Using proteomics to characterise storage-induced aggregates in acidic whey protein isolate drinks

Formation of insoluble aggregates in acidic whey protein isolate (WPI) beverages during storage is a quality concern. Earlier studies showed that changes in processing methods from 95 °C for 180 s–120 °C for 20 s could prevent it. In the present study, WPI drinks were stored for up to 12 months and insoluble aggregates formed in re-solubilised WPI and its liquid phase analysed by proteomics. Insoluble aggregates were found to be enriched in caseinomacropeptides (CMP). Increased peptide formation by weak acid hydrolysis, especially of CMP, was found at 120 °C. Further enhanced hydrolysis of CMP was obtained by deamidation as well as by the presence of the genetic variant A of CMP. Batch variations may therefore be assigned to variations in CMP as well as variations in the distribution of genetic variants of A and B in different WPI batches used for the production of the WPI products.