Microencapsulation of Coffee Pulp Extract (Coffea arabica) with Maltodextrin and Whey Protein Isolate: Physicochemical Characterization, Antioxidant Capacity, and Antimicrobial Activity

Coffee production generates large volumes of by-products rich in bioactive compounds with biological potential, such as coffee pulp. This study evaluated microencapsulation by freeze-drying of aqueous coffee pulp extract using maltodextrin, whey protein isolate, and a 1:1 combination of both as wall materials. Lyophilization yields ranged from 78.99% to 81.49%. SEM analysis revealed a lamellar morphology characteristic of freeze-dried powders in all formulations. FT-IR suggested molecular interactions between wall materials and extract compounds, with Amide I and II bands attenuated in EMP. TGA showed a distinctive degradation event at 513 °C in EMP, which was absent in the controls without extract. Encapsulation efficiency exceeded 94% in all formulations, with EPR and EMP reaching values close to 99%. Among the formulations, EPR showed the highest antioxidant capacity in ABTS and FRAP assays. All formulations showed inhibitory and bactericidal activity against Escherichia coli and Staphylococcus aureus, with EMD showing the lowest minimum bactericidal concentration against E. coli (1 mg/mL). These results indicate that each wall material could confer different properties to the microparticles, supporting freeze-drying microencapsulation as a strategy for the valorization of bioactive compounds from coffee pulp.