Soybean minor constituents

Table 10.1. General Composition (dry seed weight basis) of Soybean Minor Constituents ...

Minor Constituents. All four oilseeds contain minor constituents that affect the use of the defatted seeds, especially in feeds and foods. Percentages of phytic acid [83-86-3] (3), for example, are soybean, 1.0—1.5 (30) cottonseed kernels, 2.2—3.8 (25) peanut kernels, 0.8 (25) and sunflower, 1.6-1.7 (31). 

Minor constituents tocopherols and phytosterols. Vegetable oUs are the primary source of tocopherols in the average diet. Canola oil is a relatively rich source of tocopherols (refer to Table 6) it is similar in total tocopherol content to com oil, cottonseed oU, safflower oil, and sunflower oil (60-70 mg/100 g). Only soybean... 

Isoflavones are minor constituents of soybeans whose consumption is believed to have beneficial effects (9-11). The benefits of isoflavones have encouraged the direct consumption of soy protein in the United States. The concentration of isoflavones changes with variety and growing conditions and has been reported to be 1.2-2.5 mg/g in U.S. beans (9), 0.5-2.3 mg/g in Korean beans (10), and 0.2-3.5 mg/g in Japanese beans (11). 

The total acetone insolubles content of commercial acetylated lecithin products can vary from about 52% to about 97%, the remainder being soybean oil (or another food-grade triglyceride or fatty acid as a natural constituent or added diluent), natural pigments, sterols, and other minor constituents present in crude lecithin from the soybean. The acetylated lecithin meets all the compositional requirements of the U.S. Food Chemicals Codex (54). 

Oil recovered by solvent extraction or mechanical pressing is termed crude soybean oil and contains various classes of lipids. It consists primarily of neutral lipids, which include tri-, di- and monoacylglycerols, free fatty acids, and polar lipids such as phospholipids. It also contains a minor amount of unsaponifiable matter that includes phytosterols, tocopherols, and hydrocarbons such as squalene. Trace metals are found in soybean oil in ppm concentration. When the oil is refined, concentrations of all minor constituents are reduced. The typical composition of crude and refined soybean oil is shown in Table 2.2. 

Phospholipids can be obtained from various sources, two of which are oilseed lecithins and egg yolk lecithins. The phospholipid composition of soybean lecithin appears to vary according to the method of extraction. PC content ranges from 29 to 46% PE, from 21 to 34% and PI, from 13 to 21%. Other minor constituents are phosphatidylserine, phosphatidic acid, lyso-PC, lyso-PE, and lyso-PI. In addition to soybeans, lecithin has been found in many other oilseeds, including peanuts, cottonseed, sesame, safflower, and sunflower, among others. 

Lecithin and cephalin are common phosphatides found in edible oils. Soybean, canola/rapeseed, com, and cottonseed are the major oils that contain significant quantities of phosphatides. Alkaline treatment used for FFA reduction is also capable of removing most of the phosphatides from these crade oils. Tocopherols are important minor constituents of vegetable oils, which are natural antioxidant that retard the development of rancidity. 

Soybeans and soybean products contain high levels of protein, carbohydrates, and lipids (Table 11.6.1). As minor components of complex mixtures, isoflavones must first be separated from the bulk of the matrix constituents prior to analysis. Efficient extraction methods for isoflavones should account for their diverse structures, chemical properties, and the food matrix of which they are constituents. This unit describes a practical way of extracting isoflavones from soybean products in their natural forms using readily available solvents and laboratory equipment. 

Phospholipids (Figure 3) are constituents of membranes and are only minor components of oils and fats, sometimes responsible for cloudiness. They are usually removed during degumming, the residue from soybean oil processing being a source of phospholipids used as food emulsifiers. The term lecithin is used very loosely for such material, and it may variously mean phosphatidylcholine, mixed glycerophospholipids, or cmde phospholipid extracts from various sources. Where possible, more specific nomenclature or the source and purity should be used (14). 

Standard-grade, commercial lecithin from the soybean is a complex mixture. It comprises phospholipids, triglycerides, and minor amounts of other constituents (i.e., phytoglycolipids, phytosterols, tocopherols, and fatty acids). The composition and molecular arrangement of this heterogeneous mixture of compounds defines a product that is low in apparent polarity and has a strong tendency to promote water-in-oil (w/o)-type emulsions (31). 

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