Effect of the type of brewing water on the sensory and physicochemical properties of light-scented and strong-scented Tieguanyin oolong teas

Abstract

Variations in the quality of brewing water profoundly impact tea flavor. This study systematically investigated the effects of four common water sources, including pure water (PW), mountain spring water (MSW), mineral water (MW) and natural water (NW) on the flavor of Tieguanyin tea infusion. Brewing with MW resulted in a flat taste and turbid aroma, mainly due to the low leaching of tea flavor components and complex interactions with mineral ions (mainly Ca²⁺, Mg²⁺). Tea infusions brewed with NW exhibited the highest relative contents of total volatile compounds, while those brewed with PW had the lowest. NW and MSW, with moderate mineralization, were conducive to improving the aroma quality of tea infusion and were more suitable for brewing both aroma types of Tieguanyin. These findings offer valuable insights into the effect of brewing water on the sensory and physicochemical properties of oolong teas.

Keywords: (+)-Catechin (PubChem CID: 1203); (−)-Catechin gallate (PubChem CID: 6419835); (−)-Epicatechin (PubChem CID: 72276); (−)-Epicatechin gallate (PubChem CID: 367141); (−)-Epigallocatechin (PubChem CID: 72277); (−)-Epigallocatechin gallate (PubChem CID: 65064); (−)-Gallocatechin (PubChem CID: 9882981); (−)-Gallocatechin gallate (PubChem CID: 199472); Brewing water; Taste-contributing metabolites; Tieguanyin oolong tea; Volatile components.

Fig. 1

Physicochemical properties of water samples. A & B: the pH & conductivity of waters samples; C & D: the concentrations of anions & metal cations in water samples; E: the correlation of water quality ions with their pH and conductivity. Original & Boiled: water before & after heating. PW: pure water; MSW: mountain spring water; MW: mineral water; NW: natural water. Data are means (±SD) of three replicates. ^a,b,c,d Different letters in the same column indicate significant differences between mean values (p < 0.05).

Fig. 2

The sensory attributes of tea infusions brewed with four different water samples. A: The flavor evaluation of LST and SST brewed with four different water samples; B: The pH of LST and SST tea infusions; C: The conductivity of LST and SST tea infusions; D: The color of tea infusions of LST and SST brewed with four different water samples. LST: light-scented Tieguanyin; SST: strong-scented Tieguanyin; PW: pure water; MSW: mountain spring water; MW: mineral water; NW: natural water. Data are means (±SD) of three replicates. ^a,b,c,d Different letters in the same column indicate significant differences between mean values (p < 0.05).

Fig. 3

The solid content in tea infusions brewed with four different water samples and the analysis results of PLS-DA of the non-targeted components. A: The solid content of LST and SST brewed with four different water samples respectively; B: The score scatter plots of PLS-DA of LST and SST; C & D: Heat maps of non-targeted components with VIP ≥ 1 in LST and SST. LST: light-scented Tieguanyin; SST: strong-scented Tieguanyin; PW: pure water; MSW: mountain spring water; MW: mineral water; NW: natural water. Data are means (±SD) of three replicates. ^a,b,c,d Different letters in the same column indicate significant differences between mean values (p < 0.05).

Fig. 4

Overview of volatile components in tea infusions brewed with four different water samples. A: Quantitative distribution of chemical classes of volatile compounds; B: Relative abundance of different types of volatile compounds; C & D: Venn plot of LST and SST. LST: light-scented Tieguanyin; SST: strong-scented Tieguanyin; PW: pure water; MSW: mountain spring water; MW: mineral water; NW: natural water. The numbers in the Venn plot represent the number of identified metabolites. Data are means (±SD) of three replicates. ^a,b,c,d Different letters in the same column indicate significant differences between mean values (p < 0.05).

Fig. 5

The analysis results of PLS-DA of the volatile compounds in tea brewed with four different water samples. A: Score plot of PLS-DA of LST; B: Score plot of PLS-DA of SST; C: Heat maps of volatiles with VIP ≥ 1 in LST; D: Heat maps of volatiles with VIP ≥ 1 in SST. LST: light-scented Tieguanyin; SST: strong-scented Tieguanyin; PW: pure water; MSW: mountain spring water; MW: mineral water; NW: natural water.