Ultrasound-assisted encapsulation of annatto seed oil: Retention and release of a bioactive compound with functional activities

• We evaluated the ultrasound-assisted encapsulation of annatto seed oil with gum Arabic.
• Microparticles obtained by freeze-drying presented high oil entrapment efficiency.
• Geranylgeraniol retention ranged from 80 wt.% to 86 wt.%.
• Kinetics releases of geranylgeraniol were influenced by the morphology and particle size.

This paper brings forward the encapsulation of annatto seed oil (rich in geranylgeraniol) assisted by high intensity ultrasound using gum Arabic (GA) as stabilizing agent. We studied the effects of time (min) and ultrasonication power (W) over the emulsion characteristics. After forming microparticles from the best emulsion using freeze-drying (FD) and spray-drying (SD) techniques, we evaluated particle size distribution, moisture, water activity, surface oil, entrapment efficiency, encapsulation efficiency, geranylgeraniol retention, oxidative stability and kinetic release of geranylgeraniol, a biocompound with functional activities. The combined intensification of time and ultrasonication power reduced the superficial mean diameter (D32) and polydispersity (PDI) of emulsions. Drying the continuous phase of the optimized emulsion (smallest D32 = 0.69 ± 0.03 μm) using FD and SD formed microparticles with different morphological characteristics, Brouckere diameter (D43), particle size distribution, moisture and water activity. SD process led to microparticles with the highest oil encapsulation efficiency (85.1 ± 0.1 wt.%) as a consequence of their lowest surface oil (SO). However, GA-FD microparticles presented the highest oil entrapment efficiency (97 ± 1 wt.%). Geranylgeraniol retention (80–86 wt.%) was similar for both drying techniques. GA-FD microparticles were more stable against oxidation through accelerated test Rancimat, even though presenting higher SO. This behavior is associated with the likely phase transition on the GA-SD matrix. The difference on the kinetic release of geranylgeraniol is linked to the difference on the particles morphology and particle size distribution.