Processing technology of tea

Quang H. Luong, MSc.Department of Food Engineering

Faculty of Food Science and TechnologyNong Lam University – Ho Chi Minh City

Apr 22, 2023 2

Course grading Seminar: 30% Midterm exam/Lab. Report/assignment: 20% Final exam: 50%

Apr 22, 2023 3

Contents- General introduction of tea

- Flavonoids and other components of tea

- Technology of tea products (Green, black, Oolong,…teas)

Apr 22, 2023 4

History of tea Reading of reference materials Since 1690, E. Kaempfer named the bush “Thea”

sinensis In 1753, C. Linné named Camellia sinensis Camellia sinensis (L.) O. Kuntze

Apr 22, 2023 5

Countries grow tea plant

World tea market share in 2009

Apr 22, 2023 6Courtesy: http://www.vietnam-tea.com/overview.html

Apr 22, 2023 7

Tea growing areas of Vietnam

Fig. 2 Vietnam and its location

Hà Giang,Tuyên Quang, Cao Bằng, Lạng SơnVĩnh Phúc, Phú Thọ, Sơn La, Hòa Bình, Bắc Thái

Nghệ An, Hà Tĩnh, Thanh Hóa

Lâm Đồng, Gia Lai, Kon-tum

Apr 22, 2023 8

Teas and health benefits Tea as a panacea Anti-carcinogenic activity

Lung cancer, prostate cancer, breast cancer, skin cancer; stomach, pancreatic, oesophageal, and colon cancers

Anti-inflammatory and anti-microbial properties Dental and oral diseases AIDS

Cardioprotective and neuroprotective properties Heart disease Parkinson’s and Alzheimer’s diseases

Apr 22, 2023 9

Flavonoids and other components in tea

Apr 22, 2023 10

O

OHOH

R1

OR2OH

HO

OH

OH

OH

C

O

X =

Forms of Catechin

(-)-Catechin: R1 = R2 = H

(-)-Gallocatechin: R1 = OH, R2 = H

(-)-Catechin gallate: R1 = H, R2 = X

(-)-Gallocatechin gallate: R1 = OH, R2 = X

Apr 22, 2023 11

O

OHOH

R1

OR2OH

HO

OH

OH

OH

C

O

X =

(-)-Epi form

(-)-Epicatechin: R1 = R2 = H

(-)-Epigallocatechin: R1 = OH, R2 = H

(-)-Epicatechin gallate: R1 = H, R2 = X

(-)-Epigallocatechin gallate: R1 = OH, R2 = X

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Technology of tea products

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Plucking

Preservation

Processing

Core stages

Apr 22, 2023 17

Plucking of T-leaves and flushes

Courtesy: http://tea-plucking.blogspot.com/

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Categories of tea Based on fermentation level

Unfermented tea (Green tea) Full fermented tea (Black tea) Partly fermented tea (Oolong tea, Pouchong tea)

Based on tea-shape Loose, compressed form (tea brick), and powder teas

Based on processing-method Raw and scented teas

Apr 22, 2023 19

Courtesy: http://greentealovers.com/greenteatypeschina.htm

Apr 22, 2023 20

Courtesy: http://www.cookscorner.net/Tea/Antioxidants.html

Apr 22, 2023 21

Green tea processing

Tea leaves and flushes

Green tea productSteaming/Panning

Rolling Packaging

ClassificationDrying

Apr 22, 2023 22

Oolong tea processing

Tea leaves and flushes Oolong tea product

Sunned withering

Indoor withering Drying

Special rollingPanning

Packaging

Apr 22, 2023 23

OTD - Black tea processing

Tea leaves and flushes Black tea products

PackagingWithering

Rolling Classification

DryingFermentation

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Dried scented tea processing

Tea panning(MC = 1.5 – 2%wb)

Additive preparing(Drying, grinding)

Blending(15 min.)

Scented incubation(Temp. = 80 - 85 oC)

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Tea blending with fresh flowers

Tea

Mixing

Flower

Turning Screening

DryingNatural cooling

Flower mixing Flower screening

‘Fresh flower scented tea’

Apr 22, 2023 26

Soluble powder tea processing

Tea leaves and flushes Rolling/Grinding

Extraction Drying/steaming

Aroma strippingFiltration

Freeze drying Concentration

Spray dryingSoluble tea powder

Packaging

aroma aroma

Apr 22, 2023 27

Tea extracts and their applications Strong infusions

Strong infusion are made by soaking tea leaves in alcohol/water mixtures (the catechin content is about 2% w/v)

Soft extracts Soft extract are made by concentrating the strong infusion to a water

content of 20-25% (the catechin content is about 20% w/w) Dry extracts

Dry extract are made by spray drying the strong infusion after they have been concentrated to 40-50% solids (Catechin ~ 25% w/w)

Partly purified extracts Purified catechins

Apr 22, 2023 28

Tea material

Develop new T-productsStudy on bioactivity

In vitro

Study on animal

Sample

Blingding

Commercial T-refine

Products from T-catechins

Study on human beings

mechanism, toxic, digest, dose,…

Trends in studying and developing new products from tea

Apr 22, 2023 29

T-preservation

RH of air (%) 30 45 60 62 70 80 85 96

EMC of tea(%) 5,8 6,7 8,7 9,0 10,4 12,2 14,8 20,5

Table 1. Relationship between equilibrium MC of tea and RH of air

Apr 22, 2023 30

T-preservationTable 2. The effect of packaging vs. MC of tea

Types of packagingMC of tea (%)

0 After 30 days

Glass flask with head-pin 7,5 7,5

Tin box 7,5 7,5

Wrap by hands, 2 layers of paper 7,5 12,8

Carton box with T-paper wrapping 7,5 13,8

Carton box with anti-humidity paper 7,5 12,7

Control (T without-package) 7,5 14,0

Apr 22, 2023 31

T-packaging

Apr 22, 2023 32

End of lecture, continuing slides for reference

Free glutamate in foods

Apr 22, 2023 33

Gre

en te

a

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O

OHOH

H

OHOH

HO

(-)-Catechin

Apr 22, 2023 35

O

OHOH

OH

OHOH

HO

(-)-Gallocatechin

Apr 22, 2023 36

O

OHOH

H

OOH

HO

OH

OH

OH

C

O

(-)-Catechin gallate

Apr 22, 2023 37

O

OHOH

OH

OOH

HO

OH

OH

OH

C

O

(-)-Gallocatechin gallate

Apr 22, 2023 38

O

OHOH

R1

OR2OH

HO

OH

OH

OH

C

O

X =

Các dạng (-)-Catechin

(-)-Catechin: R1 = R2 = H

(-)-Gallocatechin: R1 = OH, R2 = H

(-)-Catechin gallate: R1 = H, R2 = X

(-)-Gallocatechin gallate: R1 = OH, R2 = X

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Aroma bamboo rotationer

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Flavonoids in tea

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Green T. Black T

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Apr 22, 2023 50Department of Food Engineering, FST, NLU