Volatile compound responsible for aroma of tea

The flavor of tea can be divided into two categories: aroma, which consists mainly of volatile compounds; and taste, which consists mainly of non-volatile compounds.

Aroma is one of the critical aspects of tea quality which can determine acceptance or rejection of a tea before it is tasted. There are more than 630 compounds have been reported responsible in tea aroma.

The three basic types of tea; green, oolong and black have different quality characteristics, including aroma, taste and color, and appearance.

All of these aromas are generated from four main pathways: carotenoids as precursors, lipids as precursors, glycosides as precursors, and Maillard reaction pathway.

Carotenoids are important precursors of tea volatile compounds, especially the C9- to C13-aromas. Ionone and damascone are important C13-carotenoid-derived compounds that constitute an essential aroma note in black tea.

Tea contains many amino acids, but theanine, specific to the tea plant, is the most abundant, accounting for 50% of the total amino acids. Amino acid degradation is involved in the biogenesis of the tea aroma. Chlorophyll, carotenoids, lipids and volatile compounds are not major constituents in a tea brew but they also play an important role in the development of the aroma.

During black tea processing, including withering, rolling and fermentation, the lipids are degraded to produce flavor volatiles by hydrolytic or oxidative action of enzymes on glycolipids and phospholipids.

The major fatty acid derivatives include alcohols, aldehydes and lactones. C6 and C9 alcohols and aldehydes are key contributors to the “fresh green” odor of tea. Methyl jasmonate, an important fatty acid derivative, is a major contributor to the jasmine-like aroma of oolong tea.
Volatile compound responsible for aroma of tea

Epicatechins compound in tea

Green tea is another excellent dietary source of polyphenols. The most abundant the polyphenolic compound in green tea is epigallocatechin gallate (EGCG); other catechins such as epicatechin (EC), epigallocatechin (EGC) and epicatechin gallate (ECG) are also present.

The active constituents responsible for photoprotective efficacy in green tea are called epicatechins or epicatechin derivatives. These epicatechins are also commonly called as ‘polyphenols’ and are easily soluble in water and organic solvents like acetone, ethanol, etc.

During processing of tea, these epicatechins get polymerized and from more complex polymerized molecules called theaflavins and thearubigins. A typical black tea contains 3-10% epicatechins, 3-6% theaflavins, 12-18% thearubigins and other components.

Studies have shown that polyphenol provide antioxidants and anti-inflammatory activities in nature and have been shown to possess anti-carcinogenicity activity.
Epicatechins compound in tea

Green tea to burn fat

There are countless health benefits associated with drinking green tea. For centuries the people have been drinking and using green tea as cure for several elements. It is a fat buster extraordinaire.

Green tea is a major contributor to fat burning. The catechin polyphenols found in green tea effectively increases the metabolic rates of the body and food intakes.  With strong fat burning abilities, it can help burning about 266 extra calories a day.

Green tea contains three major components that promote fat loss: catechins, caffeine and theanine.

Studies suggest that green tea compounds promote fat loss by inhibiting both gastric and pancreatic lipase the enzymes that digest triglycerides, and fatty acid synthetase, the enzyme responsible for synthesizing fatty acids into the form in which they can be stored in the body’s adipose cells.

Research at Tuft University indicates that green tea activates fat burning genes in the abdomen to speed weight loss by 77 percent.

Research published in the Journal of Nutrition found that overweight adults who drank 4 to 6 cups of green tea daily lost at least 7 percent more abdominal fat than those who didn’t drink green tea.
Green tea to burn fat

Color of tea

Shade of color in made tea and the infusion of color are two attributes besides the aroma and taste in the evaluation of various kinds of tea.

When hot water is poured onto tea leaves, the compounds contained in the tea leaves are extracted and color appears, in this case of green tea, the desired color is greenish or yellowish green without any trace of red or brown color.

The liquid should remain clear on cooling without turbidity, and the infused leaf should be green with no sign of discoloration due to damage.

It is mainly determined by the chlorophyll content and the ration of chlorophyll A which is dark green in color and chlorophyll B which is yellow green in color.

When green tea is extracted for a long time, the color changes to a reddish one. Thus, when green is taken for example in a thermos to a picnic, the tea extract turns reddish brown in color and moreover the taste and aroma of the tea deteriorate.

The color of black tea is black in made tea and orange-red in an infusion. These colors are formed by the theaflavin and thearubigin. Theaflavin is yellow in clor and thearubigins is red in color.

Semi-fermented Oolong tea is generally green-brown color in made tea and a yellowish red color in an infusion.
Color of tea

Polyphenols in tea

Tea is the most widely consumed beverage in the world after water. The daily consumption is around 3 billion cups per day.

Regular intake of tea is associated with improved antioxidant status in vivo, which may contribute to lowering the risk of coronary heart disease, stroke, and certain type of cancers.

The polyphenols in tea mainly include the following six groups of compounds: flavonols, hydroxy-4-flavonols, anthocyanins, flavones, flavonols, and phenolic acids.

Among these, the flavonols mainly catechins are most important and occupy 60-80% of the total amount of polyphenols in tea.

The tea plant is known to contain seven kinds of major catechins and traces of various other catechin derivatives.

These catechins are present in all part of the tea plant; 15-30% are present in the tea shoots, and there is also a high content in the second and third leaves.

About 90-95% of the flavonols undergo enzymatic oxidation to products which are closely responsible for the characteristics color of tea infusion and its taste.

During the manufacturing of tea, the content of polyphenols increases slightly at the beginning of withering but decreases right after.

Although the trend for the changes of polyphenols appears similar in different varieties the absolute content of polyphenols are different among them.
Polyphenols in tea

Effect of Green Tea Bioactive Compounds on Bone Health

Epidemiologic evidence showed an association between green tea consumption and the prevention of age-related bone loss in elderly women and men. Green tea support healthy bones and teeth both by protecting osteoblast from destruction by free radicals. Green tea also found to inhibiting the formation of osteoclasts.

The green tea protects bone health by proposed mechanisms:
*Green tea and its bioactive components increased osteoclastic apoptosis through a caspase-3 activation mechanism.

*Bioactive ingredients in green tea enhance bone formation, by enhancing osteoblastogenesis and suppress bone resorption in various bone loss models.

Green tea polyphenols increase serum osteocalcin, bone mineral density (BMD), trabecular volume, strength of femur, trabecular thickness and bone formation.

*Green tea and its active components are proven to mitigate the deterioration of bone microstructure as well as the loss of bone mass and strength due to aging, aging plus sex hormones deficiency or chronic inflammation.

*Mitigating bone loss through antioxidative reaction.

*Mitigating bone loss through anti-inflammatory action. Green tea and theaflavin enriched tea plant extract reduces expression of inflammatory mediators and cytokines in animal models.

*Through its high content of fluoride and vitamin K1.
Effect of Green Tea Bioactive Compounds on Bone Health

Good quality of tea

The quality of tea is the summation of the desirable attributes comprising internal and external things like aroma, flavor, strength, color and briskness.

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 with aromatic, sweet and delicate are desired characteristics.

The quality of tea varies from garden to garden. Although the qualities of second flush it is still the best quality. This means good quality tea should be able to give several infusions from the same leaves.

The good quality tea also once adding with water, it will quickly sink to the bottom of the cup.

Gold tip or tippy eta leaves are considered to be of good quality. Hand-rolled tea leaves have a better tip than machine rolled ones.

The factors affecting the quality of include:
*Polyphenol and the enzyme content in tea leaves.
*The finest tea is from higher elevations of 900-2100 meters. Many high quality tea plants are cultivated at elevations of up to 1500 meters.
*Soil
*Processing technique

In general tea in bags is not of as good a quality as loose tea. But many of the better tea companies are combining the quality of loose tea with the ease and convenience of a tea bag with great success.
Good quality of tea

Health Benefits of Tea

Tea Beverage
In general a flurry of discoveries about tea's health benefits, plus renewed appreciation of its ancient heritage, has pushed tea to the fore. Its antioxidants appear to lower cholesterol levels, improve cardiovascular health and help guard against some cancers. And some experts believe its flavenoids may inhibit the growth of plaque on teeth.

Tea's active ingredients are caffeine in combination with the tannin that gives it its pungency and much of its aroma and flavor (which essential oils also enhance). The New York Academy of Medicine held a symposium on "Pharmacological and Physiological Effects of Tea" in 1955 and found that, for reasons they could not explain, tea, unlike coffee, does not cause nervousness, insomnia, or stomach irritation when drunk in quantity.

The scientists' tests showed a cup of tea gives both an immediate and a delayed lift without secondary depressing effects later on. They agreed tea is a good agent for relieving fatigue and aids clearness of thought and digestion alike.

The Tea Cure
For years, studies in China and Japan have shown that the folklore about tea does contain some truth -- it does promote longer life. Japanese smokers have only half the lung cancer rate as American smokers. In areas of Japan where the most tea is drunk, the rate of stomach cancer is the lowest. In a study of 6,000 Japanese women, those who drank 5 cups or more of green tea per day cut their risk of strokes by 50 percent.

"Drinking tea with meals in Japan and China," says a cancer researcher at the University of British Columbia, "is thought to be a major reason for low cancer rates in these countries." Long-term consumption of black tea -- the kind that most Americans and Europeans drink -- and of other foods such as apples containing chemicals called flavonoids was associated with a much lower risk of stroke in a study of 552 Dutch men.

Flavonoids are natural vitaminlike compounds. They make blood cells called platelets less prone to clotting, and act as antioxidants, countering the artery-damaging potential of highly reactive free radical chemicals. In the study, men with a high flavonoid intake had a 73 percent lower risk of stroke during 15 years of follow-up, compared with men with a low intake of flavonoids. The men in the study got about 70 percent of their flavonoids from drinking black tea.

Men who drank more than 4.7 cups of tea a day had a 69 percent reduced risk of stroke compared with men who drank less than 2.6 cups a day, said the researchers of the National Institute of Public Health and Environmental Protection in Bilthoven, the Netherlands. Tea also helps prevent tooth decay in several ways. It contains a solid dose of fluoride and works better than the antibiotic tetracycline. According to researchers at the Tokyo Dental College, it fights the kinds of bacteria in the mouth that cause gum disease and the eventual loss of the teeth. It also kills the greatest cavity-causing bacteria in the mouth, Streptococcus mutans.

In addition, researchers in Australia announced that a cup of tea could be the next weapon in the fight against skin cancer. A study by the Commonwealth Scientific and Industrial Research Organization revealed that mice made to sip black tea suffered 54 percent fewer cancers than those that drank water. Both sets of test animals were exposed to levels of ultraviolet rays that an average Australian receives.

Earlier studies on black tea have shown that it can be effective against some forms of cancer and may even prevent heart and liver disease.

Properties in green and black tea called antioxidants are thought to be active agents against skin cancer. In the past 10 to 15 years, a growing body of research has shown that foods and vitamins with a strong anti-oxidant effect may reduce the risk of many diseases, including cancer and aging. Human trials using black tea as a preventative against skin cancer began in Australia in 1997.
Tea Beverage