New Scientist - USA (2021-11-20)

20 November 2021 | New Scientist | 51

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What you need
Oysters
Butter
Garlic
Hot sauce
Lemon juice
Champagne? Oh, go on then

I LOVE raw oysters, so hoped to

write a column saying there is

no need to worry about food

poisoning. When I looked into it,

though, I found cause for concern.

But there are safe ways to enjoy

delicious oysters.

Folklore has it that oysters can

be eaten in any month with an

“r” in it – in other words, avoiding

the summer months, when they

spawn. This discernment may

date back to ancient times.

By measuring parasitic snails

in oyster shells, a study of a

4300-year-old human habitation

in Georgia, US, found that ancient

people mostly harvested oysters

in the autumn, winter and spring.

During the spawning season,

oysters convert their resources

into sperm or eggs, which renders

them less palatable. People may

also have avoided taking oysters

in summer to allow populations

to recover.

Nowadays, farmed oysters are

available and good to eat all year

round and are among the most

sustainable seafoods. Since the

1980s, many farmed oysters have

been triploid: they have three sets

of chromosomes and are therefore

infertile. These oysters grow faster

than natural oysters and remain

firm and plump in the summer.

As filter-feeders, oysters can

pick up pathogens lurking in the

water. To reduce this risk, they

are usually kept in clean water for

42 hours after harvesting in the

UK, a process called depuration.

Sadly, this isn’t completely

effective – particularly with

respect to norovirus, one of

The humble oyster inspires passion in many and fear in others.

Sam Wong looks at a scientifically sound way to eat them

The science of cooking

In praise of oysters

the most common causes of

gastroenteritis. A 2017 report

found that between 100 and

1000 copies of the norovirus

genome may remain in each gram

of oyster tissue after depuration.

Just 10 copies are thought to

constitute an infectious dose.

In the UK, about 13,000 people a

year experience illness after eating

seafood, usually raw oysters. Given

that more than 13 million oyster

meals are served each year, you

might consider this a low risk. But

recent headlines about raw sewage

discharged around British coasts

may make you think twice.

Fortunately, cooked oysters

are delicious too. The simplest

method is to oven cook oysters

at 220°C for 10 minutes. Heat will

cause the shell to open, so place

them on a wire rack or a bed of salt

to stabilise them, so the juice
doesn’t leak out. Once cool
enough to handle, use a knife
to gently separate the oyster
from the shell. To serve, spoon
on some melted butter with
garlic, hot sauce and lemon juice.
Champagne is another
traditional accompaniment to
oysters, and a study identified
a reason behind this pairing.
Oysters and champagne contain
compounds that activate umami
taste receptors: glutamate from
dead yeast cells in champagne and
nucleotides in the oyster muscles.
Combined, they create a stronger
perception of umami than either
The science of cooking does on its own. ❚
appears every four weeks

Next week
Stargazing at home

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

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