Enhanced wetting behaviours of whey protein isolate powder: The different effects of lecithin addition by fluidised bed agglomeration and coating processes

The effect of lecithin addition on the wettability of whey protein isolate (WPI) powders was investigated in this study. Different concentrations of lecithin solution (0.5%, 2% and 5% w/v) were added by fluidised bed agglomeration and Wurster coating processes. The formed WPI powders, with different particle sizes, were used to compare the densities, porosity and shapes properties, as well as the wetting behaviours, including wetting time, contact angles, water absorption by capillary flow and the strength of films formed at the powder/water interfaces. It was found that, if lecithin was used as bridges to adhere primary particle in agglomeration, the formed granules had large particle size, lower bulk density, higher porosity and more irregular shapes. The influences of the coating process on these properties were shown to be less significant, as lecithin was layered on the outside of the particle surfaces. Those physical and structural modifications in WPI powders caused the improvements in the wettability by different degrees. High coverage of lecithin by coating process gave the particles a more advantageous first step of wetting, showing smaller initial contact angles and weaker protein films; while the porous structures by agglomeration process resulted in quicker water penetration by capillary flow. They were both rate controlling factors for wetting process, as the limited contribution was found if only controlled by any one of these factors. Consequently, high coverage of lecithin, high porosity of particles and large particle sizes were all necessary for enhancing the wetting behaviours of WPI powders. (C) 2017 Elsevier Ltd. All rights reserved.