Influence of water quality on nutritional and sensory characteristics of green tea infusion.

Impact of water quality on the nutritional and sensory characteristics of green tea infusion was
studied. The total soluble tea solids, catechins and L-theanine concentrations were significantly
higher in infusions prepared from water having lower total dissolved solids (TDS, 0.59 to 13.0
ppm), conductivity (1.12 to 26.20 mS), and pH (6.04 to 6.90). The difference in extractability was
explained using the mass transfer equation dNT/dt5kLAs(CTe2CTL); where dNT/dt-mass transfer
rate, kL-mass transfer coefficient, As-surface area, CTe-equilibrium concentration, and CTL-concentration
in bulk liquid. The major catechins reduced (�84–93%) in the infusions prepared from
water with higher TDS (315 to 338 ppm), conductivity (630 to 679 mS), and pH (7.65 to 8.05),
accompanied with undesirable color changes during storage following the first-order kinetics. Tea
cream and turbidity were much higher with water having higher calcium concentration (51.60 mg/
L). The study recommended water with low TDS, conductivity and pH for hot-infusions and
beverages.
Practical applications
The study was initiated to select a suitable type of water for the preparation of green tea infusion
and ready-to-drink (RTD) beverages. For infusion, the extractability of the nutrients as well as the
sensory characteristics are important. Accordingly, ultra-pure (UP), packaged drinking (PD), or
reverse osmosis (RO) water may be used for the preparation. But, in the case of RTD beverages,
the physical stability and visual appearance are also equally important for consumer acceptance, as
they are held in storage and distribution before being consumed. Furthermore, the results indicated
that stability of catechins need to be considered as a parameter for the selection of water.
Even though UP, PD, or RO meets all these criteria, economic considerations propel RO water for
RTD production. Thus the inferences obtained from this scientific study has practical relevance in
the selection of appropriate quality of water for the preparation of green tea beverages.