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

A specific pattern of aggregation of beta-lactoglobulin (beta lg) leading to stable, non-sedimenting monodispersed spherical microgels (M beta lg), was identified upon heating a 1.0 wt% solution of demineralised beta lg at 70 and 85 degrees 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 beta lg and formation of intermediate aggregates were investigated using different chromatographic methods. Upon heating, beta lg 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 M beta lg. With prolonged heating time, formation of M beta lg 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 degrees C) or favourable (pH 5.7, 85 degrees C), either small M beta lg or insoluble particulates, formed by aggregation between M beta lg, were formed. (c) 2008 Elsevier Ltd. All rights reserved.