Modification of molecular conformation of spray-dried whey protein microparticles improving digestibility and release characteristics.

This study reports on the preparation of riboflavin-loaded whey protein isolate (WPI) microparticles, using desolvation and then spray drying. Ethanol desolvation led to the exposure of embedded hydrophobic amino acids of WPI to riboflavin, facilitating the formation of riboflavin-WPI complexes. The extent of desolvation and cross-linking influenced the morphology of the spray-dried microparticles, while the moisture content of microparticles decreased with desolvation and increased with crosslinking. The modification of WPI conformation upon desolvation could be retained in the dry state via spray drying. The gastric resistance, release site and release characteristics of microparticles were readily adjusted by varying the ethanol and calcium ion contents from 0 to 50% v/v and from 0 to 2 mM, respectively. The sample prepared from 30% v/v ethanol without calcium crosslinking displayed rapid peptic digestion in less than 30 min. The samples from 30% v/v ethanol at 1 and 2 mM Ca2+ exhibited excellent gastric resistance and intestinal release.