Genetically Improved Crops - The Oxford Topic of Food, Politics, and Society - page 81

or phenotype. A similar approach is being used to derive soybean varieties contain-
ing some oligofructan components that selectively increase the population of benefi-
cial species of bacteria in the intestines of humans and certain animals and that inhibit
growth of harmful ones (Bouhnik 1999).
Macronutrients: Novel Lipids
Genomics, specifically marker-assisted plant breeding, combined with recombinant
DNA technology provide powerful means for modifying the composition of oilseeds
to improve their nutritional value and provide the functional properties required for
various food oil applications. Genetic modification of oilseed crops can provide an
abundant, relatively inexpensive source of dietary fatty acids with wide-ranging health
benefits. Production of such lipids in vegetable oil provides a convenient mechanism
to deliver healthier products to consumers without requiring them to make signifi-
cant dietary changes. Major alterations in the proportions of individual fatty acids have
been achieved in a range of oilseeds using conventional selection, induced mutation,
and, more recently, post-transcriptional gene silencing. Examples of such modified
oils include low- and zero-saturated fat soybean and canola oils, canola oil contain-
ing medium-chain fatty acids (MCFA) whose ergogenic potential may have appli-
cation in LDCs, high stearic acid canola oil (for trans fatty acid-free products), high
oleic acid (PUFA), λ-linolenic (GLA; 18:3 n-6) stearidonic acids (SDA; C18:4 n-3),
very-long-chain fatty acids (Zou, 1997), and omega-3 fatty acids (Yuan and Knauf
1997). These modified oils are being marketed, and many countries have a regulatory
system in place for the premarket safety review of novel foods produced through con-
ventional technology.
Edible oils rich in monounsaturated fatty acids provide improved oil stability, flavor,
and nutrition for human and animal consumption. High-oleic soybean oil is naturally
more resistant to degradation by heat and oxidation and thus requires little or no postre-
fining processing (hydrogenation), depending on the intended vegetable oil application.
Oleic acid (18:1), a monounsaturate, can provide more stability than the polyunsaturates
linoleic (18:2) and linolenic (18:3). Antisense inhibition of oleate desaturase expression
in soybean resulted in oil that contained > 80% oleic acid (23% is normal) and had a sig-
nificant decrease in PUFA (Kinney and Knowlton, 1998). Dupont has introduced soy-
bean oil composed of at least 80% oleic acid and linolenic acid of about 3% and over 20%
less saturated fatty acids than commodity soybean oil. Monsanto's Vistive contains less
than 3% linolenic acid, compared with 8% for traditional soybeans. This results in more
stable soybean oil and less need for hydrogenation. The genetically modified version
Vistive gold (MON 87705) is engineered to reduce linolenic acid content by suppressing
FATB and FAD2, endogenous enzymes that play a role in the biosynthesis of fatty acids.
This alteration more than triples oleic acid content, raising it from approximately 20%
to 70% of all fatty acids, and reduces the levels of linoleic acid, stearic acid, and palmitic
acid present in seeds (Vistive Gold Soybeans 2011).