Academic
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IELTS Reading Practice Test 6.
Passage 1
Biology of Bitterness
A.
There is a reason why grapefruit juice is served in little glasses: most
people don’t want to drink more than a few ounces at a time. Naringin, a
natural chemical compound found in grapefruit, tastes bitter. Some people like
that bitterness in small doses and believe it enhances the general flavor, but
others would rather avoid it altogether. So juice packagers often select
grapefruit with low naringin though the compound has antioxidant properties
that some nutritionists contend may help prevent cancer and arteriosclerosis.
B.
It is possible, however, to get the goodness of grapefruit juice without the
bitter taste. I found that out by participating in a test conducted at the
Linguagen Corporation, a biotechnology company in Cranbury, New Jersey.
Sets of two miniature white paper cups, labeled 304and 305, were placed
before five people seated around a conference table. Each of us drank from
one cup and then the other, cleansing our palates between tastes with water
and a soda cracker. Even the smallest sip of 304 had grapefruit ‘s
unmistakable bitter bite. But 305 was smoother; there was the sour taste of
citrus but none of the bitterness of naringin. This juice had been treated with
adenosine monophosphate, or AMP, a compound that blocks the bitterness in
foods without making them less nutritious.
C.
Taste research is a booming business these days, with scientists delving
into all five basics-sweet, bitter, sour, salty, and umami, the savory taste of
protein. Bitterness is of special interest to industry because of its untapped
potential in food. There are thousands of bitter-tasting compounds in
nature.They defend plants by warning animals away and protect animals by
letting them know when a plant may be poisonous. But the system isn’t
foolproof. Grapefruit and cruciferous vegetable like Brussels sprouts and kale
are nutritious despite-and sometimes because oftheir bitter-tasting
components. Over time, many people have learned to love them, at least in
small doses. “Humans are the only species that enjoys bitter taste,” says
Charles Zuker, a neuroscientist at the University of California School of
Medicine at San Diego. “Every other species is averse to bitter because it
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