ABSTRACT
The conformational stability of beta-lactoglobulin increases in D2O over that in H2O. This is concluded from an increase in peak temperature by about 3 degrees C of differential scanning calorimetry (DSC) thermograms and from a decrease in overall aggregation rate. However, effects of pH and salt concentration on the heat-induced aggregation (reaction kinetics, DSC thermograms and aggregate growth) are similar in H2O and D2O. This indicates that the mechanism of heat-induced aggregation of beta-lactoglobulin is not significantly affected by replacement of H2O with D2O.
Subject(s)
Deuterium Oxide , Lactoglobulins/chemistry , Calorimetry, Differential Scanning , Hydrogen-Ion Concentration , Kinetics , Sodium Chloride , WaterABSTRACT
We give a quantitative treatment of the destabilization of three types of milk protein dispersions. For this we consider the proteins as adhesive-hard-sphere bio-colloids. If the attractive interactions become strong enough the system passes the percolation threshold and gels. Macroscopic properties of these gels are studied by measuring viscoelasticity and permeability coefficients. These coefficients are related to structural (fractal) properties of the gels which were measured using scattering and confocal scanning laser microscopy (CLSM) techniques. The behaviour of the protein gels can be understood on a qualitative level.
Subject(s)
Gels/chemistry , Milk Proteins/chemistry , Milk/chemistry , Animals , Chemical Phenomena , Chemistry, PhysicalABSTRACT
A quantitatively correct kinetic model for the temperature-induced denaturation and aggregation of beta-lactoglobulin is presented. The model recognizes an initiation, a propagation and a termination step by analogy with polymer radical chemistry. The decrease in native beta-lactoglobulin is predicted to follow order 3/2, in agreement with experimental results. The size of the protein polymer particles is predicted to be proportional to the square root of the initial beta-lactoglobulin concentration. The scattered light intensity is proportional to the product of concentration and size of the protein polymer particles. The initial increase in scattering intensity of the particles therefore scales with the initial squared beta-lactoglobulin concentration. The influence of other reaction conditions, e.g. ionic strength and pH, can be incorporated via the reaction constants of the reaction kinetic pathway.
