Brewing conditions and post-brewing handling shape the catechin profile and stability of tea infusions.

This study investigated how brewing conditions and water mineralization affect catechin extraction and composition, and catechin stability during heating and acidification in green tea. Commercial green and black teas were brewed with boiling water or under manufacturer-recommended conditions. Catechins and caffeine were quantified by HPLC, with total polyphenols and DPPH radical-scavenging activity also determined. Brewing with boiling water increased catechin extraction, with a preferential increase in gallated catechin content. Increasing water mineralization reduced catechin extraction and decreased the relative abundance of EGCG. In the selected green tea infusion, EGCG retention after 1 h incubation at 80 °C decreased markedly with increasing water mineralization, from 38.4% in distilled water to 1.4% in mineral water. Acidification with lemon juice maintained EGCG retention at approximately 95% irrespective of water type and largely preserved DPPH radical-scavenging activity. These findings demonstrate that brewing and post-brewing conditions affect catechin content, relative catechin composition, and stability.