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A review in crop biotechnology that is being used to enhance locally …

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Crop biotechnology to enhance nutritional quality
- The Application of Biotechnology to Nutrition: An Overview


The nutritional concerns of westernized populations stem from the quality and composition of foods rather than from inadequate quantity. For example, the recognition that trans-fatty acids found in foods containing hydrogenated vegetable oils and shortenings may have undesirable effects on blood lipids [14] has caused the food industry to reexamine its use of these ingredients. One solution would be to use oils or shortenings rich is stearic acid, an 18-carbon saturated fatty acid that does not have undesirable effects on blood lipids [15]. Via biotechnology, canola has been made to over-express stearic acid by repressing the D9 desaturase enzyme; the resulting vegetable oil requires little or no hydrogenation, has no trans-fatty acids and provides the food processing qualities of a hydrogenated oil without the hydrogenation process [16]. While such a product could provide a solution to the food processing industry, current fatty acid labeling regulations provide a disincentive to the use of such a product. Because the U.S. FDA requires that the stearic acid content of a product be reflected in the saturated fat declaration in labeling [17], the substitution of high stearic acid oil for a hydrogenated oil in a processed food product could result in an increase in saturated fat content of the product. Furthermore, the FDA has proposed that a "trans-free" claim cannot appear on the labeling of products that contain more than 0.5 g saturated fatty acids [18]. Since consumers understand that saturated fats have undesirable effects on blood lipids and should be limited in the diet, a product with more stearic acid, even though it does not elevate lipids, will be represented negatively in labeling.

Another approach to improve the functional properties of vegetable oils while avoiding hydrogenation and the generation of trans-fatty acids is to over-express oleic acid (18:1 n-9) at the expense of linoleic (18:2 n-6) and linolenic acids (18:3 n-6). The reduction of polyunsaturates makes the oil less susceptible to oxidative rancidity, an important consideration in food processing and food service applications. By silencing the gene for the D12 desaturase enzyme, oleic acid conversion to linoleic acid is minimal, and instead oleic acid accumulates in the oilseed. Soybean oil with 85% oleic acid and less than 5% total polyunsaturates has been produced via this transformation process [19], and the oxidative stability of the oil was shown to be similar to that of a fully hydrogenated frying shortening.

As of this writing, there are no commercialized food products of biotechnology containing animal or human genes. The technology is available, but public acceptance issues may be deterring their development. Nevertheless, researchers at the University of California at Davis have succeeded in inserting and expressing the genes for several human milk proteins—lactoferrin, lysozyme and the alpha-1 antitrypsin protein—in rice for the purpose of improving infant formulas [20]. Such a product could provide a test case for the debate over whether there are socially acceptable circumstances where human genes could be used in commercial, genetically enhanced food products. Such products also would necessitate the development of policies and practices to assure that rice (or any other vehicle) containing human proteins would be segregated from the general food supply and that pediatricians and consumers would be fully informed about the product.

There has been much concern in the media and among consumer activist groups about the possibility of inadvertently inserting an allergen into a genetically enhanced crop, causing it to be allergenic to certain people. Developers of genetically improved crops take several measures to assure the risk of such an inadvertent event is very small [21]. The "flip-side" of this situation is that genetic engineering techniques are being used to reduce, if not eliminate, allergens in food. For example, workers in Japan have reduced the content of an allergenic protein in rice by silencing the gene expressing the protein [22]. Other researchers are working to reduce the allergenicity of peanuts [23] and wheat [24].

Genetic engineering techniques are also being used to put vaccines in foods. Potatoes have been developed to contain vaccines against a variety of diseases, including cholera [25], Norwalk virus [26] and hepatitis B [27]. One draw back from the use of potatoes as the vehicle is that they must be eaten raw. Dr Charles Arntzen, a pioneer in this field, is now inserting a vaccine against hepatitis in bananas, a more palatable vehicle when eaten raw and a food that can be readily eaten by small children [28]. The benefits of food-borne vaccines are that they could be provided for a fraction of what it costs to develop and administer vaccines as injections. However, there are many questions about how these products would be controlled, so again new policies and procedures will need to be developed. Issues such as proper distribution, quality control and control of access will need to be resolved.

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