Honeys Research Articles

Application of Spatial Offset Raman Spectroscopy (SORS) and Machine Learning for Sugar Syrup Adulteration Detection in UK Honey.

Honey authentication is a complex process which traditionally requires costly and time-consuming analytical techniques not readily available to the producers. This study aimed to develop non-invasive sensor methods coupled with a multivariate data analysis to detect the type and percentage of exogenous sugar adulteration in UK honeys. Through-container spatial offset Raman spectroscopy (SORS) was employed on 17 different types of natural honeys produced in the UK over a season. These samples were then spiked with rice and sugar beet syrups at the levels of 10%, 20%, 30%, and 50% w/w. The data acquired were used to construct prediction models for 14 types of honey with similar Raman fingerprints using different algorithms, namely PLS-DA, XGBoost, and Random Forest, with the aim to detect the level of adulteration per type of sugar syrup. The best-performing algorithm for classification was Random Forest, with only 1% of the pure honeys misclassified as adulterated and <3.5% of adulterated honey samples misclassified as pure. Random Forest was further employed to create a classification model which successfully classified samples according to the type of adulterant (rice or sugar beet) and the adulteration level. In addition, SORS spectra were collected from 27 samples of heather honey (24 Calluna vulgaris and 3 Erica cinerea) produced in the UK and corresponding subsamples spiked with high fructose sugar cane syrup, and an exploratory data analysis with PCA and a classification with Random Forest were performed, both showing clear separation between the pure and adulterated samples at medium (40%) and high (60%) adulteration levels and a 90% success at low adulteration levels (20%). The results of this study demonstrate the potential of SORS in combination with machine learning to be applied for the authentication of honey samples and the detection of exogenous sugars in the form of sugar syrups. A major advantage of the SORS technique is that it is a rapid, non-invasive method deployable in the field with potential application at all stages of the supply chain.

Polish honeys exhibit activity against Pseudomonas aeruginosa isolated from wounds

Pseudomonas aeruginosa is recognized as an opportunistic pathogen and a common contributor to wound infections. This study focused on evaluating the antibacterial activity of selected Polish honeys against P. aeruginosa. Six bacterial strains isolated from wounds and four types of honeys (multifloral, linden, buckwheat, and heather) were utilized. The minimal inhibitory concentrations (MIC) were determined through the micro-dilution method employing 96-well plates, while antibiofilm activity was assessed using fluorescence microscopy after a 4-hour incubation period with the honeys. Results indicated diverse antibacterial efficacy among honeys, with linden and heather honeys demonstrating the most potent activity. Linden honey displayed an average MIC of 20.8%, while heather honey exhibited an MIC of 25%. Both honeys significantly reduced biofilm formation, with linden honey achieving a reduction of 54-67% and heather honey of 45-58%. Buckwheat and multifloral honeys exhibited lower activity, demonstrating average MIC levels of 37.5% and 41.7%, respectively, and a biofilm reduction below 20%. Conclusively, Polish honeys exhibited promising activity against both planktonic and biofilm forms of P. aeruginosa. These findings suggest potential applications in wound healing treatments, emphasizing the need for further research in this area. The study contributes valuable insights to the limited literature on the antibacterial activity of Polish honeys.

Honey differentiation with FTIR-ATR spectroscopy – Comparison with physicochemical parameters of a Polish honey sample set

The varietal discrimination of honey is important because its bioactive properties, as well as specific characteristics, depend on the botanical origin. The present study aimed to verify the discriminatory power of Fourier-transform infrared spectroscopy (FT-IR) for differentiating Polish honeys and compare the results with the discrimination power of a model built on the basis of selected physicochemical parameters. For this purpose, buckwheat, rape, acacia, heather, goldenrod, and coniferous honeydew honeys were collected from trustworthy apiaries in different regions of Poland. The samples were further authenticated using pollen analysis and tested by means of FT-IR and the attenuated total reflection (ATR) technique. Basic psychochemical parameters were also assessed. The obtained data were analyzed by means of principal component analysis (PCA) and linear discriminant analysis (LDA). The obtained models were validated with a leave-one-out cross-validation (LOOCV) procedure. PCA analysis confirmed the usefulness of the ATR FT-IR method as a honey differentiation tool. The LDA for the FT-IR model allowed to correctly classify 26 out of 32 samples (81.3% accuracy), which was only slightly lower than for data the model based on the physiochemical characteristics (27 out of 32 samples and 84.4% accuracy), revealing a certain potential of FT-IR as fast evaluation method.

Influence of different heat treatment regimes on the change of chemical composition and antibacterial activity of bee honey

The studies of the chemical composition and antibacterial activity of heather honey (Calluna vulgaris) subjected to heat treatment at 35–40°C for 12 hours were carried out. The temperature range (38–40°C), at which decrease in the H2O2 concentration, decrease in D-glucose-1-oxidase activity and increase in the 5-hydroxymethylfurfural content, was identified. The degree of chemical changes was directly proportional to the temperature and time of thermal exposure. The correlation between changes in the chemical composition and antibacterial activity of honey against test microorganisms Escherichia coli (strain 1257), Staphylococcus aureus (strain 209-P) and Bacillus cereus (strain 96) was established. The obtained results showed that heating honey to 37 °C even for 12 hours didn’t cause undesirable changes in its chemical composition and decrease in antibacterial activity. Thus, this temperature regime can be considered more gentle and recommended for use in the heat treatment of this food product.

Advantages of a Multifaceted Characterization of Honey, Illustrated with Irish Honey Marketed As Heather Honey

Advantages of a Multifaceted Characterization of Honey, Illustrated with Irish Honey Marketed As Heather Honey

Multi-Element Profile Characterization of Monofloral and Polyfloral Honey from Latvia.

Honey is of scientific interest mainly due to its health-promoting and antibacterial properties, which are also associated with its floral origins. However, the methods for confirming honey floral origins are quite limited and require improvements. One method suggested in the search for a multi-method approach to evaluating the floral origins of Latvian honey is inductively coupled plasma mass spectrometry (ICP-MS). This study investigated the multi-element profile of 83 honey samples of well-specified floral origins. The main findings included using Ba, Ca, Cs, Fe, and Rb as indicator elements for heather honey. The chemometric evaluation supported the use of ICP-MS for distinguishing heather honey from other types of honey. The Latvian polyfloral honey multi-element profile was defined and compared to honey samples with other geographical origins. Additionally, the multi-element profiles of buckwheat, clover, and polyfloral honey proteins were investigated to clarify whether the majority of elements were bound with proteins or not. Preliminary results indicated that Ca, K, Mg, Mn, Na, and Sr were mainly found in non-protein-bound forms, while the majority of Al, Cu, Ni, and Zn were in the form of large chemical structures (>10 kDa).

Correlations of flavonoids content and antioxidant activity in bee honey from Bosnia and Herzegovina

In this study, it was performed identification and quantification of flavonoids (apigenin, chrysin, hesperetin, kaempferol, luteolin, naringenin, and quercetin) and flavonoid glycosides (rutin and vitexin) in total 49 samples of five different honey types from Bosnia and Herzegovina: meadow honey (MH, 22 samples), forest (FH, 10), acacia (AH, 7), chestnut (CH, 5), and heather honey (HH, 5). Additionally, evaluation of correlations between FC and total hydrophilic antioxidant score (antioxidant activity against both: ROO· + OH·) in supernatants (s) and in bulk (noncentrifuged) solution (b) of these honey types was performed. Moreover, correlations between flavonoids content (FC) and previously reported antioxidant activity against both peroxyl and hydroxyl free radicals (AC(ROO·) and AC(OH·)) for the same honey samples was examined. High performance liquid chromatography with photodiode array detector (HPLC-DAD) and isocratic elution mode was used as method of analysis. Flavonoids were extracted by solid phase extraction (SPE). The average contents of three flavonoids (chrysin, naringenin, and luteolin) in MH were statistically higher than in AH (p**&lt;0.01). Also, the average content of naringenin in FH was statistically higher than in CH (p*&lt;0.05). We observed a high (positive) linear correlation between FC and AC(ROO·) in s of four honey types (FH, AH, HH, CH) (R2=0.920). If we correlate FC and AC(ROO·)s of three honey types (FH, AH, HH), linearity is very high (R2=0.968), and for FH, AH, CH linearity is complete. The correlation between FC and AC(ROO·) in b of the same honey types is similar, but lower. The correlation does not exist between FC and AC(OH·) neither in s nor in b of five or four honey types, but for FC to both (AC(OH·)s and AC(OH·)b) of three honey types (FH, AH, CH), linearity is moderate (R2=0.732 and R2=0.696, respectively). Keywords: antioxidant activity, correlations, flavonoids, honey, HPLC-DAD.

Multivariate Statistical Approach for the Discrimination of Honey Samples from Galicia (NW Spain) Using Physicochemical and Pollen Parameters.

Raw honey is a food with a close relation to the territory in which it is produced because of factors such as soil conditions, weather patterns, and plant communities living in the area together. Furthermore, beekeeping management affects the properties of honey. Protected Geographical Indication Miel de Galicia protects the honey produced in Galicia (Northwest Spain). Various types of honeys (362 samples) from this geographical area were analyzed using chemometric techniques. Principal component analysis was favorable to analyzing the physicochemical and pollen variables with the greatest weight in the differentiation of honey. The linear discriminant analysis correctly classified 89.8% of the samples according to the botanical origin using main pollen spectra and physicochemical attributes (moisture, pH, electrical conductivity, diastase content, phenols, flavonoids, and color). Regarding unifloral honey, blackberry, eucalyptus, and heather honeys were correctly grouped, while five chestnut honeys and fourteen samples of honeydew honeys were misclassified. The chestnut and honeydew honeys have similar physicochemical properties and frequently similar pollen spectra profiles complicating the differentiation. Experimental evidence suggests the potential of multivariate statistics in the characterization of honey of the same geographical origin. Therefore, the classification results were good, with electrical conductivity, total phenol content, total flavonoid content and dominant pollens Eucalyptus, Erica, Rubus and Castanea sativa as the variables of higher importance in the differentiation of botanical origin of honeys.

Characterization and Classification of Spanish Honeydew and Blossom Honeys Based on Their Antioxidant Capacity.

Honey is a very appreciated product for its nutritional characteristics and its benefits for human health, comprising antioxidant, anti-inflammatory, antifungal, and antibacterial activities. These attributes depend on the specific composition of each honey variety, with the botanical origin as one of the distinctive features. Indeed, honeydew and blossom honeys show different physicochemical properties, being the antioxidant capacity, mainly relying on the phenolic compound content, one of the most important. In this work, Folin-Ciocalteu (FC) index, total flavonoid content (TFC), and the antioxidant capacity based on the ferric reducing antioxidant power (FRAP) assay were determined for a total of 73 honeys (50 blossom honeys and 23 honeydew honeys). Mean content of oxidizable species (FC index) ranges from 0.17 to 0.7 mg eq. gallic acid g-1, with honeydew honeys being the ones with higher values. Regarding TFC, mean values above 1.5 mg eq. quercetin g-1 (method applied in the absence of NaNO2) were obtained for honeydew honeys and heather honey. Lower and not discriminatory values (below 0.3 mg eq. epicatechin g-1) were obtained in the presence of NaNO2. The maximum antioxidant capacity was observed for thyme honeys (2.2 mg eq. Trolox g-1) followed by honeydew and heather honeys. Individually, only the FC index was able to discriminate between honeydew and blossom honeys, while the other spectroscopic indexes tested allowed the differentiation of some honey types according to the botanical origin. Thus, a holistic treatment of the results was performed using partial least square discriminant analysis (PLS-DA) for classification purposes using FC, TFC, and FRAP results as data. Honeydew and blossom honey were satisfactorily discriminated (error 5%). In addition, blossom honeys can be perfectly classified according to their botanical origin based on two-class PLS-DA classification models.

Characterization of Ikaria Heather Honey by Untargeted Ultrahigh-Performance Liquid Chromatography-High Resolution Mass Spectrometry Metabolomics and Melissopalynological Analysis.

Honey represents a valuable food commodity, known since ancient times for its delicate taste and health benefits due to its specific compositional characteristics, mainly the phenolic compound content. “Anama” honey is a monofloral honey produced from the nectar of Erica manipuliflora plant, a heather bush of the Greek island of Ikaria, one of the Mediterranean’s longevity regions. “Anama” is characterized by a unique aroma and taste, with a growing demand for consumption and the potential to be included in the list of products with a protected designation of origin. The aim of this study was to determine the chemical and botanical profile of authentic Anama honey samples and find similarities and differences with honey samples of a different botanical origin from the same geographical area. Untargeted Ultrahigh-Performance Liquid Chromatography-Hybrid Quadrupole-Orbitrap High-Resolution Mass Spectrometry (UHPLC-HRMS) metabolomics study was conducted on authentic heather, pine, and thyme honey samples from Ikaria and neighboring islands. The Principal Component Analysis (PCA), Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA), and differential analysis were performed using the entire metabolic profile of the samples and allowed the identification of chemical markers for sample discrimination. Thirty-two characteristic secondary metabolites (cinnamic acids, phenolic acids, flavonoids, terpenes) and other bioactive phenolic compounds, some of them not previously reported in a heather honey (aucubin, catalpol, domesticoside, leonuriside A, picein among others), emerged as potential chemical indicators of Anama honey. Melissopalynological analysis was also carried out to decipher the botanical and geographical origin of Anama honey. The relative frequency of the pollen of dominant plants of the Ericaceae family and a multitude of nectariferous and nectarless plants contributing to the botanical profile of Anama was evaluated. The identification of the pollen sources enabled a potential correlation of differentially increased secondary metabolites and chemicals with their botanical origin. The physicochemical profile of Anama was also determined, including the parameters of pH, color, electrical conductivity, diastase, moisture, as well as sugars, supporting the high quality of this heather honey.

Antioxidative, Antibacterial and Antiproliferative Properties of Honey Types from the Western Balkans.

This paper presents the physicochemical characteristics and antioxidative, antibacterial and antiproliferative effects of nineteen samples of different honey types (acacia, linden, heather, sunflower, phacelia, basil, anise, sage, chestnut, hawthorn, lavender and meadow) collected from different locations in the Western Balkans (Republic of Serbia, Kosovo, Bosnia and Herzegovina, and Northern Macedonia). Physicochemical parameters (moisture, pH, electrical conductivity, free acidity, and hydroxymethylfurfural [HMF]) were analysed. Based on the obtained results, all tested honey samples were in agreement with EU regulation. The antioxidant potential of honey samples was assessed by determination of total phenolic content (TPC) and evaluation of scavenging activity towards diphenilpicrylhydrazyl radicals (DPPH·). The highest phenolic content was found in basil honey (101 ± 2.72 mg GAE/100 g), while the lowest was registered in rapeseed honey (11.5 ± 0.70 mg GAE/100 g). Heather, anise, phacelia, sage, chestnut and lavender honey samples were also rich in TP, containing 80–100 mg GAE/100 g. DPPH scavenging activity varied among the samples being the highest for lavender honey (IC50 = 88.2 ± 2.11 mg/mL) and the lowest for rapeseed honey (IC50 = 646 ± 8.72 mg/mL). Antibacterial activity was estimated in vitro using agar diffusion tests and measuring minimal inhibitory concentration (MIC). Among investigated bacterial strains following resistant potencies were determined: Escherichia coli > Escherichia coli ATCC 8739 > Enterococcus faecalis > Proteus mirabilis > Staphylococcus aureus > Staphylococcus epidermidis. The linden honey from Fruška Gora (MIC values of 3.12% and 6.25% against Staphylococcus aureus and Staphylococcus epidermidis, respectively) and phacelia honey (MIC values of 6.25% and 3.12% against S. Staphylococcus aureus and Staphylococcus epidermidis, respectively) showed the strongest antibacterial activity. Antiproliferative activity was evaluated using the colorimetric sulforhodamine B (SRB) assay. The highest antiproliferative activity was obtained from linden honey sample 1 (IC50MCF7 = 7.46 ± 1.18 mg/mL and IC50HeLa =12.4 ± 2.00 mg/mL) and meadow sample 2 (IC50MCF7 = 12.0 ± 0.57 mg/mL, IC50HeLa = 16.9 ± 1.54 mg/mL and IC50HT−29 = 23.7 ± 1.33 mg/mL) towards breast (MCF7), cervix (HeLa) and colon (HT-29) cancer cells. Active components other than sugars contributed to cell growth activity.

Selected mechanisms of the antimicrobial effect of honey in the aspect of drug resistance of bacteria

The aim of the study was to review the available literature on the significance of factors and mechanisms of the antimicrobial effect of honey and the possibilities of using them to stabilize or inhibit the growth of selected Gram-positive and Gram-negative pathogenic bacteria particularly capable of developing drug resistance. It can be concluded from data in the literature that the factors and mechanisms of the antimicrobial effect of honey are numerous and diverse. Honey can be effective in fighting microbes due to its physical, chemical and biological properties. The mechanisms of the antimicrobial effect of honey include, above all, high osmotic pressure, low pH caused by the presence of organic acids and hydrogen peroxide, high content of phenolic compounds, lysozyme (to a limited extent) and methylglyoxal in manuka honey and defenazine-1 in Revamil honey. Based on the presented research results, it was observed that the level of antibiotic activity of honey depends on its variety, geographic origin, concentration of honey solution, but also on the type of bacterial strain tested and its resistance. Bactericidal and bacteriostatic effects of various varieties of honey have been found in certain Gram-positive bacteria (manuka honey – Staphylococcus aureus; Scottish heather honey – Staphylococcus epidermidis) and Gram-negative bacteria (undiluted Thai honeys – Escherichia coli; 3% (v/v) solution of honey – Salmonella enterica; manuka honey – Pseudomonas aeruginosa biofilm). The high level of antibiotic activity of honey against these bacteria species is a potential opportunity to support therapies in cases of infections caused by these microorganisms, which can help fight the problem of drug resistance. The possibility of inhibiting or limiting the development of pathogenic bacteria without resorting to antibiotics would also have a mitigating impact on the growing problem of antibiotic resistance. However, it is advisable to extend the spectrum of research in this area to include bacteria species for which the current experimental results are mutually contradictory (Listeria monocytogenes, Enterococcus faecalis) and to include in the research microorganisms that have not yet developed drug resistance. In addition, both for economic reasons and due to the limited supply, alternative varieties of honey should be researched more extensively in research, apart from manuka honey which is most often used in experiments by scientists. In addition to the unquestionable advantages of honeys, it is important to remember that they can be contaminated with spores of Clostridium botulinum and Bacillus cereus.

An Investigation of The Biological Activity of Monofloral Honey Produced in South-Western Anatolia

In this study, monofloral honeys (chaste, thyme, citrus, and heather) which were obtained from different sources from members of Beekeeping Associations in South-West Anatolia were studied for their antioxidant capacity, total phenolic amounts, total flavonoid amounts, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and urease inhibition activities. Antioxidant capacity of honey samples was determined by β-carotene, DPPH, ABTS+ and CUPRAC activity methods. In honey samples, the highest antioxidant activity was found in citrus honey with β-carotene/Linoleic acid color opening with IC50: 7.99 mg/mL, and DPPH free radical removal activity with IC50: 5.28 mg/mL in thyme honey. In CUPRAC activity, it was determined that the highest activity was found in heather honey with IC50: 1.69 mg/mL, in terms of ABTS+ removal activity IC50: 2.80 mg/mL in chaste honey, and metal chelating activity IC50: 1.56 mg/mL in thyme honey. The total phenolic and flavonoids amounts of honeys ranged from 2.31 and 27.15 (μg PEs/mg) to 4.95 and 25.24 (µg QEs/mg), respectively. In addition, AChE inhibition IC50: 24.25 mg/mL in thyme honey, BChE inhibition IC50: 27.93 mg/mL in thyme honey, and urease inhibition IC50: 34.89 mg/mL with citrus honey were determined concerning the highest activity, consecutively.

Determination of Floral Origin Markers of Latvian Honey by Using IRMS, UHPLC-HRMS, and 1H-NMR.

The economic significance of honey production is crucial; therefore, modern and efficient methods of authentication are needed. During the last decade, various data processing methods and a combination of several instrumental methods have been increasingly used in food analysis. In this study, the chemical composition of monofloral buckwheat (Fagopyrum esculentum), clover (Trifolium repens), heather (Calluna vulgaris), linden (Tilia cordata), rapeseed (Brassica napus), willow (Salix cinerea), and polyfloral honey samples of Latvian origin were investigated using several instrumental analysis methods. The data from light stable isotope ratio mass spectrometry (IRMS), ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS), and nuclear magnetic resonance (NMR) analysis methods were used in combination with multivariate analysis to characterize honey samples originating from Latvia. Results were processed using the principal component analysis (PCA) to study the potential possibilities of evaluating the differences between honey of different floral origins. The results indicate the possibility of strong differentiation of heather and buckwheat honeys, and minor differentiation of linden honey from polyfloral honey types. The main indicators include depleted δ15N values for heather honey protein, elevated concentration levels of rutin for buckwheat honey, and qualitative presence of specific biomarkers within NMR for linden honey.

Unifloral Autumn Heather Honey from Indigenous Greek Erica manipuliflora Salisb.: SPME/GC-MS Characterization of the Volatile Fraction and Optimization of the Isolation Parameters.

For long heather honey has been a special variety due to its unique organoleptic characteristics. This study aimed to characterize and optimize the isolation of the dominant volatile fraction of Greek autumn heather honey using solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS). The described approach pointed out 13 main volatile components more closely related to honey botanical origin, in terms of occurrence and relative abundance. These volatiles include phenolic compounds and norisoprenoids, with benzaldehyde, safranal and p-anisaldehyde present in higher amounts, while ethyl 4-methoxybenzoate is reported for the first time in honey. Then, an experimental design was developed based on five numeric factors and one categorical factor and evaluated the optimum conditions (temperature: 60 °C, equilibration time: 30 min extraction time: 15 min magnetic stirrer velocity: 100 rpm sample volume: 6 mL water: honey ratio: 1:3 (v/w)). Additionally, a validation test set reinforces the above methodology investigation. Honey is very complex and variable with respect to its volatile components given the high diversity of the floral source. As a result, customizing the isolation parameters for each honey is a good approach for streamlining the isolation volatile compounds. This study could provide a good basis for future recognition of monofloral autumn heather honey.

Chemical and Antioxidant Characterization of the Portuguese Heather Honey from Calluna vulgaris

The Calluna vulgaris honey produced in Portugal, concerning its phenolic compounds and abscisic acids profiles, as well as its antioxidant activity and the protective effect against oxidative damage in human erythrocytes were herein performed for the first time. The phenolic and abscisic acid profiles were tentatively identified by LC-MS/MS (17 compounds). The total content of phenolics and abscisic acids was 15,446.4 µg/g of honey extract, with catechin derivatives and abscisic acids being major constituents. The highest scavenging capacity was found against reactive nitrogen species. Additionally, the honey extract prevented ROO•-induced oxidative damage in erythrocytes collected from human blood, by inhibiting hemolysis, lipid peroxidation and hemoglobin oxidation. In conclusion, C. vulgaris honey contains high content of catechin derivatives and abscisic acids that may be responsible for its biological activity, characterized by a strong antioxidant capacity, which adds up to the nutritional value of this delicacy.

A Rheological Analysis of Biomaterial Behaviour as a Tool to Detect the Dilution of Heather Honey.

Heather honey is a valuable and rheologically special type of honey. Its above-average selling price may motivate its intentional violation with a mixture of honey from another botanical origin, the price of which is lower on the market. This work deals with the rheological properties of such devalued heather honey in order to determine the changes in the individual rheological parameters depending on the degree of dilution of the heather honey. For this purpose, a differently diluted heather honey sample series was created and the following rheological parameters were determined: hysteresis area, n-value, yield stress (τ0), parameter B (Weltman model), parameter ϕ, or parameter C (model describing the logarithmic dependence of the complex viscosity on the angular frequency). Part of the work was research into whether the set parameters can be used as comparative parameters. It was found that the hysteresis area does not appear to be a suitable relative comparison parameter due to the high variability. The parameters that appear to be suitable are the relative parameters n-value and the parameter ϕ, which showed the greatest stability. The change in the determined rheological parameters is, depending on the degree of dilution, non-linear with a step change between the samples containing 40% (w/w) and 60% (w/w) of a heather honey.

The Composition, Physicochemical Properties, Antioxidant Activity, and Sensory Properties of Estonian Honeys

Thirty honey samples from different regions of Estonia were investigated to determine the chemical compositions, physicochemical properties, bioactive compounds, and sensory characteristics of typical honeys from a northern climate. The physicochemical parameters, such as electrical conductivity, moisture content, free acidity, hydroxymethylfurfural, diastase, and invertase activity were measured. The color was measured and expressed by L*-, a*-, and b*-coordinates. Sensory parameters were determined by using “fruity”, “floral”, “berry-like”, “herbal”, “woody”, “spicy”, “sweet”, and “animal-like” as the main odor and flavor attributes. The total polyphenol and flavonoid contents were in the range of 26.2–88.7 mg gallic acid equivalents (GAE) per 100 g and 1.9–6.4 mg quercetin equivalents (QE) per 100 g, respectively. The identified polyphenols showed the highest intensities of caffeic acid, coumaric acid, and abscisic acid and its derivatives. The protocatechuic acid intensity was highest in honeys containing traces of honeydew elements and of cinnamic acid and myricetin in heather honey. The water-soluble antioxidant values were 37.8–311.2 mg ascorbic acid equivalents (AAE) per 100 g and the lipid soluble antioxidant values were 14.4–60.7 mg Trolox equivalents (TE) per 100 g. The major amino acid in the analyzed honeys was proline, with variable values depending on the honey’s botanical source. Correlations were calculated based on the results obtained. It was revealed that the typical Estonian honey has floral, berry-like, sweet, and rather mild sensory characteristics. Most of the honeys lacked stronger spicy, woody, and animal-like attributes. The typical color of Estonian honey is quite light.

Antibiofilm Activity of Heather and Manuka Honeys and Antivirulence Potential of Some of Their Constituents on the DsbA1 Enzyme of Pseudomonas aeruginosa.

Heather honey was tested for its effect on the formation of biofilms by Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Salmonella Enteriditis and Acinetobacter baumanii in comparison with Manuka honey. At 0.25 mg/mL, Heather honey inhibited biofilm formation in S. aureus, A. baumanii, E. coli, S. Enteriditis and P. aeruginosa, but promoted the growth of E. faecalis and K. pneumoniae biofilms. Manuka honey inhibited biofilm formation in K. pneumoniae, E. faecalis, and S. Enteriditis, A. baumanii, E. coli and P. aeruginosa, but promoted S. aureus biofilm formation. Molecular docking with Autodock Vina was performed to calculate the predictive binding affinities and ligand efficiencies of Manuka and Heather honey constituents for PaDsbA1, the main enzyme controlling the correct folding of virulence proteins in Pseudomonas aeruginosa. A number of constituents, including benzoic acid and methylglyoxal, present in Heather and/or Manuka honey, revealed high ligand efficiencies for the target enzyme. This helps support, to some extent, the decrease in P. aeruginosa biofilm formation observed for such honeys.

CARACTERIZACIÓN PALINOLÓGICA DE LAS MIELES DE LA LLANURA DEL RÍO SENGUERR (CHUBUT-ARGENTINA)

In order to know the plants used by honeybees in the Senguerr river plains, a palynological analysis of 19 samples of honey was made. Most samples had less than 2000 grains/g. Fifty-seven types of pollen were identified. Main sources of nectar belong to the following families: Fabaceae, Rosaceae, Brassicaceae and Asteraceae. Honeys were classified as monofloral Melilotus sp. (8 samples), monofloral Rosaceae (wild and cultivated, 2 samples) or of mixed floral origin (9 samples). The analized honeys may be distinguished by a pollen association of Trifolieae, Brassicaceae, Rosaceae, Acaena sp., Glycyrrhiza astragalina Gillies ex Hook. & Arn. and Cyperaceae.