantly different than the starting material (raw leaves) (P < 0.001).

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Changes in the composition of raw tea leaves . . .

tea product contained only 0.14 chlorophyll a and 0.04 chlorophyll 1st firing stages, both high heat processes with longer processing
b, corresponding to a 16.7-fold decrease from the original value. times than the respective 2nd roasting and 2nd firing stages. It is
also noteworthy that processing induced an overall 78% increase
Flavonoid and alkaloid content in catechin, from 5.55 to 9.89. Most of the catechin increase was
Figure 3 illustrates the separation by HPLC of green tea seen at the 2nd firing stage. These results show that some catechins,
flavonoids (catechins) and alkaloids extracted from tea leaves when especially epigallocatechin, are highly susceptible to heat-induced
exposed to processing conditions used to prepare Kamairi-cha degradation, while others are much less so.
C: Food Chemistry

green tea. No gallocatechin or theaflavins were found in any of the Table 3 also shows that the theobromine and caffeine content re-
extracts. Table 3 shows the tea content during processing of the 7 mained the same and that the theophylline content increased dur-
catechins and 3 alkaloids analyzed by HPLC. Kamairi-cha tea pro- ing the firing stage and final cooling of the leaves. There was no sta-
cessing caused an overall loss of 14% of catechins, with no signifi- tistical difference in total alkaloid content between any of the pro-
cant loss of total alkaloids. cessing steps. Caffeine concentrations, the most abundant of the 3
Epigallocatechin sustained the largest loss (87%) of any of the alkaloids, remained largely unchanged during all processing steps.
analyzed tea components, decreasing (in milligrams per gram dry We do not know why theophylline levels rose during the firing stage.
wt) from 9.53 in the raw leaves to 1.22 in the finished product. Perhaps the alkaloid is more easily extracted from the dried leaf.
Most of that loss occurred at the 2nd rolling. Gallocatechin gallate However, the low values for theophylline listed in Table 3 do not al-
and epicatechin also sustained significant losses (44% and 22%, re- low definitive conclusions about changes that may have occurred.
spectively). Gallocatechin gallate decreased from 6.43 to 3.61 and
epicatechin decreased from 8.91 to 6.93. While epicatechin expe- Theanine content
rienced a gradual loss throughout the processing sequence, gallo- Because teas also contain the biologically active amino acid
catechin gallate had significant reductions at the 1st roasting and theanine, we also determined its content in the final green tea

6 A E Figure 3 --- HPLC

6 chromatograms of
extracts from tea
4 leaves during
8 4
processing of Korean
8 Kamairi-cha. (A): Raw
7 7 leaves; (B): 1st
5 roasting; (C): 1st
9 5 9
1 2 3 1 2 3 rolling; (D): 2nd
roasting; (E): 2nd
0 20 40 60 0 20 40 60 rolling; (F): 1st firing;
(G): 2nd firing; (H):
tea. Peaks: (1)
theobromine; (2)
theophylline; (3)
B F epigallocatechin; (4)
caffeine; (5) catechin;
(6) epicatechin; (7)
epigallocatechin
Absorbance, 280 nm

gallate; (8)
gallocatechin gallate;
(9) epicatechin
gallate; (10) catechin
0 20 40 60 gallate. Theaflavins
0 20 40 60 (not present in these
extracts) elute
between 55 and
65 min.
C G

0 20 40 60 0 20 40 60

D H

0 20 40 60 0 20 40 60
Retention time (min) Retention time (min)

C410 JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 5, 2009

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Changes in the composition of raw tea leaves . . .

Total catechins

92.53 ± 2.84d
Table 3 --- Changes in alkaloid (theobromine, theophylline, and caffeine) and catechin (epigallocatechin [EGC], catechin [C], epicatechin [EC], epigallocatechin
gallate [EGCG], gallocatechin gallate [GCG], epicatechin gallate [ECG], and catechin gallate [CG]) contents in tea leaves during the preparation of Korean
product. The theanine content (in milligrams per gram dry wt) of

107.95 ± 3.31
110.32 ± 4.54
103.73 ± 3.67
101.58 ± 2.21
95.54 ± 2.23
95.91 ± 3.83
102.25 ± 1.22
Kamairi-cha green tea of 21.67 ± 0.42 (n = 3) was much higher than
the range of 6.1 to 11.4 we previously reported for 8 commercial
green teas sold in the United States (Friedman and others 2005).

Conclusions

1.26 ± 0.29
0.98 ± 0.22
0.95 ± 0.18
1.11 ± 0.18
1.05 ± 0.21
1.29 ± 0.07
1.42 ± 0.16
1.50 ± 0.15
CG T he results obtained in this study indicate that pan-frying of

C: Food Chemistry
tea leaves harvested in Korea induces nearly quantitative re-
ductions in moisture and chlorophyll content of the final green
Kamairi-cha tea product. Processing of the raw leaves to produce
26.98 ± 2.68
29.55 ± 2.06
29.56 ± 2.62
29.27 ± 0.96
28.06 ± 0.77
29.60 ± 1.86
31.41 ± 0.76
26.43 ± 1.22
Kamairi-cha tea induced a 14% loss in total catechin content. There
were no overall losses in alkaloid content. The concentration of
ECG

the minor catechin (catechin) increased by 78%. Three other mi-

nor catechins, epigallocatechin, gallocatechin gallate, and epicat-
echin, decreased by 87%, 44%, and 22%, respectively. There were
4.27 ± 0.82b,d

3.02 ± 0.13b,d
4.22 ± 0.06d
3.84 ± 0.38d
4.87 ± 0.50d

3.71 ± 0.11d
3.61 ± 0.20d
no significant changes in the most abundant catechins epigallocat-
6.43 ± 0.29

echin gallate and epicatechin gallate. The final product contained

GCG

no theaflavins (normally found in black and occasionally in green

teas) and a high amount of theanine.
It is also interesting to note as to which processing stages in-
45.36 ± 2.15b
49.29 ± 1.44
52.73 ± 3.82

47.70 ± 1.22
46.67 ± 2.00
46.10 ± 3.11
47.58 ± 0.63
42.95 ± 2.38

duced changes in composition. Moisture content changed signif-

EGCG

icantly at the 1st roasting and at the firing stages. These are also the
stages at which we found the largest losses of gallocatechin gallate.
Gallocatechin gallate may be most susceptible to moisture levels or
to heat applied. Much of the epigallocatechin present was lost dur-
9.48 ± 0.66b,d
7.35 ± 0.62e

9.89 ± 0.56d

ing the 2nd rolling. In addition, there was a smaller loss of epigallo-
5.55 ± 0.86
6.15 ± 0.54

6.13 ± 0.37
6.44 ± 0.09
7.19 ± 0.46

indicates significantly different than previous step.

catechin gallate during the 1st rolling. Rolling is sometimes referred

C

to as bruising, as it releases some of the leaf juices that may induce

oxidation reactions. It appears that epigallocatechin may be highly
susceptible to chemical oxidation. Catechin increased significantly
6.93 ± 0.72d
8.91 ± 0.45
7.43 ± 0.33
8.32 ± 0.39
7.62 ± 0.32
7.44 ± 0.33
7.38 ± 1.11
7.45 ± 0.18

during the 2nd firing. We noticed that the content of this catechin
was more variable through the processing steps; values increased,
EC

decreased, then increased again, possibly as a result of poor ex-

tractability. Alternatively, epimerization could also be responsible
for some of this variability, as well as for some of the variations in
1.01 ± 0.04b,d
5.91 ± 1.43d

1.33 ± 0.11d
1.20 ± 0.01d
1.22 ± 0.08d
9.53 ± 0.78
9.21 ± 0.83
7.97 ± 1.21

losses seen in the other catechins. For example, epicatechin could

EGC

have epimerized to catechin, which in turn could have partially

degraded. With the 2 processes of epimerization and degradation
working together, the losses of individual catechins are difficult to
Total alkaloids

predict.
26.57 ± 0.49
27.30 ± 2.58
25.72 ± 1.24
25.48 ± 1.31
25.98 ± 0.34
25.21 ± 1.42
28.02 ± 0.25
26.87 ± 0.76
Listed values are expressed as average (mg/g dry weight) ± SD; n = 3. Shading

Overall, with a catechin loss of only 14%, the health-promoting

potential Kamairi-cha tea appears promising. The total catechin
content of this pan-fried green tea of approximately 92.5 mg/g ap-
Significantly different than the starting material (raw leaves) (P < 0.001).
Significantly different than the starting material (raw leaves) (P = 0.002).

proaches the highest amount of 100 mg/g previously determined

Significantly different than the previous processing step (P < 0.001).
Significantly different than the previous processing step (P = 0.002).

among 24 commercial green teas sold in the United States (Fried-

25.13 ± 0.48
26.04 ± 2.58
24.44 ± 1.23
24.27 ± 1.03
24.63 ± 0.33
22.82 ± 1.42
25.59 ± 0.24
24.44 ± 0.75
Caffeine

man and others 2005, 2006b). This high-quality tea with unique
flavor attributes has the potential to be an important addition to
commercial teas and tea products.
The described observations will hopefully stimulate needed
1.06 ± 0.09c,d

studies on maximizing the levels of beneficial tea ingredients dur-

1.04 ± 0.06b,d
conditionsa Theobromine Theophylline

0.91 ± 0.02d
0.22 ± 0.05
0.11 ± 0.01
0.11 ± 0.02
0.11 ± 0.02
0.11 ± 0.01

ing each of the multiple processing steps to which harvested tea

leaves are exposed during production of commercial green teas and
tea products.
Finally, whether exposure of tea leaves during pan-frying to up to
Kamairi-cha green tea.A

approximately 300 ◦ C will degrade potentially toxic acrylamide that

1.52 ± 0.05d
1.22 ± 0.09
1.15 ± 0.14
1.17 ± 0.11
1.10 ± 0.14
1.24 ± 0.04
1.35 ± 0.06

1.37 ± 0.06

may be formed in teas roasted at lower temperatures (Mizukami

and others 2006; Friedman and Levin 2008) merits further study.

References
2nd roasting
Processing

AOAC. 1965. Official methods of analysis. 10th ed. Washington, D.C.: Assn. of Official
See Table 1.
1st roasting
Raw leaves

2nd rolling

Green tea

Analytical Chemists. 361 p.

1st rolling

2nd firing
1st firing

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