Volatile metabolites or pollen characteristics as regional markers of monofloral thyme honey?

Abstract

Thirty‐one monofloral thyme honeys were collected from professional beekeepers from four different regions in Greece during harvesting year 2012–2013. Aqueous solutions of honeys were subjected to headspace solid‐phase microextraction coupled to gas chromatography with mass spectrometry to record complete volatile pattern, whereas pollen screening was accomplished using the melissopalynological analysis. The primary objective was to investigate the volatile pattern and whether specific volatile metabolites or pollen grain percentages could serve as regional markers. Results showed that 37 volatile compounds, belonging to different classes, were identified and semi‐quantified, using the internal standard method. Application of multivariate analysis showed that ten volatile metabolites recorded significant variations (p<0.05) according to geographical origin of thyme honey. Linear discriminant analysis classified honeys according to geographical origin providing a classification rate of 92.3% using the cross validation method based on the statistically significant volatile metabolites. This was not the case for the overall correct classification rate based on pollen grain percentages which was only 51.6%. Volatile compounds analysis, apart from the specific information on the development of monofloral thyme honey aroma, proved to be a fast and more accurate tool for its discrimination according to production area, compared to melissopalynology.

Valorization of Prickly Pear Juice Geographical Origin Based on Mineral and Volatile Compound Contents Using LDA

“…An optimization procedure was followed, in a preliminary experiment, in order to determine the most appropriate parameters for the extraction of volatile compounds from the headspace of prickly pear juice. These included: sample volume (5 and 10 mL), equilibrium time (10, 20, 25, and 30 min), sampling time (10 and 20 min), sample volume, extraction temperature (40, 42, and 45 °C), and salt (0, 20, and 30% w / v ) addition [18,19]. Based on (i) the number of volatiles determined, (ii) the MS qualification results, (iii) the limited furan derivatives identified, and (iv) the spectra intensity along with the agreement in volatiles identified during the analysis of replicates, the optimum analysis conditions were found to be: 25 min equilibration time, 20 min sampling time, 5 mL sample volume, addition of salt (30% w / v ), and 42 °C water bath temperature (Supplementary Table S8 and typical chromatograms (Figures S1–S8)).…”

“…The vials were maintained at 42 °C in a water bath under continuous stirring at 800 rpm during the headspace extraction. The stirring procedure usually improves the extraction efficiency [19]. For this purpose, a magnetic stirrer (cross shaped and coated with PTFE) with a diameter of 10 mm (Semadeni, Ostermundigen–Bern, Switzerland) was placed inside the vials.…”

“…An electron ionization system was used with an ionization energy of 70 eV. Solvent delay was set at 5 min to avoid co-elution of ethanol, since the internal standard was dissolved in ethanol [19]. Finally, a split ratio of 2:1 was used in the analysis.…”

Honey Volatiles as a Fingerprint for Botanical Origin—A Review on their Occurrence on Monofloral Honeys

“…As stated in Section 2.1, the percentage of pollen grains needed to classify a honey as monofloral is variable, ranging from 8% to 20% of Arbutus pollen for strawberry tree honey, >45% of Erica pollen for heather honey and >86% of Castanea pollen for chestnut honey [44]. Given the new challenges in the international market or domestic regulations, which may demand a higher percentage of dominant pollen grains for the characterization of particular monofloral honey types, volatile compound analysis may provide a faster and more accurate tool for botanical and geographical origin identification, by identifying the specific volatile metabolites [67].…”

Response Surface Methodology to Optimize the Isolation of Dominant Volatile Compounds from Monofloral Greek Thyme Honey Using SPME-GC-MS

“…In a later study, Karabagias et al, [27] reported 2-phenylacetaldehyde, ethyl nonanoate, benzaldehyde, and 2-phenylethan-1-ol as dominant volatile compounds in 42 monofloral thyme honey samples from Greece. Four years later Karabagias et al, [28] reported 2-phenylacetaldehyde, 2-phenylacetonitrile, benzaldehyde, and 2-furancarboxaldehyde as characteristic volatile compounds in 31 thyme honey samples.…”