IsohexaneNew Solvent for Cottonseed Oil Processing
Chemical engineer Peter Wan takes a sample to see how well isohexane compares
to other hydrocarbon solvents in removing vegetable oil from meal.
Consider cottonseed oil. It fries the humble potato chip, an American picnic
classic. Summer sunbathers glisten with tanning oil made from it.
Cottonseed was the first major vegetable oil used in the United States. In
the 19th century, hydraulic presses were used to remove the oil. Later,
continuous screw-type presses offered more efficiency. The shortage of oil for
soaps, food, and explosives during World War I prompted the use of
petroleum-based solvents to get more oil from the seeds.
Now a scientist with the Agricultural Research Service may have found a more
efficient way to meet industry's needs. The key: switching from hexane, the
current oil removing solvent, to isohexane, which has several benefits.
"We found that substituting isohexane for hexane in production required
little or no change in the cottonseed crushing operation," says chemical
engineer Peter J. Wan. "We tested isohexane in plants operating at full
capacity and saw both savings in energy and more product produced per
Scientists at ARS began to study alternative solvents during the energy
crisis of the 1970's.
At first, their goal was to find more effective solvents, such as acetone,
to remove oil and undesirable pigments. Later, renewable solvents that didn't
rely on petroleum sources became the focus. But the ideal
candidateethanolproved too costly.
During the 1980's and 1990's the focus switched to achieving cleaner, safer,
and cost-effective production, so the search for alternative solvents
A research team led by Wan decided to give isohexane a try. The National
Cottonseed Products Association also supported him, and some of its members
offered their mills to test the new solvent.
"Our experience with isohexane was positive. We saw good extraction and
some energy savings," says Billy Clark, president of Yazoo Valley Mill in
"We even reran the test to confirm results. We had no trouble getting
isohexane from the supplier for that second test."
"Cottonseed processors have always been industry leaders," says
David Kinard, director of research and education for the century-old National
Cottonseed Products Association. "Alternative production methods that
increase efficiency are appreciated by everyone."
The cottonseed industry represents a billion-dollar U.S. market, says Wan.
Each year, 1.4 billion pounds of cottonseed oil are consumed, and their main
use is in snack-making.
"Cottonseed oil is considered the "gold standard' for frying
potato chips," says Scott Sanford, who is with the USDA's Economic
Research Service. "It's also replacing animal fat in some fast-food
"Provided isohexane is economically priced, any oilseed processor could
benefit from using it," says Wan. "For example, they'd save energy,
because it takes less steam to recover isohexane from the meal and oil during
processing." -- By Jill Lee, ARS.
Wan is in the USDA-ARS Commodity Utilization Research Unit, Southern
Regional Research Center, 1100 Robert E. Lee Blvd., New Orleans, LA 70124;
phone (504) 286-4450 ext. 450.
"Isohexane -- New Solvent for Cottonseed Oil Processing"
was published in the August 1996
issue of Agricultural Research magazine.