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This research was aimed to study the sugar composition of fifty-four representative artisanal honeys from the northern Iberian plateau. Moisture, specific rotation, and crystallization indexes were also determined. Sugars were analyzed by gas chromatography-flame ionization detector (GC-FID) after Pourtallier´s derivatization procedure. Fourteen carbohydrates were reliably quantified: two monosaccharides, five disaccharides, six trisaccharides and one tetrasaccharide. Honeydew honeys showed the highest disaccharides (6.71%) and trisaccharides (1.81%) averages and the lowest monosaccharides (63.10%) average, in contrast to heather honeys that had the lowest disaccharides (4.93%) and trisaccharides (0.69%) averages and the highest monosaccharides (70.96%). Chestnut honeys possessed low concentrations of monosaccharides, sucrose, trehalose, and trisaccharides. Clover and lavender honeys possessed high monosaccharide and disaccharide percentages. As expected, lavender samples showed the highest sucrose concentrations (0.05-5.18%). Isomaltose contents were particularly high in honeydew (1.17-2.49%) and chestnut (1.34-1.74%) samples, and low in lavender (0.6-1.16%) honeys, the latter also being low in raffinose (0.01-0.05%). Moisture percentages (14.4-18.6%) indicated optimum honey ripeness. Averages for all groups of samples were levorotatory. In contrast to honeydew and chestnut honeys, lavender samples showed the fastest granulation tendency. In the analyzed honeys, the higher the percentage of isomaltose was, the lower the crystallization tendency the honeys exhibited.

Nowadays, researching potentially functional properties of honey such as antimicrobial activity is interesting due to the overwhelming problem of bacteria strains resistant to antibiotics, and the expected higher value for honey that consumers constantly demand. In this research, we compared three different methods (agar dilution, broth dilution, as well as agar well diffusion), to analyse honey's antimicrobial activity against Staphylococcus aureus, using 56 unpasteurized honeys from different botanical origins. Agar well diffusion method showed to be a rapid and low cost screening method, using less medium and material, to distinguish the samples with and without antibacterial activity. Agar dilution and broth dilution procedures gave similar values. However, the latter proved to be faster and much more informative, providing with minimal antimicrobial and bactericidal concentrations. Higher values of antimicrobial activities were found in honeydew honeys, polyfloral honeys, Calluna vulgaris and Erica spp. honeys. Conversely, Lavandula spp. samples showed lower antimicrobial activity against Staphylococcus aureus.

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