Swelling and dissolution in cleaning of whey protein gels

Fluid dynamic gauging was used to study swelling and dissolution, under alkaline conditions, of heat-induced gels prepared from solutions of β-lactoglobulin (βLg), a whey protein isolate and whey protein concentrate. Recent developments in the understanding of the cleaning behaviour of proteinaceous dairy foulant, obtained using heat-induced βLg gels, are summarised. The thickness-time profiles for βLg gels exhibited Fickian behaviour, whilst the whey protein-based systems showed linear swelling behaviour. The pH values at which the latter gels started to swell were significantly higher than those observed for βLg, while they all showed a pH/volume fraction threshold for dissolution. These differences in swelling and dissolution behaviour are related to the structure of the gels, i.e. fine stranded vs. particulate, and suggest that the key step in the alkaline dissolution of industrial dairy foulants is the conversion of particulate gels to the fine-stranded form.