54 | New Scientist | 16 April 2022The back pages Almost the last word
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My partner insists that
food cooked in a microwave
tastes inferior to that cooked
conventionally, but I disagree.
Is there really a difference?Talia Morris
Cape Tribulation, Queensland,
Australia
There is a difference between
what happens to food cooked in a
microwave and when it is heated
during conventional cooking.
A microwave cooks food by
heating the water molecules in
the food, essentially boiling it
from the inside out, whereas
conventional cooking applies
dry heat to the outside of the food,
cooking it from the outside in.
Food with a high water
content that is cooked in a
microwave tastes just like it has
been boiled, but if you microwave
food with a lower water content,
the little moisture it originally
had gets steamed out of it,
leaving the food unpalatably
dry and brittle.Stuart Farrimond
Author of The Science of Cooking,
Trowbridge, Wiltshire, UK
It depends on what you are
cooking. Traditionally steamed
vegetables tend to be hard to
discriminate from those
steamed in a microwave.
Many other foods – especially
those that would normally be
fried or roasted – will never taste
as good in the microwave.
The key to why so many
foods taste great is the Maillard
reaction. This is an assemblage
of countless reactions between
amino acids and sugars at
temperatures above around
130°C, resulting in a multitude
of flavour compounds thatORICHTE
R/GET
TY
IMAGESconvey many lip-smacking
aromas and tastes.
These processes (also known
as browning reactions) are
responsible for bread becoming
toast, the roasted flavour of
coffee and the meaty flavour
of seared steak and roasted
meat. Cooking meat in a pot of
boiling water will never give it
a brown, meaty crust, as liquid
water won’t reach 130°C.
In the same way, microwave
cooking – which involves the
heating of water within the
food (to a depth of around 1
to 3 centimetres, rather than
“from the middle” as is often
claimed) – generally won’t get
much hotter than 100°C, the
boiling point of water. Hence
these wondrous flavours will
never be created.It is, however, a myth to think
that microwaves only heat water,
and so it is possible to roast nuts in
one: spread some nuts coated in
a little oil across a microwaveable
plate and cook at 1-minute
intervals, shaking them each time.Danny Colyer
Bristol, UK
Before the days of domestic
microwave ovens, my parents
used to visit the railway station
cafe to enjoy a pasty with the
deliciously soggy pastry that
you only get from heating in
a microwave.
Food cooked in a microwave
typically retains more moisture
than food cooked in a conventional
oven, affecting both flavour and
texture. Personally, I prefer food
heated in the microwave.Jeremy Jackson
London, UK
Microwaved food is often more
evenly cooked, whereas that
heated conventionally has a lovely
spectrum: rare inside and crunchy
on the outside. Imagine bacon or a
juicy steak cooked in a microwave.
This is why some microwave
ovens also have a grill function.Patchwork leaf
What is going on to create this
amazing multicoloured leaf
pattern? (pictured, right)Chris Daniel
Glan Conwy, Conwy, UK
Most leaves are green due to the
pigment chlorophyll, but other
colours, such as oranges, reds
and blues, may also be present
due to less efficient photosynthetic
pigments like anthocyanins,
carotenes and xanthophylls whose
main role is to protect the leaf from
strong light. The patterned colour
of leaves is called variegation – it
is a reduction in pigmentation
due to inherited (that is, genetic)
characteristics of the plant,
random mutations or viruses.
The purpose of variegation is
a matter of debate. The deficiency
of chlorophyll means that the plant
may not produce all the energy it
needs, but in the plant’s habitat,
sunlight may be sufficiently strong
for this not to be important. It may
be more difficult for a plant with
patterned leaves growing in the
dappled light of a forest floor to be
detected and eaten by herbivores.
This survival strategy might
outweigh the disadvantage
of reduced photosynthesis.Noel Ellis & Cathie Martin
John Innes Centre, Norwich,
Norfolk, UK
Alan Paton & Rafael Govaerts
Royal Botanical Gardens, Kew,
London, UK
It is helpful to know the species of
plant to be able to suggest causesThis week’s new questions
Watery origins How and where was water first created?
Bill Richardson, Riverview, Michigan, USBasis of belief Humans believe in many things, often with
no solid evidence. So does belief give us an evolutionary
advantage, or is it just something that survived regardless?
Gerald Lambert, Northleigh, Devon, UKWater, water everywhere – but
where and when did Earth’s
water form?“ These browning
reactions create the
roasted flavour of
coffee and the meaty
flavour of seared steak
and roasted meat”