New Scientist 14Mar2020

14 March 2020 | New Scientist | 51

VIRUSOWY/ALAMY

Sam Wong is social media

editor at New Scientist.

Follow him @samwong1

Science of cooking online

All projects are posted at

newscientist.com/cooking Email: [email protected]

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GARLIC can be big and fiery or

soft and mellow. Understanding

the chemistry of its flavour can

help us amplify or tame it.

If you sniff a bulb of garlic,

it doesn’t have a strong smell.

But if you bite into raw garlic,

it will produce a pungent aroma

and a burning sensation in your

mouth. This is garlic’s chemical

defence, evolved to deter animals

from eating the plant.

It is caused by a chemical called

allicin, which activates the same

pain-sensing receptors that

respond to the capsaicin in chilli

peppers. Allicin isn’t present in

garlic until its cells are damaged

and stores containing an enzyme

called alliinase break open. The

enzyme acts on alliin, a derivative

of the amino acid cysteine, to

produce allicin.

Allicin has antibacterial

and antifungal properties as it

inhibits enzymes called cysteine

proteases, which pathogens use

to invade the tissues of their hosts.

This is possibly why garlic has

been touted as a medicine for

thousands of years – Hippocrates

recommended it for wound

healing, for example.

Garlic becomes less fiery

when you cook it, because

alliinase is inactivated, stopping

allicin production. Allicin is also

unstable, quickly reacting to form

other odorous compounds. Some

of these can persist in the mouth

for hours after eating garlic,

giving rise to garlic breath. If this

happens, eating an apple or salad

can help, as enzymes found in

many raw fruits and vegetables

convert these compounds into

odourless molecules.

When we mince or chop garlic,

we damage lots of cells. When we

leave its cloves intact and cook

them slowly, it becomes sweet and

mellow instead. Here are two ways

to prepare garlic that bring out

different sides of its personality.

First, the fiery one: a Lebanese

garlic sauce called toum. Peel two

bulbs’ worth of garlic (roughly

120 grams) and blend in a food

processor with half a teaspoon of

salt. With the blade still running,

slowly add 125 millilitres of

vegetable oil, then a tablespoon

of lemon juice. Repeat until you

have added 500 ml of oil and four

tablespoons of lemon juice in total.

The result should be smooth

and mayonnaise-like. Garlic

contains emulsifiers that coat

droplets of fat, allowing them

to become suspended in water,

but the oil must be added very

slowly to make it work. If the

emulsion breaks, add an egg

white to the mixture and

blend again. Toum is a perfect

accompaniment to grilled meat,

roasted vegetables or falafel.

Garlic confit is a great way

to appreciate its mellower side.

Peel two bulbs’ worth of garlic

and cover them with olive oil in

a small saucepan. Cook over a very

low heat for 45 minutes to an hour,

until soft. Keep the cloves in the oil

in a jar in the fridge. Mash them

on toast, add to salads or eat them

with pretty much anything. ❚

Understand garlic’s chemistry and you can add sweetness

or fire to your food, says Sam Wong

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Sam Wong is social media

editor at New Scientist.

Follow him @samwong1

Science of cooking Week 11

Bring out the best in garlic

Science of cooking online

All projects are posted at

newscientist.com/cooking Email: [email protected]

What you need
Garlic
Vegetable oil
Salt
Lemon

For next week
Plain flour
Salt
Vegetable oil

Next week
Noodles: get to grips
with gluten for silky,
hand-pulled noodles