Flavor release from lactose/protein matrix during storage: Effects of lactose crystallization and powder microstructure

Glass-forming carbohydrates are widely used to encapsulate volatile flavor substances to avoid excessive flavor release and increase storage stability. The objective of this study was to investigate the effects of the crystallization of lactose on the microstructures of powders, as well as subsequent influences on flavor release from lactose-containing matrices. Mixtures of lactose and whey protein isolate were used to constitute the wall materials in ratios of 0:1, 1:4, 1:1 and 4:1 (w/w). Ethyl acetate (EA) was used as a model core material and microparticles were prepared by freeze-drying. Microparticles with higher lactose contents had lower glass transition temperatures and exhibited increased water adsorption behaviors at various water activities (0.33, 0.54 and 0.75 aw). A rapid decrease in flavor retention was found in matrices with high lactose contents, especially during storage at 0.75 aw. X-ray diffraction and crystallinity analysis proved that the degrees of crystallization of lactose in the encapsulation systems differed, which was induced by differences in water activities. Images of microstructures showed that the formation of crystals caused structural modifications of the powder. Consequently, EA particles were prone to accumulate and migrate to the surface of the powder, which resulted in considerable release of EA flavor. [Display omitted] •Ethyl acetate (EA) encapsulated by lactose/WPI (4:1) was unstable.•The powders with higher lactose content caused the most EA flavor escaping.•Lactose crystallization led to structural modification of microparticles.•EA particles tended to accumulate onto the surface of powders at high RH.