# Microencapsulation of Idesia polycarpa Oil: Physicochemical Properties via Spray Drying vs. Freeze Drying

## TL;DR

This study compares spray drying and freeze drying for microencapsulating Idesia polycarpa oil, showing spray drying offers better stability and aroma retention.

## Contribution

The study introduces a novel comparison of spray drying and freeze drying for microencapsulating Idesia polycarpa oil using a soy protein isolate/maltodextrin system.

## Key findings

- Spray drying produced spherical microcapsules with higher solubility, encapsulation efficiency, and oxidative stability.
- Freeze drying resulted in porous microcapsules with higher emulsifying activity but lower stability and efficiency.
- Spray drying's dense matrix suppressed lipid oxidation and retained key odorants, while freeze drying increased molecular diffusion.

## Abstract

This study systematically compared spray drying (SD) and freeze drying (FD) for microencapsulating Idesia polycarpa oil using a soy protein isolate/maltodextrin (SPI/MD) wall system. SD produced predominantly spherical and compact microcapsules with higher solubility (51.33%), encapsulation efficiency (81.9%), and superior oxidative stability (oxidation induction period, 6.05 h), together with improved thermal resistance, indicating its suitability for applications requiring enhanced stability and aroma retention. In contrast, FD yielded irregular and porous microcapsules with significantly higher emulsifying activity (29.12 m2 g−1, p < 0.05) but lower solubility and encapsulation efficiency. Integrated physicochemical characterization-including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), particle size and polydispersity index (PDI), ζ-potential, differential scanning calorimetry (DSC), oxidative stability index (OSI) measurements, and volatile profiling via odor activity value (OAV) analysis—revealed clear process-dependent structure–function relationships. The denser SPI/MD matrix formed during SD restricted lipid molecular mobility and oxygen diffusion, thereby suppressing lipid oxidation and promoting the retention of key lipid-derived odorants. Conversely, the porous structure generated by FD facilitated interfacial functionality but increased molecular diffusion pathways. Overall, this work demonstrates that SPI/MD-based microencapsulation functions as a molecular stabilization platform for highly unsaturated plant oils and provides mechanistic guidance for selecting drying strategies to tailor Idesia polycarpa oil microcapsules for specific food applications.