Whole soybeans

Soybeans have been used as food in the Orient since ancient times and various methods have been developed to make soybeans as palatable as possible. In recent years, a large number of these simply processed soyfoods are emerging in the West. Tofu and tempeh are the most popular and have the fastest growth rate of any soyfood in America. Tofu is made by coagulating the protein with a calcium or magnesium salt from a hot-water extracted, protein-oil emulsion of whole soybeans. 

Lynch et al. (5 7) found non-heme iron absorptions, as measured by single test meals, for black beans, lentils, mung beans split peas, and whole soybeans to be low (0.84 to 1.91%). This suggests that many commonly consumed legumes are poor sources of iron whether legumes other than soy may have an "offsetting" enhancing effect on heme-iron absorption cannot be predicted. 

Whole soybeans contain 360-370 g/kg CP, whereas soybean meal contains 410-500 g/kg CP depending on efficiency of the oil-extraction process and the amount of residual hulls present. The oil has a high content of the polyunsaturated fatty acids, linoleic (08 2) and linolenic (08 3) acids. It also contains high amounts of another unsaturated fatty acid, oleic (08 1) and moderate amounts of the saturated fatty acids, palmitic (06 0) and stearic (08 0). 

Several reports show that properly processed whole soybeans can be used effectively in broiler (Parvu et al., 2001) and layer (Sakomura et al., 1998) diets as a partial or complete replacement for soybean or other protein meals, although the digestibility of this ingredient may be more variable than with conventional soybean meal (Opapeju et ah, 2006). 

However, whole soybeans may have adverse effects on the carcass fat of broilers. A standard recommendation is that the soybean product should be limited to supplying a dietary addition of 20g/kg soybean oil in order to ensure an acceptable carcass fat quality and good pellet quality. This may require that the incorporation rate of soybeans in the feed of finishing broilers should not exceed lOOg/kg. 

Table 4.1.34A. Soybeans cooked (IFN 5-04-597). The product resulting from heating whole soybean seeds without removing any of the component parts. (From CFIA, 2007.)...

Sol-Morales, M., Palmquist, D.L. and Weiss, W.P. (2000) Milk fat composition of Holstein and Jersey cows with control or depleted copper status and fed whole soybeans or tallow. J. Dairy Sci., 83, 2112-2119. 

Irreversible Insolubilization of Soybean Protein During Drying. Soymilk is an economical high-protein food of high nutritive value produced by grinding soaked whole soybeans with water, heat-... 

Tofu is a white gelatinous curd with a unique texture in which large amounts of water are held (Fig. lU). The texture is soft, smooth, and elastic. Typical percentages of water, protein, oil, carbohydrate and ash in tofu are 88.0, 6.0, 3.5, 1.9 and 0.6, respectively. In Japan, 270,000 metric tons of whole soybean and 65,000 metric tons of defatted soybean meal are used in making tofu and its derivatives. 

The AFIA (31) has further elaborated on quality factors and feed applications of whole (fuU-fat) soybeans. Whole soybeans must be properly heated to provide optimum protein nutrition for critical animals, especially poultry, swine, lambs, and calves as well as pets and fur-bearing animals. 

Underheating of whole soybean may fail to destroy the trypsin inhibitor and reduce urease and lipase activity, resulting in low protein efficiency for critical feeds. An underheated soybean meal greatly increases the need for vitamin D to prevent rickets in turkey poults. Overheating of whole soybeans tends to inactivate or destroy the essential amino acids lysine, cystine, and methionine and possibly others (31). 

Laboratory tests such as urease activity, protein dispersibility index (PDI), nitrogen solubility index (NSI), thiamine, and water absorption have been found valuable in monitoring daily production for protein quality. But biological chick and/or rat assays are the only reliable means currently available for predetermining the nutritional value of whole soybean protein they must be conducted periodically to verify results of chemical tests (31). If whole soybeans are to be used in a mixture containing 20% or more soybean meal, 5% or more urea, and 20% or more molasses, or an equivalent mixture, and exposed to hot, humid storage conditions, it is advisable that the urease activity of the whole soybeans not exceed 0.12 increase in pH (31). Extruded or roasted soybeans properly treated for cattle to increase bypass protein should have urease values of less than 0.05 pH rise. A urease rise of 0.05-0.20 is an indication of proper treatment for swine and poultry. 

Whole soybean may be fed to gestating swine (ground form) and to mature ruminants (whole or rolled form). However, feeding whole soybeans to all other livestock will result in reduced performance and is not recommended. Extruded soybeans may be fed to all livestock, especially swine and poultry. Extmded soybeans fed to lactating dairy cattle increase by-pass protein but most often will reduce butterfat. Roasted soybeans may be fed to aU livestock, especially mature ruminants. Roasted soybeans fed to lactating dairy cattle will increase by-pass protein and slightly increase butterfat. 

M-J Kiang, Dry Extrusion of Whole Soybeans, Insta-Pro International, Des Moines, Iowa, 1993. 

The term dry extruder is applied to a particular type of single-screw machine. These machines were originally designed solely for processing whole soybeans. For this operation, the addition of moisture was not necessary because the high oil content of the beans acted as a lubricant during extrusion. Thus, the machines could reasonably be referred to as dry extruders. ... 

Recent experience has shown that these machines tend to process whole soybean more efficiently if the material is preconditioned with steam prior to extrusion. This finding, together with other recent work, has shown that simple extruders can be made more versatile and efficient in the context of producing compounded feed products (such as aqua feeds and pet foods) if raw materials are preconditioned with steam before extmsion. This has led to the retrofitting of many of these dry extenders with steam conditioners and has hence blurred the distinction between dry and wet/steam extenders (8). It has thus become a little confusing to continue to call these simple machines dry extmders. A typical dry extmder with a preconditioner is shown in Figure 2. 

Since the 1960 s, when whole soybeans first began to be used in intensive animal production, there has been a massive increase in the quantities of soy produced around the world. Although the bulk of this production is processed into a host of useful products ranging from margarine to ink, a significant proportion is now used as full-fat soy for animal feeding. Part of this increase in full-fat soybean meal production and use has been a result of recognition of the value of this material as a concentrated source of nutrients (8). 

Whole soybeans contain not only high-quality protein (38 2%), but also a rich source of energy as a result of the oil they contain (18-22%). They have the potential of supplying major amounts of both energy and protein to all types of livestock and poultry feed. Collective terms that are being used to describe processed soybeans range from full-fat soybeans, heat-processed soybean seeds, heat-treated soybeans, to simply whole soybeans. More specific references are seldom used to correctly identify the processing method. 

Although many reviews and publications are available regarding the nutritional value of processed whole soybeans, few have realized the effect of the processing method on the nutritional value, particularly, the energy value. The following is a summary of selective relevant publications of interest. 

Stillborn et al. (19) compared the effect of three processing techniques on broiler performance. They reported a significantly higher body weight and better feed efficiency (P <. 05) with whole soybeans processed by the dry extruder as compared with the wet extruder or the roaster. 

Ruminants. Aldrich and Merchen (27) studied the effect of heat treatment of whole soybean on protein digestion by mminants. They reported that increasing the extmsion temperature from 220°F to 320°F at 20°F increments resulted in a linear decrease of in situ degradation of soybean protein. As expected, raw soybean protein degraded very fast. The extent of degradation was 84.1%, 45.7%, 40%, 40.9%, 36.7%, and 30.4% for the raw, 220°F, 240°F, 260°F, 280°F, 300°F, and 320°F treatments, respectively. In other words, extmded soybean at 320°F had a bypass protein value of 69.6% as compared with 15.9% for raw soybeans. 

Socha and Satter (28) conducted a study to determine the production response of early lactation cows fed either solvent-extracted soybean meal, raw soybeans, extruded whole soybeans, or roasted soybeans with alfalfa silage as the sole forage source. They reported that dry matter intakes were lower for cows on the raw and roasted soybean treatments. Cows on the extruded soybean diet produced more milk, milk protein, and more 3.5% fat-corrected milk than cows fed the other diets. Body weight changes and body condition scores did not differ among the various treatments. 

Defatting. When tofu, a protein curd made from whole soybean, was treated with Molsin, in addition to volatile compounds, nonvolatile fatty materials were liberated including triglygerides, fatty acids, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol, sito-steryl-D-glucoside, genistein, saponins, etc. (84). 

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