Famous nutritionist Yu Ruomu pointed out: “According to modern research in medicine, biology, and nutrition, most of the components that regulate human metabolism are also present in Tea.” Scientific analysis has identified over six or seven hundred substances in tea, including organic chemical components such as polyphenols, alkaloids, proteins, amino acids, vitamins, pectins, organic acids, polysaccharides, sugars, enzymes, pigments, etc. These can be summarized into several categories.
I. Polyphenols
Polyphenols are a collective term for phenolic organic compounds found in tea, making up 15% to 35% of its total weight. The primary component affecting taste is tannin, which imparts astringency. Catechins account for approximately 70% of the total polyphenol content and are crucial in determining the color, aroma, and flavor of the tea.
Polyphenols are a significant class of compounds distinguishing tea from other plants and are the primary components responsible for tea's health benefits. The most notable function of polyphenols is their antioxidant properties, acting as a preservative for the human body. A well-known comparison of antioxidant capacities indicates: 2 cups of tea = 4 apples = 5 onions = 7 cups of orange juice. According to Professor Yang Xianqiang, a doctoral supervisor at Zhejiang University, polyphenols can inhibit and prevent the formation of free radicals produced by human metabolism, protecting internal organs and delaying aging.
II. Alkaloids
The alkaloids in tea include caffeine, theobromine, theophylline, and adenine. Caffeine is the most abundant, giving tea its characteristic bitterness, accounting for 2% to 5% of the tea's total weight; the other alkaloids are present in much smaller quantities.
The content of caffeine varies significantly across different parts of the tea plant, with the highest concentration in the leaves and lower amounts in the stems. In new shoots, caffeine levels decrease as the leaves age and change seasonally, typically higher in summer than in spring. Caffeine is easily soluble in water and is an important component contributing to the taste of tea, as well as a distinguishing feature between real and fake tea. Caffeine has various pharmacological effects on the human body, such as stimulating alertness, promoting diuresis, improving blood circulation, and aiding digestion.
III. Proteins
Although proteins make up 15% to 30% of tea, less than 2% is soluble in water. Based on drinking 10 grams of dried tea daily, the intake of protein would only be 0.2 grams. Considering the daily requirement for protein is 70 to 90 grams, the contribution of tea to protein intake is negligible.
IV. Amino Acids
Amino acids, the building blocks of proteins, constitute 1% to 4% of the total weight of tea. Twenty-six types of amino acids have been identified in tea, including theanine, glutamic acid, and asparagine, among others. The total amount of amino acids fluctuates significantly by season, with the highest levels in spring, lowest in autumn, and intermediate in summer, contributing to the fresh and pleasant taste of spring teas.
Amino acids are the main contributors to the fresh and refreshing flavor of tea, balancing the bitterness from polyphenols and caffeine while also developing different aromas, making them an essential part of high-quality teas.
V. Sugars
Sugars in tea include monosaccharides, disaccharides, polysaccharides, and small quantities of other sugars, comprising 20% to 25% of the total weight. Only about 5% of these sugars dissolve during brewing, making tea a low-sugar beverage suitable for both healthy individuals and those with diabetes.
Monosaccharides and disaccharides, known as soluble sugars, are easily soluble in water and contribute to the taste of tea. Polysaccharides, which do not dissolve in water and make up more than 20% of the dry weight, are crucial for assessing the tenderness of tea. Lower tenderness is associated with higher polysaccharide content, while higher tenderness corresponds to lower levels.
VI. Pectin
Pectin and related substances in tea are metabolic products of sugars, accounting for around 4% of the total weight. Their presence facilitates the shaping process during manual rolling in Tea processing and affects the viscosity of the tea liquor. Soluble pectin is one of the main components contributing to the thickness and glossiness of the tea liquor.
VII. Lipids
Lipid substances in tea include fats, phospholipids, glycolipids, sugar esters, and sulfur esters, constituting roughly 8% of the total weight. They play a positive role in forming the aroma of tea.
VIII. Tea Pigments
Pigments in tea consist of lipophilic and hydrophilic pigments, making up only about 1% of the total weight. Lipophilic pigments, which are not water-soluble, include chlorophyll, xanthophylls, and carotenoids. Hydrophilic pigments comprise flavonoids, anthocyanins, and oxidation products of polyphenols, such as theaflavins, thearubigins, and theabrownins.
Lipophilic pigments are primarily responsible for the color of dried tea and the appearance of infused leaves. The color of the six major tea types is closely related to the content, composition, and transformation of pigments in the tea.
Modern medical science considers the extraction and practical application of tea pigments in medicine as a sign of the emergence of tea medicine and the transition from national Drink to national medicine.
IX. Vitamins
Tea contains abundant vitamins, making up 0.6% to 1% of the total dry weight. Vitamins are divided into water-soluble and fat-soluble categories.
Fat-soluble vitamins include vitamin A, vitamin D, vitamin E, and vitamin K, with vitamin A being the most abundant. Fat-soluble vitamins are not water-soluble and cannot be directly absorbed through tea consumption.
Water-soluble vitamins include vitamin C, vitamin B1, vitamin B2, vitamin B3, vitamin B5, vitamin B11, vitamin P, and inositol, with vitamin C being the most abundant. People can absorb certain nutrients through tea consumption.
Vitamins are essential for the human body, and they can be obtained in moderate amounts through Tea drinking.
There are many more organic chemical components in tea, but due to space constraints, they will not be detailed here. In addition to organic components, tea also contains inorganic components, primarily phosphorus, potassium, calcium, magnesium, iron, etc., collectively referred to as ash. Ash content is one of the requirements for tea export inspections, generally not exceeding 6.5% for exported samples. Generally speaking, the more water-soluble ash content, the better the quality of the tea.
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