Microstructural influence on physical properties and release profiles of sesame oil encapsulated into sodium alginate-tamarind mucilage hydrogel beads

Abstract

Ionic gelation of alginate has become one of the most widely used encapsulation techniques, with the main drawback that alginate hydrogels exhibit highly porous structural networks, which promotes high rates of release of encapsulated core materials. To retard the diffusion and loss of oil, and in turn to develop new alternatives as wall materials, this work aims to analyze the effect of structural properties of hydrogel beads prepared with sodium alginate (SA) and two blends of SA - tamarind seed mucilage (SA-TSM) as wall materials, in the release profiles of sesame oil (SO) encapsulated by ionic gelation. Three emulsions were formed using SA, or SA-TSM blends in mass ratios 1:1 and 1:2, with an SO dispersed phase fraction of 0.02 and mass ratio of wall material:SO 1:1. The resulting emulsions were dropped into a 2.5 % wt. CaCl2 solution to produce three different systems of hydrogel beads. They were characterized by their morphology, size, physical properties, oil encapsulation, swelling, and release performance. According to the results obtained, the hydrogel beads showed an ellipsoidal-like geometry with a mean size of ∼2.46 mm. SA-TSM hydrogel beads showed higher encapsulation efficiency (> 73.45%) than SA beads (61.49%). The kinetic curves of SO release showed two regions: a “burst effect” at short times followed by a "lag time" release. The Korsmeyer-Peppas model performed the best fit (R2 > 0.90) for the release of SO, indicating a diffusion-controlled Fickian transport mechanism for all the beads, the effective diffusion coefficients ranged from 5.18 × 10−11 to 6.46 × 10−11 m2/s. Therefore, TSM directly influences the structural and physical properties of SA-TSM hydrogel beads, demonstrating efficient structural support and filler function in the formation of wall materials, improving the encapsulation and controlling the release rate of SO in comparison with SA hydrogel beads.