Eleftherios Alissandrakis

Ultrasound-assisted extraction of volatile compounds from citrus flowers and citrus honey

The volatile fraction of honey is believed to facilitate satisfactory discrimination between honeys of different botanical origin. A new methodology for extracting volatile compounds was developed, using n-pentane:diethylether organic solvent and a water bath with ultrasound assistance. Analysis of the extracts of four Citrus species’ flowers showed linalool to be the predominant compound (11.3% in lemon, 51.6% in orange, 80.6% in sour orange and 75.2% in tangerine). The extracts from citrus honey were predominated by an array of linalool derivatives (more than 80% of the total extract). (E)-2,6-dimethyl-2,7-octadiene-1,6-diol was the predominant compound (44.7%), while significant proportions of 2,6-dimethyl-3,7-octadiene-2,6-diol (15.4%) and (Z)-2,6-dimethyl-2,7-octadiene-1,6-diol (7.2%) were also present.

Solid-phase microextraction/gas-chromatographic/mass spectrometric analysis of p -dichlorobenzene and naphthalene in honey

Protection of honeycombs from the Wax moth, Galleria mellonella, involves the use of physical, biological or chemical control methods. As chemical control may result in residues in the extracted honey, the presence of p-dichlorobenzene and naphthalene residues was investigated by solid-phase microextraction (SPME) coupled to gas-chromatographic/mass spectrometry (GC/MS). The method was linear between 5 and 200 µg kg–1 honey for p-dichlorobenzene and 1 and 200 µg kg–1 for naphthalene. Limits of detection were 1 and 0.1 µg kg–1, respectively, for p-dichlorobenzene and naphthalene, while relative standard deviations were 2.6 and 7.9%, respectively. Application of the method to 90 unifloral Greek honeys revealed that, in 25.6% of the samples, the concentration of either one of the pesticides exceeded the maximum residue level (MRL). Maximum concentrations were 163.03 µg kg–1 honey for p-dichlorobenzene and 193.74 µg kg–1 honey for naphthalene. Naphthalene was found in traceable amounts in 78.9% of the samples, but only 5.6% of them contained concentrations above the MRL, which indicates the use of pre-contaminated honeycomb foundations or built combs. Nevertheless, because naphthalene is naturally present in some plant species growing in Greece, the contribution of nectar from such a floral source should not be overlooked.

Pyrethroid target site resistance in Greek populations of the honey bee parasite Varroa destructor (Acari: Varroidae)

The mite Varroa destructor is the most serious pest of honey bees worldwide and its control is mainly based on the use of synthetic acaricides, which, in many cases, has led to the development of resistance. In Greece, evidence of resistance to the pyrethroid tau-fluvalinate goes back to the early 1990s. In the present study we examined the presence of resistance mutations at the voltage gated sodium channel (VGSC) gene, encoding the target of pyrethroids. The frequency of resistance mutations was examined by genotyping 113 V. destructor individuals from seven localities in Greece The nucleotide sequencing of the IIS4-IIS5 region of the VGSC gene revealed two amino acid replacements at position 925: a leucine to valine substitution (L925 V) and a leucine to isoleucine substitution (L925I). This is the first report of L925I mutation in European populations of V. destructor that has so far been identified only in USA. No mutations at two other “hot spot” resistance positions, 918 and 929 of the VGSC gene encompassing position 925 were identified. Resistant alleles were predominant (53%) and most of them (83%) corresponded to the L925I substitution. Genotyping results showed the presence of homozygous wild type 925L (44.2%) individuals as well as homozygous resistant 925I (39.8%) and 925 V (7.1%), while heterozygous individuals (925I/L, 925I/V, 925 V/L) were present at low frequency (5.3, 2.7 and 0.9 respectively). Our results clearly show the presence of pyrethroid resistant mutations in high frequency in Greek Varroa populations.

Monitoring of royal jelly protein degradation during storage using Fourier-transform infrared (FTIR) spectroscopy

Summary Royal jelly protein degradation was monitored by Fourier-transform infrared (FTIR) spectroscopy. The samples of royal jelly were stored at room temperature for 10 weeks at 4°C and -20°C for 31 weeks. The FT-IR spectra were then recorded and the ratio of peak area in 1545 (amide II) and 1656 cm−1 (amide I) was calculated. The ratio of peak areas associated with the degradation of proteins. It was observed that the ratio increased over time and with increasing storage temperature. The protein of royal jelly is maintained for three days at room temperature, seven weeks at 4°C and 21 weeks at -20°C.

Studying of quality parameters and organic contaminants in honey samples

Honey is valuable food for mankind since the ancient times. It was the only sweetener till the start of the industrial sugar mass production. As honey plays an important role in our nutrition and its positive effects on health is well known, it is very important to study the nutritional properties and the origin of different honey samples. The usually determined quality parameters of honey: pH values, water content, sugar content, acidity, HMF content, enzyme activity, pollen content, amino acid content, ash content, etc. It is also important to know the content of the organic contaminants in honey. A short time ago there were some quality problems with Hungarian and Greek honey in the European Union. A toxic material (para-dichlorobensene) was found in honey originated from Greece. The amount was higher than the allowable limit in the ELf. Therefore, it is necessary to build up a good and applicable traceability system for honey. During the past few years the traceability concept has become increasingly familiar in many sectors of the food industry. Traceability is an essential tool for ensuring both production and product quality. The opportunity to connect traceability with the whole documentation and control system represents an effective means for boosting the consumers perception of a foods safety and quality. In our work we have done, which quality parameters can be used for a good identification system. We have analyzed the following parameters of national and Greek honey types: mineral contents (trace elements), pH values, sugar content, acidity, HMF content, diastase activity. We have also analyzed the para-dichlorobensene in the honey samples. The samples were taken directly from Hungarian beekeepers (all professionals) and supermarkets (area of geographical origin unknown). We have measured also Greek honey. The samples were originated from some Greek islands, near Athens and from some Greek supermarkets. For the traceability it is necessary to know the following parameters: element content-free amino acids content-pollen content. Besides, it is important to analyze organic contaminants in honey.