Effect of hydrogen carbonate in brewing water on the aroma of tea infusions.

Tea aroma is significantly influenced by hydrogen carbonate (HCO₃ ^-) in brewing water. This study investigated the impact of HCO₃ ^- in water on the aroma of brewed tea infusions using sensory evaluation, headspace solid-phase microextraction, and gas chromatography-mass spectrometry techniques. As the concentration of HCO₃ ^- in water increased, the purity of tea aroma diminished, while attributes related to cooked flavors and sweetness intensified; this effect is particularly pronounced at high temperatures and prolonged brewing times. HCO₃ ^- changed the concentration of volatiles, resulting in a significant decrease in concentrations of dimethyl sulfide, β-ionone, and other compounds. Furthermore, the presence of HCO₃ ^- markedly decreased EGCG content while increasing GCG content in tea infusion; these variations in catechin concentrations were correlated with changes in dimethyl sulfide and β-ionone concentrations. These findings enhance the understanding of flavor chemistry concerning tea and water, provide valuable insights for the scientific selection of tea brewing water.