Catechin

Catechins are a class of flavonoid polyphenols found most abundantly in green tea, unfermented cacao, and some fruits. They are among the most studied plant-derived antioxidants, with epigallocatechin gallate (EGCG) in green tea attracting the most clinical research attention.

Catechins belong to the flavan-3-ol subclass of flavonoids and are characterized by a benzopyran ring structure with hydroxyl groups that confer their antioxidant and metal-chelating properties. The major catechins in green tea are: epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), with EGCG comprising approximately 50–60% of green tea's total catechin content.

In the zero-proof beverage context, catechins are important for two reasons: flavor and function. Functionally, EGCG has been studied for effects on metabolism, cardiovascular risk, cognitive function, and anti-inflammatory pathways, with a growing evidence base that supports cautious functional claims. Flavor-wise, catechins are primary contributors to the astringency of green tea — the drying sensation that some consumers love and others find off-putting. Managing catechin extraction levels (through water temperature, steeping time, and leaf grade) is the primary craft challenge of tea-based zero-proof beverages.

In kombucha production, the catechins in the tea base are transformed during fermentation by the SCOBY microbiome. Bacterial enzymes and organic acids modify catechin structures, reducing astringency and producing new phenolic compounds not present in the original tea. This transformation is part of what gives fermented tea beverages a distinctly different flavor profile from both the unfermented tea and from simple tea dilution.

A nutritional nuance: catechin bioavailability from beverages is highly variable and is affected by food matrix, gut microbiome composition, and individual metabolism. Estimates suggest only 10–30% of consumed catechins reach systemic circulation. Food pairing and fermentation can increase bioavailability — a practical argument for consuming catechin-rich zero-proof beverages with meals rather than on an empty stomach.