ABSTRACT
Combination of ß-lactoglobulin (ß-Lg) and lactoferrin (Lf), biomacromolecules derived from bovine whey, was used in the formation of supramolecular structures by thermal gelation technique to adjust the pH. Furthermore, the influence of the molar ratio, temperature, pH, and heating time in the formation of supramolecular structures were also studied. The characterization of the protein supramolecular structures was performed using dynamic light scattering, zeta potential measurements, molecular spectrofluorimetry, and circular dichroism spectroscopy. The thermal behavior of the pure proteins was investigated by differential scanning calorimetry. The protein denaturation temperatures were of around 85°C for the ß-Lg and around 52°C and 85°C (a small portion) for the Lf. The protein molar ratio of 2:1 Lf/ß-Lg was used to form the structures, whose characterization showed that the best conditions of supramolecular structure formation occurred at pH6.5 and at temperatures of 62.5°C. In those conditions, more stable systems with reduced hydrophobic surface and average sizes between 30 and 100nm were generated. The correlation between pH and temperature suggests that the method of preparation of the supramolecular structure affects its size during storage.
Subject(s)
Lactoferrin/chemistry , Lactoferrin/metabolism , Lactoglobulins/chemistry , Lactoglobulins/metabolism , Multiprotein Complexes/chemistry , Multiprotein Complexes/metabolism , Animals , Calorimetry, Differential Scanning , Cattle , Hot Temperature , Hydrophobic and Hydrophilic Interactions , Lactoferrin/analysis , Lactoglobulins/analysis , Multiprotein Complexes/analysis , Protein Stability , Spectrum AnalysisABSTRACT
The study of protein interactions has generated great interest in the food industry. Therefore, research on new supramolecular structures shows promise. Supramolecular structures of the whey proteins α-lactalbumin and glycomacropeptide were produced under varying heat treatments (25 to 75°C) and acidic conditions (pH3.5 to 6.5). Isothermal titration calorimetry experiments showed protein interactions and demonstrated that this is an enthalpically driven process. Supramolecular protein structures in aqueous solutions were characterized by circular dichroism and intrinsic fluorescence spectroscopy. Additional photon correlation spectroscopy experiments showed that the size distribution of the structures ranged from 4 to 3545nm among the different conditions. At higher temperatures, lower pH increased particle size. The foamability of the supramolecular protein structures was evaluated. Analysis of variance and analysis of regression for foaming properties indicated that the two-factor interactions between pH and temperature exhibited a significant effect on the volume and stability of the foam.
