Fabrication and characterization of Idesia polycarpa-derived conjugated linoleic acid microcapsules by spray drying: In vitro digestion and release kinetics

Conjugated linoleic acid (CLA) was efficiently produced from Idesia polycarpa oil by alkaline isomerization (conversion rate 99.34 ± 0.12 %) and microencapsulated with soy protein isolate (SPI) and maltodextrin (MD) by spray drying to obtain IP-CLA-ME. The microcapsules exhibited high encapsulation efficiency (82.38 ± 2.5 %), mean particle size of 781 ± 23 nm, and good electrokinetic stability (−33.9 ± 4.6 mV). SEM and CLSM revealed uniform oil distribution, while FTIR and XRD confirmed structural integrity and wall–core interactions. Encapsulation markedly improved oxidative induction time (260 ± 8 min vs. 161 ± 5 min for IP-CLA) and thermal resistance. In vitro digestion showed a biphasic release, reaching 76.33 ± 0.87 % at 360 min, best fitted by a zero-order model (R 2  = 0.9234). These results demonstrate that SPI–MD microencapsulation effectively stabilizes CLA and enables sustained release, supporting its potential for functional food and nutraceutical applications.