Use of rotary fluidized-bed technology for development of sustained-release plant extracts pellets: potential application for feed additive delivery.

The aim of this study was to develop sustained release plant extracts as a potential alternative to antibiotic growth promoters for growing pigs. Pellets with a core based on microcrystalline cellulose and 3 active compounds (eugenol, carvacrol, and thymol) were prepared using rotary fluidized-bed technology. Two particle sizes were produced that had a mean size of approximately 250 and 500 mum. Results show the process was able to produce pellets with a spherical and homogenous form when 10% of the active compounds were incorporated into the core. When active compounds were increased to 20%, the pellet became stickier, and the yield decreased from 90 to 65%. Different amounts of coating in the form of an aqueous-based ethylcellulose (EC) dispersion (Surelease) were applied to the core to modify the release of active compounds. The efficacy of the coating was evaluated in vitro using a flow-through cell apparatus. The time to achieve 50 and 90% dissolution increased with the increase in particle size (P < 0.05) and the increase in EC-coating level from 10 to 20% (wt/wt; P < 0.05), indicating the ability of the process to slow release depending on particle size and the amount of polymer applied. Differences in the release of the active compounds were observed in the same formulation of pellets, except for the formulation with small 10%-EC-coated particles, in which the active compounds were rapidly dissolved (more than 85% in 15 min or less). For all other formulations, the dissolution time for eugenol was always faster than for thymol or carvacrol. The close monitoring of plant extract behavior in the gastrointestinal tract could become a key factor in the continued use of phyto-molecules as alternatives to antibiotic growth promoters and in optimizing the balance between cost and efficacy. Different microencapsulation technologies can be used, of which the rotary fluidized bed warrants consideration because of the quality of the products obtained.