Mechanism of formation of stable heat-induced β-lactoglobulin microgels

Abstract

A specific pattern of aggregation of β-lactoglobulin (βlg) leading to stable, non-sedimenting monodispersed spherical microgels (Mβlg), was identified upon heating a 1.0 wt% solution of demineralised βlg at 70 and 85 °C under mild acidic pH conditions (pH 5.7–5.9). The structural properties were determined by dynamic light scattering and transmission electron microscopy. Kinetics of aggregation of βlg and formation of intermediate aggregates were investigated using different chromatographic methods. Upon heating, βlg lost its native state, and aggregated into intermediate oligomers that ultimately led to larger soluble aggregates (SA). As heating time increased, SA interacted further to form Mβlg. With prolonged heating time, formation of Mβlg resulted in an increase in pH that promoted a change in the aggregation pathway. Subsequent aggregation led, in this case, only to SA. If the balance between physico-chemical factors enhancing aggregation was unfavourable (pH 5.9, 70 °C) or favourable (pH 5.7, 85 °C), either small Mβlg or insoluble particulates, formed by aggregation between Mβlg, were formed.