2.3.1. Reagents

Glycerol standard (≥99%) and starch soluble (for analysis) were purchased from Merck (Darmstadt, Germany). Glacial acetic acid (≥99.8%), potassium iodide (≥99.5%), sodium chloride (≥99.5%), sodium hydroxide (≥98%) and buffer solution (pH 4, 7 and 10) were purchased from Honeywell (Charlotte, NC, USA). Sodium acetate trihydrate (99%) was purchased from PENTA chemicals (Prague, Czech Republic) and conductivity standard (1413 μS/cm, 20 ◦C) was purchased from LLG International (Meckenheim, Germany). Iodine (99.5+) and zinc acetate dihydrate (for analysis) were from Fisher Chemical (Waltham, MA, USA). Potassium hexacyanoferrate (II) trihydrate (98+%) was purchased from Alfa Aesar (Ward Hill, MA, USA). Sodium bisulfite was purchased from Acros Organics (Geel, Antwerp, Belgium).

### 2.3.2. Moisture Content

Moisture content at 20 ◦C was determined from the refractive index of honey using a honey refractometer (Hanna, HI, USA). Initially, 2 g of honey was weighed and liquefied in an ultrasonic bath for a few minutes at 35 ◦C. Then, a small amount of liquefied, homogenized sample was spread on the surface of the prism and we marked the measurement on a percentage scale.

### 2.3.3. pH and Free Acidity

The determination of pH and free acidity was held by titration to pH 8.3 at 20 ◦C, according to the 'Harmonised Methods of the International Honey Commission (IHC)' [38]. A pH/conductivity device (Hanna, HI 9811-5, USA) was employed. The free acidity of honey measured the content of free acids, expressed in milliequivalents/kg honey (meq/kg).
