COLL 36 |
| Ganesan Narsimhan, Department of Agricultural and Biological Engineering, Department of Agricultural and Biological Engineering, Purdue University, 1146 ABE, West Lafayette, IN 47907 |
| Beta-Lactoglobulin (BLG) solutions at pH 5.5 and 7 were heated at 80 C for various times upto 30 min. Changes in the secondary structure upon heating were inferred from circular dichroism studies at different conditions. The surface hydrophobicity of BLG, as measured from the flourescence of 1-8-ANS probe bound to hydrophobic patches, was found to increase with heating times thus indicating a change in the tertiary conformation. This loss of tertiary conformation upon heating led to an increase in the area occupied by a protein molecule at the air-water interface as measured by spread monolayer isotherm using a Langmuir trough. Heating of BLG also led to an increase in interfacial shear elasticity and viscosity at air-water interface. Measurement of coarsening of bubble sizes due to coalescence in foams stabilized by native and heated BLG using microscopy indicated an enhancement in foam stability for heated proteins. The dynamics of adsorption at air-water interface, interfacial rheology and foam stability of native (pH 7) and molten globule (pH 2) alpha lactalbumin are compared. The rate of changes in surface pressure and surface concentration as well as their steady state values were found to be higher for molten globule conformation than those for native protein, the more flexible protein in the molten globule state being able to overcome the high electrostatic energy barrier. Syneresis in standing foam as monitored by magnetic resonance imaging was found to be retarded by the presence of higher concentrations of xanthan gum and higher protein concentrations. A mathematical model for syneresis accounting for the structure of foam was employed for the prediction of evolution of liquid holdup profile at the top of the foam and compared with experiments. Thin film stability analysis was employed to compare the initial rates of coalescence of foam for native and heat treated proteins. |
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ACS Award in Colloid and Surface Chemistry Symposium Honoring Clay Radke
Division of Colloid and Surface Chemistry |