Characteristic drying curve behavior of whey and casein micelle proteins via thin-film drying

Abstract

Drying characteristics of milk whey protein concentrate (WPC) and micellar caseins (MC) were investigated through a custom-designed mobile thin-film dryer. Several mixtures containing different WPC to MC ratios were tested in drying experiments. Both the constant drying period and falling rate period were identified. It was noticed the initial drying rates at constant drying period were slightly hindered by the presence of protein even at low concentrations. The drying kinetics was investigated by the characteristic drying curve (CDC) method and the drying behavior at the falling rate period was evaluated by a specific parameter n. As the result, while WPC exhibited a uniform master characteristic drying curve through different drying conditions, samples with certain amount of MC showed the more “scattered” curves, which lead to a wide distribution of n. Besides, it was observed that a thin layer of crust formed during the drying process. The analysis of the drying characteristics of MC led to a meaningful correlation with the morphology and structural properties. As the morphology of the crust was determined by the velocity and temperature of the impinging air, it became an inherent limitation for this thin film drying method to investigate materials with such crust formation phenomena.