The Change in the Flavor of Green and Black Tea Drinks by the

Chapter 34

The Change in the Flavor of Green and Black Tea Drinks by the Retorting Process Hideki Masuda and Kenji Kumazawa

Downloaded by CORNELL UNIV on August 5, 2016 | http://pubs.acs.org Publication Date: January 15, 2000 | doi: 10.1021/bk-2000-0754.ch034

Material R & D Laboratories, Ogawa and Company, Ltd., 1-2, Taiheidai, Shoocho, Katsuta-gun, Okayama 709-4321, Japan The retorting process is responsible for the off-flavor of canned drinks. The quantitative change in the volatile components of the green and black tea canned drinks by the retorting process is not sufficient for explaining the results of sensory evaluation. In this study, the potent components responsible for the off-flavor were found using an aroma extract dilution analysis ( A E D A ) . Many off-flavor components were proposed to be generated from the nonvolatile precursors by a nonenzymic reaction.

Drinks of green, black, and oolong teas together with coffee beverages are very popular in Japan. In general, the manufacturing process of a canned tea drink is as follows: extraction with hot water, filtration, cooling, addition of ascorbic acid, p H adjustment, filling, seaming, retorting, and cooling. The off-flavor of the tea drink is mainly generated by the retorting process (1-3). The amounts of the off-flavor components in a tea drink have been analyzed by G C and G C - M S . However, the quantity of the off-flavor components alone is not a satisfactory explanation to support the difference in the sensory evaluation by the retorting process. Recently, aroma extract dilution analysis ( A E D A ) has been used to study the characteristic odors of green and/or black teas (4,5). This current study focuses on the flavor change in green and black tea canned drinks during the retorting process using A E D A .

Experimental Leaves of the green (sencha, 200 g) and black teas (darjeeling tea, 200 g) were collected in 1998. Extraction was carried out with hot water (4 L , 70°C) for 5 min, followed by filtration. The extract (about 3 L ) was immediately cooled to 20 and filled into cans (190 mL/can). The pH's of green and black tea extract were 5.7 and 5.4, respectively. The cans were retort-sterilized at 121 °C for 10 min, followed by cooling to room temperature. The pH's of green and black tea were 5.6 and 5.1, respectively.

© 2000 American Chemical Society

Parliment et al.; Caffeinated Beverages ACS Symposium Series; American Chemical Society: Washington, DC, 2000.

337


338 The contents were distilled under reduced pressure (40 °C/20 mm H g ). The distillates (about 600-700 mL) were concentrated by the adsorptive column method (column: Porapak Q, 10 g, eluate: dichloromethane). The internal standard solution (100 μL) prepared from methyl undecanoate (5.15 mg) in dichloromethane (10 mL) was added to the concentrate. The column concentrate was evaporated (less than 40 °C/460 mm Hg) and concentrated in a stream of nitrogen. A G C - M S analysis was performed using a Hewlett-Packard 5890 Series II gas chromatograph connected to a HP-5972 mass spectrometer. A D B - W A X fiised-silica capillary column (60 m χ 0.25 mm i.d., film thickness: 0.25 μιη) was employed. The operating conditions were as follows: initial oven temperature, 80°C or 40°C then to 210°C at 3°C /min; injection temperature, 250°C; carrier gas, 1 mL/min He; split ratio, 1/50 or split-less. A n A E D A was performed using a Hewlett-Packard 5890 (GC) fitted with a glass sniffing apparatus and T C D . A D B - W A X fiised-silica capillary column (30 m χ 0.53 mm i.d., film thickness: 1 μπι) was employed. The operating conditions were as follows: initial oven temperature, 40°C then programmed to 210°C at 5°C/min; injector temperature, 250°C; carrier gas, 4.4 mL/min He; splitless injection. The F D factors were obtained using A E D A (6). The extract was stepwise diluted with dichloromethane until the odorous compounds were no longer detected by G C sniffing.

Results and Discussion Figure 1 shows the sensory descriptive analysis for the green and black tea canned drinks. The retort green tea had more a floral, sweet, clove-like, and heavy odor compared to the nonretort green tea. However, the green odor which is the characteristic odor of fresh green tea, was found to be decreased by the retorting process. On the other hand, in the retort black tea, the sweet, clove-like, heavy, and putrid odor increased compared with the nonretort black tea. Table I shows the odorous components of the canned green and black tea drinks which were detected by G C sniffing. The black tea had more detectable peaks than the green tea. In addition, the number of components with increased FD-factors in black tea was more than that of the green tea. These results seem to be mainly attributable to the different manufacturing process between the green and black teas. The characteristic manufacturing process of the green tea includes steaming, during which the oxidizing enzyme in the tea leaves is inactivated and the green color of tea leaves is maintained. Therefore, most of the volatile components of the green tea are considered to be originally contained in the fresh leaves (7). On the other hand, black tea is produced by withering and fermentation process during which the enzyme reaction and nonenzymic browning reaction occur (8-10). Therefore, most of the volatile components of the black tea are believed to be formed during the course of manufacturing. Consequently, many more flavor precursors are contained in the green tea than in the black tea.



339

••-nonretort

Figure I. Sensory descriptive analysis of the green (top) and black tea canned drinh (bottom).


3

Table I. Odorous Components of the Canned Green and Black Drinks Peak No. 1 2 3 4 5 6 7 8

b

RI

927 972 1013 1050 1082 1112 1133 1216

Odor Description stimlus milk-like green milk-like green green green meaty

Component

FDNG 10 10 nd 10 nd nd nd 10 C

3-methylbutanal 2,3-butanedione unknown 2,3-pentanedione hexanal unknown unknown 4-methoxy-2-methyl2-butanethiol unknown (Z)-4-heptenal

8

8

8

g

FDRG 100 100 nd 10 nd 100 nd 10 d

8

8

8

FDNB 500 500 100 10 500 10 10 nd

FDRB 1000 500 100 10 500 100 10 nd 100 500

e

8

f

8


h

9 10

1218 1247

11 12

1300 1309

13

1349

14

1379

metallic

15

1389

meaty

green withered grass-like orange-like mushroomlike popcornlike

nd 10

nd 10

10 500

octanal l-octen-3-one

10 100

10 100

nd 10

nd 10

unknown

100

1000

100

100

(Z)-l,5-octadien-3one 4-mercapto-4-methyl2-pentanone dimethyl trisulfide (Z)-3-hexenol unknown unknown methional, 2-ethyl3,6-dimethylpyrazine

500

500

500

500

1000

1000

10

10

8

8

8

8

h

16 17 18 19 20

1391 1395 1411 1436 1456

putrid green nutty nutty raw potatolike, nuty

21

1476

nutty

22 23 24

1505 1520 1535

25

1550

26

1570

fatty, green fruity burdocklike green, floral roasty

27

1598

green

2-ethyi-3,5dimethylpyrazine

nd 10 nd 10 5000

nd 500 10 10 500

5000 500 10 10 5000

10

10

500

500

10 nd 10

10 nd 10

100 10 10

100 10 10

10

1000

10000

10000

100

10

500

100

1000

1000

g

8

8

8

8

8

1

(£,£)-2,4-heptadienal benzaldehyde unknown h

nd nd nd 10 500

(Z)-4-decenal , linalool tetrahydrothiophen-3one (£,Z)-2,6-nonadienal

8

nd

8

100

8


341


Table I. Continued b

RI

Component

FDNG nd

FDRG nd

FDNB 100

FDRÉ 100

Peak No. 28

1608

29

1626

Odor Description camphoraceous roasty

30 31 32 33

1648 1675 1699 1715

honey-like Sour Fatty, sweet Green

34 35 36 37 38 39

1743 1762 1776 1786 1814 1824

sour powdery green minty fatty honey-like

40

1849

green, burnt

41

1858

rosy

Geraniol

42

1868

floral, burnt

43

1878

nd

8

44

1908

floral, sweet sweet

geranyl acetone, guaiacol, a-ionone Unknown Unknown

nd

8

10

10

10

45

1959

woody, green

β-ionone, (Z)-jasmone

nd

8

nd

8

10

10

46

1963

green

nd

8

nd

8

100

100

47

1980

48 49 50 51 52 53

2010 2047 2074 2090 2167 2195

sweet, lactonic sweet lactonic sour spicy clove-like clove-like

heptanoic acid, (Z)-3hexenoic acid maltol, 1,5-octanolide Unknown 1,4-nonanolide octanoic acid Unknown Eugenol 2-methoxy-4vinylphenol

unknown 2-acetylpyrazine, 2-acetyl-3methylpyrazine phenylacetaldehyde isovaleric acid unknown (Z)-3-hexenyl-(Z)-3hexenoate valeric acid Unknown Unknown methyl salicylate (£,£)-2,4-decadienal p-damascone , β-damaseenone hexenoic acid h

e

d

C

8

8

8

10

100

100

100 nd nd 500

500 nd nd 500

1000 500 500 100

1000 500 500 100

8

nd

8

8

8

8

nd 10 nd nd nd 100

nd 10 nd nd nd 1000

10 nd 100 1000 100 1000

10 10 10 1000 100 10000

100

100

1000

1000

100

1000

5000

5000

10

10

500

500

8

10

10

8

8

8

8

8

g

g

nd

8

10

10

10

10

8

nd 100 nd nd 100 1000

8

10 500 10 10 100 100

10 500 10 10 100 1000

nd 100 nd nd 100 100 8

8

8

8

hj

Continued on next page.


342 Table I. Continued Peak No.

Rf

54

2223

Odor Descriptio η grasy

FDNG

Component

C

2-aminoacetophenone jasmin lactone (£)-methyl jasmonate (2T)-methyl jasmonate Indole Coumarin

FDRG

FDNB"

1

FDRÉ

100

10

10

g

10 10 100 1000 10

10 10 100 100 10

10 10 100 500 10

g

nd 100

10 500

10 500

10


h

55 56 57 58 59

2274 2351 2400 2444 2467

60 61

2502 2588

sweet floral floral animalic eamphoraceous, sweet animalic vanillalike

nd 10 100 1000 10

Skatole Vanillin

nd 100

g

a

FD factors of 10 or above were measured. Calculated Kovat's retentions on DB-WAX. FD factors of nonretorted green tea canned drink. FD factors of retorted green tea canned drink. F D factors of nonretorted black tea canned drink. FD factors of retorted black tea canned drink. Not detectalbe. Newly identified components in green tea. 'Newly identified components in black tea. C

d

e

f

g

h

Linalool (no. 25) and geraniol (no. 41) which increased during the retorting process seemed to be mainly responsible for the floral odor of the retort green tea. These potent components are reported to be formed from the corresponding precursors by nonenzymic hydrolysis during the retort processing (11-14). On the other hand, the retort black tea had a characteristic putrid odor. Dimethyl trisulfide (no. 16) contributes significantly to the off-flavor of the black tea because of the extremely low threshold value: 0.005-0.01 ppb (15). Dialkyl trisulfide was reported to be derived from the corresponding dialkyl disulfide that was formed from the S-alkyleysteine sulfoxide by disproportionation in allium plants (16). It has been further reported that in cruciferous vegetables, dimethyl trisulfide was formed from methyl methanethiosulfinate that was derived from S-methylcysteine-L-sulfoxide, and hydrogen sulfide via a nonenzymic reaction (17). Interestingly, we found 2-methoxy-4-vinylphenol (no. 53), which is a frequent component responsible for off-flavors to be very important because of its clove-like odor. 4-Vinylphenol has been previously reported to be one of the significant components responsible for the off-flavor in the retort green tea (18). However, in our study, 2-methoxy-4-vinylphenol was found to be the potent off-flavor component instead of 4-vinylphenol. The lower threshold value of 2-methoxy-4-vinylphenol (3 ppb) compared with that of 4-vinylphenol (10 ppb) is considered to be the major reason (15). 2-Methoxy-4-vinylphenol is believed to be formed from ferulic acid in turn generated from its glycoside by decarboxylation during heating (19,20).


343 Furthermore, other common components for the off-flavor, β-damascone (no. 39), βdamascenone (no. 39) and methional (no. 20) were assumed to be responsible for the sweet and heavy odors, respectively. Figure 2 shows the quantitative changes in the off-flavor components which showed increased FD-factors by the retorting process in the canned green and black tea drinks. The other off-flavor components were not detectable because of their lower concentrations. Except for 2-ethyl-3,6-dimethylpyrazine which showed no change in the retorting process, other off-flavor components showed similar increases in the amount. This agreed with the result of A E D A study.


Conclusions The off-flavor of the green and black tea canned drinks was mainly generated by the retorting process. The characteristic off-flavors of the retort green and black teas were floral and putrid, respectively. The potent off-flavor components were found using A E D A . Linalool and geraniol seemed to be mainly responsible for the off-flavor of the retort green tea. Dimethyl trisulfide was considered to significantly contribute to the off-flavor of the retort black tea. Furthermore, 2-methoxy-4-vinylphenol, one of the common off-flavor components, was important for the clove-like odor.

Acknowledgements We are grateful to M r . Yasuhiro Harada, M r . Tatsuo Kato, Mr. Kazuhiro Sakai, and Mr. Noriaki Kobayashi for their helpful advice.

References

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(Z)-3-hexenol

methionaJ

2-ethyH3,6dimethylpyrazine

linalool

tetrahydrothiopherr-3one

0

phenylacetaldehyde 1

β -damascenone Ρ

geraniol

2-methoxy-4vinylpheno!

0.5

•

1

1

1

1.5

1

2.5

Component/I.S.

2

i

3

3.5

• retort U nonretort


4

4.5


0.5

1

Component/I.S.

1.5

2

• retort H nonretort

2.5

Figure 2. The quantitative ratios of the off-flavor components to the internal standard in the green (top) and black tea canned drinks (bottom).

dimethyl trisulfide

methional

2-etnyh3,edimethylpyrazine

tetrahydrothiophen-3one

β -damascenone

2-ιιιβ1ίιοχν^4vinylphenol

indole



346

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The Change in the Flavor of Green and Black Tea Drinks by the

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