Microstructure and lactose crystallization properties in spray dried nanoemulsions

The objective of this study was to characterize lactose crystallization behaviour and microstructure of spray dried nanoemulsions with different fat globule sizes (FGS). Powders of the same composition (57.7% w/w lactose, 12.3% w/w sodium caseinate, 27.7% w/w sunflower oil, and 2.3% w/w water) but different FGS (mean diameters 1100nm and 160nm) prior to spray drying were manufactured. Differences in lactose crystallization were studied using dynamic vapour sorption (DVS) and polarized light microscopy (PLM). Crystallization kinetics was modelled using the Avrami and Yang equations. Results showed that lactose crystallized in three dimensions and more rapidly in powders with a smaller FGS. PLM images showed a higher rate of crystal formation for smaller FGS powders when stored for up to 4 days at 55% relative humidity. Confocal laser scanning microscopy (CLSM) and cryo-scanning electron microscopy (Cryo-SEM) images indicated the more evenly distributed small fat globules inside powder particles prepared from spray-dried nanoemulsions. The surface of powder particles was uneven and ruptured post lactose crystallization. Crystals of presumptive anhydrous α- and β-lactose (5:3 molar ratio) appeared after humidification. Results showed powder particles of the same composition were altered in lactose crystallization characteristics by changing the FGS of emulsions pre spray drying. Graphical abstract
Source: Food Structure - Category: Food Science Source Type: research