Ovalbumin Gels Research Articles

INSTRUMENTAL MEASUREMENTS

INSTRUMENTAL MEASUREMENTS: Resistance to Tear: An Instrumental Measure of the Cohesive Properties of Muscle Food Products. (Res. Note) J. H. MacNeil and M. G. MastINSTRUMENTAL MEASUREMENTS: A Small Sample Back Extrusion Test for Measuring Texture of Cooked Rice. V. G. Reyes, Jr. and V. K. JindalINSTRUMENTAL MEASUREMENTS: The Wheat Research Institute Chomper, an Instrument that Measures Crumb Flexibility. D. W. Baruch and T. D. AtkinsINSTRUMENTAL MEASUREMENTS: Using the Wheat Research Institute Chomper to Assess Crumb Flexibility of Staling Bread. D. W. Baruch and T. D. AtkinsINSTRUMENTAL MEASUREMENTS: Rapid Testing Method for Characterizing the Rheological Behavior of Gelatinizing Corn Starch Slurries. (Note) J. F. Steffe, M. E. Castell Peres, K. J. Rose and M. E. ZabickINSTRUMENTAL MEASUREMENTS: Rheological Changes of Fortified Wheat and Corn Flour Doughs with Mixing Time. L. L. NavickisINSTRUMENTAL MEASUREMENTS: Comparison of Starch Pasting Properties in the Brabender Viscoamylograph and the Rapid Visco‐Analyzer. L. B. Deffenbaugh and C. E. WalkerINSTRUMENTAL MEASUREMENTS: Measuring Kernel Hardness Using the Tangential Abrasive Dehulling Device. J. W. Lawton and J. M. FaubionINSTRUMENTAL MEASUREMENTS: Bingham Award Lecture—1989. The Role of Instrument Inertia in Controlled‐Stress Rheometers. 1. M. KriegerINSTRUMENTAL MEASUREMENTS: Technical Note: Strain‐Measurement Error in a Constant‐Stress Rheometer. D. W. Giles and M. M. DennINSTRUMENTAL MEASUREMENTS: Technical Note: Strain‐Measurement Error in a Constant‐Stress Rheometer. D. W. Giles and M. M. DennINSTRUMENTAL MEASUREMENTS: Characteristics of a Modified Wisconsin Breakage Tester. (Technical Note) H. J. Lyon, S. G. Schmitt, C. J. Bern and C. R. Hurburgh, Jr.INSTRUMENTAL MEASUREMENTS: Impact Parameters Related to Post Harvest Brusing of Apples. G. H. Brusewitz and J. A. BartschINSTRUMENTAL MEASUREMENTS: Characterization of the Perceived Texture of Thickened Systems by Dynamic Viscosity Measurements. R. K. Richardson, E. R. Morris, S. B. Ross‐Murphy, L. J. Taylor and I.C.M. DeaGENERAL PRINCIPLES: Modelling of Flow Properties of Starch Pastes Prepared by Different Procedures. M. HarrodGENERAL PRINCIPLES: Apparent Concentration: A Method to Predict the Flow Properties of Viscous Foods for Process Applications. M. HarrodGENERAL PRINCIPLES: Time‐Dependent Flow Behavior of Starch Pastes, With Food Process Applications. M. HärrödGENERAL PRINCIPLES: Intrinsic Viscosities and Apparent Specific Volumes of Amino Acids and Sugars. ‘Effective Size’ and Taste of Sapid Molecules. S. E. Kemp and G. G. Birch, M. 0. Portmann and M. MathlouthiGENERAL PRINCIPLES: Effect of Succinylation on the Functional and Physiochemical Properties of Bovine Serum Albumin. Margaret C. Murphy and Nazlin K. HowellGENERAL PRINCIPLES: Effect of Extrusion Temperature on Physico‐Chemical Properties and Biological Value of Soybean‐Protein. E. Horváth, J. Petres, É, Gelencsér and B. CzukorSENSORY EVALUATION: Adaptation of Collaborative Methodology to the Sensory Evaluation of Foods by Scoring. P. MolnárFACTORS AFFECTING TEXTURE: Factors Related to Longissimus Tenderness Among Alternative Methods of Lean Beef Production. W. Vanderwert, P. J. Bechtel, D. L. DeVol, F. K. McKeith, L. L. Berger and R. D. ShanksFACTORS AFFECTING TEXTURE: Predicting the Effect of Drying Conditions on the Textural Properties of Roasted Peanuts. Y.‐C. HungFACTORS AFFECTING TEXTURE: Effect of Maturity and Storage Time on the Bruise Susceptibility of Peaches (cv. Red GIobe).Y.‐C. Hung and S. E. PrussiaFACTORS AFFECTING TEXTURE: Mechanical Properties of Kappa Carrageenan‐Locust Bean Gum Mixed Gels with Added Sucrose. S. M. Fiszman and L. DuranFACTORS AFFECTING TEXTURE: Effect of Hydrolysis of Lactose and Sucrose on Firmness of Ice Cream. J. B. Lindamood, D. J. Grooms and P.M.T. HansenFACTORS AFFECTING TEXTURE: Effect of Chemical Additives on Toughening of Fillets of Frozen Alaska Pollack (Therugru chulcogrumrnu). D. J. Krueger and 0. R. FennemaFACTORS AFFECTING TEXTURE: Effect of Mixing and Moisture Modification on Toughening and Dimethylamine Formation in Alaska Pollock Mince during Frozen Storage at −10°C. G. Boer and O. FennemaFACTORS AFFECTING TEXTURE: Rheological Properties of Heat‐Induced Ovalbumin Gels Prepared by Two‐step and One‐step Heating Methods. N. Kitabatake, Y. Tani and E. DoiFACTORS AFFECTING TEXTURE: Physical and Sensory Evaluation of Lean White Cakes Containing Substituted Fluffy Cellulose. E. B. Fondroy, P. J. White and K. J. Prusa

Rheological Properties of Heat‐Induced Ovalbumin Gels Prepared by Two‐step and One‐step Heating Methods

ABSTRACTOvalbumin gave a transparent solution, transparent gel, or opaque gel on heating at low ionic strength, but a turbid gel, or turbid suspension at high ionic strength (one‐step heating). The ovalbumin solution, once heated at low ionic strength, gave a transparent gel with a second heating at high ionic strength (two‐step heating). Textural parameters of hardness and adhesiveness, viscoelastic parameters from creep curves, breaking energy and water‐holding capacity of these gels were measured. Transparent gels by the one‐ or two‐step heating were firm and elastic and had high water‐holding capacity. Turbid gels by one‐step heating were soft and less elastic and had low water‐holding capacity. The relationship between gel properties and structure was discussed.

Structure of glycinin and ovalbumin gels

Research on the structures of heat-induced gels of glycinin and ovalbumin is reviewed. Both glycinin and ovalbumin gels are thought to have a so-called ‘string of beads’ structure. In glycinin gels one building unit of the string (a bead) has been thought to be a whole molecule. This means that heat-denatured glycinin molecules do not dissociate into their constituent subunits. An alternative explanation which includes dissociation and reassociation of glycinin has been presented. Heated ovalbumin solutions make transparent gels, turbid gels, clear solutions or turbid suspensions containing aggregates, depending on the pH, ionic strength and protein concentration of the medium. The transparent solutions contain linear polymers of high molecular weight. Ovalbumin gels are thought to be formed by a network of linear polymers. The ‘string of beads’ model has been accepted as the structure of some globular protein gels including glycinin, ovalbumin, serum albumin, ribonuclease and lysozyme. However, how the heat-denatured asymmetric protein molecules combine to make an ordered string has not been explained.

Determination of Cross‐link Density in Egg White Gels from Stress Relaxation Data

ABSTRACTThe concentration of permanent cross‐links in egg white gels was determined using stress relaxation experiments and equations derived from the theory of rubber elasticity. Cross‐link densities of 1.2–1.3 covalent cross‐links/molecule were observed. The concentration of covalent cross‐links, most likely disulfide bonds, was only slightly higher for gels formed in water as compared to those formed in 0.6M NaCl‐0.2M phosphate buffer at pH 6.0. These results differ from the 3—4 cross‐links/molecule previously reported for ovalbumin gels in 0.6M urea.

Thermotropic gelation of ovalbumin 1. Viscoelastic properties of gels as a function of heating conditions and protein concentration at various pH values

A study has been undertaken of stress relaxation in ovalbumin thermotropic gels with a concentration of 8–20%, depending on time and temperature of heating (respectively, 20–60 min, 70°–110°C), at pH 2.5–10.0. In all instances, the dependence of the initial gel elasticity modulus on heating has a single maximum. Gelation conditions corresponding to this maximum are considered optimal. Optimal gelation time is 30 min, regardless of pH. On the other hand, the optimal heating temperature depends on pH. To the right and left of the isoelectric point of protein (2.5≤pH<4.0 and 5.5<pH≤10.0) the optimal temperature is 80°. However, in the vicinity of the isoelectric point (4.0≤pH ≤5.5) the optimal temperature rises considerably. Gels produced to the right and left of the isoelectric point belong to the homologous group A, while gels produced in the point vicinity belong to another homologous group B. Light scattering data proves group A gels to be more homogeneous optically. These gels may be supposed a single-phase system, while group B gels are two-phase-systems. For each group, the dependence of the relaxation modulus (G) of gels on heating conditions, pH and protein concentration (X1,X2,X3,X4), as well as on time of relaxation (t) may be generally described asG(X1,X1,X1,X1,t)=Ge(X1,X2,X3,X4)f(t), whereGe is the equilibrium value of the elasticity modulus, and f(t) the relaxation function. Thus, a change in the parameters only affects the value of the equilibrium elasticity modulus, and exerts no effect on the relaxation time spectrum. For this reason, all the relaxation curves obtained may be transformed into two normalized relaxation functions:∼f(t)=f(t)/f(1)=G(X1,X2,X3,X4,t)/G(X1,X2,X3,X4, 1)

Turbidity and Hardness of a Heat-induced Gel of Hen Egg Ovalbumin

The turbidity and hardness of a heat-induced gel prepared from ovalbumin were examined at various pHs and ionic strengths. Depending on the conditions of the medium, a transparent solution, transparent gel, turbid gel, or turbid suspension was obtained by heating. The hardness was a maximum with the conditions that gave a transparent or slightly turbid gel. The gel and coagulums were solubilized by 1% SDS, but not by 6 m urea or 50 mm mercaptoethanol. The solution obtained by SDS treatment contained polymers shorter than octamers.

Thermally induced protein gelation: gelation and rheological characterization of highly concentrated ovalbumin and soybean protein gels.

AbstractIn order to optimize the use of proteins as functional ingredients in foods, one needs more insight into the effects of environmental conditions (pH, ionic strength, and temperature) on the functional properties of protein. This paper summarizes the results of an extensive study on heat‐induced gelation of ovalbumin (egg‐white protein) and soybean protein in the concentration range from 10 to 35 g/100 g. It was the aim of the study to relate the rheological properties of thermally induced protein gels to the microstructure of the gel and the physicochemical properties of the constituent protein. The gelling behavior of the protein was quantified with rheological techniques, and the physical properties of the gels were determined, at small and large deformations. From the swelling/dissolving behavior of the gels in various media, the nature of the crosslinks was determined qualitatively. The microstructure of the gels was determined with electron microscopy. Nmr‐spectroscopy was applied in order to elucidate changes in conformation during heating. It was found that the formation of a continuous covalently crosslinked network is not a prerequisite for thermally‐induced protein gelation. The properties of a gel strongly depend on the pH at which the gel is formed. When heat‐set at high pH(pH∼10), a homogeneous, strong, and almost transparent gel is formed, consisting of flexible crosslinked protein gels. Heat‐setting at low pH (pH 5) leads to the formation of a heterogeneous and weak gel, which easily exudes water. This gel consists of crosslinked aggregated protein. The ionic strength of the solvent in which the protein is dissolved and heat‐set has a much lower effect on gel properties.

Turbidity and hardness of a heat-induced gel of hen egg ovalbumin.

The turbidity and hardness of a heat-induced gel prepared from ovalbumin were examined at various pHs and ionic strengths. Depending on the conditions of the medium, a transparent solution, transparent gel, turbid gel, or turbid suspension was obtained by heating. The hardness was a maximum with the conditions that gave a transparent or slightly turbid gel. The gel and coagulums were solubilized by 1% SDS, but not by 6 m urea or 50 mm mercaptoethanol. The solution obtained by SDS treatment contained polymers shorter than octamers.

The Viscoelastic Behavior of Heat‐Set Ovalbumin Gels Explained in Terms of a Transient‐Network Model

The transient network model for concentrated dispersions, presented in a previous paper, is used for the interpretation of the viscoelastic behavior of heat‐set ovalbumin gels. The gels consist of a water phase and a network‐shaped phase of denatured ovalbumin molecules, which are crosslinked and entangled by sulphur bridges, hydrogen bridges, and hydrophobic bonds. The local stresses inside the dispersed phase are calculated from the local deformation and a modified Maxwell‐type constitutive equation that is used for the description of the rheological behavior of this phase. Subsequently, the macroscopic stress tensor is calculated making use of the concepts of the transient network model. Some remarkable model stress predictions are presented and interpreted. Linear viscoelastic measurements on the ovalbumin gels are used to quantify model parameters. Subsequently, the sample's behavior in simple shear and uniaxial compression experiments, including stress relaxation, are compared with model predictions. The model is thus found to satisfactorily describe the system's rheological behavior.

Thermotropic gelation of ovalbumin: 2. Boundary conditions on the formation and the concentration dependence of equilibrium elastic modulus for thermotropic ovalbumin gels

Studies were made on the boundary conditions for thermotropic ovalbumin gelation at pH within the range 2.5 to 10.0. The pH dependence of the gelation threshold, C 0, and denaturation temperature, T d, were obtained. The dependence C 0(pH) has a sharp minimum close to the isoelectric point (pl). Over pH range 2.5 to 4.0 the dependence T d(pH) is linear; although above pI it shows unusual behaviour. T d increases smoothly, becoming a constant value ( T d=80°C) at pH 7. Analysis of the temperature dependence of Leu's line integral intensity in the p.m.r. spectrum of ovalbumin shows that the temperature threshold of thermotropic gelation closely approximates to T d. A diagram for the state of an ovalbumin -water system was constructed in temperature-concentration-pH coordinates. The dependences of the initial shear modulus for thermotropic ovalbumin gels on the concentration (0.06≤C≤0.25 g/ cm 3 were obtained at pH 4.0, 7.0, 8.5, 10.0. They are equivalent to the concentration dependence of the equilibrium elastic modulus E e(C). The dependences obtained may be reduced to the theoretical master dependence of Hermans, E e (rm C ̃ ) , where C ̃ = C/ C 0 is the reduced concentration. Hermans' theory, based o the model for random cross-linking of linear identical macromolecules without cyclization, adequately describes the equilibrium elastic properties of thermotropic ovalbumin gels.

Effects of Surface Hydrophobicity, Net Charge and SH Groups on Thermal Coagulation and Gelation of Ovalbumin

Age-related cataracts, which probably form due to insolubilization of lens proteins, can lead to loss of vision. Although the exact reason is unknown, lens protein aggregation may be triggered by increases in PTMs such as d-β-, l-β- and d-α-Asp isomers. These isomers have been observed in aged lens; however, there have been few quantitative and site-specific studies owing to the lack of a quick and precise method for distinguishing between d- and l-Asp in a peptide or protein.We describe a new method for detecting peptides containing Asp isomers at individual sites in any protein by using an LC–MS/MS system combined with commercial enzymes that specifically react with different isomers. We also summarize current data on the effect of Asp isomerization on lens crystallins.The new technique enabled the analysis of isomers of Asp residues in lens proteins precisely and quickly. An extensive proportion of Asp isomerization was observed at all Asp sites of crystallins in the insoluble fraction of aged lens. In addition, d-amino acid substitutions in crystallin-mimic peptides showed altered structural formation and function. These results indicate that isomerization of Asp residues affects the stability, structure and inter-subunit interaction of lens crystallins, which will induce crystallin aggregation and insolubilization, disrupt the associated functions, and ultimately contribute to the onset of senile cataract formation.The mechanism underlying the onset of age-related diseases may involve isomerization, whereby d-amino acids are incorporated in the l-amino acid world of life.This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

A Comparison Between Ovalbumin Gels Formed by Heat and by Guanidinium Hydrochloride Denaturation

ABSTRACTOvalbumin was denatured by heat or by addition of 6M guanidinium hydrochloride (GuHCl) at pH 2.5. Denaturation by heat led to immediate gel formation whereas denaturation by GuHCl yielded gels only after subsequent removal of the denaturant. The two types of gels formed were compared by using texture measurements. Chemically denatured molecules had the largest hydrodynamic volume and also formed the hardest gels (protein concentration: 6% w/v). This difference in gel hardness was, however, much enhanced if the denaturant was slowly removed from the protein solution. Hence, the rate of gel formation appears to be of greater consequence than the degree of protein unfolding for the hardness of the gels formed.

Studies on ovalbumin-s-ovalbumin transformation. Part IV. Changes in the heat-induced gelling properties of ovalbumin during its conversion to s-ovalbumin.

Both ovalbumin and s-ovalbumin gave maximumgel strength at both sides of the isoelectric point. Maximumgel forming pHs of s-ovalbumin were almost the same as those of ovalbumin, but maximumgel strength values of s-ovalbumin were much smaller than those of ovalbumin. Although the gel strength of both proteins increased with increased heating temperature, the gel strength of s-ovalbumin was much smaller than that of ovalbumin at every heating temperature. About the results of creep experiments, all heat-induced gels were analyzed as a four-element model and the magnitude of all the parameters of both s-ovalbumin and intermediate was smaller than that of ovalbumin. Scanning electron microscopic studies showedthat the structure of ovalbumin gels was very fine comparing those of s-ovalbumin and the intermediate.

THE RHEOLOGY OF GELS

ABSTRACTThe following aspects of the rheological behavior of polysaccharide and protein gels are discussed with particular emphasis on recent investigations: (1) Viscoelasticity of gels; (2) Validity of rubber elasticity theory; (3) Rupture strength of gels; and (4) Single‐point measurements of gel strength.It is concluded that in contrast to most food materials gels show linear viscoelastic behavior up to strains of the order of 0.1. Results obtained from creep and stress relaxation experiments would suggest that noncovalent crosslinks in gels move or break when the gel is stressed. Activation energies associated with crosslink breakage have been estimated from the temperature dependence of viscoelastic parameters. For gelatin and polysaccharide gels energies ranging from 5–65 Kcals/mole have been reported.The stiff and extended nature of polysaccharide chains make it unlikely that polysaccharide gels obey rubber elasticity theory, though it is possible that this theory holds for gelatin gels and also for ovalbumin gels in 6 M urea.It is emphasized that the rupture strength of a gel is not necessarily related to its elastic modulus and therefore ‘single point’ measurements of ‘gel strength’ based on rupture tests will not always rank a series of gels in the same order as tests which involve small deformations without rupture. One of the reasons for this is that the elastic modulus and rupture strength depend in different ways on the primary molecular weight of the polymer from which the gel is formed.

アルカリ変性オボアルブミンゲルの粘弾性について

アルカリ変性オボアルブミンゲルの粘弾性について