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today we're going to talk about a topic
that has been heavily heavily requested
in the past via messages for D ABS
emails all that stuff it's also been a
topic that's caused some confusion in
previous videos I've made we're talking
about what is the perfect temperature to
use when brewing a cup of coffee how hot
should my water be when I'm making drip
or filter coffee of any kind espresso
brewing temperature is a whole other
topic but I will get to that another
time another day today it's just about
filter coffee there is this idea that
has persisted but if you use boiling
water to make a coffee then it will
taste don't you see it online in books
kind of everywhere I'm not sure that's
true now there is a correlation between
brewing water temperature and extraction
generally speaking
the hotter the brew water is the more
energy it provides for chemical
reactions and one of those reaction
groups is stuff going into solution and
again certain compounds certain flavors
go into solution at different rates at
different temperatures so there's a link
unquestionably but this idea of burning
the coffee this really makes no sense to
me coffee beans have been roasted up at
220 degrees C plus often they've
experienced really high temperatures a
hundred degree C water isn't gonna
further those kind of reactions it's not
going to cause the coffee to be roasted
any darker it's not gonna create much in
the way of flavors the way that roasting
does what it might do is extract some
bitter tasting flavors some burnt ashes
smoky tasting things if you brew very
dark roasted coffee at very high
temperatures that may be where this came
from but we're gonna take a more
rigorous approach today I'm going to
investigate what happens if you use just
boiled water to make a coffee because
we're not going to just track the
temperature inside the kettles we're
going to track the temperature in the
coffee that's brewing we're going to use
a word it's a bad word I'm sorry it's
not an appetizing word it's amongst the
least appetizing words in coffee though
I think museology is probably worse but
we're going to talk about this slurry
right and the slurry is the grounds in
the water as they mix together either in
the top of say a brewing cone or inside
let's say a French press right that
combination of coffee and water that's
the slurry that's the temperature
most interested in here's how this works
attached to this thermometer is a small
temperature probe going into the grounds
and it's just underneath the grounds
right now well we're going to use it to
measure the temperature of the slurry
I'll boil this kettle and then I'll pour
a bloom this is 30 grams of coffee and
so I'll do a 60 to 80 gram bloom and
I'll wait 45 seconds and then I'll
complete the brew and during that brew
we'll be able to see how the temperature
of the slurry increases and what kind of
temper gets up to even though I'm using
this as close to the boil as possible
let's go
so obviously this was a preheated brewer
and the grounds in there were a little
bit warm but still the temperature is
nowhere near our kettle temperature and
bear in mind during a 45 second bloom
we're getting to the end of now this
water has cooled down further still
let's keep brewing so as expected the
temperatures coming up and it should be
pretty stable now now the end of the
brew at this point we're at peak
temperature what's gonna happen now is
that evaporative cooling is gonna start
to pull some heat out of this you can
see steam rising that's pulling energy
out of the brew constantly and again
this slurry this thermal mass as it
drains through is getting smaller and
smaller and smaller
so we'd anticipate a gentle decline in
brew temperature at this point let's let
it drain out so there it is it didn't
even get past 91 degrees Celsius and
this kettle I'll admit is capped
actually in 98 degrees Celsius but even
if I'd got it to 102 degrees more I
might not have got past 93 degrees
Celsius in the slurry this is a plastic
comb this was a preheated brewer the
grounds were a little bit warm
there aren't many environments that I
could have made this a hotter brew and
yet this slurry got nowhere near a
hundred degrees Celsius and I think the
light roasts you need to have the
hottest water you can get so that your
slurry temperature is as hot as it can
be but I will confess a pour-over is a
very different thing to a French press
there's a much slower delivery of water
there's a smaller thermal mass there are
a bunch of challenges of maintaining
slurry temp here that you might not have
here so now the French press what we're
gonna do is very simple we're going to
boil a kettle of water here we've got 45
grams of coffee I'm gonna add 600 grams
of water for my 75 grams of liter ratio
and we'll see what happens what will
happen to the brew temperature the probe
is in here it'll be in sort of top of
the slurry where it's at its absolute
hottest
whoops here we go straight off the boil
600 grams so again it's only gonna get
cooler from here on out we were never
close to boiling even though the water
was very very hot now I know you're
thinking you're thinking you've got me
because was this french-press preheated
no it was not should we find out what
happens if we do preheat the French
press I think we should but while I prep
and clean up and reset I'm gonna tear
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so same experiment all over again except
now this is nicely preheated what will
it do to the brohn temperature
so again pre-heated as much as I could I
could have done more but at what point
am I actually getting any sort of return
on my investment of temperature little
bit hotter but not a lot hotter so it's
really pretty much impossible unless you
had let's say a dual walled stainless
thing the you to aggressively preheated
with boiling boiling water it's really
hard to get to very high temperatures
wherein you will extract some very
bitter very harsh flavors from medium to
light roasts this doesn't mean that the
highest possible temperature is the best
for every single coffee not at all what
I would say is if a coffee is a darker
more developed roast and you enjoy that
know that it's going to be easier to get
those very bitter very harsh kind of
ashy smoky flavors out of them don't
brew quite as hot brewing in essentially
the mid to high 80s in terms of Celsius
will yield a kind of smoother less
bitter result that should still be
plenty extracted if you are getting
bitter burnt kind of tastes then you can
just back off that temperature a little
bit but for certainly most specialty
coffee it's really pretty hard to gather
temperature wrong you've got to work
really really hard to have a high
temperature here there's a couple of
exceptions to the rule I think things
like siphons are beautiful and they can
brew incredibly hot and at very high
temperatures if you don't pay attention
to that but broadly if you're pouring
water from a kettle as soon as you can
after the kettles boiled certainly with
medium and with light roasts now in this
video I haven't really touched on the
opposite side of the scale right when
you brew with cold cool tepid water all
of that kind of stuff the topic of cold
brew is one that is heavily requested
obviously you'll understand a little bit
that you can't extract as much with cold
water as you can with hot that has a
number of implications and some people
think that's a good thing and some
people think that's a terrible thing
I'll address this in future don't worry
about that but we're not going to go
into cold brew at any point now
originally your thoughts on this is this
a surprise were you expecting a
different kind of result
as this made sense of something that
seemed oh so confusing to you before
what did I miss what didn't I talk about
in this video what would you like to see
me explore further in the future I'd
love to hear from you leave me a comment
down below we wanna say thank you so
much for watching
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