Effects of aging on the shelf life and viscoelasticity of gellan gum microcapsules

Abstract Microcapsules are of great interest for applications such as targeted drug delivery and encapsulation of functional food ingredients. While it is intuitive that such products age over time and have a finite shelf life, there are few studies on how the properties of microcapsules change with aging. Here, we examine the aging of edible, gellan gum microcapsules both qualitatively and quantitatively. We found that changes occur in the structure, color, stability, and even the density of individual microcapsules. Further, we performed extremely precise measurements of the rheological properties of the microcapsules using a cantilevered-capillary force apparatus and showed the necessity of method development in order to correctly interpret the data and carry out similar studies in the future. For the aged microcapsules, we observed a transformation from relatively soft and purely elastic to increasingly more stiff and viscoelastic under small deformations, as well as plastically deforming at larger deformations. Ultimately, the microcapsules were found to completely lose their integrity by spontaneously shedding the outer shell and aggregating.