So we all know what a bloom is, but what
the heck is a foam slurry?
By definition a foam is a light frothy
mass
of fine or small bubbles that form in or
on the surface of a liquid, and a slurry
is a watery mixture of insoluble matter.
In coffee brewing a foam is formed when
we first apply hot water to ground
coffee.
In English, we call this a bloom, though
in this initial state
the coffee slurry should be referred to
as a foam or
foam slurry. So why should we care? Well,
if you ever wondered why it's not
recommended to pour
all your water in at once, or better yet,
why some people recommend pouring two
times versus three times
the dry mass of ground coffee for their
initial bloom, taking a closer look at
the bloom
will give us some interesting clues. So
during the blooming process
you can see the coffee instantly
transform into a foam
and float to the top. Considering
that this is a conical shaped dripper,
there's a larger volume of coffee
floating above the fluid line
compared to below. Note that throughout
this entire process,
fluid is continually draining and only
percolating to a small percentage of the
coffee slurry below.
So if we poured additional water in this
first pour, we'd only be adding
excess water below the foam, and again
that excess water
will only be percolating through a small
percentage of the total slurry below. So
here's a look at another foam being
formed.
At this volatile stage the outgassing is
so aggressive,
that the water from the kettlepoor isn't
able to break the foam
apart. This is the case with manual
agitation as well, which is why at this
specific stage of the bloom,
using manual agitation with a stick or
spoon solely to break up the foam,
isn't an efficient use of energy. What I
would recommend, is focusing on the lower part of the slurry,
to dislodge any dry pockets that your
kettle pour
would have left behind. This will
typically increase the flow rate
as knocking out any hydrophobic
particles will help optimize the
conductivity through the filter paper.
So why is it usually recommended to
wait during a bloom?
Well this goes back to deflection. So
during this outgassing of Co2,
water is actually being deflected from
efficiently saturating the coffee
cellulose
in exchange for flavor compounds. This is
why it's primarily recommended
to wait after the first pour. After the
foaming and degassing has subsided,
there's a lot less deflection, and a
kettle pour can break the foam apart
allowing particles to re-incorporate back
into the total slurry.
After all this incorporation,
additional fluid can now percolate
through a larger volume of the total
slurry.
So to sum it up, foams float. During the
first pulse
or a bloom phase, a majority of the
coffee is floating above the surface of
the fluid.
This means that adding additional fluid
only fills up below the foam
and only percolates to a small
percentage of the slurry below.
Foams are strong. As dry coffee
transforms into a foam,
it's incredibly tenacious and difficult
to break apart.
So rather than using manual agitation to
break the foam apart,
you should probably spend your time
inspecting the lower part of the slurry
for any dry patches
unless you're trying to saturate and
reincorporate dry patches that you see
on top
of the slurry. Be patient
You'll often hear that it's best
practice to wait around 30 to 45 seconds
after the first pour.
A basic rule of thumb for how much you
should wait after the first pour
is until all of the movement has
subsided. That means that most of the
bubbling,
foaming, or draining has either slowed or
stopped.
But at the end of the day we're all
brewing with different roast profiles,
tools, and techniques, that there are
really no hard rules.
This is because the volatility or the
Co2 content of the coffee
is greatly dependent on the roast
profile,
temperature of the water used, the grind
profile, and how long the coffee has
rested since roast date.
So if you look outside your territory or
region, you'll notice that there's a huge
variety of recommendations
on how much to bloom and how long to
wait, and these reasons aren't right or
wrong,
they're specifically based on the
culture and the kinds of roast profiles
that are used for brewing.
It also includes the different kinds of
techniques and the different kinds of
history and lineage
that brewing has within their specific
region. So personally when I brew,
I'm always visualizing the foam, and how
much water there is below
the foam line. Other people believe that
there's a lot of flavor development
going on
during the bloom so they don't want to
disturb it, and they actually want to
incubate it
or develop it further. So the best thing
to do is to pay
attention to what's happening, how fast
is the water draining,
versus how much you've applied, how much
foam and volatility there is when you
first bloom.
But above all, see what works for you -
inside your environment, with the tools
that you use,
and the coffee that you like brewing! In
the comments below, let us know what your
blooming technique is.
How much water do you use to how much
dry coffee? How long do you wait?
What results do you have? Also, if you
have an interesting blooming technique,
let us know that as well. I'm always looking
for some funky recipes to try out!
Note: this is specifically a
demonstration of the foam created in the
slurry.
To achieve this cutaway view, a front
portion of the filter paper
also had to be removed. Since this dripper
has no filter paper on the front,
the cutaway footage is not intended to
be a one-to-one representation
of all the dynamics in the slurry. Though
along with any shortcomings this method
of observation may have,
understanding brewing techniques from
every perspective possible is still
important and worth exploring. So if you
like this video
give a thumbs up and subscribe to brew
you and we'll see you
next time. Cheers!
 
