Formulation and Evaluation of Propolis-Loaded Alginate Capsules by Ionic Gelation Technique

Abstract

Propolis can be used as a stand-alone dietary supplement and has the potential to be used as an active ingredient in pharmaceuticals or functional foods because it has been shown to have various health benefits attributed to its phenolic compositions. However, its low solubility in water and strong taste and aroma limits the incorporation in food systems; it is thought that the different encapsulation techniques serve as an effective method to protect bioactive compounds while also helping to mask the taste of propolis and preserve its antioxidant properties. In this study, propolis extracts with final solvents of alcohol, honey, and glycerol were encapsulated using the ionic gelation method with sodium alginate (Na-Alg) at concentrations of 0.5%, 1.5%, and 2% and CaCl2. The nine encapsulated propolis samples' physicochemical, microtextural, and bioactive properties were compared. Since the durability of the capsules until they reach the intestine is crucial, changes in color and bioactivity in digestive fluids after simulated gastric digestion were also assessed. The optical characterization of the capsules revealed that encapsulation with 1% Na-Alg resulted in mechanically weak, deformed, and heterogeneous capsules for all solvent bases. Increasing the Na-Alg concentration led to more uniform and homogeneous capsule structures. When 1.5% and 2% Na-Alg were used, the membranes effectively trapped the core material, producing successful capsules. Among the solvents, honey-based propolis extracts formed the best capsules. None of the samples with different bases and Na-Alg ratios lost their encapsulated form in the simulated gastric fluids. Considering the commercialization potential of the products, the combination of 1.5% honey-based propolis and the Na-Alg ionic gelation coating method is recommended as the most suitable approach.