Dynamic modelling of whey protein–saliva interactions in the mouth and relation to astringency in acidic beverages

Whey proteins in acidic beverages (pH < 4.5) are astringent, producing a dry mouth-feel. Astringency is thought to be caused by interaction of food components with saliva, often leading to aggregate formation. Such interactions decrease saliva lubrication, form rough particles, and probably increase friction on oral surfaces – changing mouth-feel. Dynamic in vitro models were constructed to reproduce the likely interaction of whey proteins with saliva in the mouth during the course of beverage ingestion. Aggregate formation in the models was examined for numerous whey protein solutions under different conditions. Trends observed in the models were consistent with previous reported sensory evaluations of whey protein astringency. For example, maximum turbidity changed little in the models with increasing protein concentration, consistent with literature describing little increase in astringency with increasing protein concentration. Modelling mouth conditions, to measure protein–saliva interactions, related to astringency better than mixing saliva and protein in simple ratios.