Structural investigation of beta-lactoglobulin gelation in ethanol/water solutions

The aggregation and gelation properties of beta-lactoglobulin (BLG), a glob ular protein from milk, was studied in hydro-ethanolic solutions (50/50% (v /v)) at room temperature. The phase state diagrams as a function of pH and ethanol concentration showed that a gel structure appeared after a period r anging from 1 min to 1 week depending on the physico-chemical conditions. T he aggregation kinetics, studied by infrared spectroscopy and dynamical rhe ological measurements, highly depended upon the pH; the process being the f astest at pH 7. Alcohol-induced aggregation of BLG was characterized by the formation of intermolecular hydrogen bonded beta-sheet structures. Small a ngle neutron scattering indicated that the aggregates structures in the fin al gels were similar at pH 7, 8 and 9. Through the data obtained at the mol ecular and macroscopic levels, it can be concluded that the kinetics of gel ation were pH dependent while the spatial arrangements of the aggregates we re similar in the final structures. The heterogeneous structures formed in hydro-ethanolic gels could be analysed in terms of a phase separation, the syneresis being the final visible state. (C) 1999 Elsevier Science B.V. All rights reserved.