Synergistic antifungal activity and substitution of sorbate with cyclodextrin‐based aqueous extracts of propolis bioactives

Abstract

Propolis phytochemical extracts prepared using a “green” method based on aqueous extraction with cyclodextrin were studied for antifungal activity as a natural alternative to sorbate in food spoilage. The synergistic antifungal effects between “propolis green extract” (PGE) and potassium sorbate (PS) were examined against three common food spoilage yeast species, Torulaspora delbrueckii, Millerozyma farinose, and Brettanomyces bruxellensis by culture, combined with flow cytometry for the evaluation of microbial injury. Growth kinetics showed that the antifungal effect was depended on the concentration of the PGE and the yeast species. Interestingly, flow cytometry revealed a synergy between PGE and PS on cell viability which was not evident by culture. The results suggest that PGE could be used for natural food preservation through direct cell death or microbial injury as part of hurdle technology. Practical applications There is a growing demand for clean label foods, containing natural additives based on bioactives from plants, which can replace artificial ones, and can act as antioxidant and antimicrobial agents. Plant-derived biomolecules (phenolic substances, terpenoids, and flavonoids) are widely studied for their functionality as food antioxidants and preservatives. They have already been incorporated in food matrixes in the form of extracts. Propolis green extract developed in the current study could be used as a natural antimicrobial in food matrices.