Protein encapsulation in alginate hydrogel beads: Effect of pH on microgel stability, protein retention and protein release

Hydrogel beads (microgels) are promising delivery systems for encapsulation and release of proteins because they can be fabricated from food-grade biopolymers using mild processes. In this study, a model globular protein (whey protein) was encapsulated in calcium-alginate beads (D43 = 290–520 μm) fabricated using an extrusion device with a vibrating nozzle. Protein-loaded beads were fabricated at three different pH values (pH 3, 5 and 7) to study the influence of protein-alginate electrostatic interactions on protein encapsulation, retention, and release. Protein encapsulation and retention was highest at low pH, while protein release was highest at high pH. Confocal microscopy and spectrophotometry measurements indicated that increasing the pH could trigger protein release from alginate beads formed at pH 3. These results suggest that hydrogel beads are suitable for encapsulation and pH-triggered release of proteins, which may be advantageous for certain food applications.