Environmental Engineering Reference
In-Depth Information
Million gallons
Million liters
3040
800
2280
600
400
1520
200
760
0
0
1999
2002
2005
2008
FIGure 20.4 (see color insert)
Biodiesel consumption in the United States.
soybean oil. The remainder of the oil (~85%) is made up of unsaturated fatty acids or 18:1, 18:2, and
18:3. Transgenic, induced, and natural mutations, including those combining two or more genes, have
been used in breeding soybeans for enhanced and improved oil content. Several genes have been
discovered that affect fatty acid levels in soybeans, enabling breeders to combine genes to tailor novel
fatty acid profiles desired for various end uses. Research since the 1970s has led to a greater under-
standing of how to genetically alter the fatty acid of soybean oil. Because consumer and end-user
preferences for soybean oil are changing, breeding is needed to modify the fatty acid composition in
soybean oil to fulfill these new demands in industrial, food, and other products (Wilson 2004).
Soybean research priorities have been set, with guidance from consumers and end-users, to ini-
tially target fatty acid profiles that have the highest probability to facilitate expanded use of soy-
bean oil in edible and industrial applications in the United States (Wilson 2004). The most visible
of these programs was “The Better Bean Initiative” launched in the United States in 2000 by the
United Soybean Board. This program's aim is to add value in the oil and protein seed components
by genetically changing objectionable characteristics. These deliberations have focused on three
different oil phenotypes: saturates, oleic acid, and linolenic acid (Table 20.1). Modification of these
oils through breeding and biotechnology is being emphasized to develop the desired fatty acid
phenotypes. It is impractical to commercially develop all oil phenotypes. Perhaps the most desired
phenotype for soybean oil is less than 7% saturates [palmitic (16:0) and stearic acids (18:0)], more
than 55% oleic acid (18:1), and less than 3% linolenic acid (18:3) because of its multiple uses in many
food and industrial applications (Wilson 2004).
Human health concerns and improved cold flow of biodiesel have stimulated research to develop
soybeans with less saturated fat. The U.S. Food and Drug Administration's requirement for a food
to be labeled “low in saturated fat” is less than 1 g of saturated fat per serving. This means that
the fatty acid composition of vegetable oil should contain less than 7% total saturated fat to make
such a claim. Lowering soybean from 15% saturated fat to 7% or less will make soybean oil more
attractive to food manufacturers and health-conscious consumers while additionally improving the
cold flow of biofuels made from soybean oil (Wilson 2004). On the other hand, soybean oil high in
saturated fats would make hydrogenation less necessary and is in demand for making margarines
and shortenings without
trans
-fats for the evolving health-conscious society.
Increased oleic acid (18:1) in soybean oil is important because of its health benefits and increased
oxidative stability. A diet in which fat consumption is high in 18:1 is associated with reduced cho-
lesterol, arteriosclerosis, and heart disease (Grundy 1986; Wardlaw and Snook 1990; Chang and
Huang 1998). High oleic acid content also increases oxidative stability and extends the utility of
soybean oil at high cooking temperatures. It also will significantly increase soybean oil use in
pharmaceuticals, cosmetics, and industrial products such as lubricants and biodiesel. To improve
acceptance of soydiesel, a high 18:1 level combined with lower saturates (16:0 + 18:0) is needed.
This will improve ignition and cold flow in cooler climates (Wilson 2004).
