Introduction Green tea has become a very popular drink worldwide because of its health

benefits attributed to high polyphenol (~30 %) and l-theanine content (~1-2 %). Green tea extracts are usually spray dried and further processed into Ready-To-

Drink (RTD) green tea beverages. Response surface methodology was employed to optimize thermal extraction of

green tea by controlling 3 key parameters namely, water-to-tea ratio (WTR), temperature and time. Important organoleptic characteristics concerned with quality of RTD beverage such as tea cream (%), colour of extract and turbidity were measured.

Chemical quality parameters were introduced for assessing green tea extracts

Materials and Methods

Conclusion

Made green tea (Tata Tea, India) Extracts were prepared from green tea with 3 different WTR (30:1, 45:1, 60:1; v:w)

over 3 extraction periods viz. 20, 40 and 60 min at 3 different temperatures of 70°C, 80°C and 90°C. Tea cream contents and turbidity were measured at beverage strength (0.29 % w/v).

Analyses Total soluble solids (TSS) and yield - Nagalakshmi et al., 1984 Total polyphenols - International Standard (ISO ⁄CD, 2005) L-theanine - Chen et al., 2008

Results and Discussion

Optimized conditions Recovery/Yield, g/g-GT

Response parameter WTR Temperature

(C)

Time

(min)

Extract Infusion

Specific

condition

Common

condition*

ESY 44:1 90 44 0.288 0.287 0.226

PP Recovery 43:1 90 50 0.173 0.173 0.108

L-T Recovery 50:1 90 45 0.0117 0.0116 0.007

Sample PES (g/g) TES (mg/g)

Tea Solids (mg/ml)

Turbidity (NTU)

Colour

L a b

Infusion 0.465 33.5 2.66 47.2 56.04 -1 6.73

Extract 0.602 40.4 2.94 122.5 51.41 -1.92 26.78

Effect of temperature and time on PP recovery

70

80

9020

30

40

50

60

0.12

0.13

0.14

0.15

0.16

0.17

0.18

0.136

0.145

0.155

0.164

0.173Optimum - 0.173 g/g Infusion - 0.108 g/g

45:1

7075

8085

902030

4050

60

10

10.5

11

11.5

Temperature (°C)Time (min)

L-Th

eani

ne re

cove

ry (m

g/g)

11.3

11.6

11.0

10.6

10.3

Optimum – 11.7 (mg/g)

Infusion – 7.57 (mg/g)

45:1

Effect of temperature and time on L-Theanine RecoveryEffect of temperature and WTR on ESY

3035

40

45

50

55

60 70

75

80

85

90

0.25

0.26

0.27

0.28

0.29

0.263

0.271

0.255

0.286

0.278

50 min

Optimum - 0.288 g/g

Infusion – 0.226 g/g

3035

4045

5055

60 70

75

80

85

90

0.12

0.13

0.14

0.15

0.16

0.17

0.18

Water-to-tea ratio

Temperature (°C)

PP R

ecov

ery

(g/g

)

0.144

0.153

0.162

0.172

0.135

Effect of temperature and WTR on PP recovery

50 min

Optimum - 0.173 g/g

Infusion – 0.108g/g

3035

4045

5055

60

7075

8085

90

10

10.5

11

11.5

Water-to-tea ratio

Temperature (°C)

L-Th

eani

ne R

ecov

ery

(mg/

g)

11.3

10.2

10.6

10.9

11.6

Effect of Temperature and WTR on L-Theanine recovery

Optimum – 11.7 mg/g

Infusion – 7.57 mg/g

50 min

10 20 30 40 50 600.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

ESY (0.278-0.302) g/g

PP recovery (0.149-0.193) g/g

L-Theanine recovery (10.8-12.8) mg/g

Turbidity (94-122.5) NTU

Tea Cream (2.8-7.9) %

Time (min)

Nor

mal

ized

Val

ue

Effect of time on tea quality parameters

65 70 75 80 85 90 95 1000.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

ESY (0.252-0.302) g/g

PP Recovery (0.136-0.193) g/g

L-Theanine Recovery (11.9-12.8) mg/g

Turbidity (111-122.5) NTU

Temperature C

Nor

mal

ized

Val

ue

Effect of temperature on tea quality parameters

Acknowledgement

Optimizing yield and quality of green tea extractSamriddh Mudgala,c, C.S. Murugesha, L. Jaganmohan Raob, B. Manohara, R. Subramaniana

aDepartment of Food EngineeringbDepartment of Plantation Products, Spices and Flavour Technology

Central Food Technological Research Institute (CSIR), Mysore 570 020, IndiacDepartment of Biotechnology, National Institute of Technology, Warangal 506 004, India

Email: subbu@cftri.res.in

The extraction conditions were optimized with equal focus on polyphenols

recovery and l-theanine recovery

The conditions standardized also co-extracted other tea components

responsible for tea cream formation which could be addressed by an effective

clarification process

Chemical quality parameters PES and TES were introduced for assessing the

green tea extracts which could be used as benchmark quality parameters in

the user industry

Box-Behnken Design explained the extraction phenomena and the model

obtained provided close fit to the experimental results

The work demonstrated an optimization approach for obtaining the extract with

greater solids yield rich in polyphenols and l-theanine having significant

practical applications

Samriddh Mudgal is thankful to Director, CFTRI for providing the opportunity and Chandini S. Kumar for valuable suggestions.

Table 1: Tea solids, polyphenols and l-theanine recovery under specific and common optimized extraction conditions

Table 2: Comparison of infusion and extract* quality

ESYMaximum ESY of 28.8% was achieved at 44 min of extraction at 90C which is 27.4% higher than the recovery obtained under normal brewing conditions (100:1 WTR; 75C and 5 min).

PP RecoveryMaximum PP recovery recorded was 0.173 g/g for 50 min of extraction which was 60.2% higher than normal brew.

L-Theanine RecoveryL-theanine recovery increased up to 44 min of extraction and maximum recovery achieved was 54.5% higher than the normal brew.

Effect of temperature and time on ESY

70

75

80

85

90 20

30

40

50

60

0.265

0.27

0.275

0.28

0.285

0.29

0.287

0.279

0.283

0.283

0.276

0.269

0.272

Optimum - 0.288 g/gInfusion - 0.226 g/g

45:1

* Obtained under optimized conditions

*Common optimized conditions - 45:1; 50 min; 90ºC