SOYBEAN PROTEIN Precipitation from Water and Alkaline Dispersions by Acids and by Electrodialysis

Smith, A. K.; Circle, Sidney J.

doi:10.1021/ie50358a029

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…3, electrodialyzed soybean "whey"; , electrodialyzed soybean "whey" plus 10 per cent of formaldehyde; •, acid-precipitated soybean protein; , electrodialyzed soybean protein; O, electrodialyzed soybean protein plus 10 per cent of formaldehyde. electrodialyzed proteins confirms the conclusion reached in an earlier paper (20) that the proteins prepared in the manner indicated do not differ greatly in their properties. The isoelectric point of the electrodia- lyzed soybean protein was shifted by the action of 10 per cent of formaldehyde from a pH value of 4.2 to 3.9, while that for the electrodialyzed soybean "whey" shifted from a pH value of 5.1 to 4.4.…”

Section: Soybean Protein Preparationssupporting

confidence: 89%

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The Effect of Formaldehyde on the Isoelectric Points of Some Proteins, Determined by Microelectrophoresis.

Circle¹,

Smith²

1941

J. Phys. Chem.

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The action of formaldehyde on proteins is of practical as well as theoretical interest. Formaldehyde has long been used industrially to increase the water resistance of proteins, especially casein, in the fields of plastics and coatings. Formaldehyde is also extensively employed as a preservative and fixative for biological specimens and to block off the amino groups in the titration of the acid groups of proteins and amino acids.An appreciable literature has accumulated concerning the nature of the reaction of formaldehyde with proteins and amino acids. Since reviews on this subject are available (7, 10, 23), it will not be discussed in detail. All the theories possess in common the postulate that the formaldehyde reacts with the free basic (amino, guanidino, or imino) groups of the protein or amino acid, but they differ in the complexities of the structures proposed for the product.According to the postulated reactions, the free basic groups on the micelle or molecule are rendered relatively inactive by the action of the formaldehyde. This should lessen the positive charge on the micelle and result in a shift of the isoelectric point to a lower pH value, since at any given pH the protein is less basic than before.It has been demonstrated by Smith, Max, and Handler (21) that the points of minimum solubility of casein and soybean protein are shifted to lower pH values by the action of formaldehyde. Gerngross and Bach (4) found that in gelatin solutions containing 10 per cent formaldehyde the isoelectric point of one gelatin sample shifted from a pH of 5.05 to 4.6 and of another from 4.75 to 4.3, as determined by an electrophoretic transference technique. Also, Swyngedauw ( 22), from a study of electroosmosis in gelatin gels before and after formaldehyde treatment, claims that formaldehyde does not combine with gelatin on the acid side of the isoelectric point but does on the basic side. Mudd and Joffe (15) studied the modification of antibodies by formaldehyde and showed a shift to

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Section: Soybean Protein Preparationssupporting

confidence: 89%

“…), and air-dried at room temperature. Details on the separation of soybean protein from the oil-free meal will be found in an earlier publication (20). Briefly, the proteins used in this study were prepared and designated as follows:…”

Section: Methodsmentioning

confidence: 99%

The Effect of Formaldehyde on the Isoelectric Points of Some Proteins, Determined by Microelectrophoresis.

Circle¹,

Smith²

1941

J. Phys. Chem.

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“…Early investigations (12) indicated that in the isoelectric precipitation of soy protein the type of acid used to lower the pH of extract does not affect precipitation yields. This was confirmed by our results.…”

Section: Precipitation Of Curdmentioning

confidence: 99%

Isolation of soybean protein: Effect of processing conditions on yields and purity

Cogan

Yaron

Berk

et al. 1967

J Americ Oil Chem Soc

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Tile process of soybean-protein isolation, comprising extraction in dilute calcium hydroxide and precipitation with hydrochloric acid at pH 4.5, was evaluated from the viewpoint of the effect of processing conditions on yields and product purity. The course of extraction and the effect of particle size and agitation indicate that the process is quite rapid even when coarse meal is treated under mild agitation. The heattreatment history of the meal is the main factor governing the extraction and isolation yields. The precipitation yield is unaffected by temperature. Two steps of curd washing were found to suffice for maximum product purity. The purity is also improved considerably by preliminary sifting of the meal.

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“…Each of a series of soybean protein samples was given a different degree of alkali treatment. Considerable data on the preparation of soybean protein appeared in an earlier publication (7). One hundred grams of oil-free soybean meal ground to pass a 100-mesh sieve were stirred with 1000 ml.…”

Section: Adhesive Strengthmentioning

confidence: 99%

Soybean Protein. Adhesive Strength and Color

Smith¹,

Max²

1942

Ind. Eng. Chem.

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Many organic and inorganic bases were found to be effective in retarding the rate of change of the various properties of the alcohol, but only n-butyl amine and piperidine will be reported at this time.To separate samples of furfuryl alcohol were added, by weight, 0.1,0.3, and 3.0 per cent n-butyl amine and piperidine, respectively. As was the case in the thermal stability study, approximately 40 cc. of each sample were then sealed in Pyrex glass tubes, placed in bombs, and heated in an oven at 150' C .for the indicated period of time.The differences between the physical properties of the stabilized and control samples, prior to heat treatment, are due to the presence of the stabilizer. It is evident from the data that both n-butyl amine and piperidine greatly retard the rate of intermolecular dehydration of furfuryl alcohol, as measured by the amount of water split out. When calculated (as in Figure 2) in terms of per cent furfuryl alcohol transformed to C10H1003, after 10.5 hours a t 150" C. the alcohol alone is transformed to the extent of 33 per cent; in the presence of 0.1 per cent of the stabilizers, this value is only 0.4 per cent with n-butyl amineThe results obtained are given in Table 11. and 1.1 per cent with piperidine. There is no advantage in employing these stabilizers in concentrations higher than 0.1 per cent of the furfuryl aleohol, and there is the disadvantage of discoloring the latter to a greater extent.In hydrogenating furfuryl alcohol to tetrahydrofurfuryl alcohol, a considerable amount of high-boiling residue is obtained. We believe that a sizable proportion of this residue results from the formation of furfuryl alcohol condensation products such as have been described. Use of stabilizers in the hydrogenation process may therefore lead to higher yields of tetrahydrofurfuryl alcohol. Literature CitedAssoc. Official Agr.The adhesive strength, hydrolytic cleavage with sodium hydroxide, and dispersion characteristics of soybean protein are interrelated. Undenatured soybean protein gives low adhesive values when dispersed in alkaline salts but high adhesive values when dispersed in sodium hydroxide. A mild hydrolytic treatment of soybean protein with sodium hydroxide will change the dispersibility of soybean protein so that it will have good adhesive strength when dispersed in alkaline salts but not so good as the undenatured protein dispersed in sodium hydroxide. The dithionite salts (NaZStOd and ZnSSO4) are the best agents so far discovered for bleaching soybean protein. Coated paper has been prepared in the laboratory which shows the undenatured soybean protein to have higher adhesive strength and a lighter color than a good grade of commercial casein.

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SOYBEAN PROTEIN Precipitation from Water and Alkaline Dispersions by Acids and by Electrodialysis

Cited by 10 publications

References 7 publications

The Effect of Formaldehyde on the Isoelectric Points of Some Proteins, Determined by Microelectrophoresis.

The Effect of Formaldehyde on the Isoelectric Points of Some Proteins, Determined by Microelectrophoresis.

Isolation of soybean protein: Effect of processing conditions on yields and purity

Soybean Protein. Adhesive Strength and Color

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