Soybeans flour, solubility

Characteristically, legume seeds are rich in protein and contain intermediate to high levels of lysine and threonine which are important in balancing the deficiencies of these essential amino acids in cereal diets. Certain legume proteins, such as soybean, also exhibit strong functional properties, especially water solubility, water and fat binding and emulsification. Thus soybean flours, protein concentrates and isolates have been used widely as nutritional supplements and functional ingredients in foods. 

Foam properties related to seed type. Soybean flour suspensions produced thick egg white-type foams at all pH levels tested except at 4.0 (Figure 14 47). Although the increase in capacity of suspensions at pH values 6.5 and 4.0 was identical, a medium thick foam was produced by the latter. At pH 4.0, the level of soluble protein in the suspension was significantly lower than at the higher pH values the latter three percentages of protein were similar. A decline in foaming capacity at pH... 

The solubility of soybean extract, soybean flour, and milk powder had a positive influence on the results from SmF. For milk powder, the higher amount of water decreased the damaging effects of sterilization, especially regarding the texture, increasing enzyme production. 

Soybean flour will wet and swell in plain water but will not disperse to yield useful adhesive properties. For this purpose, treatment with a soluble alkaline material is necessary. Almost any organic or inorganic alkali will disperse wetted soybean flour to some degree. However, soybean wood glues of maximum bonding efficiency require dispersion with several percent of a strong alkali such as sodium hydroxide or trisodium phosphate... 

Amylase has been prepared from defatted hawk eye soybean flour. The enzyme-concentration dependence of the initial velocity for the hydrolytic reaction was investigated at pH 5.4 in a range of the enzyme concentrations and it was found that the initial velocity was proportional to the enzyme concentration in this range. The hydrolyses of maltodextrin (DPn = 74.4) and soluble starch catalysed by soybean /3-amylase were investigated in the pH range from 3.0 to 9.1 at 25 C, and and kjnax each substrate were determined at each pH. The pH-rate profile showed a bell-shaped curve, and the pH optimum was at 5.85. From Dixon plots of V and the pAT values were found to be 3.5 and... 

Soybean flour first came into use as an adhesive in the 1920s, when a method was developed for extracting the oil from the soybean meal without altering the solubility of the protein. Soybean flour was widely used as a wood adhesive before World War II. It is still an important adhesive in many phases of the wood utilization industry, with much of its use in combination with casein or blood or both (see Lambuth in Chapter 10 of the second edition of this Handbook). 

Figure 14. Foam capacity and protein solubility properties of defatted soybean, peanut, field pea, and pecan seed flour suspensions at various pH values (4T)...

These data demonstrate that changes in foam properties of liquid cyclone processed cottonseed flour are inducible by treatment with succinic anhydride. Gel electrophoretic and solubility data show that there are alterations in the physical and chemical properties of proteins, and in certain cases these changes improve foam properties, that is, improve solubility and polypeptide dissociation of proteins at the interface of the foaming solution. Similar results have been reported for succinylated soybean and sunflower seed proteins (44. 46). 

Suspensions of field pea flour at pH 6.7 and 8.2 (including the two-step adjustment) contained similar high quantities of soluble protein at pH 4.0, most of the protein was Insoluble. Foam capacity of suspensions was higher at pH 8.2 than at 4.0 and 6.7. The two-step pH adjustment did not improve foam capacity over that of the one-step change as shown with the soybean and peanut products. The foam produced at pH 4.0 was thinner than those at pH 6.4 and 8.2 the latter three products had similar consistencies. 

Observations made in this study indicate that protein solubility was more closely related to the type of foam produced than to increase in capacity. For example, soybean and peanut seed flour suspensions contained higher levels of soluble protein than field pea and pecan suspensions and produced foams of much thicker consistency and smaller air cells. 

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 ). 

Lin et al. (15) showed that sunflower meal was superior to soybean and sunflower concentrates or isolates In emulsion capacity. McWatters and Cherry (9) compared select functional properties of defatted soybean, peanut, field pea, and pecan flours and showed that major seed storage proteins were important in emulsifying and foaming properties. Protein solubility was related to the quality of the emulsions and foams. Behavioral characteristics contributed by nonprotein components that occur naturally In the seeds, especially carbohydrates, were Implicated. 

Despite much research to demonstrate new uses, only about 3% of the available soybean meal is processed into edible flours and protein concentrates (>65% protein) and isolates (>90% protein). The flash desolventizer was developed to reduce protein denaturation and produce highly soluble protein food ingredients from soybeans (Fig. 11.17). Integrating these desolventizing systems with subsequent cooking systems produces edible protein flours with a broad spectrum of protein dispersibility characteristics. The system includes a desolventizing tube, a flake separator, a circulating... 

Two processes are currently used to prepare protein-based films the wet method ( casting ), which involves the solubilization of protein and a plasticizer in a solvent followed by the formation of a protein network on evaporation of the solvent and the dry method, which is based on thermoplastic characteristics of proteins and combines the use of pressure and heat to plasticize protein chains [25, 32]. Dehulled soybean, after solvent defatting and meal grinding, becomes a fat-free, low fibre soy flour (48.5% protein). The soy flour, after leaching out of the water/alcohol soluble sugars, is termed soy protein concentrate (above 65% protein). The soy protein concentrate, if it is further extracted by alkali and reprecipitated by acidification, becomes the purest commercially available soy protein isolate (above 90% protein). 

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