Impact of Spray Drying and Fluidized Bed Drying on Whey Protein Phospholipid Concentrate: Microstructural Analysis, Bioactivity, and Functionality

Whey protein phospholipid concentrate (WPPC) is a valuable coproduct of whey protein isolate that represents a rich source of bioactive compounds with potential health-promoting benefits.Powdered forms of dairy ingredients are highly valued for their convenience and extended shelf life.However, drying is a crucial process that can affect microstructure, bioactivity, and physicochemical properties.This study investigated the effect of 2 drying methods, spray drying (SD) and fluidized bed drying (FBD), on the properties of SD-WPPC and FBD-WPPC, respectively, with an industry-scale spraydried WPPC (I-SDWPPC) also included as a control to represent scaled-up production.After rehydration, FBD-WPPC exhibited a particle size (2.22 m) comparable to SD-WPPC (1.72 m) and I-SD WPPC (2.72 m) and the mean milk fat globule diameters did not differ substantially among FBD-WPPC (10.93 m), SD-WPPC (11.51 m), and I-SD WPPC (11.29 m).Furthermore, confocal laser scanning microscopy revealed larger aggregates of protein and fat in the SD-WPPC and I-SD WPPC, whereas FBD-WPPC showed a more uniform protein distribution with distinct fat clusters.FTIR analysis indicated that FBD-WPPC retained the most native-like protein secondary structure, SD-WPPC displayed moderate structural changes, and I-SD WPPC exhibited the most pronounced alterations, with decreased -helix and random coil contents and increased -sheet and -turn contributions.Xanthine oxidase activity normalized to protein content was significantly higher in FBD-WPPC than in both spray-dried powders, which did not differ from one another, demonstrating the influence of drying method on MFGM-enzyme stability.Protein oxidation, as measured by carbonyl content, was determined to be the lowest in I-SD WPPC but significantly not different among samples.Both primary (lipid hydroperoxides; LOOH) and secondary (TBARS) lipid oxidation products showed no significant differences among FBD-WPPC, SD-WPPC, and I-SD WPPC.Overall, these results provide new insight into how different drying methods and processing scales influence the microstructure and physicochemical properties of WPPC, informing future development of functional dairy coproduct powders.