Soybean proteins stability

Foam properties related to salt. The addition of sodium chloride to soybean protein suspensions caused them to form high-capacity, low-stability foams (13). It was suggested that foam capacity increased because salt improved protein solubility at the interface of the colloidal suspension during foam formation, but retarded the partial denaturation of the surface polypeptides of proteins that are necessary for protein-protein interaction and stability. 

Immobilized soybean peroxidase stability after ten washes and even after storage of the sample suspensions in a refrigerator (4°C) for 5 months The protein-coated microcrystals [20]... 

The protein stabilized emulsions formed were made up of 40 % (w/w) soybean oil and 60 % (w/w) protein dispersion of 2.5 % (w/w) protein content. A quantity of 50 grams was emulsified... 

The Bowman Birk trypsin inhibitor is the smaller trypsin inhibitor with MW -S.OkD and binding sites for trypsin and chymotrypsin (Birk, 1985). BBI is more heat-stable than the Kunitz inhibitor probably resulting from its great proportion of disulfide cross-linking at 7 per mole BBI. Although BBI is present in much lower amounts in raw soybeans, its relative heat stability may be the main reason for the residual STI activity in moist-heated soybean protein products. Friedman and Brandon (2001) reported about 7 pg/mL BBI in soy-based infant formula as measured by ELISA while Dipietro and Liener (1989) reported <0.1 pg/mg (their limit of detection by ELISA) for SIR... 

Wolf, W.J. G.E. Babcock A.K. Smith. Purification and stability studies of the 1 Is component of soybean proteins. Arch. Biochem. Biophys. 1962, 99, 265-274. 

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. 

Comminution also may be used to examine the stability of dispersed phases such as oil droplets. Depending on the viscosity of the product one simply mixes it or breaks it up in a solvent (usually water but, for example, use fresh soybean oil for chocolate), a buffer or the appropriate dyes (below). For instance, we mix easily dispersible foods (cream cheese, ice cream mix or tablespreads) with dyes on slides in a ratio of about 1 1 before examination. Where the dye is a diachrome (that is, highly colored) or is fluorescent in the absence of the substrate (for example, Acridine Orange) some attempt must be made to remove excess, uncomplexed dye molecules which might confound the interpretation. This can be done by reduction of the dye concentration or by making the preparation thinner. The advantage of these simple techniques is that a battery of microchemical tests to identify protein, lipid and carbohydrate can be completed on multiple samples in a very short time period. 

Non-dairy creams (cream alternatives) are O/W emulsions stabilized by milk proteins. A relatively thick adsorption layer provides stability, mostly by steric stabilization and partly by electrostatic stabilization [829]. Figure 13.3 shows an example of a soybean-oil and milk-protein emulsion stabilized by fat globules and protein membranes. Stabilizers, such as hydrocolloid polysaccharides, are added to increase the continuous phase viscosity and reduce the extent of creaming. They must be stable enough to have a useful shelf-life but de-stabilize in a specific way when they are... 

Henriksen A, Mirza O, Indiana C et al (2001) Structure of soybean seed coat peroxidase a plant peroxidase with unusual stability and haem-apoprotein interactions. Protein Sci 10 108-115... 

It is likely that protein binding and other macromolecular interactions also play a role in stabilizing the rRNA structures. A recent analysis12 reveals that the binding of specific ribosomal protein to rRNA in vitro results in changes within the rRNA modification patterns. Because the experiments detailed herein examine a population of rRNA within the cell, and thus may be analyzing a variety of RNA conformations, it is remarkable that very consistent results are observed. However, the consequence of polysome assembly and translation on the structure of the rRNA and how these structures might be distinct are not addressed in this analysis. In vitro DMS modification of soybean RNA has revealed some differences in base reactivity relative to that observed on RNA modified in vivo as described herein.36 ... 

Cottonseed oil has long sold at a slight premium over soybean oil because of greater stability to oxidation, and desirable flavor in fried snack foods such as potato chips. However, gossypol content, and lower protein quality put the meal at a price disadvantage. Feeding whole cottonseed to dairy cattle, whose rumen microorganisms can detoxify... 

Soybeans owe their dominance of the oilseed market to the value of their protein, which is much greater than that of other oilseeds. Of the oilseed meals produced in 2003, 129.58 million MT out of a total of 185.69 milllion MT was soybean meal (1). Of the money made on extracting soybeans, the meal accounted for between 51% and 76% of the total in the last 10 years. Soybean oil of typical composition performs well as a salad oil, but it is usually hydrogenated for use as a margarine stock or frying oil. Soybean oil s stability to oxidation also is limited by its content... 

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