Effect of Water Hardness on Catechin and Caffeine Content in Green Tea Infusions

Abstract

The health benefits of green tea are associated with its high catechin content. In scientific studies, green tea is often prepared with deionized water. However, casual consumers will simply use their local tap water, which differs in alkalinity and mineral content depending on the region. To assess the effect of water hardness on catechin and caffeine content, green tea infusions were prepared with synthetic freshwater in five different hardness levels, a sodium bicarbonate solution, a mineral salt solution, and deionized water. HPLC analysis was performed with a superficially porous pentafluorophenyl column. As water hardness increased, total catechin yield decreased. This was mostly due to the autoxidation of epigallocatechin (EGC) and epigallocatechin gallate (EGCG). Epicatechin (EC), epicatechin gallate (ECG), and caffeine showed greater chemical stability. Autoxidation was promoted by alkaline conditions and resulted in the browning of the green tea infusions. High levels of alkaline sodium bicarbonate found in hard water can render some tap waters unsuitable for green tea preparation.

Quality characteristics of green Tea's infusion as influenced by brands and types of brewing water

“…[ 21 ] in which pH of tea infusions decreased significantly (p < 0.05) after brewing with hard alkaline water. This indicated that the brewing process had an effect of lowering the pH value of tea infusion [ 6 ]; Xu et al. , 2017) that might be due to the extraction of compounds in the tea leaves such as organic acids, phenols, carboxylic groups, and amino acids.…”

“…reported that interaction between catechins and water components and caused the flavour profile of the infusions to be affected by the water composition. The use of tap water for tea preparation is the most common method used by casual tea consumers [ 6 ]. However, the sensory preferences for tap water infused tea were inconsistent which might be due to the variation of water composition of tap water in different regions.…”

“…It was suggested that using mineral water to brew green tea infusion could significantly influence the quality attributes of the brew. Mineral salts can exert a variety of effects on extraction mechanism of green tea infusion [ 6 ].…”

Effects of in vitro simulated digestion on the antioxidant activity of different Camellia sinensis (L.) Kuntze leaves extracts

“…Theaflavins are present in smaller amount in fermented teas [23]. Caffeine is another characteristic component of tea and is present in considerable amount, almost regardless of the kind of tea [24][25][26].…”

Anti-Influenza with Green Tea Catechins: A Systematic Review and Meta-Analysis

“…However, EGCG bioavailability shows high interindividual variability related to gastrointestinal absorption, stability of the molecule, nutritional environment, and administration conditions. It is important to note that green tea catechins are more stable at low temperatures and acidic pH conditions [ 20 , 21 , 22 ]. An in vitro study showed that EGCG catechins prevented influenza virus replication by blocking hemagglutinin (HA) in the adsorption phase [ 23 , 24 , 25 ].…”