Tea - A General Overview

Camellia sinensis var. sinensis

• Originated in China - sinensis is derived from the word for China in Latin
• Smaller leaves
• Resistant to colder temperatures

Camellia sinensis var. assamica

• Native to the Assam region in northeastern India
• Larger, broader, and more robust leaves
• Adapted to warm, humid climates

• Chamomile: Made from whole or crushed flowers of chamomile - a daisy-like plant. Has a yellow appearance, and is steeped in hot water
• Rooibos: Rooibos (in Afrikaans) - literally meaning red bush, is a herbal tea made from the leaves of the rooibos plant, native to the Western Cape in South Africa. It gets its name from the red appearance of the leaves after they have undergone oxidation ^[3]. It can be enjoyed in many ways, uniquely as a 'red cappuccino', where ground coffee is substituted for finely ground rooibos leaves, which are extracted in a similar way in an espresso machine before the addition of foamed milk ^[4]
• Ginger: Prepared from the rhiozme (underground stem) of the ginger plant, which is commonly known as ginger root. Ginger tea is usually made by steeping slices of ginger root in hot water, and is often complimented with lemon, sugar or honey

Landrace

• Landraces are plant populations that have naturally adapted to a specific local environment over time, typically without human intervention
• 'A landrace is a dynamic population(s) of a cultivated plant that has historical origin, distinct identity and lacks formal crop improvement, as well as often being genetically diverse, locally adapted and associated with traditional farming systems' ^[5]

Field Clone

• A field clone is a cultivar (cultivated variety) selected from plants in the field based on desirable traits, such as flavour, disease resistance, processing suitability, yield, and more
• There are several methods for cloning tea plants, with the most common being the use of cuttings. A healthy shoot with a few leaves is taken, treated with a rooting hormone, planted in soil, and left for several weeks to allow roots to develop. This results in a genetically identical plant, and is an example of asexual reproduction
• 'A cultivar, as a taxon, is an assemblage of plants that (a) has been selected for a particular character or combination of characters, and (b) remains distinct, uniform, and stable in these characters when propagated by appropriate means' ^[6]

Open pollination

• Open pollination refers to the natural fertilisation process where tea plants are pollinated by insects, wind, or other natural means without interference by humans
• This process can result in the creation of favorable new varietals and contributes to a genetically diverse crop population, however it also leads to inconsistency among the crops

Controlled Hybridization

• Some varietals excel in certain traits but fall short in others. By selectively crossbreeding them, new varietals with significantly improved characteristics can be developed
• There are many research stations around the world performing this sort of work, such as the Tea and Beverage Research Station in Taiwan, which has produced over 20 cultivars, including the well-known Jin Xuan variety ^[7]

White Tea

• Minimally processed tea with very little oxidation
• Known for its delicate, subtle flavor profile

Yellow Tea

• Rare tea that undergoes a unique "yellowing" process
• Similar to green tea but with a mellower flavor

Green Tea

• Unoxidized tea that preserves the natural color of the leaves
• Known for its fresh, grassy flavor profile

Oolong Tea

• Partially oxidized tea, between green and black tea
• Wide range of flavors depending on oxidation level

Black Tea

• Fully oxidized tea with a robust flavor
• The most common type of tea consumed worldwide

Dark Tea (Pu-erh)

• Post-fermented tea that improves with age
• Known for its earthy, woody flavor profile

• Turkey: Tea is a large part of Turkish culture, and you'll spot it everywhere you go. The average consumption of 3.16 kg/capita works out as 3-4 cups of tea a day. Black tea is the tea of choice in Turkey, and the state owned company Çaykur reports that they purchase approximately 55-60% of the fresh tea produced in the region, depending on the year ^[11]. Turkey used to subject tea exports to a 145% tariff to protect domestic production, but this has since been reduced, for example, there is now no tariff on tea imported into the UK ^[12]
• Ireland: Tea was introduced to Ireland less than 300 years ago, and it is the hot beverage of choice. Barry's and Lyons, both originating at the beginning of the 20th century in Ireland, are two favourites. Barry's is still family owned, and makes up nearly 40% of tea sales in Ireland ^[13]. Irish Breakfast Tea is a a blend of black teas known for its high Assam content — a tea from the Assam region in northeastern India — characterised by a strong, malty, and robust flavor

Dry Leaf Composition

Figure 3: Pie chart showing the composition of tea by percentage of dry weight ^[14]

Brewed Green Tea Composition

Figure 3: Pie chart showing the composition of a typical green tea beverage, %wt/wt Solids ^[15]

Brewed Black Tea Composition

Figure 3: Pie chart showing the composition of a typical black tea beverage, %wt/wt Solids ^[15]

• Polyphenols: Polyphenols are groups of chemical compounds called phenols, and the polyphenolic fraction of tea represents 30 to 40% of the dry leaf content ^[15]. Most of this can be acccounted for by flavonoids, a large class of naturally occuring compounds in plants. They fall into six groups, with flavanols and flavonols making up the majority of them in tea. The major flavanols of interest in tea are EC (epicatechin), ECG (epicatechin gallate), EGC (epigallocatechin) and the most abundant, EGCG (epigallocatechin gallate) ^[16], there are 4 more of less significance. Together, these account for around 25% of the dry leaf content. Flavonols make up a much smaller percentage of the dry leaf content, and include kaempferol, quercitin, and myricitin. Polyphenols are responsible for the bitterness in brewed tea and the astringency, a drying, roughing, and puckering sensation in the mouth, similar to what is felt when drinking a dry red wine ^[17]
• Caffeine: Caffeine is the most widely consumed central-nervous-system stimulant in the world, and accounts for around 1.5-4% of the dry weight of tea leaves ^[18]. It is part of the alkaloids, a broad class of naturally occurring organic compounds that contain at least one nitrogen atom. Alkaloids are secondary metabolites that generally mediate ecological interactions, providing a selective advantage to the organism rather than contributing directly to its growth, development, or reproduction. Many alkaloids have a bitter taste ^[19], and caffeine is no exception, acting as a natural insecticide due to its bitterness. Theobromine is another alkaloid in tea, but exists in much smaller quantities
• Amino Acids: There are around 500 amino acids that exist in nature, and they are essential building blocks that construct protein. While these only make up 4% of the dry leaf content, they are of significant importance. Making up over 50% of these amino acids is L-theanine ^[20], which is of interest due to its contribution to the desirable umami qualities of tea ^[21], and its synergistic effect with caffeine ^[22]
• Carbohydrates: Carbohydrates, one of the 3 macronutrient groups, are molecules comprised of carbon, hydrogen and oxygen. Monosaccharides are the simplest form, followed by disaccharides (two monosaccharides joined together), oligosaccharides (generally 3-10 monosaccharides joined together) and finally polysaccharides, which are very long chains of monosaccharides. Cellulose, a polysaccharide and key structural component of plant cell walls, makes up around 7% of the dry leaf weight, however it doesn't make it into the final cup due to its insolubility in water. It is for this reason that it is well-suited for making teabags. Many carbohydrates within the dry leaf do make it into the final cup, such as sucrose, myo-inositol, glucose and fructose ^{[23] [24]}