Handbook of Solvents - George Wypych - ChemTech - Ventech!

14.10 Food industry 923
14.10 FOOD INDUSTRY - SOLVENTS FOR EXTRACTING VEGETABLE
OILS
Phillip J. Wakelyn
National Cotton Council, Washington, DC, USA
Peter J. Wan
USDA, ARS, SRRC, New Orleans, LA, USA
14.10.1 INTRODUCTION
Many materials including oils, fats, and proteins, for both food and nonfood use, are recovered
from diverse biological sources by solvent extraction. 1,2 These materials include animal
tissues (e.g., beef, chicken, pork and fish); crops specifically produced for oil or protein
(e.g., soy, sunflower, safflower, rape/canola, palm, and olive); by-products of crops grown
for fiber (e.g., cottonseed and flax); food (e.g., corn germ, wheat germ, rice bran, and coconut);
confections (e.g., peanuts, sesame, walnuts, and almonds); nonedible oils and fats
(castor, tung, jojoba); and other oil sources (oils and fats from microbial products, algae,
and seaweed). There are many physical and chemical differences between these diverse biological
materials. However, the similarities are that oils (edible and industrial) and other
useful materials (e.g., vitamins, nutriceuticals, fatty acids, phytosterols, etc.) can be extracted
from these materials by mechanical pressing, solvent extracting, or a combination of
pressing and solvent extraction. The preparation of the various materials to be extracted varies.
Some need extensive cleaning, drying, fiber removal (cottonseed), dehulling, flaking,
extruding, etc., all of which affect the solvent-substrate interaction and, therefore, the yield,
composition, and quality of the oils and other materials obtained.
Historically, the advancement of processing technology for recovering oils and other
useful materials has been primarily driven by economics. For thousands of years stone
mills, and for several centuries simple hydraulic or lever presses were used as batch systems.
The continuous mechanical presses only became reality during the early 1900s. It was
not until the 1930s, that extraction solvents were used more widely, which greatly enhanced
the recovery of oil from oilseeds or other oil bearing materials.
In solvent extraction crude vegetable oil and other useful materials are dissolved in a
solvent to separate them from the insoluble meal. Many solvents have been evaluated for
commercial extraction. Commercial hexane has been the main solvent for the oilseed processing
industry since the 1940s 1,2 because of its availability at reasonable cost and its suitable
functional characteristics for oil extraction. However, the interest in alternative
solvents to hexane has continued and is motivated by one of a combination of factors: desire
for a nonflammable solvent, more efficient solvent, more energy efficient solvent, less hazardous
and environmentally friendly solvent, solvent with improved product quality, and
solvents for niche/specialty markets. Today commercial isohexane (hexane isomers) is replacing
commercial hexane in a few oilseed extraction operations and other solvents (e.g.,
isopropanol, ethanol, acetone, etc.) are also being used for various extraction processes or
have been evaluated for use as extracting solvents. 3-6
With greater flexibility of operating hardware and availability of various solvents with
tailored composition, the oilseed industry does have expanded options to choose the unique
composition of solvents to obtain the desired final products. While the availability, cost,