Hello dear friends of science and cunning
SciFoxes, I want to introduce you to my next
workshop. So, we want to make delicious gummy,
gel- like candy pearls (in short I´ll call
them guck pearls) - such that can be found
in boba tea - and which look like fish caviar.
Guck pearls consist of a gel like skin or
shell and a liquid filling, you can eat them
pure, decorate dishes or make drinks more
interesting with them. For the little sly
SciFoxes we will fill the guck pearls with
colored juice (orange, raspberry, cherry).
Adult SciFoxes may also use spirits like liqueur.
In addition to the fruit juice or liqueur
we will need two "chemicals", two more unusual
substances in the kitchen: Firstly, we need
calcium - for example, calcium tablets
(European food additive number E509, Calcium
Chloride) Secondly, we need a substance called
sodium alginate which is made from algae (seaweed).
This can be purchased as a white powder and
it tastes like nothing. (European food additive
code E401). When calcium comes together with
sodium alginate, another chemical - calcium
alginate - will be formed -- a very gucky
gel-like substance which acts as the shell
of our liquid filling. We dissolve a pinch
of sodium alginate in a glass of fruit juice.
The result is a viscous alginate solution.
We may add some food coloring if we like.
Then we dissolve in a second glass a calcium
tablet in water and wait until the solution
is clear and transparent. Before we get to
the actual experiment, I want to demonstrate
how to identify the two solutions physically
and chemically. The calcium solution is completely
clear - as water. The calcium particles that
are dissolved in the solution are way too
small to see -- they are even invisible to
a microscope. A light beam passes completely
unhindered through the solution. It's "optically
empty". The particles in the alginate solution
are significantly larger than the calcium
particles. A beam of light does not pass quite
as undisturbed through the solution -- this
is called a colloidal solution and it shows
characteristic light scattering (Tyndall effect).
The presence of Calcium can be easily shown
chemically. In this workshop I will show you
how calcium is detectable by its red flame
color. But back to our guck pearls. We slowly
(one drop after the other) add the alginate
solution to the calcium solution, which we
stir constantly. The alginate droplets get
covered immediately with a gel-like skin of
calcium alginate. We let the drop sit for
a while in the calcium solution. The longer,
the thicker the gel shell. After about 1 minute,
we can take the pearls out of the calcium
solution. We´ve made nice spherical pearl,
with gel-like shell and a liquid core. The
process is called spherification . In this
workshop I will show you how to vary the experiment,
thus making massive gel spheres or gel like
spaghetti. See you in the workshop, all the
best and bye.
