| It’s of great interest for flavor chemistry and scientific brewing of tea to study the water quality and tea brewing manner.Several common household water were used in our experiments and their physics and chemistry properties, micro structures and sensory qualities were determined. Then, trials for investigating the effect of different water on the quality, health compounds and function of green tea infusion were designed. Especially, we firstly studied the impacts of water on the sensory characteristics of green tea main monomers and antioxidant ability of EGCG. Moreover, whether separating tea infusion from tea leaves influence the quality and functional components of green tea were studied. The main results are as followed:1. Tap water, natural drinking water, mineral water and pure water had different physics and chemistry properties, and their tastes were different. In general, the tastes of pure water and mineral water were similar. The contents of total dissolved solids and pH value of water decreased significantly after boiling. Besides, the contents of elements in waters determined by Atomic emission spectrometer (ICP-AES) also decreased except Ca, Fe and S. Raman spectrum showed that water molecules had different vibration energies, so the sorting order of micro elements contents of water is tap water>natural drinking water>mineral water>pure water. The water will have adverse; taste if micro elements content is exorbitant.2. Water quality had great influence on the green tea infusion, especially on color and taste. Their sensory evaluation scores ranked as follows:mineral water> natural drinking water>pure water>tap water. However, the contents of aqueous extract and polyphenols in tea infusions made with pure water and mineral water were higher than that with other water. The polyphenol contents in different water were ranked as follows:pure water (10.0 mg/mL)>mineral water (8.28 mg/mL)>natural drinking water (8.06 mg/mL)>tap water (6.64 mg/mL). Moreover, the DPPH radical scavenging capacities of tea infusions brewed by different water were pure water (80.0%)> mineral water (77.5%)> natural drinking water (74.4%)> tap water (70.1%). These results suggested that mineral water and pure water are better than other water for brewing green tea.3. Mineral water was the best among the tested waters to keep the natural tastes of EGCG, theanine and glucose monomers, and tap water was not good for that. Furthermore, the color and antioxidant ability of EGCG dissolved by different water were significantly different. The order of EGCG antioxidant ability in different waters from strong to weak was pure water, natural drinking water, mineral water and tap water. The ABTS and DPPH free radical scavenging ability of pure water was higher than that of tap water by 13.0% and 23.8%. The pH of water might affect EGCG stability, and EGCG had complexation reaction with metal ions. In conclusion, mineral water was better for the taste of main monomers, and pure water was better for the antioxidant ability of EGCG solution.4. Whether separating tea leaves and infusions after the first brewing could influence the quality and components of green tea infusion were studied. For the first tea infusion, the separating treatment gave better sensory quality. For the second tea infusion, the separating treatment lead to better taste quality and higher extract contents. In general, the separating treatment caused the higher contents of amino acids and catechins, and lower contents of caffeine and aqueous extract. In conclusion, separating tea leaves and infusions after first brewing is not only good for tea infusion color and taste, but also good for keeping nutritional compounds and the health functions. |
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