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Green Tea: The Plants, Processing, Manufacturing and Production

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Green tea is sourced from Camellia sinensis (L.) O. Kuntze (Theaceae), the same species from which white, oolong, black and pu-erh teas are derived. The various tea types are classified on the basis of their processing, and the associated oxidation and fermentation levels which influence taste and aroma profiles. Green tea is a minimally oxidized and non-fermented tea. Catechin polyphenols are the primary compounds responsible for the claimed health benefits of green tea, including its antioxidant and anti-inflammatory properties. Caffeine contributes to green tea's stimulant properties, while the amino acid theanine contributes to its relaxing properties. Significant variation of catechin and caffeine content occurs between green tea types depending on environmental growth conditions and processing. Most often, green teas are sourced from the sinensis variety of the tea plant while black teas are sourced from the assamica variety. China is the center of origin of green tea production. Today, green tea is produced in over 20 countries in tropical, sub-tropical and temperate regions. It is the most widely consumed beverage after water, due to its health, sensory, stimulant, relaxing and cultural properties. The quality of green tea is impacted by numerous factors involved in cultivation, harvest, processing, storage and preparation that influence chemistry, taste, aroma, morphology and bioactivity of tea leaves. s0015 THE PLANTS: BOTANICAL CLASSIFICATION AND DISTRIBUTION s0020 Botanical Identification p0015 The tea plant was first described taxonomically in 1753 by Carl Linnaeus in Species Plantarum. He referred to the tea plant as Thea and later refined the species into black tea (Thea bohea) and green tea (Thea viridis). By the early 1900s, taxonomists recognized that green and black tea were both from the same species, Camellia sinensis (L.) O. Kuntze. p0020 Camellia sinensis is an evergreen tree or shrub. It has yellow-white flowers and long, serrated leaves. Flowers are axillary, solitary, or up to three in a cluster. They are 2.5e3.5 cm in diameter and have six to eight petals. The outer petals are sepaloid and the inner petals are obovate to broadly obovate. There are numerous stamens 0.8e1.3 cm in length. Young leaves have short 19
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CHAPTER 2
c0002 Green Tea: Plants,
Processing,
Manufacturing and
Production
Selena Ahmed*, John Richard Stepp
y
*Department of Biology, Tufts University, MA, USA
y
Department of Anthropology, University of Florida, Gainesville, FL, USA
s0010 INTRODUCTION
p0010 Green tea is sourced from Camellia sinensis (L.) O. Kuntze (Theaceae), the same species from
which white, oolong, black and pu-erh teas are derived. The various tea types are classified on
the basis of their processing, and the associated oxidation and fermentation levels which
influence taste and aroma profiles. Green tea is a minimally oxidized and non-fermented tea.
Catechin polyphenols are the primary compounds responsible for the claimed health benefits
of green tea, including its antioxidant and anti-inflammatory properties. Caffeine contributes
to green tea’s stimulant properties, while the amino acid theanine contributes to its relaxing
properties. Significant variation of catechin and caffeine content occurs between green tea
types depending on environmental growth conditions and processing. Most often, green teas
are sourced from the sinensis variety of the tea plant while black teas are sourced from the
assamica variety. China is the center of origin of green tea production. Today, green tea is
produced in over 20 countries in tropical, sub-tropical and temperate regions. It is the most
widely consumed beverage after water, due to its health, sensory, stimulant, relaxing and
cultural properties. The quality of green tea is impacted by numerous factors involved in
cultivation, harvest, processing, storage and preparation that influence chemistry, taste, aroma,
morphology and bioactivity of tea leaves.
s0015 THE PLANTS: BOTANICAL CLASSIFICATION AND DISTRIBUTION
s0020 Botanical Identification
p0015 The tea plant was first described taxonomically in 1753 by Carl Linnaeus in Species Plantarum.
He referred to the tea plant as Thea and later refined the species into black tea (Thea bohea) and
green tea (Thea viridis). By the early 1900s, taxonomists recognized that green and black tea
were both from the same species, Camellia sinensis (L.) O. Kuntze.
p0020 Camellia sinensis is an evergreen tree or shrub. It has yellow-white flowers and long, serrated
leaves. Flowers are axillary, solitary, or up to three in a cluster. They are 2.5e3.5 cm in diameter
and have six to eight petals. The outer petals are sepaloid and the inner petals are obovate to
broadly obovate. There are numerous stamens 0.8e1.3 cm in length. Young leaves have short
19
Tea in Health and Disease Prevention. DOI: 10.1016/B978-0-12-384937-3.00002-1
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white hairs on their underside and young branches are grayish yellow and glabrous. Current
year branchlets are purplish red. Terminal buds are silvery gray and sericeous. Petioles are
4e7 mm in length, pubescent, and glabrescent. Leaf blades are elliptic, oblong-elliptic, or
oblong. Seeds are brown, subglobose, and 1e1.4 cm in diameter. Flowering of Camellia sinensis
occurs from October through February and fruiting occurs from August to October (Min and
Bartholomew 2010).
p0025 The tea plant belongs to the Theaceae botanical family. The Theaceae (Mirb. ex Ker Gawl.) is
part of the order Ericales (Bercht. and J.Presl) in the Asterid branch of eudicots (Angiosperm
Phylogeny Group III 2009). This family includes approximately 600 species (Tsou 1998).
The only autapomorphy (a distinctive anatomical feature unique to a terminal group) that
identifies Theaceae is a specialized pseudopollen (Tsou 1998).
s0025 Varieties
p0030 here are four varieties of Camellia sinensis including Camellia sinensis var. assamica,Camellia
sinensis var. sinensis,Camellia sinensis var. dehungensis, and Camellia sinensis var. pubilimba.
Commercial tea is primarily produced from the former two varieties, Camellia sinensis var.
assamica, or the broad-leaf variety of the tea plant, and Camellia sinensis var. sinensis, or the small-
leaf variety of the tea plant. Green tea is most often sourced from the small-leaf variety because it
has a sweeter taste than the broad-leaf variety that is usually used for black and pu-erh tea
production. However, both varieties can be used to produce white, green, yellow, red, black and
pu-erh teas.
p0035 The Yunnan-Guizhou Plateau is the center of differentiation of the two main commercial
Camellia sinensis varieties. Tea plants occur as the broad-leaf variety south of 25!N in the
Yunnan-Guizhou Plateau and as the small-leaf variety north of this latitude, with various
hybrid types being found in between (Ming 1992). Tea plants of the broad-leaf variety are
quickly growing plants of either tree or bush form, suitable for warm, tropical and sub-tropical
environments (Banerjee 1992). Individuals of the small leaf variety grow as shrubs or dwarf
plant forms and are more suitable for colder, temperate climates. Differentiation between the
two commercial Camellia sinensis varieties is further defined by matK and rbcL nucleotide
sequence polymorphisms of the chloroplast locus (Katoh et al. 2003; Stoeckle et al. 2011).
s0030 Distribution
p0040 The tea plant naturally grows in the understory of broad-leaved evergreen forests at altitudes
between 100e2,200 m. The native tea growing area, or ‘tea belt’, encompasses southwestern
China (Yunnan, Sichuan, Guangxi and Guizhou provinces), northern Laos, northern Vietnam,
Myanmar, Cambodia, and northeastern India. Some forest-growing tea plants are also found
outside of the tea belt in eastern China, Japan, southern Korea, Thailand and Taiwan. The
center of diversity of Camellia sinensis is in the Upper Mekong River Region of Yunnan Province
of southwestern China (Chen and Pei 2003; Chen et al. 2005). Today, tea plants are primarily
found in terraced landscapes in the tea belt and other tropical, subtropical and temperate
regions where tea cultivation has been introduced, including Sri Lanka, Indonesia, central
Africa, Turkey, Argentina and Russia. Tea plants are found between latitudes 42!N and 30!S in
areas that fit the specific ecophysiological requirements of tea cultivation (see Cultivation
section below).
p0045 Tea seeds were initially dispersed through waterways such as the Mekong River and by human
exchange. It is unlikely that animals disperse tea seeds over long distances because of the seeds’
large size. The broad-leaf Camellia sinensis var. assamica is prevalent across the tea belt and the
small-leaf Camellia sinensis var. sinensis prevails in Eastern China, Taiwan, Japan, India’s
Darjeeling, and tea-growing countries outside of Asia (Ming 1992). The biogeographic
distributions of the Camellia sinensis varieties are a function of adaptation, cultivation history
and taste preferences. The small-leaf variety primarily used for green and white tea production
20
SECTION 1
Tea, Tea Drinking and Varieties
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is generally cultivated in eastern China, Taiwan, and Japan. This variety is also grown in India’s
Darjeeling region to produce delicate black teas. The broad-leaf variety is generally cultivated
in western China, Myanmar, and Assam to produce black, green, and pu-erh teas. However,
both varieties can be used to produce different tea types and both varieties can be found across
these regions. Hybridization occurs where the Camellia sinensis varieties overlap, resulting in
a highly heterogeneous botanical product (Takeda 1990).
p0050 The distribution and naming of the two commercial Camellia sinensis varieties is linked to
British colonial relations with China and India. Tea became popular with Europeans after their
forays in Eastern China in the 17th century. At that time, China was the global supplier of tea,
exporting the small-leaf variety of the tea plant. The British were forced to find other sources of
tea to fulfill demand when Chinese tea became inaccessible during the Opium Wars in the mid
19th century. They turned to the cultivation of tea in India, which soon became the primary
source of tea for the British Empire. While India did not commercially produce tea before the
1800s, tea plants grew in forests in Assam and were harvested and used by indigenous
communities. Tea specimens that were collected from Assam were distinguished from tea
plants from eastern China as a separate variety, the two being respectively termed Camellia
sinensis var. assamica and Camellia sinensis var. sinensis. It was later recognized that the assamica
variety also grows in forests and indigenous tea production systems in southwestern China
where its center of diversity has been identified.
p0055 The British East India Company led commercial tea cultivation in India by transferring tea
germplasm and technology from China (Murray 1852). Scottish botanist Robert Fortune was
sent to smuggle and transport tea from China to India in 1848 (Fortune 1853). Fortune used
Wardian cases, transportable greenhouses invented by Nathaniel Bagshaw Ward, to transport
thousands of tea seeds and seedlings from eastern China to India’s Darjeeling region. The
British East India Company also brought trained tea farmers and producers from China to
transfer knowledge of tea cultivation and processing. Forest tracts were cleared across
Darjeeling and Assam for tea plantations, in which both the broad-leaf and small-leaf varieties
were cultivated.
s0035 CULTIVATION
p0060 Tea has been cultivated for at least 1500 years. Cultivation of tea is possible in areas that receive
over 120e150 cm of rain annually, and have temperatures of 12e30 !C. Optimum growing
conditions are 250e300 cm annual rainfall and average temperatures of 18e20 !C (Williges
2004). Cultivation may occur from sea level to 2,200 meters, with some tea cultivars found as
high as 3,000 m. Higher altitudes are often associated with higher tea quality. At least five
hours of direct or 11 hours of indirect sunlight daily are required for tea cultivation. Soils must
be well-drained, sandy, thoroughly aired, deep and nutritious with a healthy layer of humus
and low pH. Drought, water logging, excessive heat, and frost are harmful for the growth of tea
plants and may result in a lower quality product in terms of chemistry, taste, aroma, and
bioactivity. Tea plants are often raised in controlled nursery conditions or other protected
conditions for their first two to four years. They are classified as immature at this time and are
not harvested. Once tea plants mature, they are transplanted to the field and are ready for
harvest.
s0040 Propagation and Breeding
p0065 Tea plants cross-pollinate and are self-incompatible (Banerjee 1992). They are propagated
sexually by seeds or asexually by vegetative cuttings of clonal propagules. Grafting may be also
used for vegetative propagation of tea plants where seedlings may be used as rootstocks. Tea
plants cultivated from seeds generally give lower yields, require less fertilization and produce
a heterogeneous stand and product compared to plants propagated by vegetative cuttings. Seed
propagation also results in tea plants with an extensive taproot that helps protect soils, prevent
CHAPTER 2
Green Tea: Plants, Processing, Manufacturing and Production
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erosion and enhance fertility. Historically, tea plantations were created through seeds and
some producers and consumers prefer the heterogeneous product yielded by this method.
p0070 In contrast, many large-scale producers prefer clonal propagation by vegetative cuttings
because of the uniform product yielded by this method. Clonal propagules need greater
fertilization compared to tea plants grown from seed because of their lack of a taproot. This
means that they are often associated with poor soil because the short tap root limits soil
microbial interactions. Vegetative cuttings were found to require 45e60 kg nitrogen (N),
4e7 kg phosphorus (P), 20e30 kg potassium (K) and 4 kg calcium (Ca) per hectare to yield
4 tons of leaf (Rehm 1989). In addition, clonal propagules generally require greater agro-
chemical inputs and have narrower genetic diversity compared to tea plants grown from seed.
Some environmental conditions favor clonal proagules, while others result in greater
vulnerability for clonal propagules compared to seed plants (Williges 2006). Grafting has been
used to select for various traits from two different cultivars, and has a benefit over clonal
propagation in that the resulting plants have a taproot system similar to plants grown from
seed. Tap roots help protect soils and maintain fertility. This propagation method has been
adapted as an alternative method to enhance fertility, along with other management practices
such as intercropping, alley cropping and organic agriculture.
p0075 Tea plants are bred for desired traits through selection and hybridization. These focus on
morphology, yield, resistance to abiotic and biotic stress, therapeutic properties, taste and
aroma. Selection and hybridization have resulted in over a thousand cultivars and landraces
with diverse characteristics. For example, for a grafted plant, a rootstock may be selected from
a drought tolerant cultivar and combined with a scion from a high yielding cultivar with
specific chemistry, taste and aroma profiles. The resulting composite plants combine the
selected characteristics from both cultivars. Selection has been the main process of breeding tea
plants because of the lack of success of controlled hybridization crosses. However, selection is
limited by the natural history of the tea plant. Limitations to breeding tea include the perennial
nature of the plant with a long gestation period, self-incompatibility, short flowering time of
two to three months and the long period of time needed for seed maturation ebetween 12e18
months (Mondal et al. 2004). Selection is further limited by the low availability of mutants
with tolerance to specific biotic and abiotic stresses, low success rate of hand pollination, low
propagation rate, and differences of flowering time and fruit bearing capability. More recently,
producers have tried to breed tea plants through the development of transgenic plants but this
also has had limited success because of inefficient transformation.
s0045 Shrub Formation
p0080 The majority of tea plants cultivated globally are grown in compact rows and are pruned as
roughly rectangular shrubs at a height of 1e1.2 m in what is termed a picking or plucking table
(Figure 2.1). Formation of a plucking table serves to expedite harvest and to maximize yields
per area. Young tea plants are usually laterally cut approximately 23 cm above the soil to
encourage lateral growth and formation of a shrub. Pruning is done throughout the year,
between harvest seasons or annually to encourage growth and maintain the form of the
picking table. Deep pruning occurs every four to five years.
s0050 Pests and Disease
p0085 Tea plants have a number of naturally occurring predators including the short-hole borer
beetle (Xyleborus fornicatus), red spider mite (Oligonychus coffeae),coccinellid and staphylinid
larvae, lace-wing larvae, and Typhlodromus and Phytoseius mites (Williges 2006). Some tea
pests such as the short-hole borer beetle cause severe damage to the frame of tea plants.
Insecticides have conventionally been used to control tea pests. Tea plants are also vulnerable
to blister blight disease from the fungus Exobasidium vexans. This fungus is eliminated by direct
SECTION 1
Tea, Tea Drinking and Varieties
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exposure to sunlight and thus shade trees are removed in areas that are susceptible to infes-
tation. Copper based fungicides are also used to eliminate to blister blight disease.
s0055 TEA HARVEST: PLUCKING AND SEASONS
s0060 Plucking
p0090 Most green tea types are produced using young, tender leaves. The leaf unit harvested varies with
the specific type of green tea. Many green tea types include the terminal bud, the internodes and
1e3 leaves immediately below the bud (Figure 2.2). For some other green tea types, the
harvested unit consists of a single young leaf. Older leaves are generally not used to produce
high-quality green teas because these leaves are rough with an astringent flavor. Tea leaves are
plucked by hand, or are mechanically harvested by a plucking machine. Many high quality green
teas are hand plucked. Farmers may hand pluck up to 30 kilos of fresh tea leaf per day. Hand
plucking is the most labor intensive and expensive process in tea cultivation and has been
replaced in many instances by mechanized pluckers to increase labor productivity and decrease
labor costs. Leaves are plucked from the same plant at intervals of four days to two weeks.
f0010 FIGURE 2.1
Tea Plucking Tables in Terrace Tea Production System. Tea plants in terrace plantations are grown in compact rows to
optimize yields per area and are maintained as shrubs by pruning heights at a height of 1e1.2 m for ease of harvest.
f0015 FIGURE 2.2
Harvested Unit. The young tender leaves of tea plants are harvested to produce most types of green tea. Many high quality
teas consist of the terminal bud, internodes, and two to three leaves immediately below the bud.
CHAPTER 2
Green Tea: Plants, Processing, Manufacturing and Production
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s0065 Harvest Seasons
p0095 The tea harvest calendar is based on the availability of young terminal buds and adjacent leaves
of the tea plant and is partly determined by the proportion of daylight and darkness in a day.
There are three to four tea harvesting seasons, depending on the latitude and altitude of a tea
production system. At latitudes above 16 !N and below 16 !S where tea plants receive less than
11 hours of sunlight for over six weeks, tea plants go into dormancy from late fall to the end of
winter. Leaf growth resumes in the spring after a period of dormancy. These areas have three
harvest seasons including spring, summer or monsoon season, and autumn. The winter
dormancy is regarded an important contributor to good quality tea because in the spring
harvest season it encourages the young shoots to release aromatic compounds that are not
found in teas of later harvests. At latitudes below 16 !N and above 16 !S, tea plants continue to
produce new leaf shoots throughout the year. These areas have four harvest seasons. Harvest
seasons may be preceded by pruning tea plants in order to encourage new leaf growth.
p0100 In southwest China, tender buds and leaves sprout during three continuous seasons from
spring to autumn. Spring starts in early to mid March and runs through mid May; it is regarded
as the main harvest season, giving the best quality tea. The monsoon or rainy season proceeds
the spring season and runs through August. Tea leaves are perceived to have the lowest quality
during the rainy seasons on the basis of their taste, aroma and health promoting properties,
and farmers may receive half the price for dried leaf during this period compared to the spring
season (Ahmed 2011a). Excessive rainfall leads to soil exhaustion through leaching and
possibly impacts the physiological responses of the plant itself. The autumn season, termed the
‘rice flower season’ in parts of southwestern China, follows the rainy season and lasts till early
to mid November. Autumn tea is of higher quality than rainy season tea but lower quality than
the spring season. Some farmers report that the spring harvest season has started earlier each
year over the past decade because of increased temperatures (Ahmed 2011a). This may be the
result of microclimate variability or global climate change.
p0105 Tea plants in India and Japan are also plucked during three harvest seasons. The spring season
in India starts in late February to early March and runs through April. Spring tea is charac-
terized as full-bodied, aromatic, slightly bitter and astringent. The pre-monsoon or summer
season runs from mid May to mid June or end of June and the monsoon harvest starts early to
mid June through August. Monsoon season tea is often not harvested because of its low quality
as judged by a mild taste and aroma. The autumn harvest starts in September to the end of
October and this tea is characterized as more full-bodied than monsoon tea but less sharp than
spring tea. In Japan, the spring season starts in mid April to early May and runs to end of May
or early June. Over half the year’s harvest is collected during the spring. The summer harvest
starts in mid June to early July and runs to the end of August to early September. Tea leaves are
often not harvested during the hottest and most humid parts of the summer season when the
quality is the lowest. The fall harvest starts end of September and runs into October.
p0110 In Sri Lanka, tea plants are continuously harvested all year round and do not enter dormancy.
The topography of the tea garden in Sri Lanka plays a critical role in determining the arrival of
the monsoon, and the associated tea quality. Tea plants located in cultivation systems in the
southwest region are potentially exposed to monsoons from May to August when tea quality is
the lowest. Tea quality is highest for winter and spring teas that are produced December to
March. Plants located in tea cultivation systems in the northwest region are exposed to
monsoons from October to January. The most valued teas from these cultivation systems are
produced from May to September before the monsoon season.
s0070 PROCESSING
p0115 A cup of tea prepared from processed leaves tastes, smells and appears notably different
than an infusion from fresh tea leaves because of a series of biochemical changes that occur
SECTION 1
Tea, Tea Drinking and Varieties
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during processing. Fresh tea leaves have a bitter taste and are rich in volatile compounds
and aroma precursors. Processing is among the most important factors for flavor and
promotes the development of volatile compounds, reduces bitterness, deactivates enzymes,
reduces moisture content, and transforms fresh tea leaf into the six different colors used to
classify tea: white, green, yellow, blue-green, red and black. The primary steps of green tea
processing following harvest include post-harvest spreading out, fixing, rolling, shaping and
drying. Upon harvest, tea leaves are promptly processed to transform their flavor and
prevent degradation of biochemical profiles and spoilage. On average, four to six kilos of
fresh tea leaf are processed into one kilo of dried tea leaf, which contains 1,000e12,000
young shoots.
p0120 The cultivation, processing and preparation of green tea as a skilled practice and art
developed in China during the 8
th
century by Buddhist monks, and was disseminated to
the public by one monk in particular; Lu Yu, in The Classic of Tea. Buddhist monks were
instrumental in spreading the practice of tea production and consumption. They culti-
vated tea plants in and around their monastery gardens that they would harvest, process
and drink during meditation and use as a tonic to maintain wellbeing. Diversification
of tea products expanded during the Ming Dynasty (1368e1644) in China when
producers began to experiment with new processing techniques. Today, there are
numerous types of green tea, characterized by a range of cultivation and processing
methods (Table 2.1).
t0010 TABLE 2.1 Examples of Types of Green Tea
Types of Green Tea Production Characteristics
Biluochun (Pi Lo Chun;
Green Snail
Springtime)
Chinese tea often cultivated among plum, apricot
and peach trees; Originally produced in Jiangsu
Province; Floral aroma and fruity taste; Tightly rolled
to resemble tiny snails
Genmaicha (Popcorn
tea)
Japanese pan-fried Sencha tea blended with
toasted hulled rice
Gunpowder (Pearl tea) Chinese tea grown primarily in Zhejian province;
Tightly rolled in pellet form
Gyokuro (Jade Dew) High-quality Japanese tea often from Yabukita
cultivar; Tea production systems are covered with
shade for 14e20 days prior to harvest; Flat pointed
leaf; Delicate flavor and sweet aroma; Pale green
infusion
Hou Kui (Monkey King) Chinese tea grown primarily in Fujian province;
Orchids are cultivated in the production system
Kukicha Japanese tea of stems, stalks and twigs; Nutty and
creamy flavor
Long Jing (Lung Ching;
Dragonwell)
Pan-fried Chinese tea grown primarily in Xi Hu
region of Zhejian province; Processed as a roasted
flattened leaf; Jade color
Matcha Powdered Japanese tea; Mostly produced in the Uji
region; Cultivated primarily in the shade; Commonly
used in Japanese tea ceremony
Sencha Popular steamed Japanese green tea; Greenish
golden infusion; Vegetal grassy aroma
Tian Mu Qing Ding Chinese tea grown primarily in Zhejian province;
Fine, delicate leaf; Sweet and mild taste
Xin Yang Mao Jian
(Tippy Green)
Chinese high-altitude tea grown primarily in Henan
province; Tippy pointy leaves with fine hairs
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s0075 Post-Harvest Spreading of Leaves
p0125 Following harvest, tea leaves for green tea production may be spread out on bamboo mats or
other surfaces for one to three hours. Leaves are occasionally turned during the spreading
process. Spreading leaves promotes the hydrolysis of non-water soluble carbohydrates and
pectins, formation and accumulation of non-gallated catechins, releases the grass-like odor
characteristic of fresh tea leaves, and evaporates some moisture in fresh leaves for better
fixation. Spreading height, duration and leaf turning times differs for various tea types. Not all
green tea types involve spreading leaves post harvest. Approximately 30% of moisture content
is lost during the spreading process and prepares the leaf for the next step of processing
involving heat application.
s0080 Fixing
p0130 Fresh tea leaves are exposed to heat for approximately 10e15 minutes in a process known as
fixing. Fixing deactivates enzymes in leaf shoots in order to prevent oxidation and fermenta-
tion and to maintain a green color. Tea shoots contain enzymes which are responsible for the
biochemical metabolic pathways that cause the growth of tea plants. The main relevant
enzymes in tea plants include polyphenol oxidase, catalase, peroxidase and ascorbic acid
oxidase (Xu and Chen 2002). These enzymes have high activity after tea leaves are plucked and
must be deactivated by applying high heat in the fixing process. Different enzymes have
different levels of activity depending on leaf position, plucking method, seasons and cultivars
(Obanda et al. 1992). Also, enzymes differentially respond to temperature fluctuations. For
example, tender shoots generally have higher polyphenol oxidase activity than mature shoots
and require higher fixing temperatures. Fixing also serves to dry tea leaves. Approximately 40%
of the water content is lost from leaves during fixing (Zhen et al. 2002).
p0135 Fixing methods for green tea include pan-frying and steaming. The pan-frying method involves
places leaves directly on a dry pan exposed to a high heat source. It developed in China during
the Song Dynasty (960e1127; Xu and Chen 2002) and is the main way of processing green tea.
Steaming involves placing leaves over perforated steamers that release steam blasts from
heated water. This is the prevalent fixing method in Japan. Steaming usually preserves more
color, polyphenolic content and antioxidant bioactivity than pan fixing.
p0140 Fast, even and high-temperature fixing is a feature of green tea processing, and is important for
high quality tea. Fixing temperatures range from 100e200 !C for artisanal processed green teas
and 220e330 !C for machine fixed green teas (Xu and Chen 2002). Processors often adjust
temperature during fixing with higher temperature in the beginning and lower temperature
towards the end. The temperature for pan-frying is around 180 !C and the temperature for
steaming is around 100 !C. Low fixing temperatures can result in reddening of leaves. Exces-
sively high temperatures scorch and dry the leaves, and result in their yellowing and browning
and giving a smoky flavor. High temperatures also hydrolyze leaf proteins. Over-drying of tea
leaves is unfavorable for the rolling step that follows and often results in broken pieces.
s0085 Rolling, Shaping and Drying
p0145 Following fixing, leaves are rolled in order to disrupt their cell walls, release leaf moisture and
shape the final product. Rolling times vary between ten minutes and one hour. Young leaves
are rolled under lighter pressure and for shorter duration compared to older leaves, in order
to prevent the leaf breakage and yellowing that results from hydrolysis of chlorophyll and
auto-oxidation of polyphenols (Xu and Chen 2002). Rolled tea leaves are shaped into
various forms including twists, round, flat, needle, flaky, compressed and ground powder.
The grade of tea is commercially judged by the size of the leaf pieces. Whole buds and young
leaves are a superior grade to the broken leaf pieces, which are called fannings, and the dust
found in many mass produced teabags. Finally, the shaped leaves are dried by pan-drying,
basket drying, sun-drying or baking. Depending on the method, drying takes from twenty
SECTION 1
Tea, Tea Drinking and Varieties
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minutes to overnight. Pan-drying produces a tea product with a tighter shape that maintains
greater aroma compared to tea that is air-dried in sunlight.
s0090 CHEMISTRY AND BIOCHEMICAL CHANGES DURING GREEN TEA
PROCESSING
p0150 Catechins, a group of polyphenolic flavan-3-ol monomers and their gallate derivatives, are the
primary compound responsible for the health-related claims of green tea including its
antioxidant and anti-inflammatory properties (Zhen 2002). The major catechins in tea are
(")-epicatechin (EC), (")-epigallocatechin (EGC), (")-epicatechin-3-gallate (ECG), and
(")-epigallocatechin-3-gallate (EGCG). EGCG is the most widely-studied green tea
compound, with the most recognized health claims of all tea compounds. Caffeine, a meth-
ylxanthine alkaloid, contributes to green tea’s stimulant properties while theanine (gamma-
glutamylethylamide), an amino acid and glutamic acid analog, contributes to green tea’s
relaxing properties. Caffeine and theanine have a synergistic physiological effect in enhancing
mental alertness. Catechins and caffeine are secondary metabolites that serve as defense
compounds in plants. They provide plants with resistance to pathogens and predators (Ames
et al. 1990), reduce oxidative stress, and protect from other environmental variables. The
amounts found naturally in plants vary with environmental conditions (Chung et al. 1998).
p0155 Catechins and caffeine also vary in green tea and other plant products due to processing. The
total catechin content of various green tea types (Dragonwell, Gunpowder, Gyokuro, Jasmine
Pearl and Sencha) were found to vary more than 10-fold, from 21.38 to 228.20 mg/g of dry
plant material for water-infused extracts (Unachukwu et al. 2010). In addition, a quantitative
analysis of catechin content, total phenolic content and antixodant activity of the same green
tea type from different producers revealed strikingly different amounts of most catechins and
antioxidant activity (Unachukwu et al. 2010). These findings highlight that not all green tea
types have the same chemistry and therapeutic properties. Furthermore, significant variation in
biochemistry and therapeutic properties occurs even in a particular type of green tea
depending on the producer and environmental conditions.
p0160 Some tea phytochemicals are impacted more by production, storage and preparation than
others. The polyphenol catechins have the highest concentrations in fresh leaves. As the leaves
are heated, rolled, and dried during processing, the catechin content decreases as leaves
undergo oxidation, hydrolysis, polymerization and transformation. For example, the
biochemical changes during processing result in a tea product with at least 15% less
polyphenol content than freshly plucked tea leaves. Caffeine, on the other hand, is less
sensitive to heat and does not undergo considerable reduction during processing. Thus, while
the antioxidant properties derived from catechins are reduced during processing, the stimulant
properties from caffeine persist. However, green tea processing is beneficial for stabilizing and
increasing the shelf life of catechins by deactivating the enzymes responsible for oxidation
(Astil et al. 2001).
p0165 Some proteins are hydrolyzed into free amino acids by high temperatures and humidity. Amino
acids are important aroma precursors and many are transformed into volatile aromatic substances
during green tea processing. As a result, only a minority of the approximately 600 aroma
compounds identified in processed tea are found in fresh leaves. For example, theanine content
increases during the fixing, rolling and drying processes of some types of green tea. Consequently,
some types of processed green tea have higher amino acid content than fresh tea leaves, and the
ratio of tea polyphenols to amino acids changes during processing aspolyphenols decrease while
some amino acids increase. Volatile, lower boiling compounds are released during the initial
fixing stage of processing, which involves high temperatures, leaving compounds with higher
boiling points. It is important to note that other types of tea, such as black tea end up with lower
theanine contents after processing, due to the higher temperatures used.
CHAPTER 2
Green Tea: Plants, Processing, Manufacturing and Production
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p0170 Levels of soluble carbohydrates may also increase during processing. For example, starch
compounds in tea leaves hydrolyze and produce more soluble sugars under high temperatures
and humidity. Chlorophyll, the main pigment in fresh and dried tea leaves, is reduced by
approximately half from fresh shoots to dried shoots by increased temperature, pH changes
and hydrolysis (Xu and Chen 2002). The application of heat during processing also causes the
oxidation of water-soluble flavonols, which contribute to the yellow color of green tea
infusions.
s0095 STORAGE, PREPARATION AND FLAVOR
s0100 Storage
p0175 Tea constituents undergo degradation, oxidation, epimerization, and polymerization reactions
during storage, as the leaves interact with ambient oxygen, moisture, light, and temperature
fluctuations. There is a significant reduction of polyphenolic catechin levels within six months
of production. For example, epigallocatechin gallate (EGCG), the most abundant green tea
catechin, was shown to decrease by 28% during 6 months of storage under home-like
conditions, while epigallocatechin (ECG), the second most abundant tea catechin, decreased
by 51% (Friedman et al. 2009). Storing tea in sealed packaging in cool dark conditions helps
increase its shelf life (Chen et al. 2001).
s0105 Preparation
p0180 Historically, green tea was prepared as an extracted soup from pressed tea cakes and water. Salt
was added to heighten aroma. Drinkers consumed the tea leaves in the soup along with the
infusion. Today, green tea is primarily prepared by steeping loose tea leaves or a tea bag in hot
water and drinking the infusion. Brewing duration, leaf amount, water temperature and
number of infusions to prepare green tea varies with the type of green tea and drinker pref-
erences. The color of green tea infusions is greenish, yellowish green or yellow without any
trace of the red or brown color found in oolong and black teas.
p0185 Considerable ritual and ceremony may be involved in preparing a cup of tea using loose leaves;
such as through the Chinese gongfu cha dao (‘way of tea’ with ‘effort’, ‘work’, or ‘skill’) method
that is based on multiple infusions of steeping leaves. Drinkers consider that this brewing
method optimally releases the aroma, taste, color, and physiological properties of tea, thus
providing for a ‘balanced composition’ that brings out its nuanced essences (Ahmed et al.
2010). Alternatively, tea may be prepared from mass produced tea bags for convenience. This
preparation method may constrain leaves from optimally interacting with water and the
material of the bag can also interfere with the extraction process, leach constituents, and
impart a taste to the tea (Castle et al. 2007). In addition, tea bags that contain fannings and
dust are more influenced by oxidation processes during storage than whole tea leaves, because
a larger surface area is exposed to oxygen and light. On the other hand, the increased surface
area of smaller tea particles results in greater interactions with water during brewing, and
heightens the extraction efficiency of the final brew (Ahmed 2011b). There is, however, great
variability in tea products and some high-end producers offer quality biodegradable teabags
containing whole-leaf tea.
s0110 Flavor
p0190 The main flavor descriptors of green tea are bitter and sweet. Table 2.2 indicates other common
flavor characteristic descriptors used to describe tea. Bitter is a characteristic associated with
cultivation, and sweet is a characteristic associated with processing. Some high quality teas are
perceived to be bitter in the mouth and sweet in the throat. For other high quality teas, bitter
and astringent have negative connotations while aromatic, sweet and delicate are desired
characteristics. Smooth and light teas are often considered ordinary. Teas that induce salivation
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often indicate a high quality while dryness indicates poor production practices. Older tea
plants are generally considered to produce more complex teas than younger plants.
p0195 Some tea cultivars produce higher quality green tea, with greater levels of amino acid and
polyphenolic constituents. High altitude environments that have warm days and cool nights
promote the development of aromatic constituents in tea leaves. Higher application of
nitrogen has been shown to increase amino acids in the leaves (Zhen 2002). Precipitation
during the monsoon season is associated with lower quality tea, while shade over tea plants is
associated with higher quality (Ahmed 2011a). Shade over tea plants also encourages leaf
tenderness, aroma and smoothness of flavor. For example, tea plants used for the production
of Gyokuro green tea in Japan are covered for two weeks before harvest to impart a smooth and
sweet taste profile to the leaves. Sencha green tea produced from the same region and cultivar,
but without shade, has a sharper taste than Gykuro.
s0115 GLOBAL GREEN TEA PRODUCTION
p0200 China is the largest producer and consumer of green tea, responsible for approximately 73%
of total world production. In 2008, China dedicated 1,215,174 ha of agricultural land to
produce over 1,200,000 tons of tea, an area that constituted 43% of the global tea production
area of 2,806,443 ha (FAO 2010). The total land area dedicated to tea production in China
has expanded by over 300% since the early 1960s. Following China, Japan produces
approximately 15% of the world’s green tea. Vietnam and Indonesia are also notable green tea
producers, each covering approximately 5% of global green tea production. While India is
among the top producers of tea worldwide, it produces primarily black tea. Green tea
production and consumption has notably increased over the past six decades and this trend is
forecast to continue as tea gains prominence in health and disease prevention worldwide.
s0120 SUMMARY POINTS
o0010 1. Green tea is sourced from Camellia sinensis (L.) O. Kuntze (Theaceae), the same plant as
white, oolong, black and pu-erh teas.
o0015 2. The various tea types differ on the basis of processing, and also by their associated
oxidation and fermentation levels, which influence taste and aroma profiles. Green tea is
a minimally oxidized and non-fermented tea. Commercial tea is primarily produced from
two plant varieties: Camellia sinensis var. assamica, the broad-leaf variety of the tea plant,
and Camellia sinensis var. sinensis, the small-leaf variety of the tea plant. Green tea is often
sourced from the small-leaf variety because it has a sweeter taste than the broad-leaf
variety, which is considered more suitable for black and pu-erh teas. However,
both varieties can be used to produce white, green, yellow, red, black and pu-erh teas.
t0015 TABLE 2.2 Common Flavor Characteristics to Describe Tea
Acidic Metallic
Astringent Earthy
Bitter Smooth
Bitter with a
sweet aftertaste
Mellow
Floral Acrid
Fruity Burnt
Grassy Creamy
Salty Moldy
Smoky Vegetal
Sour Fishy
Sweet Full
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o0020 3. Catechin polyphenols are the primary compounds responsible for the health claims of
green tea, including its antioxidant and anti-inflammatory properties. Caffeine
contributes to green tea’s stimulant properties while the amino acid theanine contributes
to its relaxing properties. Significant variation in catechin and caffeine content occurs in
green tea types depending on environmental conditions and processing.
o0025 4. Green tea quality is determined by cultivation, harvest, processing, storage and
preparation variables and is judged on the basis of chemistry, taste, aroma, morphology
and bioactivity.
o0030 5. Tea plants can be cultivated in areas with over 120 cm of annual rain, temperatures of
12e30 !C, and altitudes from sea level to 2,200 m. Soils suitable for tea production are
well-drained, sandy, thoroughly aired, deep and nutritious with a healthy layer of humus
and low pH.
o0035 6. Tea plants are propagated sexually by seeds, asexually by vegetative cuttings of clonal
propagules or partially asexual by grafting.
o0040 7. Most green tea types are produced using young tender leaves. There are three to four tea
harvest seasons depending on latitude and altitude.
o0045 8. Green tea processing involves plucking, post-harvest spreading, fixing, rolling, shaping
and drying. Various biochemical changes occur during green tea processing and storage.
Levels of the polyphenolic catechin compounds decrease as leaves undergo oxidation,
hydrolysis, polymerization and transformation from processing while caffeine remains
relatively stable. There is significant reduction of polyphenolic catechin levels during
storage within six months of production of up to 50% decrease of some compounds.
o0050 9. The main flavor descriptors of green tea are bitter and sweet.
o0055 10. China is the largest producer and consumer of green tea and contributes approximately
73% of world production.
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Non-Print Items
Abstract:
Green tea is sourced from Camellia sinensis (L.) O. Kuntze (Theaceae), the same species from which white, oolong, black and
pu-erh teas are derived. The various tea types are classified on the basis of their processing, and the associated oxidation and
fermentation levels that influence taste and aroma profiles. Green tea is a minimally oxidized and non-fermented tea. Catechin
polyphenols are the primary compounds responsible for the health claims of green tea, including antioxidant and anti-
inflammatory properties. Caffeine contributes to green tea’’s stimulant properties, while the amino acid theanine
contributes to its relaxing properties. Significant variation in catechin and caffeine content occurs in green tea types
depending on environmental conditions of growth, and processing conditions.
Most often, green teas are sourced from the sinensis variety of the tea plant while black teas are sourced from the assamica
variety. China is the center of origin of green tea production. Today, green tea is produced in over 20 countries in tropical, sub-
tropical and temperate regions. It is the most widely consumed beverage after water for its health, sensory, stimulant, relaxing
and cultural values. The quality of green tea is impacted by numerous factors involved in cultivation, harvest, processing,
storage and preparation that influence the chemistry, taste, aroma, morphology and bioactivity of tea leaves.
Keywords: Camellia sinensis, tea production, tea distribution, tea harvest seasons, tea types, tea quality, tea flavor.
... Baishakhi De and Tridib Kumar Goswami 6 tea plants gets limited by shallow and compacted sub-soils; a groundwater table of at least 90 cm deep favors the good growth of tea plants (Ahmed and Stepp 2013;Verma et al. 2018). ...
... Tea gardens are regularly hoed and manured; oil cakes and green fertilizers are widely used. Pruning of the plant is an essential part of tea cultivation that helps in growth and maintenance of the proper shape of the tea bush (Verma et al. 2018) Baishakhi De and Tridib Kumar Goswami 8 manufacturing parameters are to be properly controlled to retain the natural leaf quality along with its color and aroma (Chaturvedula and Prakash 2011; Ahmed and Stepp 2013;Khurshid et al. 2016;Verma et al. 2018). ...
... Sencha is a popular steamed Japanese green tea with greenish golden infusion and vegetal grassy aroma. Matcha is a powdered green tea having popular use in Japanese tea ceremony; the pan fried Chinese tea processed as a roasted flattened leaf and of jade color; Tian Mu Qing Ding is a Chinese variety of green tea processed from fine delicate leaf with a sweetish mild taste; Tippy green or Xin Yang Mao Jian is a Chinese variety of tea grown at high altitude primarily in Henan province; Kukicha is a variety of Japanese green tea with nutty and creamy flavor prepared from the stems, stalks and twigs; Hou Kui or monkey king is also a variety of Chinese green tea grown primarily in Fujian province; Jade dew or Gyokuro is a high quality Japanese tea prepared from flat pointed leaf providing a pale green infusion with delicate flavor and sweet aroma; gunpowder or pearl tea is a tightly rolled pellet form of Chinese green tea grown primarily in Zhejian province; popcorn tea or genmaicha is a Japanese pan fried sencha tea blended with toasted hulled rice; Biluochun is a variety of Chinese green tea with floral aroma and fruity taste, tightly rolled to resemble tiny snails and thus are known as green snails and are produced in Jiangsu province (Ahmed and Stepp 2013). ...
Chapter
Full-text available
Due to its wide range of properties, green tea has extensively been turned out as an important substance to be examined experimentally by the analysts. Out of its various properties, the antineoplastic activity of green tea is exclusively acknowledged. Green tea shows therapeutic potential in case of cancers of cervical, lung, colon, liver, stomach, leukemia, prostate, breast, and many other organs. Green tea extract possesses some carcinoma preventive bioactive components such as polyphenols, proline, lysine, catechin, ascorbic acid, and epigallocatechin-3-gallate. Earlier investigations have favoured the relationship between the reasonable intake of green tea polyphenols and the decreased cancer possibility. Various mechanisms have been proposed to determine the application of green tea components as an anticancer agent. These mechanisms incorporate modulation of the immune system and cell signalling pathways, regulation of cell cycle, anti-oxidant activity, and inhibition of receptor tyrosine kinase pathway. Further, drug tolerance and several harmful side effects have long been a crucial complication in the treatment of tumor. The treatment by chemotherapy has also been transformed from single-drug remedy to multiple-drug remedy. Earlier research results indicated that the amalgam of green tea and chemo-remedial drugs could synergistically intensify the effectiveness of therapy and lessen the worse after-effects of antitumor agents in tumor sufferer. Therefore, we have focused on the use of green tea constituents either alone or in combination with other agents for the treatment of different types of cancers with upgraded life expectancy.
... Tea from Camellia sinensis can be categorised into three types depending on the level of formulations i.e., green (unfermented), oolong (partially fermented) and black (fermented) tea. The term 'fermentation' here means exposure of the leaves to air (oxidation) while drying without any addictive during the process ( Sinija and Mishra, 2008 ;( Ahmed and Stepp, 2013 ); Reygaert 2017 ). The major chemical component of interest in green tea was polyphenol which is majorly flavonoid. ...
... Therefore, flavonoids have been regarded as promising -glycosidase inhibitors ( Shoretoglu and Sari, 2020 ). Investigations have proved the health benefit of green tea to be anti-cancer, anti-fungal, anti-viral, anti-HIV, antioxidant, anti-inflammation, anti-cholesterolaemia ( Takatoshi et al., 2006 ;( Ahmed and Stepp, 2013 ); Reygaert, 2017 ). In the present study, effects of aqueous extract of Camellia sinensis on -glucosidase inhibition and in lowering glycaemic index of white bread were investigated In vitro and in vivo respectively. ...
Article
Full-text available
High glycaemic index diet and α-glucosidase activity have been implicated in postprandial hyperglycaemia. Regulation of α-glucosidase activity and high glycaemic index diet has promising consequence on curbing the prevalence of type-2 diabetes mellitus. The present study investigated inhibitory effect of aqueous extract of Camellia sinensis (green tea) on α-glucosidase activity and glycaemic index of white bread. In vitro inhibition of α-glucosidase activity using p-nitrophenyl glucopyranoside as substrate and Camellia sinensis aqueous extract as inhibitor was investigated. Likewise, in vivo study on effect of the tea on glycaemic index of white bread using 30 healthy participants was carried out. The outcomes of the investigation revealed that Camellia sinensis aqueous extract reduced the activity of α-glucosidase to 17.50% with IC50 of 202.12 µg/mL. The mode of inhibition was mixed competitive. It also lowered the glycaemic index (GI) of white bread by 39.71% when bread consumption was delayed for 5 minutes after the extract consumption. In conclusion, report has shown that agent that reduces postprandial hyperglycaemia has an important role to play in the handling type-2 diabetes mellitus. This agent does this by lowering the GI of carbohydrate-rich food and/or inhibiting the activities of α-glucosidase enzyme. This study shows that aqueous extract of Camellia sinensis has a great potential to reduce the undue postprandial hyperglycaemia.
... For the production of green tea, freshly harvested leaves are rapidly steamed or pan-fried to inactivate enzyme polyphenol oxidase [6]. This process approximately 10-15 minute in a process known as fixing [7]. The enzymes in leaf shoots will be deactivate in order to prevent oxidation and fermentation and to maintain IOP Publishing doi:10.1088/1757-899X/1108/1/012040 2 a green color. ...
... The main relevant enzymes in tea plants include polyphenol oxidase, peroxidase, catalase, and ascorbic acid oxidase. Fast, even and high-temperature fixing is a feature of green tea processing, and is important for high quality tea [7]. Green tea processing is then followed by rolling, shaping and drying. ...
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In industrial green tea processing, people usually use endless chain pressure (ECP) dryers and fluidized bed dryers. ECP dryers have disadvantages including case hardening, uneven dryness, high energy consumption and long drying time, while fluidized bed dryers still have disadvantages of long drying time and high hot air capacity to ensure tea leaves can be fluidized perfectly. Therefore, another alternative dryer is needed that can overcome the problems in the ECP dryer and fluidized bed dryer. This study aims to determine the comparison of drying characteristics between vibrating fluidized bed dryer (VFBD) that have been developed previously with microwave dryers. Drying condition on both dryer was set at 80oC, the airflow velocity at VFBD was 1.09 m/s. Result shows the time needed by the microwave at temperature to dry 500 grams of tea leaves to reach a constant weight is 24 minutes, whereas if using VFBD it takes 85 minute. In VFBD, the constant rate period takes 25% of total drying time, and the rest is critical and falling rate period. While in microwave drying, around 50% of total drying time is constant rate period and the rest is critical and falling rate period. The falling rate period in VFBD requires longer time, which is up to 75% of the total drying time. Highest drying rate in VFBD dryer was 0.08 gr water/gr solid.min, while microwave dryer was 0.14 gr water/gr solid.min.
... Therefore, it was thought that the components of tea leaves could be easily extracted using hot water. Steaming is a unique process of green tea manufacturing in Japan that can preserve the color, polyphenolic content, and antioxidant activity of tea leaves (Ahmed & Stepp, 2013). Thus, it can be inferred that steamed tea is more valuable than the functional characteristics of roasted tea (Donlao & Ogawa, 2018, 2019. ...
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Japanese green tea (Sencha) is mainly manufactured by six processing steps: steaming, primary rolling, rolling, secondary rolling, final rolling, and final drying. The morphology and microstructure of tea leaves were observed, and total polyphenol content (TPC) and total antioxidant activity indexed by FRAP and DPPH were evaluated in tea leaves and infusions during processing. Folds or wrinkle-like microstructures on the tea leaf surface increased during processing, particularly during the primary rolling (PR) step. Leaf shape also mainly collapsed during the PR step. In tea leaves, the values of TPC, DPPH, and FRAP during processing ranged from 189 to 283 mg GAE/g dry matter (DM), 2670–4363 μmol FeSO4/g DM, and 1519–2327 μmol TE/g DM, respectively, whereas in the hot water extraction as a tea infusion decreased and ranged from 14 to 135 mg GAE/g, 391–2961 μmol FeSO4/g DM, and 219–1049 μmol TE/g DM, respectively. These functional attributes increased mainly from steaming (ST) to rolling (RL) steps. The results indicated that the processing conditions at each step, especially at the steps for ST, PR, and RL, influenced the apparent quality of the final tea leaf products and the functional properties of tea leaves and infusions.
... (2,3). Green tea (GT), unlike black and oolong tea, is not fermented causing the active constituents in the plant to stay untouched (4,5). The main GT components are polyphenols, particularly cate chin (6). ...
... Tea (Camellia sinensis (Linnaeus) O. Kuntze) was first taxonomically described in 1753 by Carl Linnaeus in Species Plantarum. Two species of tea have been identified, namely black tea (Thea bohea) and green tea (Thea viridis) [1]. Four varieties of C. sinensis have been identified, including C. sinensis var. ...
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Tea is one of the most important non-alcoholic beverage drinks worldwide and gaining further popularity as an important health drink. It is served as morning drink for 2/3rd of world population daily. Although conventional breeding and propagation contributed significantly for last several decades for varietal improvement, due to the limitations of conventional breeding coupled with the demand for increasing productivity with lower cost of production, application of biotechnology becomes an alternative approach. Therefore, apart from a dozen of tea research institutes globally, several other groups are working on tea and related genera that have registered many valuable information with several achievements. The present review deals with progress in-depth of various aspects of biotechnological works such as micropropagation and alternative approaches, cell and organ culture techniques, genetic transformation, DNA markers as well as organelle genome and gene cloned from tea and related genera which will be valuable information for the workers working on various aspects of Camellia biotechnology.
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Appearance does not easily identify the dried plant fragments used to prepare teas to species. Here we test recovery of standard DNA barcodes for land plants from a large array of commercial tea products and analyze their performance in identifying tea constituents using existing databases. Most (90%) of 146 tea products yielded rbcL or matK barcodes using a standard protocol. Matching DNA identifications to listed ingredients was limited by incomplete databases for the two markers, shared or nearly identical barcodes among some species, and lack of standard common names for plant species. About 1/3 of herbal teas generated DNA identifications not found on labels. Broad scale adoption of plant DNA barcoding may require algorithms that place search results in context of standard plant names and character-based keys for distinguishing closely-related species. Demonstrating the importance of accessible plant barcoding, our findings indicate unlisted ingredients are common in herbal teas.
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Pu-erh (or pu'er) tea tasting is a social practice that emphasizes shared sensory experience, wellbeing, and alertness. The present study examines how variable production and preparation practices of pu-erh tea affect drinkers' perceptions, phytochemical profiles, and anti-oxidant activity. One hundred semi-structured interviews were conducted in Yunnan Province to understand the cultural and environmental context of pu-erh tea tasting. The gong fu cha dao ('way of tea' with 'effort,' 'work,' or 'skill') method of brewing tea through multiple infusions was employed to evaluate green and black pu-erh samples from smallholder agro-forests and terrace plantations. Ranking interviews, High Performance Liquid Chromatography (HPLC), and the 1-1-diphenyl-2-picrylhydrazyl (DPPH) assay were conducted to characterize color and taste profiles, Total Catechin Content (TCC), Total Methylxanthine Content (TMC), and free radical scavenging capacity (IC(50)). Significant variation was found among pu-erh samples based on: (1) agro-ecosystem mode of production by TCC (P<0.0001) and TMC (P<0.0265), (2) processing method for TCC (P<0.0001), TMC (P<0.0027), and free radical scavenging capacity (P<0.0001), (3) infusion sequence for TMC (P<0.0013), (4) taste rankings for TCC (P<0.0001), TMC (P<0.0001), and IC(50) (P<0.0059) and, (5) color rankings for TMC (P<0.0009) and IC(50) (P<0.0001). Samples rated as bitter and bitter-sweet contained the greatest TCC and free radical scavenging capacity. This research demonstrated that production environment, processing methods, and infusion sequence in preparing tea are related to the phytochemical profile, free radical scavenging activity, and flavor of tea. Findings contribute to the ethnomedical literature by supporting previous studies that have hypothesized that the taste of plants, particularly bitterness, may guide societies in the search for medicinal plants and beneficial phytochemicals.
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The genus Camellia includes some 82 species which are mostly indigenous to highlands of south-east India (Sealy, 1958). Tea is the most important of all Camellia spp. both commercially and taxonomically. Since all Camellia spp. do not produce the brew that goes into the cup that cheers (Banerjee, 1988a), taxonomy plays a major role in the identification of true teas among the Camellia spp. for commercial exploitation. Many non-tea species of Camellia are however used as ornamental plants.
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The publication of the third Angiosperm Phylogeny Group (APG) classification (APG III. 2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Botanical Journal of the Linnean Society161: 128–131) has resulted in the need for a revised systematic listing of the accepted families. This linear APG III (LAPG III) sequence of families is presented here. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 128–131.
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Nucleotide sequences of ribosomal RNA maturase (matK) regions in chloroplast (cp)DNA were determined to assess genetic diversity within cultivated teas. One hundred-eighteen cultivated teas from India, Bangladesh, Myanmar, Thailand, Laos, Vietnam, China and Japan were analyzed. The 1,230 aligned nucleotide sequences of the matK DNA of the cultivated teas showed 13 variations. These variations in the matK defined 10 different types (CJ, AA, AB, AC, AD, AE, IC, IM, TM and TV). By nucleotide alignment analysis, the matK nucleotide sequences in the samples from Japan and eastern China and from tea estates in India and Bangladesh were divided into CJ and AA types. On the other hand, the matK in the teas of Yunnan in China and southeast Asian countries shared 9 types (AA, AB, AC, AD, AE, IC, IM, TM and TV). The matK sequences of southeastern cultivars were fragmented into smaller population clusters as compared to the eastern samples. In addition, these matK types were classified into three groups. The CJ, AA and AB types were placed in the group Camellia sinensis (var. sinensis and var. assamica). The AC, IC, IM, TM and TV types had strong affinity to C. taliensis and C. irrawadiensis. AE and AD types with6-base insertions belonged to a third group. Results of the matK nucleotide sequence analysis indicated that the cultivated teas of India, Bangladesh,eastern China and Japan belonged to the group of C. sinensis. The cultivated teas in the estates of Southeast Asia region also belonged to C. sinensis. However, the native cultivars in Myanmar and southern China had a genetic similarity to C. taliensis and C. irrawadiensis. The native cultivars of Thailand and Vietnam will be associated with morphologically close taxa. In this study, we demonstrated that members of C. irrawadiensis and C. taliensis are popular cultivars found widely in the southeastern Asia. Tea cultivars of the AC, AD, AE, IC, IM, TM and TV types merit to be conserved for use as sources of desirable genes.
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We evaluated morphological, isozyme and biochemical diversity of a total of 87 accessions in the genus Camellia [Camellia sinensis var. sinensis (10), C. talinensis (7), C. sinensis var. dehungensis (3), C. crassicolumna (3) and C. sinensis var. assamica (64)]. Great variation of morphological characters was apparent within each taxa. Across the five taxa, all leaf and most flower quantitative characters showed significant differences while all fruit quantitative characters measured did not differ significantly, and, seven (i.e., life form, bud color, petal texture, pubescence on ovary, style number, stamen location and locule per fruit) of the 33 qualitative characters yield significant differences. As a whole, caffeine content had the highest variation with CV of 22.7%, water extract solid showed the least variation (13.4%) and content of polyphenols (20.0%) and free amino acids (18.8%) showed intermediate variations. Camellia taliensis and C. sinensis var. assamica had significantly higher content of polyphenols and water extract solid than in the other three taxa, while no significant differences were detected for the content of caffeine and free amino acids. For allozyme study, 14 loci presented good resolution, among which, nine loci (64%) were polymorphic in each taxon (AAT-3, FUM-1, 6PDG-1, G6PDH-1, G3PDH-1, ME-1, PGM-1, PGM-2 and SKD-1). The percentage of polymorphic loci (P) for each taxon was 21.4–50.0%. Mean heterozygosity per locus (H e ) varied 0.114–0.218. F ST value indicated that only 4.6% of the variations could be ascribable to genetic differences among taxa. Genetic relationships among the five taxa revealed by allozymes, were also exposed by the result of clustering of the morphological and biochemical characters.
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The early floral development of Camellioideae was studied. Two major evolutionary lineages were recognized for this subfamily. The earlier evolved lineage (Camellia, Polyspora, and Pyrenaria) has normally 11-14 perianth members, which are initiated in a continuous spiral and are differentiated into sepals and petals at late floral development, and numerous stamens initiated individually and centrifugally on the whole androecial region. The later derived lineage (Franklinia, Hartia, Schima, and Stewartia) has five sepals and five petals arranged in two whorls, and numerous individual stamens originating centrifugally from the five petal-opposed zones. Hartia-Stewartia and Franklinia-Schima further diverged as two branches - the former is characterized by having androecial fascicles and axile-basal placentation. The androecial fascicle is considered to be derived within this subfamily. The latter exhibits a higher degree of carpellary congenital fusion and axile-central placentaion, and as a whole, is concluded to be the most advanced group in the Camellioideae. A taxonomic treatment of the Camellioideae at the tribal level is also proposed.