No 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.

A method has been developed for isolation of 11S globulins from soybeans, broad beans, peas, sunflower seeds, and oats based on the principle of selective thermal denaturation. The preparation isolated from defatted soy meal contains 95-97 % of 11S globulin according to sedimentation velocity measurements, while its yield amounts to 1-2 g/100 g of defatted meal. The preparation isolated from defatted meal of sunflower seeds contains 95-97% of 11S globulin, and its yield is 3-5 g/100 g of meal. The preparations of 11S globulin from broad beans, peas, and oats were isolated without preliminary defatting of the meal.The preparation of 11S globulin from oat seeds is of the same purity as those isolated from soybeans and sunflower seeds, while its yield accounts for 0.2-0.5 g/100 g of meal. The preparations of 11S globulins isolated from broad beans and peas contain no impurities, according to the sedimentation data. The yield of preparations is equal to 0.5 g/100 g of meal.

No abstract

No abstract

No abstract

Application of the method of spherical indentor penetration and the method of axialdeformation of ringshaped sample (POCHETTINO viscometer) for studying the mechanical properties of biopolymer gels under simple shearing is described. A standard POLANY dynamometer equipped with special adapters was used in the investigation. A universal mould to prepare samples has been suggested. The problem of deaeration and reproducibility of the geometric parameters of the samples has been solved and the quality of their working surfaces has been improved considerably. A comparative study of the mechanical properties of aqueous gelatine gels of varied concentration (2-17.6 %) was performed under a constant loading rate to illustrate some of the possibilities of the methods. The agreement of the results of both methods could be ensured. The techniques described possess several valuable advantages, namely low labour-and material consumption, high accuracy, simplicity of sample preparation, and possibility of conducting experiments in the stress relaxation mode and under constant loading rate.

This paper deals with certain problems concerning the mechanism of thermotropic gelation of globular proteins, using ovalbumin and soy bean globulin fraction as object of study. Protein denaturation has been shown to be an indispensable condition of thermotropic gelation, while the completeness of denaturation changes controls the degree of conversion in the gelation process. The combination of the experimental data obtained indicates that thermotropic gelation involves primarily non-covalen t interactions, and hydrophobic interactions play a predominant role. The gelling ability of individual globulins and their monomeric forms have been found to correlate with the effective mean hydrophobicity according to TANFORD-BIGELOW.The phenomenon of thermotropic gelation (TG) is of considerable interest in connection with the use of globular proteins in various food systems. However the mechanism of this phenomenon and the nature of forces participating in it still remain to be studied. In this work we used gels of ovalbumin (OA) (typical monomericglobular protein) and soy bean globulin fraction (SBGF, natural blend of2S, 7S, I 1 S and 15s globulins) to ascertain the TG mechanism. About 70% of this blend are 7s and 1 IS globulins -oligomeric proteins with known structure.Under the TG we understand a method of converting solutions and suspensions of proteins (or other biopolymers) into a gelatinous state by changing the temperature. In the case ofglobular proteins gels are formed under heating. Thermograms of 0.5 % aqueous solutions of soy bean globulin fraction (1, Fig. 1 a) and their individual components (2 = 11s globulin, 3 = 7s globulin, 4 = 2.8s globulin, Fig. 1 a) and ovalbumin (Fig. 1 b). Scanning speed is 2 "C per min in DASM -1 M (USSR)