Soy protein extract

Table 6.3 Effect of soy protein/extracts containing isoflavones on OVX-induced bone...

Figure 10.4 Typical UHPLC trace of isoflavones from a soy protein extract monitored at 260 nm using a Hypersil Gold C18 column (100 x 2.1 mm 1.9 pm Waters, Milford, MA) and a 0.5-mL/min flow rate (9600 psi) of a linear gradient of 0.1 % aq. formic acid versus methanol/acetonitrile(l l). FL = flavone (internal standard), other details in figure and in text. Concentrations of ISOFLAVONE peaks (pM) D = 17.66, GLY = 6.27, G = 26.49, D-Mal = 16.76, GLY-Mal = 3.62, D-Ac = 5.87, G-Mal = 26.70, DE = 3.37, GLYCITEIN = 1.74, G-Ac = 8.33, GE = 4.36.

Gugger, E.T. and Dueppen, D.G. 1997. Production of isoflavone enriched fractions from soy protein extracts. US patent 5,702,752. December 30, 1997. 

Like soy proteins, extracted canola proteins were typically recovered by isoelectric precipitation. The precipitates, after being washed and dried, constitute the protein isolate. Due to the complex protein compositions and varietal differences among canola strains, a wide range of isoelectric points was observed, at each of which only a specific fraction of the extracted protein was precipitated, therefore protein recovery of single-step isoelectric precipitation was usually low. The highest ever reported was 65.7% of the amount of protein extracted at pH 11, obtained at pH 3.6 [32]. Moderate increase in protein yield was achieved by the same researchers with multi-isoelectric precipitation at different pH. Therefore, the further improvement in overall protein output hinges on the recovery of fractions that were not precipitated, and these proteins, due to their high solubility, are ideal for many food applications. 

Mondor M, Ippersiel D, Lamarche F, Boye J1 2004a. Effect of electro-acidification treatment and ionic environment on soy protein extract particle size distribution and ultrafiltration permeate flux. J Membr Sd 231 169-179. 

Soy protein extracts have been found to lower cholesterol in humans, an effect that appears to be... 

Commercial soy protein concentrates typically contain 70 to 72% cmde protein, ie, nitrogen x 6.25, dry wt basis. Soy protein isolates are prepared from desolventhed, defatted flakes. A three-stage aqueous countercurrent extraction at pH 8.5 is used to disperse proteins and dissolve water-soluble constituents. Centrifugation then removes the extracted flakes, and the protein is precipitated from the aqueous phase by acidifying with HCl at pH 4.5. 

A modification of the conventional soy protein isolate process has been investigated on a small pilot-plant scale. It is based on the absorption of water from the aqueous protein after extraction at pH 8.5 using temperature-sensitive polyisopyropylacrylamide gels, followed by spray drying to give a 96% protein isolate (111). 

Similar to the human studies, the animal studies are not entirely consistent, due to the different study designs (source and dose of soy protein/isoflavones time, method and length of administration age of rats, etc.). Nevertheless, a certain number of conclusions may be drawn. Overall, soy extracts or pure isoflavones show an osteoprotective effect in the ovariectomized rat model of menopausal bone loss. The time of administration is important and they must be given at the time of ovariectomy which allows prevention but not reversal of bone loss. Although the OVX-induced bone loss in the rat is a... 

In order to produce soy protein, soybeans are first dehulled, flaked, and defatted to make white flakes . Soy protein concentrates are obtained by removing a portion of the carbohydrates from defatted and dehulled soybeans. Alcohol extraction is the method most commonly used to manufacture soy protein concentrates even though it results in the loss of isoflavones. Soy protein concentrates retain most of the fiber in the original soybean and must contain at least 65% protein on a moisture-free basis to meet quality standards. The most concentrated source of soy protein is soy protein isolates (or isolated soy protein, ISP), which is required to be at least 90% protein on a moisture-free basis. It is heat-treated during processing to insure inactivation of trypsin inhibitors. Most isolated soy protein is manufactured by water extraction from defatted and dehulled soybeans and it retains the natural isoflavones. 

A greater effect is apparent in postmenopausal women compared with men. The protein component seems to play a crucial role in the cardio-protective effect of soy. When soy-extracted phytoestrogens are added to animal-derived protein (casein), no effects on lipids are observed (Greaves et al., 1999). It is therefore clear that both the proteins from soy and the phytoestrogens need to be present to have a beneficial effect on lipid. In the presence of soy protein, the lipid-lowering effect is dose dependent on the phytoestrogen present (Crouse et al., 1999). 

Greaves, K.A., Parks, J.S., Williams, J.K. and Wagner, J.D. (1999). Intact dietary soy protein, but not adding an isoflavone-rich soy extract to casein, improves plasma lipids in ovariectomized cunomologus monkeys, J. Nutr., 129, 1585-1592. 

An important caveat is that the epidemiological evidence suggesting protection from hormone-dependent cancer by isoflavone phytoestrogens is based on foods rather than isoflavone extracts, which in the future could include isoflavone-containing therapeutics. Indeed, the preparation of isoflavone extracts from soy protein could well result in the loss... 

Fig. 8. A typical commercial soy protein isolate process. The soy proteins are extracted with alkali, precipitated with acid, washed with water, redispersed and dried. (Reprinted with permission from [14], 1989 Institute of Food Technologists)...

Sato et a2- (34) demonstrated that a variety of common meat additives, inclucnrTg cottonseed flour, nonfat dry milk, spray-dried whey, wheat germ, and textured soy flour, inhibited WOF in the meat system. These products may have exerted their inhibitory effect on WOF through the Maillard reaction, since most of them contain some reducing sugars. Pratt (40) reported soybeans and soy protein concentrate had an inhibitory effect upon development of WOF and was able to demonstrate that the active components are water soluble. Fractionation and analysis of the water-soluble fraction showed the antioxidant activity was due to the presence of isoflavones and hydroxylated cinnamic acids (40). This confirms earlier work showing that the flavonoTcis present in plant extracts inhibit oxidation in sliced roast beef (41 ). 

Soy protein preparations contain a variety of biologically active compounds including saponins, fibers, trypsin inhibitors, and isoflavones (Potter, 2000). Hamsters and rats fed ethanol-extracted soy protein isolates had no ability to lower plasma cholesterol compared to intact soy protein isolates (Lucas et al., 2001 Ni et al., 1999). Extraction with ethanol is a treatment that would remove saponins, isoflavones, and other phytochemicals from the protein. Although one study showed that ethanol washing did not... 

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