Is it OK to re-boil water when making coffee?
Is it just an old wives’ tale?
My dad always told me never to re-boil water when making tea or coffee. I though he was just a little potty – until I started asking other people.
There appears to be two main lines of thought on this:
- When water boils it evaporates (of course!), therefore the salts and minerals that are present in the water will become more concentrated. I haven’t tested this, although I would assume that some might prefer coffee made with harder water (so re-boiling might be desirable), whilst other (perhaps the majority?) prefer a lower concentration of mineral; i.e. softer.
- Water (from the tap) contains dissolved oxygen, and oxygen is generally considered positive for the taste of the coffee. When the kettle boils some of the oxygen basically boils off, and re-boiling will remove even more.
Taste differences aside, if you use a percolator then re-boiling is really bad as percolators often depend on dissolved oxygen to actually function at all, so fresh water is essential.
Taste and waste!
The taste of coffee is altered by boiling water (i.e. it burns the coffee), so if you are making a quick Whole Bean (or Instant), then don’t actually boil the water. Switch off before it boils, for the best flavour.
There is a downside, however, of emptying a warm kettle and refreshing. It consumes more energy and wastes water. Try not to do that and only heat the water you need, as long as it’s more that the minimum your kettle requires to operate safely.
Espresso machines usually get to around 90°c (i.e. not reaching the normal boiling point of 100°c), so there’s another good reason – if you need another – to drink Espresso and its derivatives. Personally, I always use fresh filtered water for Espresso and that makes a difference too, for sure.
For the tea connoisseur
Actually, for tea it appears to be a bigger concern, where the dissolved oxygen makes a more significant difference to the taste – especially to specialist or connoisseur teas.
Frankly, if you’re making a cup of instant and piling in the sugar – well, you’re on your own and no-one minds if you re-boil.
For everyone else, the general view seems to be that water should always be fresh, and heated to below boiling temperature.
What do you think?
What’s your opinion? Do you like using re-boiled water? Do you prefer hard water or soft water?
Please submit your comments below!