InfoChem
What colour is your lunch?
Battenburgcake: cochineal
(pink) and annatto (yellow)
Blueberry muffin:
anthocyanins degraded
during baking (brown)
ISSUE 128 | MAY 2011
In this issue
Chemical disposal
What happens to the waste
you create in your lab?
Tomatoes: lycopene
Green leaves:
chlorophyll
Sweet red pepper:
capsanthin
Carrot: β-carotene
Nitric oxide
Leicester cheese
(orange): annatto
On-screen chemistry
Red grapes:
anthocyanins
Chorizo sausage (orange):
capsanthin
Why are both carrots and red leicester cheese orange?
David Sait looks at some of the colours you’ll find in
your food.
their distinctive colours. Tomatoes are a rich source
of lycopene, the word itself from the greek word for
tomato.
The cheese, grapes and lettuce in this lunchbox are all
different colours due to the chemicals they contain. As
these molecules have different electronic structures,
they absorb different parts of the electromagnetic
spectrum, so are seen as different colours.
Red – anthocyanins
Another class of molecules found in food are
anthocyanins, particularly in grapes and berries. These
molecules are usually red, however this is dependent
on the pH of the environment they are in.
Naturally occurring coloured molecules are often
added to processed foods to enhance the colour that
is lost during manufacture. But what are some of these
colours, where do they come from, and where might
you find them in your lunchbox?
For example, if you’ve ever used red cabbage as a
pH indicator, you’ve seen the colour change from red
(acidic), to green (alkali).
Orange & yellow – carotenoids
Carotenoids are a group of 40–50 chemicals present in
our diets, responsible for most of the yellow and orange
colours we see in foods.
Capsanthin is found naturally in sweet peppers and
is used to colour chorizo sausage. β-carotene is the
molecule which gives carrots both their colour and their
name. Annatto, an extract of US achiote trees, is used
extensively to give red leicester cheese and margarine
The magnificent
molecular messenger
Green – chlorophyll
Do you have lettuce in your sandwiches? Almost all
green plants and vegetables contain the pigment
chlorophyll, as it is a critical part of the photosynthesis
system they use to generate energy from light.
But why?
Whether consciously or not, we judge our food and
decide if we want to eat it primarily by its colour. This
is an ability we have inherited from our ancestors, who
would probably have used colour to decide if the food
that they gathered was safe to eat.
Can you dissolve bodies in
hydrogren fluoride?
Backyard chemistry
Professor Hal shows us how
to make rainbows from milk
Plus…
Prize puzzles
Editor
Karen Ogilvie
Acting editor
Laura Howes
Assistant editor
David Sait
Design and layout
Scott Ollington
Publisher
Bibiana Campos-Seijo
Infochem is a supplement to
Education in Chemistry and is
published six times a year by
the Royal Society of Chemistry,
Thomas Graham House,
Cambridge,
CB4 0WF.
01223 420066
email: [email protected]
© The Royal Society of Chemistry,
2011. ISSN: 1752-0533
www.rsc.org/infochem
Registered Charity Number 207890
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