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Saturday, June 15, 2019

Nutritional value of the tea and its types

Nutritional value of the tea and its types





Nutritional value of the tea and its types





Tea is the most beverege consumed after water. It is made with camellia sinensis leaves (family: Theaceae). The different types of tea are: green tea, oolong, white, black and Ilex. Healthy foods that contain active free radical scavengers are very popular today. The main chemical components of green tea include polyphenols, caffeine and amino acids

Tea also contains flavonoid compounds that have antioxidant properties that have many beneficial effects (Tea benefits). It is widely recognized that phenolic compounds in some foods have potential health benefits. Tea is related to the beneficial effects on human health with polyphenols as responsible components. India is one of the largest tea producing, exporting and consuming countries. This review confirms on the production, composition and beneficial effects of tea consumption on human health

Tea, a traditional drink originating in China, is the drink produced when the processed leaves of the tea plant are infused with boiling water, it is the oldest and most popular non-alcoholic caffeine. The tea plant is a small evergreen and evergreen tree that belongs to the Theaceae family. Its seeds contain a volatile oil and its leaves contain caffeine and tanin chemicals

 Description:


Scientific name: Camellia sinensis

Family: Theaceae

Common name: tea, tea bush, Cha, Chi

Leaves: bright and brilliant green

Flowers: fragrant, individually or in groups of two to four

Fruit: brownish green, containing from one to four spherical or flattened seeds

Origin: native to eastern, southern and south-eastern Asia, but today it is grown all over the world in tropical and subtropical regions


Nutritional properties


The tea includes polyphenols (phenols, tannins, catechins, flavonols, anthocyanidins and phenolic acids), alkaloids, amino acids, carbohydrates, proteins, chlorophyll, volatile organic compounds, fluorides, aluminum, tannins, minerals and trace elements. it provides folic acid (vitamin B9), some potassium and also magnesium. The greatest interest in tea and health comes from the high level of antioxidant tea polyphenols in green tea and black tea, polyphenols have beneficial effects on the circulatory system, while flavonoids act on the immune system

A group of chemicals that are responsible for the beneficial health effect of tea are polyphenols, which contain a group of plant chemicals named catechins. This type of antioxidant can protect the body's cells from oxidative damage which can lead to tumors. Tannins can help prevent heart disease and stop the course and prevent certain cancers. It acts on the nervous system to control the respiratory system and digestive system

The main chemical component of tea leaves:


Constituent: percentage (% dry leaf)

Polyphenols : 25
   Epi-gallocatechin gallate : 9-13
   Epi-catechin gallate : 3-6
   Epi-gallocatequina : 3-6
   Epi-catechin : 1-3
   Others :1-2
Flavonols and flavonols glycosides : 3-4
Flavanediols : 2-3
Polyphenolic acids and depsides : 5
Other polyphenols 3
Caffeine : 3-4
Theobromine : 0.2
Theophylline : 0.04
Amino acids : 4
Organic acids : 0.5
Monosaccharides : 4
Polysaccharides : 13-14
Protein : 15
Cellulose : 7
Lignin : 6
Lipids : 3
Chlorophyll and other pigments : 0.5
Ash : 5
Volatiles : 0.01-0.02


Tea quality and classification standards


After water, tea is the most consumed drink in the world with a per capita consumption of 120 ml / day. All tea is made from the leaves of the tropical perennial C.sensis. About 76% to 78% of the tea produced and consumed worldwide is black, 20% and 22% is green and less than 2% is long. After harvest, the difference in the color and shape of the tea leaves is due to the manufacturing process and all the various oxidation levels to which they are exposed. We can distinguish between the following type of tea:

Green tea

The main goal of green beer production is to preserve the natural polyphenols in the tea leaf so that the maximum amount of tea polyphenols is valuable in a cup of tea for good health. Due to the high temperature during steam cooking or roasting, the oxidizing enzymes of the polyphenols are desactivated and the leaves become biologically inactive. The different steps include: plucking, steam, lamination, during, selection and packaging. When making green tea, the tea leaves are steamed or roasted on the bread to inactivate the enzymes and dry them

Therefore, the components of the tea leaves are stored in dry tea leaves. When preparing tea leaves, for example 2.5 g in 250 ml of hot water for 3 minutes, about 30% of the solid materials are extracted in water. All teas are rich in polyphenolic compounds also present in red wine, fruit and vegetables. Green tea is a less fermented tea and has the highest amount of catechins than tea. The tea leaves are heated by roller immediately after the harvest to inactivate the polyphenol oxidase enzyme, which is able to oxidize the tea catechins in oligomeric and polymeric derivatives


  • Green tea leaves are not oxidized and do not ferment. It has the largest number of varieties, ech with its unique flavor and aroma. Treats swelling, allergies, acne and promotes weight loss

Black tea


The production of black tea involves the crushing of the tea leaves to promote the oxidation of enzymes and the subsequent condensation of the tea polyphenols in a process known as fermentation, which leads to the formation of flavinins and teubigo. In black tea, the microbiologically active molecules are Catechins and theaflavins. There are three forms of black tea produced: stick-shaped black tea, granular black tea and black tea bags 

Although they are made using similar processing techniques, the appearance of the end products is different. Stick-shaped black tea still retains the original shape of the tea leaves, which are easily recognizable, consisting of buds and tender leaves. Granular black tea consists from small, mechanically ground pieces, which the product to lose the original shape of the leaves. Black tea bags are granular black tea enclosed in filter paper bags with or without added flavorings


  • Black tea is a completely oxidized tea. It is generally stronger in flavor than the less oxidized ones. Black tea retains its flavor for several years and is the most consumed and drunk tea in the world. It cures anxiety, weight loss and headaches

Oolong tea


Oolong is a traditional Chinese tea produced through a unique process that includes wilting the plant in the presence of strong sunlight and oxidation before twisting and twisting. Oolong tea is a mixed of black and green tea and also called "semi-fermented". It thrives with characteristics of black tea and green tea, green tea finishing techniques and oxidation of black tea


  • Rich in polyphenols it can help stress, promote weight loss and increase metabolism

White tea


White tea is produced from new growth buds and young leaves that have been steamed to desactivate the oxidation of polyphenols and then dried. It hasn't healed and it's not rusty or just slightly rusty. White tea is considered one of the most expensive for the consumer and the most profitable for producers. The percentage of polyphenols is higher in the bud and gradually decreases with the age of the leaves. White tea has a high therapeutic value. Due to its characteristic, white tea is very famous among health-conscious people, especially in America and Europe


  • Higher than antioxidants, beneficial for stress, weight loss, detoxification

Pu-erh tea


Pu-erh or pu'er is a variety of aged dark tea and the fermentation is considered a style of tea production, in which tea leaves undergo microbial fermentation and oxidation after drying and curling. This tea improves with age

Cut-tear-curl (CTC)


The processing has three phases (crushing or cutting, tearing, curling). Tea leaves can be pulled by hand or harvested by machinery. Through the CTC machine, The sheets are processed and have a palletized appearance and always have broken dimensions. The method is less expensive to produce and produces a less bulky tea that would ferment faster and with a robust and uniform flavor

Different between green tea / black tea:


The main chemical difference between green tea and black tea is that the first tea contains simple catechins (polyphenols with a molecular weight <450 Da), while in the second, many of these have been oxidized and condensed, during the manufacturing process, to larger and darker colors. molecules including theaflavins (500-1000 Da) and thearubigins (> 1kDa). It is now observed that 50% of the unreacted precursors are composed of teasinenins (bisflavonols) formed by the oxidative coupling of EGC or EGCG. However, black tea still includes simple catechins, examples of which are epicatechin (EC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG). A cup of normally prepared green tea contains 0.5-1 g of catechins / L and black tea contains about one third of 0.5-1 g of catechins / L


Black tea / Green tea

Process : Longer fermentation / Short,no fermentation
Colour   : Red or Black / Green or yellow  
Taste     : Distinct flavour, added in sugar and/or milk / Sweet after bitter
Antioxidant : More Flavonoids / More Polyphenols 
Caffeine   : More / Less 
Quality : Depend on produced location / Better in fresh
Health benifits : Cardiovascular system to emply stomach / May irritate


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