4 April 2020 | New Scientist | 51CREATIVE^ ABOUTCUISI
NE/ALAMYThe back pages
BECAUSE of the environmental
impact of livestock farming, I
don’t cook meat often. But I can’t
resist the occasional roast. Pork
belly is one of my favourites – the
only challenge is getting the skin
to go crispy. Can science guide me
towards the perfect crunch?
The internet has plenty of tips
for ultimate crackling, but few
provide a scientific rationale and
many are contradictory. I decided
to do some research and tests.
Pork skin is about 30 per cent
collagen, a strong, tough protein
made up of three molecular chains
wound into a triple helix. Heating
it for long enough breaks it down
into gelatin, which melts away.
To make pork skin crisp, all the
collagen must break down. You
also need the skin to completely
dry out and remaining proteins
to coagulate and stiffen.
According to The Food Lab
by J. Kenji López-Alt, the key
to achieving all three is to start by
slow-roasting the meat at a lower
temperature, ensuring that the
skin is well softened. Then blast
it with high heat, so that pockets
of air and steam under the skin
expand and stretch it, making it
thinner. The high heat will quickly
firm the skin and make it crispy.
The US television cooking
show America’s Test Kitchen agrees
that slow-cooking, then rapidly
evaporating the remaining water
in the skin to make it puff up,
is what is needed. But it says
the oven can’t do the second
part quickly enough. Instead it
recommends shallow-frying
the skin in a pan at that point.Home cooks in China favour yet
another technique that draws on
restaurant methods. They start
by blanching the meat in boiling
water then poke lots of holes in the
skin. These allow moisture and fat
to escape during roasting. Some
recipes advise bathing the pork
skin-down in vinegar overnight,
which may help weaken collagen.
There is another slight variant:
before roasting, you can wrap
the meat in foil, leaving the top
open, and cover the skin in a thin
layer of salt to draw out water.
Some way through cooking, the
salt is scraped off and the meat
goes back into a very hot oven
to crisp the skin.
I tested these methods on four
400-gram pork belly pieces. Alljoints were roasted for 2 hours
at 130°C, skin side up. Then, one
came out to be pan-fried while
the others stayed in for half an
hour at 240°C.
The vinegar-soaked piece had
a smoother surface, while the
others formed bubbly, blistered
crusts. The salt-covered pieces
were slightly harder than the
others, but all were excellent:
crunchy yet easy on the teeth.
Without having tested a shorter
cooking time, I can’t be certain but
I suspect the key to success was to
give the meat plenty of time in the
oven to break down the collagen
before applying a blast of high
heat to finish off. Bear in mind
that timings will need adjusting
for larger pieces of meat. ❚Pork crackling is a delicious treat, but how do you achieve
perfection? Sam Wong puts four techniques to the testPuzzles
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art gallery challenge
and the quiz p52Feedback
Where to get free will,
plus lockdown tales:
the week in weird p53Almost the last word
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James Danckert
on the upsides of
boredom p56Twisteddoodles
for New Scientist
A cartoonist’s take
on the world p53Sam Wong is social media
editor at New Scientist.
Follow him @samwong1Science of cooking Week 14
Crunch tim e
Science of cooking online
All projects are posted at
newscientist.com/cooking Email: [email protected]What you need
Pork belly
Salt (optional)
Vinegar (optional)
Next week
Protein from plants: seitan, a
form of wheat gluten, is a great
alternative to meat - and you
can make your own