Optimization of a Water-Dispersible Powder from an Ethanolic Propolis Extract Using Fluid Milk and Milk Powders as Capping Materials

Propolis is consumed almost exclusively as an ethanolic tincture because its bioactive constituents reside in a water-insoluble resin, and the residual ethanol limits both the range of consumers who can take it and its use in aqueous foods. This study sought a capping material that converts an ethanolic propolis extract into a water- dispersible powder after ethanol removal. Among seven candidates, the casein-containing materials gave a total phenolic recovery (TPR) above 90%, whereas gum arabic and starch did not. Fluid milk, whole milk powder and skim milk powder were then compared by response surface methodology. Capping material content governed both solubility and TPR, but the two milk powders ranked in opposite order, indicating that milk fat assists phenolic retention whereas its physical state determines redispersion. Fluid milk, which supplies its fat as protein-coated globules, performed well on both responses. Under its optimized conditions (8.55 g, 675 W, 300 s), the predicted solubility and TPR of 91.84% and 98.43% were reproduced experimentally as 87.60% and 98.26%. For industrial application, the powders were further characterized: moisture content and water activity remained below 8.4% and 0.42, whiteness increased and droplet size decreased with capping material content, and scanning electron microscopy revealed discrete spherical particles.