Does it matter if I change the water in my kettle each time I boil it?
If you want to make the most flavorful brew, using fresh water every time you boil is important. Water contains dissolved oxygen, which helps bring out flavors from tea and coffee. When it’s brought to a boil, oxygen is released and minerals are concentrated.
Barry Swanson, PhD, a food science expert with the Institute of Food Technologists, explains that the oxygen in the water reacts with the aromatic compounds in tea and coffee to produce flavor. A greater concentration of minerals can give your drink a metallic tang.
“The ultimate reason is taste,” says Rich Avella, production manager, coffee and tea, for Peet’s Coffee & Tea. When you boil water over and over, “you lose some of the complex aromatics and details in flavor. When you get into quality teas and coffees—like food—you really enjoy those nuances.”
Lisa Boalt Richardson, president of the Southern Association of Tea Businesses, agrees that tea will taste flat if there isn’t enough oxygen in the water. She says when brewing tea to avoid distilled water, because it’s already been boiled to remove impurities.
Avella suggests an easy test, especially if you use very high-quality tea or coffee: Just brew two identical cups, one with freshly boiled water and another using twice-boiled water. Then do a side-by-side comparison, paying attention to the contrasts in flavor and aroma. “It’s easy to see the difference,” he says.