The extreme irritant effects of certain pepper vein extracts
on human skin, eyes, tongues and nasal passages have been
known for thousands of years, but only since about 1970 have
September 2019 SPRAY 41
these debilitating effects been used defensively...
tested the streaming spray produced by different actuators, using a poster-board target
some 20 feet away. A few minutes later, upon leaving the building, they encountered a
distraught young lady in the parking lot. She had just experienced some strange inhalation
symptoms while trying to catch up on some office work in a downstairs room. She
was greatly relieved at the explanation: traces of pepper spray had entered the air circulation
system. She felt better in the open air, got into her car and drove off.
Capsaicinoids & their measurements
The “heat-producing” capsaicinoids had not yet been defined or even isolated in 1911
when druggist Wilbur Scoville began to study them. A year later he published his “Scoville
Organoleptic Scale,” where an extremely dilute water solution of the “hot” material
was given a rating of 1.0 if 50% of professional tasters could detect any difference from a
pure water placebo control. It followed that a capsaicinoid solution rated at 1,000 SHU
(Scoville Heat Units) could be diluted 1,000-fold before reaching the 1.0 SHU baseline.
The two most awesome capsaicins have 16,000,000 SHU ratings when 100% pure. This
means that a 1.000 gram Capsaicin (C) sample could be diluted to about 16,100 liters
with water, with the “heat” still detectable by 50% of taste experts.
The structure of what is now considered to be the
major capsaicin (Capsaicin with a capital “C”) was first
defined by Hredzak in 1925. Using Hredzak’s notes,
Spaath synthesized it in 1930. The white material melting
at 65°C was almost insoluble in water and the pure
compound was quite dangerous. When touched to the
skin, it quickly produced painful blisters. The vapor
pressure was almost negligible, yet sufficient to irritate
the skin and eyes after a few minutes of exposure.
Scoville and the other early investigators were unaware
that there were at least about 10 capsaicinoids in
peppers, ginger, paprika and related fruits. All had very
similar alkylaryl molecular structures, differing only in
the position of an oxygen atom, a double bond in some,
and side-chain length. This is such a common occurrence
with natural compounds that it may have been
suspected here. Eventually, about 1984, Weaver used
liquid chromatography (LC) to separate and identify at
least five significant capsaicinoids. The several very minor
ones total only about 0.2% to 0.5% and their structures
are still a matter of some speculation. In 2000, Dr.
M.W. Dong used High Pressure Liquid Chromatography
(HPLC) to suggest that the instrumental method
was faster, more cost-effective and more accurate than
the subjective assay results from panels of expert tasters.
To produce capsaicinoid concentrates for the food industry
and (now) the aerosol industry, the pepper “rib”
matter is detached and the “hot” ingredients extracted
with suitable solvent mixtures (such as 95 volume-% ethanol).
Certain other plant ingredients are also extracted
in this process, such as coloring matter and triglycerides.
After filtration, the ethanol is removed by vacuum distillation.
After assaying for the SHU concentration, an appropriate
dilution is made, completing the batch. It may
Wilbur Scoville published
the “Scoville Organoleptic
Scale” in 1912.