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How does the water affect the tea brew?

How does the water affect the tea brew?
How does the water affect the tea brew?

Ask any tea lover and they'll tell you that the quality of the water you use to brew your tea makes all the difference. But why is that? What is it about water that can affect the taste of tea? Let's take a closer look at the science behind brewing the perfect cup of tea.

The water used to brew tea plays a factor in the colour and taste. For example, tea brewed using soft water produces brighter results than if it is brewed using temporary hard water.

The pH level of water affects the colour and taste of tea. For example, high pH water that contains bicarbonate makes the tea look darker brown because it ionises the tea polyphenols more. On the other hand, lower pH levels (as in lemon teas) make the infusion turn yellow. As for taste, some teas are better suited to softer water--such as orthodox Assam leaf teas--while others like high grown Ceylon and CTC manufactured teas taste better with temporary hard water.

Why is it not recommended to boil water more than once when making tea?

The taste, colour and mouth feel of tea all result from the combination of two primary elements: polyphenols and caffeine. By themselves, each one is astringent; however, when mixed together they produce a less harsh effect.

Did you know that water dissolved gases? These gases interact with the carbon dioxide (CO2) to create an acidic environment.The acidity level of the water you use influences how tea polyphenols ionise, which in turn affects the stability of said complex.

When you boil water, it releases carbon dioxide slowly over time. If you re-boil the water, it will actually lower the amount of carbon dioxide even more. This shift changes the levels of acidity in the water and affects how much caffeine and polyphenols are present. It also alters both the colour and flavour of your brew.

Therefore, use freshly boiled water to make tea, as boiling water twice will change the taste of the final product.

Using twice boiled water will negatively impact the taste of tea, so we only use freshly boiled water to make our tea.

Can the quality of tea be affected by over-boiled water?

If you boil water for too long, it will dramatically affect the quality of your tea. The desirable brisk taste of tea is created by the interaction of two of its main components, caffeine and polyphenols. Each component is harsh on its own but as a complex the compounds moderate each other. Acid levels in water can affect the behaviour of these components.

The water we drink contains minerals and gases that it absorbs from the ground and air. For example, carbon dioxide absorbed by air makes water slightly acidic, which then affects its colour and taste. When water is heated, this acidity level changes; however, if you let the boiled water cool down and reheat it again (or "re-boil" it), the levels of acidity will be different. This then produces tea of a different colour or strength, which ultimately doesn't make for a great cup of tea.

When tea is cooled, why does it become cloudy?

The 'tea cream' that you see when black tea cools is actually a colloidal precipitate. When cooled below 400 C, this weak complexion forms between the caffeine and polyphenols in the tea leaves (theaflavins and thearubigins). However, don't worry--this creaming down process varies from tea to tea. In black tea without milk, complexation rarely occurs because there is only 4% of caffeine present.

A similar chemical reaction occurs between the milk protein casein and various polyphenols found in tea with milk. More casein is available in milk tea, which results in a greater complexion and larger precipitation.

Why does tea get scummy, and how can I avoid it?

The scum is caused by the high molecular weight components that result from the presence of calcium and bicarbonate ions at the surface of liquid water.

There are two ways to remove the scum.

  1. By filtering out the calcium ions,

  2. By adding acids, we can convert bicarbonate ions to carbon dioxide.

A cup of very strong tea has very little scum. This is because the acidic tea polyphenols partly neutralise the bicarbonate ions, creating a less favourable environment for scum to form. It should be noted that less than one mg of scum is usually formed in a cup of tea and it is not known to be harmful to human health.

So, there you have it! The next time you're brewing a pot of tea, be sure to use distilled or filtered water for the best results. And if you want to get really scientific about it, aim for a pH level of 7. Happy brewing!


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