Page 2 - Aboud_etal2011

Characterization of Sicilian honeys
honey has been suggested as the quality assessment and botanical
origin indicator (Hausler and Montag, 1989; Tan et al., 1990). It has
also been reported that some aroma compounds can be correlated
with the geographical origin of honey. Indeed, 1-penten-3-ol,
detected in English honeys, has been considered as a specific
compound for this region (Radovic et al., 2001). Monofloral honeys
often possess a characteristic aroma suggestive of plant species
where the nectar had been collected. However, only a few
compounds seem to be really specific to certain unifloral honeys and
many of them may show only different concentration ranges.
Little information on the characterization of Sicilian honeys has 1990) with a Crison Basic 30 conductimeter. Results were expressed
been published. The purpose of the present work was to evaluate 29
Sicilian honey samples using melissopalynology spectra, water
content, pH, acidity (free, lactonic and total acidity), fructose,
glucose, saccharose, electrical conductivity, diastase activity and
colour. Moreover, head space solid phase micro extraction (HS-
PME), followed by gas chromatography (GC) provided information
on the volatiles composition which was compared to the
melissopalynological data and therefore to the botanical origin of the
honeys.
Materials and methods
Twenty-nine honeys were sampled directly from hives located in
different places of Sicily (Italy) (Table 1). All samples after
palynological analysis were kept at -20°C until physicochemical
analyses were performed. All reagents were analytical grade Sigma
or Fluke products used without any purification.
Pollen analysis
The botanical origin of the honey samples was studied according to
the method of Louveaux, Maurizio, and Vorwohl (1978). About 10
grams of each honey sample were dissolved in 30 mL of Milli-Q
grade water and centrifuged for at 1000 g for 15 minutes at 2500
rpm. The supernatant was decanted and the sediment was washed
twice with 10 mL of distilled water and then centrifuged again at
1000 g for 5 minutes at 2500 rpm. The sediment was spread on a
slide, dried at 40°C, and then mounted with stained glycerin gelatin.
Pollen grains were identified and counted under Carl Zeiss AG Light
Microscope, using x400 magnification. Pollen grains are counted
along 5 parallel equidistant lines uniformly distributed from one edge
of the 10 x 10 mm smear to the other (in total at least 500 pollen
grains are counted).
Physicochemical analyses
Moisture content was determined at 20°C with an Abbe type
refractometer (PDT/001), equipped with a thermometer having a
165
graduation of 0.5°C, and a resolution of 2 x 10-4 units of Refraction
Index (RI). Results were expressed as percentages obtained from the
Chat table by using the Wedmore method (Wedmore, 1955).
Measurements of pH were performed with a pH meter (Orion
420 A) in a solution containing 10 g of each honey sample in 75 mL of
Milli-Q grade water, by the method reported by White (White, 1958;
AOAC, 1990). Results were expressed as milliequivalent of NaOH per
Kg of honey.
Honey electrical conductivity was measured at 20°C (AOAC,
in microSiemens per centimeter (µS/cm) (Mateo & Bosch-Reig, 1997;
Krauze & Zalewski, 1991; Devillers et al., 2004).
The diastase activity was measured with the method of
Phadebas (Seigenthaler, 1975). This method was modified by
Bogdanov (Bogdanov et al., 1997; Bogdanov, 1984), Oddo and Pulcini
(1999), based on the use of an insoluble, dyed starch substrate. This
substrate is hydrolyzed by α-amylase, yielding blue water soluble
fragments, determined photometrically at 620 nm. One unit of
diastase activity (or of α-amylase) ( Schade or Gothe unit), is defined
as the amount of enzyme able to convert 0.01 g of starch using 1 g
honey in 1 h at 40°C. Results were expressed as invertase number
(IN).
Honey colour was obtained by Pfund colour grader (C221)
(HANNA instrument), based on simple optical comparison (Fell, 1978;
Aubert and Gonnet, 1983). The C221 portable microprocessor
analyzer measures the percentage light transmittance of honey colour
compared to the analytical reagent grade glycerol. The transmittance
value allows identification of the honey Pfund grade. The instrument
operates in the range of 0 to 150 mm Pfund with an accuracy of ±2
mm Pfund. The measurements were expressed in millimeters (mm)
Pfund.
HPLC analyses were conducted with an isocratic pump (Varian
model 230), having a Varian RI-4 refractive index detector and a 7125
Rheodyne injector of 10 mL loop with a Teknokroma mod. A Tracer
Carbohydrate 4.6 mm ID, 250 mm length column for measurement of
the amounts of glucose, fructose and saccharose according to the
method of Bogdanov and Baumann (1988). A mixture of acetonitrile:
water (75 : 25) was used as isocratic mobile phase with a flow rate of
1.0 mL/min. The column and the detector were thermostated at 30 ±
1°C. Chromatographic peaks were identified according to retention
times after having run analyses of standard materials purchase from
Sigma Aldrich. These, in the appropriate concentrations, were also
used for quantitative analysis.
Volatile organic fractions in honey samples were extracted by
SPME with a polydimethylsiloxane/divinylbenzene (PDMS/DVB, 65
mm) coated fiber purchased from Supelco Sigma Aldrich. The
extraction was carried out after having mixed 3 g of honey with 3 mL
of saturated NaCl solution in a 15 mL glass headspace vial with PTFE/
Silicone septa and a magnetic stirring bar. The vial was gently heated