Green tea is a rich source of polyphenols. These natural compounds are recognized for their presence in many plant-based foods and contribute to the characteristics of green tea.
Understanding Polyphenols
Polyphenols are a large and diverse group of chemical compounds found abundantly in plants. These compounds are responsible for the color, taste, and aroma of many plant foods.
Polyphenols are broadly classified into various subgroups, such as flavonoids, phenolic acids, lignans, and stilbenes. Green tea, along with fruits, vegetables, herbs, and spices, is a notable dietary source of these plant-based compounds.
Key Polyphenols in Green Tea
Green tea is particularly rich in a type of polyphenol called catechins, which are flavan-3-ols. Catechins constitute a significant portion, up to 30%, of the dry weight of green tea leaves. These compounds are distinct from those found in black tea, where fermentation processes alter the catechins into different forms.
The most abundant and well-researched catechins in green tea include epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC), and epicatechin (EC). EGCG is often the most prevalent catechin, sometimes accounting for 50% to 80% of the total catechin content in green tea. A typical brewed cup of green tea can contain a substantial amount of EGCG, potentially ranging from 200 to 300 mg.
Enhancing Polyphenol Intake from Green Tea
To maximize the extraction of polyphenols from green tea, several factors during brewing are important. Water temperature plays a role, with studies suggesting that brewing at 80-85°C (176-185°F) can be optimal for catechin extraction without introducing excessive bitterness. While some research indicates that higher temperatures, such as 100°C, can extract more total polyphenols, it may also lead to the degradation of heat-sensitive compounds like EGCG.
Steeping time also influences polyphenol content. A brewing time of 3 to 5 minutes is often recommended to extract a good amount of catechins. Longer steeping times, up to 10 minutes, can further increase polyphenol concentration, though this might also enhance bitterness. The quality and type of green tea leaves, such as loose-leaf varieties or powdered matcha, can also affect the polyphenol yield.
Proper storage is another factor in preserving polyphenol content. Polyphenols are sensitive to heat and light. Storing green tea in a cool, dark, and airtight environment helps to maintain the stability of its polyphenols. Lower storage temperatures help retain higher levels of polyphenols and catechins.