Introduction

The importance of oils and fats in human nutrition is well documented (1). Lipids form a vital component of many cell constituents and are an important source of energy. Oils and fats also contribute significantly as a functional ingredient in improving the sensory characteristics of numerous processed food products.

About 70% of edible oils are derived from plant sources (about 50 million tonnes/annum), and there are three major groups of oil-producing crops. These are temperate annual oilseeds (soy, rapeseed, sunflower, and peanut), about 60% of the total vegetable oil production; perennial tropical crops (oil palm, coconut, and babassu nut), about 25% of total oil production; and crops such as cotton and corn where the embryo is a by-product of processing. This latter group accounts for about 10% of total vegetable oil production. The remaining 5% of total vegetable oils are derived from miscellaneous niche crops such as olive (3%), linseed (1%), and sesame (1%) (2).

Many oils are also used for nonfood applications (about 2% of total production). The plant oils most commonly used for industrial purposes include coconut, castor, linseed, and soy. The predominant source of industrial fatty acids, however, is tall oil, a by-product of the wood pulp and paper mill industry (2).

The utility of a given oil in a food or industrial application is determined primarily by acyl composition of the storage triacylglycerol (TAG). For most edible oils the acyl composition of the TAG is qualitatively the same as that of the membrane lipids. That is, the same five acyl groups palmitate (16:0), stearate (18:0), oleate (18:1), linoleate (18:2), and linolen-ate (18:3) occur in both lipid classes, often in the same molar ratios. The degree of fatty acid desaturation determines both the melting range and the thermal stability of the oil (3). Industrial oils such as castor, which is rich in hydroxy-fatty acids, often contain fatty acids with functional groups other than methylene-interrupted double bonds. These functional groups determine the reactivity and cross-linking ability of oils used for such applications as paints and coatings. The number of different fatty acids used for industrial purposes, however, is currently quite small compared with the number available (over 300 different types) from nature (4).

Thus, a review of plant seed oil modification is really a review of the fatty acids that make up the oil. Here we discuss the potential for extending the range of domesticated crops, such as soybean and rape, for novel industrial and food purposes by producing new and useful fatty acids in these crops.

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