The water content of honey and agave syrup was measured via Karl Fischer titration (TitroLine 7500 KF trace, SI Analytics, Germany). Before measuring, the titrator was tested with a water standard (Merck Millipore, Germany).
The water activity aw of honey and agave syrup was determined with an AquaLab CX-2 at 22°C (Decagon Devices, USA).
After calibrating, the pH was directly measured in honey and agave syrup and as a 10% dilution (w/v) (SenTix® Mic, Xylem Analytics, Germany).
The two main carbohydrates, fructose and glucose, were quantified by HPLC (Agilent 1100 Series, Agilent Technology, Germany) with a Rezex ROA organic acid H+ (8%) column (300 mm length, 7.8 mm diameter) and a Rezex ROA organic acid H+ (8%) guard column (50 mm length, 7.8 mm diameter) from Phenomenex (Phenomenex Ltd., Germany) as described in Dörsam et al. (2017 (link)). Separation was performed with 5 mM H2SO4 for 45 min and a flow rate of 0.5 ml/min under isocratic conditions at 50°C column temperature. Carbohydrates were detected via a refractive index detector (Agilent 1200 series, Agilent Technology, Germany).
Quantification of the sugars were performed by using three different dilutions of honey or agave syrup (0.3–1 mg/ml) and an external 10-point calibration curve for each component from 10 to 500 mg/l.
All measurements were made in triplicates.
The water activity aw of honey and agave syrup was determined with an AquaLab CX-2 at 22°C (Decagon Devices, USA).
After calibrating, the pH was directly measured in honey and agave syrup and as a 10% dilution (w/v) (SenTix® Mic, Xylem Analytics, Germany).
The two main carbohydrates, fructose and glucose, were quantified by HPLC (Agilent 1100 Series, Agilent Technology, Germany) with a Rezex ROA organic acid H+ (8%) column (300 mm length, 7.8 mm diameter) and a Rezex ROA organic acid H+ (8%) guard column (50 mm length, 7.8 mm diameter) from Phenomenex (Phenomenex Ltd., Germany) as described in Dörsam et al. (2017 (link)). Separation was performed with 5 mM H2SO4 for 45 min and a flow rate of 0.5 ml/min under isocratic conditions at 50°C column temperature. Carbohydrates were detected via a refractive index detector (Agilent 1200 series, Agilent Technology, Germany).
Quantification of the sugars were performed by using three different dilutions of honey or agave syrup (0.3–1 mg/ml) and an external 10-point calibration curve for each component from 10 to 500 mg/l.
All measurements were made in triplicates.
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