The rheological properties of diluted solutions of 11 S‐globulin isolated from soybeans by using selective thermal denaturation of 2 S‐ and 7 S‐globulins

Abstract

A simple and effective method of isolating I I S-globulin (glycinin) from soybeans has bccn developed. which is based on the use of selective thermal denaturation of other components in globulin fraction. Glycinin content in the final preparation accounts for 9 7 "~. and its yield constitute about 1 g per 100 g ofdefatted flour (about 7 " o of glycinin content in flour). According to differential scanning microcalorimetry, the isolated preparation in terms of thermodynamics is identical with glycinin isolated by the method Of T~IASH-SHIBASAK~ with chromatography on hydroxyl apatite. The steady state viscosity of diluted solutions of the preparation, was studied in four solvents: A -phosphate buffer ptf 7.6, ionic strength 0.5; B --water pIi 7.1. ionic strength below 0.001 ; C -8 M guanidin . HCI; D -8 M guanidine HCI, containing 0.01 M 2-mercaptoethanol. Dependences of steady state viscosity on protein concentration (0.5 --7.0 g/dl) and temperature ( I M) 'C) were obtained. A study was also made on the fractional composition of the preparation in the indicated solvents by the sedimentation velocity method. According to the data of sedimentation velocity and viscosimetry, the molecular weights of various glycinin forms were determined. The values obtained are consistent with the published data. Analysis of the hydrodynamic properties of dodecameric and hexameric glycinin forms shows that they are similar to spheres of equal density, but of different size. In the investigated range of concentrations and temperatures, the intermolecular interactions play an insignificant role in the rheology of glycinin solutions (parameter of excluded voluhc according to MOONEY K = 0; excess cffectivc activation enthalpy in viscous flow Hf = H,(O Ho(C' = 0 ) = 0). Only in water of about 4 ' C , which is close to the temperature of glycinin precipitation. the role of intermolecular interactions is significant; this follows from the value flz = I I 7 kJ/mole.

Pulse Proteins: From Processing to Structure-Function Relationships

“…The quantification of 7S and 11S fractions present in isolates or concentrates is an essential step for calculation of L/V ratio which can be achieved using various methods described in literature. Methods include ammonium sulfate salt extraction [46], isoelectric precipitation [47], sodium dodecyl sulfate-polyacrylamide-gel electrophoresis (SDS-PAGE), gel chromatography [48], selective thermal denaturation [49], sucrose gradient centrifugation [50] and zonal isoelectric precipitation [51,52]. The effective separation and the choice of technique should be dependent on factors such as nature of sample (isolates, concentrates, seed), extraction technique employed and the level of purification required.…”

Effect of selective thermal denaturation of soybean proteins on soymilk viscosity and tofu's physical properties

“…This method is based on the difference in the thermal stability between glycinin and other protein constituents including b-conglycinin. Since the denaturation temperature of glycinin is approximately 20°C higher than that of b-conglycinin, there is a possibility to conduct thermal denaturation of b-conglycinin with glycinin's nativity being preserved (Varfolomeyeva et al, 1986). In this study, a two-step heating of soymilk was invented to denature b-conglycinin first and then glycinin.…”

“…Selective thermal denaturation has ever been employed for isolating glycinin from soybeans Varfolomeyeva et al, 1986). This method is based on the difference in the thermal stability between glycinin and other protein constituents including b-conglycinin.…”

High-resolution carbon-13 nuclear magnetic resonance study of the soybean 7S storage protein fraction in solution

“…Despite the low radio frequency power decoupling method used, some radio frequency heating of the sample was observed, which, as expected, was most pronounced for the high ionic strength samples (0.5 M NaCl) at the higher magnetic field (500-MHz NMR frequency), where the temperature rose by 11 °C, from 21 to 32 °C. No heat-induced protein conformational changes are expected to take place under the experimental conditions used (Bikbov et al, 1983;Varfolomeyeva et al, 1986).…”