ELECTROSTATIC EFFECTS ON PHYSICAL PROPERTIES OF PARTICULATE WHEY PROTEIN ISOLATE GELS

Physical properties of particulate whey protein isolate gels formed under varying electrostatic conditions were investigated using large strain rheological and microstructural techniques. The two treatment ranges evaluated were adjusting pH (5.2‐5.8) with no added NaCl and adjusting the NaCl (0.2‐0.6 M) at pH 7. Gels (10% protein w/v) were formed by heating at 80C for 30 min. The large strain properties of fracture strain (γ_f), fracture stress (σ_f), and a measure of strain hardening (R_0.3) were determined using a torsion method. Gel microstructure was evaluated using scanning electron microscopy (SEM) and gel permeability (B_gel). Overlaying σ_f and γ_f curves for pH and NaCl treatments demonstrated an overlap where gels of equal σ_f and γ_f could be formed by adjusting pH or NaCl concentration. The high fracture stress (σ_f～ 23 kPa and γ_f～ 1.86) pair conditions were pH 5.47 and 0.25 M NaCl, pH 7.0. The low fracture stress (σ_f～ 13 kPa and γ_f～ 1.90) pair conditions were pH 5.68 and 0.6 M NaCl, pH 7.0. The 0.25 M NaCl, pH 7 treatment demonstrated higher R_0.3 values than the pH 5.47 treatment. When the sulfhydryl blocker n‐ethylmaleimide was added at 2 mM to the 0.25 M NaCl, pH 7 gel treatment, its rheological behavior was NSD (p>0.05) to the pH 5.47 gel treatment, indicating disulfide bond formation regulated strain hardening. Altering surface charge or counterions, and disulfide bonding, was required to produce gels with similar large strain rheological properties. An increase in gel permeability coincided with an increase in pore size as observed by SEM, independent of rheological properties. This demonstrated that at the length scales investigated, microstructure was not linked to changes in large strain rheological properties.     

Chemical Modification of Egg White with 3, 3-Dimethylglutaric Anhydride

SUMMARY— Egg white, near its normal concentration, was reacted at 25°C, pH 9.0, with levels of 3,3-dimethylglutaric anhydride (DMGA) from 0 to 60 mol/mol egg white protein (EWP) (assuming egg white to have an average mol wt of 50,000). Analysis for amino acids and functional groups showed about 26% of the lysine residues reacted at 15 mol DMGA/mol EWP. Sulfhydryls are more resistant to reaction with 60% unreacted at 150 mol DMGA/mol EWP. Electrophoresis indicates significant changes in net charges on the protein, particularly on lysozyme which migrates anodically in six separate bands at higher DMGA levels. Ultracentrifugation sedimentation data suggest no hydrolysis or aggregation changes. Foam formation is not seriously altered, but the heat coagulation properties, as evidenced by angel cake failures, are changed. As measured by viscosity, light transmission and aerating ability, DMGA exerts a protective action against the effect of heat on these properties.     

THE VALIDATION OF A KNOWLEDGE BASED SYSTEM FOR THE DIAGNOSIS OF THE CAUSES OF CRACKING IN MASONRY STRUCTURES

Any occurrence of cracking in masonry structures needs the correct diagnosis of the cause to be made in order that suitable remedial action can be taken. In order to do this a wide range of expert knowledge is required by the investigating engineer.

This paper describes the development and testing of an intelligent knowledge based system (IKBS) which will aid engineers carrying out these types of investigations. Particular emphasis is given in the paper to knowledge acquisition and the subsequent testing of the IKBS and these issues are addressed in some detail.

The paper also highlights the importance of not only using knowledge to prove causes but also to disprove causes.The use of knowledge to disprove causes is shown to lead to shorter consultations and more accurate conclusions.     

News section

Abstract

The National Oceanic and Atmospheric Administration recently convened an Advisory Committee to help it begin the process of transferring Landsat from the government to the private sector. This advisory committee is to help NOAA determine the institutional arrangements, technical parameters and economic feasibility of such a transfer. One of the most important and least understood inputs into this process is the market for Landsat products and ground-station equipment. While at present the U.S. government represents a substantial portion of the users of Landsat data, the market for Landsat data and products in developing countries is expected to grow rapidly. However, the use of Landsat in developing countries is not well understood. This paper looks at the use of Landsat in developing countries by examining the match of remote-sensing technology to the resource information needs of these countries.     

COLD GELATION OF WHEY PROTEIN EMULSIONS

Stable and homogeneous emulsion‐filled gels were prepared by cold gelation of whey protein isolate (WPI) emulsions. A suspension of heat‐denatured WPI (soluble WPI aggregates) was mixed with a 40% (w/w) oil‐in‐water emulsion to obtain gels with varying concentrations of WPI aggregates and oil. For emulsions stabilized with native WPI, creaming was observed upon mixing of the emulsion with a suspension of WPI aggregates, likely as a result of depletion flocculation induced by the differences in size between the droplets and aggregates. For emulsions stabilized with soluble WPI aggregates, the obtained filled suspension was stable against creaming, and homogeneous emulsion‐filled gels with varying protein and oil concentrations were obtained. Large deformation properties of the emulsion‐filled cold‐set WPI gels were determined by uniaxial compression. With increasing oil concentration, the fracture stress increases slightly, whereas the fracture strain decreases slightly. Small deformation properties were determined by oscillatory rheology. The storage modulus after 16 h of acidification was taken as a measure of the gel stiffness. Experimental results were in good agreement with predictions according to van der Poel's theory for the effect of oil concentration on the stiffness of filled gels. Especially, the influence of the modulus of the matrix on the effect of the oil droplets was in good agreement with van der Poel's theory.