Vegetable oils are ubiquitous in everyday life. They are used in cooking, in making margarine and other processed foods and also in producing several non-food items such as soap, cosmetics, medicine and even paint. Along with proteins, carbohydrates and water, lipids (oils, fats, cholesterol) are classified as macronutrients - the components which make up the bulk of one's diet. New developments in oil production will bring advantages to farmers and benefits to consumers.

Oil Chemistry

Whereas oils are liquids at room temperature and fats are solids, in almost all other respects they are similar. Both contain fatty acids that vary according to the length of their carbon chains, and the degree of saturation (the extent to which hydrogen atoms are attached to the carbon atoms in the chain). This latter aspect leads to fats being described as either saturated (complete hydrogenation) or unsaturated (incomplete). Chain length and degree of saturation both influence the melting point. Vegetable oils tend to contain more unsaturated fatty acids than animal fats and that is why they are liquid at room temperature - the reverse is true for animal fats. Plants nonetheless produce fatty acids with a wide variety of chain lengths and degrees of saturation. Each combination gives different properties and, therefore, different functions of oil.

Soya is the main source

There are several different sources of vegetable oils, the most abundant being the soybean. Soybeans contain 20% oil, almost all of which is extracted when the seeds are crushed for animal feed, the main purpose for which they are grown. Like all vegetable oils, soy oil is cholesterol-free and, like most of them, is low in saturated fat. Soy oil also has a unique blend of specific fatty acids (omega-3 fatty acids and omega-6 fatty acids). The omega-3 fatty acids in soy oil are similar, although not identical, to those found in fish oil that have been shown to reduce the risk of heart disease.

Designer oils

Plant breeders have long since developed crops with oils suited to different, specific purposes. Rapeseed oil for example, naturally contains high amounts of erucic acid. As this is nutritionally undesirable, plant breeders have successfully bred rape varieties producing virtually no erucic acid. These practices are however very time consuming, taking several years to perfect. Advances in plant genetics have revealed the biochemical pathway by which plants make oils and the influence that different fatty acids have on oil characteristics. Genetic modification now makes it possible to improve the composition and properties of oils from different plants far more quickly and precisely than with traditional breeding techniques. The first genetically modified vegetable oil has a high proportion of lauric acid - desirable for many food and non-food applications. It is for example, a critical ingredient in soaps, shampoos and detergents and is also used in confectionery, icings, crackers and coffee whiteners. The oil was produced by genetically modified canola, a relative of oilseed rape. A gene from the California bay laurel tree was introduced which codes for an enzyme involved in the synthesis of lauric acid. It is now used commercially in the USA. More recently a new soybean has been developed, variety producing a less saturated and more heat stable oil. Ordinary soybean oil is often hydrogenated to make it suitable for use in baked goods and for frying. This process lowers levels of unsaturated acids. The genetically modified soybean oil precludes the need for hydrogenation and also has a healthier fatty acid composition. These beans are expected to have agronomic yields comparable to existing varieties.

Future developments

These examples provide a glimpse of the future when it is likely that, instead of developing specialised oils through plant breeding or by mixing or refining oils, they will increasingly be developed by genetic modification. Shifting the selection of the right composition to the field rather than the factory will have significant consequences for farmers and benefits for consumers. Instead of producing undifferentiated commodity crops they will deliver genetically modified varieties which produce different oils for specific uses, providing dietary benefits and wider choices for consumers.

FOOD TODAY 07/1998