Calcium Alginate Beads Loaded with Green Tea Extract: Impact of Drying Methods on Its Structure, Release Behavior, and Storage Stability

In this study, calcium alginate beads containing green tea extract were formulated by using oven and freeze-drying methods. Using calcium alginate as a carrier and guar gum as a filler ingredient, the beads were prepared through an ionotropic gelation process. The internal texture of oven-dried beads (ODBs) was more homogeneous and compact than that of the freeze-dried beads (FDBs). Based on texture analysis, the ODBs were harder because their internal structure was more rigid. The FDB showed a greater efficiency of encapsulation (74.98%) than that of the ODB (58.04%). Under alkaline conditions, oven- and freeze-dried beads exhibited higher swelling and release rates than under acidic conditions. It was found that FDB released more polyphenols and had a higher metal chelation activity (85.81%) and radical scavenging power (78.33%) than that of oven-dried beads. Both systems were well-fitted by semiempirical models. In addition, both the ODB and FDB showed a 3-fold increase in bioactivity during storage at room temperature (27 ± 2 °C).