Physicochemical, Antioxidant and Antimicrobial Properties of selected Portuguese Commercial Monofloral Honeys

The physicochemical, antioxidant and antimicrobial properties of selected Portuguese commercial honeys have been characterized aiming at establishing correlations between honey bioactivity and the physicochemical descriptors. All honey samples met the European regulations on honey quality criteria, including moisture and sugar content, free acidity, diastase activity, electrical conductivity, ashes, hydroxymethylfurfural and proline content. Antioxidant activity was evaluated based on phenolic and flavonoid content, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power (FRAP) and oxygen radical antioxidant capacity (ORAC) assays. The honeys showed antibacterial and antifungal activity with minimum inhibitory concentrations (MIC) between 6.25–25% (w/v) and minimum fungicidal concentrations (MFC) in the range 12.5–50% (w/v), respectively. The bioactivity and physicochemical parameters of honey samples were correlated and depended on the honey floral source. The darkest honey, i.e. heather honey, showed the highest antioxidant and antimicrobial activities, which can be attributed to its higher phenolic, flavonoid and protein content.