Self-assembly of caseinomacropeptide as a potential key mechanism in the formation of visible storage induced aggregates in acidic whey protein isolate dispersions

Abstract

Visible aggregates formed during storage in acidic whey protein isolate (WPI) dispersions represent a challenge to the beverage industry. Batch-to-batch variations are observed that prevents consistent quality and shelf-life prediction. Heat-treatment of WPI dispersions at 120 °C for 20 s instead of conventional heating at 95 °C for 180 s often prevents the aggregate formation, and varying levels of divalent cations were proposed to contribute to the observed batch-to-batch variations. In this study, the composition of the visible aggregates was examined. Caseinomacropeptide (CMP) was enriched in the visible aggregates compared with the surrounding clear liquid. Disruption of electrostatic interactions between glycosylated and non-glycosylated CMPs were studied by addition of calcium, acidification, and enzymatic de-sialidation. The treatment strategies each significantly decreased time-dependent turbidity development in acidic WPI dispersions. This suggests that the storage-induced aggregates may be prevented by disruption of electrostatic interactions between negatively-charged sialic acid residues and positively-charged amino acids.