The Other Chile Peppers
Where does the heat come from in chiles?
Capsaicinoids—tasteless, odorless compounds that are
insoluble in water—can cause a "rapid bite" at the
back of the palate and throat or a long, slow burn on the
Peppers produce these compounds only in glands located in
their pods' placental partition, which is the white, fleshy
membrane where the seeds are attached. The seeds become
pungent through contact with the placenta but do not
contain capsaicinoids of their own. If you want less heat,
carefully remove the seeds and placental membrane before
you use the peppers.
So why do chile peppers produce these capsaicinoids? When
mammals eat peppers, they digest the seeds, destroying
them. When birds eat peppers, they pass the seeds intact.
Mammals can taste capsaicinoids, so peppers' heat may have
evolved as a way to protect the seeds from mammals and
allow birds to eat—and spread—them.
Scoville Heat Units (SHUs), developed in 1912 by Wilbur
Scoville, are the standard industry method of measuring
capsaicinoid levels. Originally, a precise amount of the
chile was soaked in alcohol to dissolve the capsaicinoids.
This, in turn, was dissolved in sugar water until a panel
of testers no longer could detect any heat. At least three
out of five testers had to agree on the dilution level. The
SHUs reflect the number of units of sugar water it took to
reach that point.
Today, high-performance liquid chromatography is used to
measure the actual capsaicinoid content in parts per
million, which is then converted to Scoville Units. Use any
measuring system only as a guide because heat content
varies by growing conditions, age, pod condition (fresh
versus dried, for instance), and individual reactions to
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