Thermally Induced Gelation of Native and Modified Egg White‐Rheological Changes During Processing; Final Strengths and Microstructures
ABSTRACT The heat-induced gelation of native egg white (EW) and egg white modified with succinic anhydride (SEW) or oleic acid (OEW), by addition of 15 moles of reagent/50000g protein, was evaluated. Rigidity modulus (G) and mechanical energy damping were continuously monitored during heating of the samples from 5 - 95°C in a nondestructive temperature-controlled thermal scanning rigidity monitor (TSRM). A measurable increase in G and decrease in energy damping were observed at lower temperatures for OEW than for EW. In SEW the measurable rheological transitions occurred at the highest temperature ranges. Failure strength of the cooked products (gels) evaluated using torsion and uniaxial compression tests revealed large differences due to treatments. Micrographs of gels showed apparent structural differences among treatments.
- Journal of Agricultural and Food Chemistry 37(2). DOI:10.1021/jf00086a010 · 3.11 Impact Factor
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ABSTRACT: Effect of succinylation, acetylation, and reductive alkylation on substructural properties of three milk protein systems (casein, BSA, and whey proteins) was studied. Three levels of modifications were achieved in each case, and changes in the proteins' spectral properties were determined. Casein attained the highest degree of modification for all of the treatments used. Acylation enhanced denaturation and improved surface hydrophobicity of all of the proteins. Modification of BSA resulted in a red-shifted emission fluorescence peaks; however, its circular dichroic (CD) patterns showed insignificant difference from those of the native. This may imply that acylation has affected only the tertiary structure of BSA. Fluorescence and CD profiles of whey proteins and caseins showed considerable changes in their conformational makeup. It appears that acylation may have a more drastic effect on multicomponent proteins, possibly by means of perturbing their protein-protein mode of interaction.Journal of Agricultural and Food Chemistry 40(4). DOI:10.1021/jf00016a005 · 3.11 Impact Factor
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ABSTRACT: The response of 10% gelatin gels to uniaxial compression is determined in part by frictional effects at the gel-platen interface. By using teflon-coated plates, lubricated with paraffin or silicone oil, these frictional effects are effectively eliminated. The stress-strain response can then be described by the two-constant Mooney-Rivlin relation, the sum of the two parameters (C 1 +C 2 ) being about 25% lower in lubricated compression than the value obtained in simple shear and torsion. Cross-head speed (for total testing times of 0.2–3 min) had no effect on material response, but long-term stress relaxation does occur over periods of about 30 min and longer. Sample radius did not affect the response in lubricated compression but had a major effect under unlubricated conditions. No systematic change in response was seen with sample diameter to height (aspect) ratios between 9.6 and 3.1 in lubricated compression, but data scatter for a given sample diameter was worst at the lowest heights (highest aspect ratio). Agreement of all true stress versus strain data was within about 7% regardless of sample height or deformation rate.Rheologica Acta 04/1985; 24(3):265-271. DOI:10.1007/BF01332607 · 1.78 Impact Factor