Processing of soybeans

Another example is that of Okara the residue from the commercial processing of soybean contains 8% protein on wet basis, or about 40% on a dry basis.33 Thus, the wet Okara contains about 80% moisture. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Proper processing of soybeans requires precise control of moisture content, temperature and processing time. Adequate moisture during processing ensures destruction of the ANFs. Both over- and undertoasting of soybean meal can result in a meal of lower nutritional quality. Underheating produces incomplete inactivation of the ANFs and overtoasting can reduce AA availability. 

The processing of soybeans has been described in more detail elsewhere than can be done here (132-134). Oil is recovered today by either mechanical means or through the use of organic solvents. In the preindustrial revolution period, soybeans were merely pressed with lever or animal-driven screw-operated batch presses. Around the turn of the Twentieth Century, when soybeans became a viable commercial crop in the United States, steam-powered hydraulic batch presses were used. Today, electric-powered continuous screw-presses, often referred to as expellers (but this is a trademarked name for screw presses manufactured by one supplier), or continuous countercurrent solvent extractors are used. 

Soybean meal is used effectively in the formulation of pet foods, particularly for dogs, where simple corn-soybean meal mixtures perform as well as complex diets containing high levels of animal protein, and at substantially lower cost (4). Rapid growth in aquaculture over the last 10-15 years has resulted in significant new opportunities for utilization of soybean meal in finfish and shrimp diets. Whether additional heat processing of soybean meal to further reduce levels of antinutri-tional factors or supplementation with lysine or methionine or both is beneficial to performance appears to be species dependent (4, 6). 

TABLE 5. Composition of Products Obtained from Membrane Processing of Soybean and Rapeseed Oiis. 

Extrusion processing of soybeans is done for several purposes as summarized below ... 

Herman, E.M. D.L. Melroy T.J. Buckhout. Apparent processing of soybean oil body protein accompanies the onset of oil mobilization. Plant Physiol. 1990, 94, 341-349. 

Riaz, M.N. Processing of Soybeans into Ingredients. M.N. Riaz, Ed. CRC Press Boca Raton, FL, 2006, pp. 39-62. 

Sessa, D.J. Processing of soybean hulls to enhance the distribution and extraction of value-added proteins./ Sci. FoodAgric. 2003> 84, 75-82. 

Fig. 11.20. Flow diagram for enzyme- and extrusion-assisted aqueous processing of soybeans.

Protein Dispersibility Index is a standard AOCS method (Ba 10-65) for measuring the amount of heat treatment used in the processing of soybean meal products. 

Glyceride ester polyol of soybean oil is obtained by ozonolysis of the oil in the presence of variable concentrations of a primary polyol, such as glycerine or propylene glycol. Polyols produced from the combined ozonolysis, transesterilication and acetate capping processes of soybean oil with glycerine in ethyl acetate are shown in Fig. 6.2. ... 

Processing of Soybeans in Three Stages. A feed of 10000 kg of soybeans is... 

Figure 8.1. Key steps in processing of soybean oil that require control of autoxidation and photooxidation.

Toasting of soybeans by heating at 100-1 lO C to inactivate lipoxygenase and antinutritional factors (e.g. trypsin inhibitor) is important to improve the quality of soybean protein products used for either animal feed or human consumption. However, this thermal enzyme inactivation is not carried out in the conventional processing of soybean oil. Therefore, the soybean flakes must be solvent extracted without delay to minimize free fatty acid and peroxide formation in the extracted crude oil and to produce a finished oil of improved oxidative and flavor stability. 

A decrease in tbe inhibitor activity can also be achieved by soaking. A tbermal step can then follow under gentler conditions. Altbougb the processing of soybeans into protein isolates, textured protein, or meat surrogates causes a decrease in the inhibitor activity against tr)fpsin, noticeable activity can still be present (Table 16.18). Soybeans promote the growth of rats to the same extent as casein when about 90% of tbe inhibitor activity is eliminated (Table 16.19). 

However, various technologies have been developed that utilise extractions from oilseed meals and pulses as the raw material for the production of flours, protein isolates and protein concentrates. These technologies are mainly used in the processing of soybeans and, to a lesser extent, in the processing of peanuts, cotton, lupine and other oilseed meals. Additional sources of protein are whey, fishmeal and others. The final products can be various mixtures rich in proteins (often enriched by minerals and vitamins), which are mainly used in less-developed countries. 

The processing of soybeans into oil and meal began in the Orient. The oil was used primarily for human food, while the meal was used for animal feed. 

Lecithin One of the main phospholipids found in nature with important implications in metabolism and cell membranes. Lecithin is considered an important nutraceutical compound because it lowers blood cholesterol and is key to the synthesis of choline. Chemically, lecithin is the emulsifier phosphatidyl choline, and commercial lecithin consists of a mixture of different phospholipids such as phosphatidyl ethanol amine, phosphatidyl inositol, and phosphatidyl serine. Most commercial lecithin is obtained during the refining process of soybean oil. The egg yolk is also a rich source of lecithin. Lecithin is widely used in the baking, cookie, and wheat flour tortilla industries to improve dough machinability, improve texture, and retard staling. It is generally used from 0.1%-1%. 

Muley, P., Boldor, D., 2013. Scale-up of a continuous microwave-assisted transesterification process of soybean oil for biodiesel production. Transactions of the Asabe56 (5), 1847—1854. 

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