What is the ideal water temperature to make expresso coffee?
It is very important that this is the answer for expresso specifically
and not drip coffee methods.

Hello Keywestjimmy,

According to the research article titled ?Influence of extraction
temperature on the final quality of espresso coffee? published in the
Journal of the Science of Food and Agriculture, the optimal water
temperature  for Arabica, Robusta Natural and Robusta Torrefacto blend
Espresso Coffee was 92 °C.

?The aim of this work was to investigate the effects of water
temperature (88, 92, 96 and 98 °C) on the final quality of three types
of EC (Arabica, Robusta Natural blend and Robusta Torrefacto blend) in
order to select the optimal temperature. Volatile compound (analysed
by Static headspace gas chromatography/mass spectrometry) and sensory
flavour profiles were the most relevant parameters, whereas
physicochemical, taste and mouthfeel parameters were not very useful
for selecting the water temperature. For Arabica and Robusta Natural
blend ECs, 92 °C was the optimal water temperature. For Robusta
Torrefacto blend EC the overall acceptability might lead to the
selection of 88 °C as the ideal water temperature, but the high
percentages of key odorants related to roasty and earthy/musty
flavours and the  not hot enough  perception dictated the selection of
92 °C in this case as well.?

Part of this paper was presented at the 19th International Conference
on Coffee Science, Trieste, Italy

Journal of the Science of Food and Agriculture
Volume 83, Issue 3 , Pages 240 - 248

Wiley InterScience 
http://www3.interscience.wiley.com/cgi-bin/abstract/102523068/ABSTRACT



According to the National Coffee Association of USA, the water
temperature should be between 195 - 205 degrees Fahrenheit .

?Your brewer should maintain a water temperature between 195 - 205
degrees Fahrenheit for optimal extraction.  Colder water will result
in flat, underextracted coffee while water that is too hot will also
cause a loss of quality in the taste of the coffee.  If you are
brewing the coffee manually, let the water come to a full boil, but do
not overboil.  Turn off the heat source and allow the water to rest a
minute before pouring it over the grounds.?
The National Coffee Association of USA 
http://www.ncausa.org/i4a/pages/index.cfm?pageid=71


Coffeeresearch.org claims the water temperature should be stable and
somewhere between 92-96°C.
http://www.coffeeresearch.org/espresso/potential.htm



Search terms:
Ideal espresso water temperature
Espresso water temperature


I hope the information provided is helpful!

Best regards,
Bobbie7

How do you "overboil" water?  Are dissolved gasses important?

Ian G.

Ian,
Yes, when making tea or coffee, freshly boiled water should be used. 
I don't know what happens when it is boiled longer, but the water does
lose something.

As to the temperature for making coffee, an expert recommended 94°c
for brewing normal coffee, so that seems to be the optimum
temperature, regardless whether espresso or whatever.

Myoarin

Tap water and even spring water is not pure.  When water evaporates,
the minerals stay behind.  This puts a higher concentration of
minerals in the remaining water.  That is why you do not boil water
for too long.

Curious, my kettle has huge lime deposits.

I assume those came out of the water, which suggests that boiling
water /extracts/ minerals.

A conundrum.