Soy protein isolate

The effect of type and content of modified MMT on the structure and properties of bionanocomposite based on SPI and MMT was studied by Kumar et al. [209, 

Bionanocomposites based on SPI reinforced with bentonite, talc powder, zeolite, and rectorite have also been reported in the literature [212-214]. In most cases, they had improved mechanical and barrier properties as compared to unfilled matrices. 

Gelatin is prepared by the thermal denaturation of collagen, isolated from animal and fish skin and bones, with very dilute acid. Gelatin has also been successfully and largely used as a matrix to produce bionanocomposites which are reinforced with nanoreinforcements such as clays and hydroxyapatite to be used in applications ranging from packaging materials to artificial bones. 

For several years, hydroxyapatite/gelatin bionanocomposite using biomimetic coprecipitation has been pursued as a biological bone substitute because of its biocompatibility, biodegradability and its usage as a scaffold site for regeneration of new bones [221-226]. 

Collagen/hydroxyapatite (HA) bionanocomposites have also been extensively studied as bone grafts due to their composition and stractural similarity with natural 

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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. 

The protein precipitate is washed with water, redispersed at pH 7, and then spray dried. Typical commercial soy protein isolates contain greater than 90% cmde protein, dry wt basis. 

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). 

Products prepared from soy protein products and resembling chicken, ham, frankfurters, and bacon are available commercially. Soy protein isolates are used in place of milk proteins or sodium caseinate in products such as coffee creamers, whipped toppings, yogurt, and infant formulas (see Dairy substitutes). Soy protein products also are used in snacks and in baked foods. 

Protein-Based Substitutes. Several plant and animal-based proteins have been used in processed meat products to increase yields, reduce reformulation costs, enhance specific functional properties, and decrease fat content. Examples of these protein additives are wheat flour, wheat gluten, soy flour, soy protein concentrate, soy protein isolate, textured soy protein, cottonseed flour, oat flour, com germ meal, nonfat dry milk, caseinates, whey proteins, surimi, blood plasma, and egg proteins. Most of these protein ingredients can be included in cooked sausages with a maximum level allowed up to 3.5% of the formulation, except soy protein isolate and caseinates are restricted to 2% (44). 

Soybean-based ice cream products, technologically feasible, are generally not in use because of flavor problems. An acceptable ice cream has been made by replacing 50% of the nonfat milk soHds with a dried soy protein isolate made up of cheese whey (21). Chocolate flavor has been widely used to mask the flavor of soybean proteins in ice cream (see Flavors and spices). 

ALEKEL D L, ST GERMAIN A, PERESON C T, HANSON K B, STEWART J W, TODA T (2000) IsoflaVOne-rich soy protein isolate attenuates bone loss in the lumber spine of perimenopausal women. Am J Clin Nutr. 72 844-52. 

MARIOTTI F, MAKE S, BENAMOUZIG R, LUENGO 0, DARE S, GAUDICHON 0, TOME D (1999) Nutritional value of [15N]-soy protein isolate assessed from ileal digestibility and postprandial protein utilization in humans. /AmZ 129 1992-7. 

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. 

Figure 2. Relationship between calcium solubility and pH after complete digestion for four soy products. Key solid line, full-fat soy flour long-dashed line, soy protein isolate short-dashed line, soy protein concentrate and dotted line, defatted soy flour...

The in vitro digest was prepared by digesting a soy protein isolate. For each UF determination, 50 ml of the 100,000 g supernatant was introduced into the UF chamber. Values are mean S.D. for four experiments. 

Isolated Soy Proteins. Isolated soy proteins (90% protein dry basis) are highly dispersible, highly soluble, highly functional soy products (8 9, H > 17, 18) Designed to replace a portion of... 

Alekel, D.L., Germain, A.S., Peterson, C.T., Hanson, K.B., Steward, J.W. and Toda, T. (2000). Isoflavone-rich soy protein isolate attenuate bone loss in the lumbar spine of perimenopausal women, Am. J. Clin. Nutr., 72, 844-852. 

Petrakis, N.L., Barnes, S., King, E.B., et al. (1996). Stimulatory influence of soy protein isolate on breast secretion in pre- and post menopausal women, Cancer Epidemiol Biomark and Prevention, 5, 785-794. 

Sua J-E, Yuanb XY et al (2010) Properties stability and biodegradation behaviors of soy protein isolate/poly(vinyl alcohol) blend films. Polym Degrad Stab 95 1226-1237... 

Maltais, A., Remondetto, G.E., Gonzales, R., Subirade, M. (2005). Formation of soy protein isolate cold-set gels protein and salt effects. Journal of Food Science, 70, 67-73. 

Malhotra, A., Coupland, J.N. (2004). The effect of surfactants on the solubility, zeta potential, and viscosity of soy protein isolates. Food Hydrocolloids, 18, 101-108. 

Modification of Raw Materials. In order to vary the protein and soluble sugar contents, portions of soy flour (Extra Acted Soy Flour 200-1) were replaced with various amounts of sucrose and soy protein isolate (Promine F). Levels of... 

Figure 3. The effect of blending on solubility (I). Samples A, B, D, and E are soy protein isolates. Sample C is a commercial sodium caseinate. T is the temperature of the slurry after blending.

Figure 2. Water binding (grams of unfrozen water/gram of solids) by soy protein preparations, each containing 1 g of water/g of solids, as a function of protein content, where % protein (on a solids basis) = % N X 6.25 (O) soy protein isolate B (9) soy protein concentrate (/ ) soy flour (defatted) fCJl carbohydrate-enriched fraction of soy concentrate f32j.

Sucrose Elgedaily and Campbell (24] found sucrose, within the concentration range used, to have no significant effect on water absorption of three soy protein isolates. 

De Groot and Slump (40) studied the influence of alkali on soy protein isolates, monitoring the production of lysinoalanine and changes in amino acid content. They found that above pH 10, treatment at 40 C for 4 hours resulted in decreased cystine and increased LAL (Figure la). They also found that at pH 12.2 for 4 hours, lysine and cystine content steadily decreased with increasing temperatures from 20° to 80 C, and LAL content increased dramatically. At pH 12.2 and 4O C they reported that the greatest loss in cystine and increase in LAL occurred in the first hour (Figure lb). Thus they concluded that exposure of soy protein isolate at pH 12.2 for only a short time would destroy some cystine and decrease the nutritive value. 

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