New Scientist - USA (2022-01-22)

22 January 2022 | New Scientist | 51

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These articles are

posted each week at

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What you need
1 kg cucumbers
400 ml white wine vinegar,
5 per cent acidity
400 ml water
1 tbsp unrefined sea salt
1 tbsp sugar
2 tbsp mustard seeds
2 tbsp coriander seeds
Bunch of dill, roughly chopped
4 cloves garlic, thinly sliced
2 1-litre preserving jars

ALL over the world, people use acid

to preserve fruit and vegetables,

creating the sour and delicious

foods we call pickles. The microbes

that spoil our food have a hard

time growing if the pH is lower

than 4.5, but we can eat foods with

a pH as low as 2 (the lower the pH,

the more acidic the substance).

Some pickles are made by salting

vegetables or fruit, encouraging

the growth of bacteria that produce

lactic acid. These include kimchi,

which I described in a previous

issue (29 February 2020). A quicker

and simpler way to make pickles

is to add vinegar, which contains

ethanoic (aka acetic) acid and

typically has a pH of around 2.4.

For pickling, you should use

vinegar with 5 per cent acidity –

this is usually printed on the label.

As well as inhibiting microbes,

the acid stabilises plant cell walls,

helping vegetables such as

cucumbers keep their crunch.

Unrefined sea salt contains

calcium and magnesium

impurities, which also help to

reinforce the pectin molecules

in cell walls. Table salt is best

avoided because it contains

anti-caking agents that can

turn pickling liquid cloudy.

In addition to vinegar, pickling

liquids can include flavourings,

such as herbs and spices, and

sugar to balance the sour taste.

Garlic in pickles can sometimes

turn blue or green due to reactions

that produce pyrroles. These

chemicals can join together to

produce colourful polypyrroles,

a group that includes the green

pigment chlorophyll. Blue or

Keep the crunch in your cucumber for months and punch

up the flavour at the same time, says Sam Wong

The science of cooking

Stay sharp, get pickling

green pickled garlic is safe to eat.

To make a cucumber pickle, slice

small cucumbers lengthwise into

spears. Cut off and dispose of the

flower end (the one with the rough

dot), which contains enzymes

that accelerate softening. If you

are using larger cucumbers, cut

them into shorter lengths, or slice

thinly into discs instead. Mix the

cucumber with salt in a bowl and

leave overnight to draw out water.

Heat the vinegar, water, sugar

and spices in a lidded saucepan

until the sugar has dissolved, then

allow to cool. Put the garlic and dill

in the bottom of the jars. Drain the

liquid from the cucumbers, then

pack them in tightly and pour

the pickling liquid over them

so they are completely covered.

Once packed into jars,

pickles can be heat-processed

in a pressure-canning machine
to kill off any microbes and extend
their shelf life further, but this
results in a less crunchy and fresh-
tasting product. If you aren’t doing
this, the pickles should still keep in
the fridge for about two months.
Best not to try this at home, but
chemistry lecturers sometimes
make a pickled cucumber glow
by passing an electric current
through it. The high concentration
of sodium ions carries the current
through the pickle, and the yellow
glow is emitted when electrons
from excited sodium ions return
to a lower energy state. In essence,
the pickle functions as an organic
The science of cooking light-emitting diode.  ❚
appears every four weeks

Next week
Stargazing at home

Sam Wong is assistant news
editor and self-appointed
chief gourmand at
New Scientist. Follow
him @samwong1

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