A contribution to the differentiation between nectar honey and honeydew honey

Thirty genuine honey samples were analyzed for pH, acidity, water, ash, net absorbance, total polyphenols (Folin–Ciocalteau method) and glucose, fructose, melezitose and erlose (as their trimethylsilyl oximes and trimethylsilyl ethers) by capillary gas chromatography. The resulting data were used, along with palynological analysis, to characterize the samples in relation to their possible source (nectar, honeydew and mixture honeys).Some minor components (carboxylic acids and cyclitols), eluting before monosaccharides, were also determined. One of these compounds was quercitol (1,3,4/2,5-cyclohexane-pentol), a deoxyinositol which has been previously determined in Quercus sp. samples. Quercitol was present in a broad concentration range (0.01–1.50 g/100 g) in honeys whose major source was honeydew but it was never higher than 0.01 g/100 g in samples characterized as nectar honeys. Quercitol concentrations appear to be related to the presence and amount of Quercus sp. honeydew as honey source, although further research is required to confirm this.     

Classification of monofloral honeys based on their quality control data

Four hundred and sixty-nine samples of fir, cinder heather, chestnut, lavender, acacia, rape, and sunflower honey were characterized by their moisture, conductivity, diastase activity, pH, free acidity, color, hydroxymethylfurfural and percentage of fructose, glucose, saccharose, erlose, raffinose, and melezitose. A principal component analysis performed on the corresponding matrix yielded the formation of four clusters. A stepwise discriminant analysis allowed us to obtain 100% of good predictions with only conductivity, pH, free acidity and percentage of fructose, glucose, and raffinose as variables. The simulation performances of the model were estimated from an external testing set.     

Quantitative determination of physical and chemical measurands in honey by near-infrared spectrometry

Fourier transform near-infrared spectroscopy (FT-NIR) was evaluated to quantitatively determine 24 different measurands in honey. The reference values of 421 honey samples of different botanical origins were determined by classical physical and chemical methods. Partial least squares regression was used to develop the calibration models for the measurands studied. These calibrations were then validated using independent samples and proved satisfying accuracies for the determination of water (standard error of prediction: 0.3 g/100 g), glucose (1.3 g/100 g), fructose (1.6 g/100 g), sucrose (0.4 g/100 g), total monosaccharide content (2.6 g/100 g) as well as fructose/glucose ratio (0.09) and glucose/water ratio (0.12). The prediction accuracy for hydroxymethylfurfural, proline, pH-value, electrical conductivity, free acidity and the minor sugars maltose, turanose, nigerose, erlose, trehalose, isomaltose, kojibiose, melezitose, raffinose, gentiobiose, melibiose, maltotriose was poor and unreliable. The results demonstrate that near-infrared spectrometry is a valuable, rapid and non-destructive tool for the quantitative analysis of some measurands related to the main components in honey.     

The oligosaccharide composition of some New Zealand honeys

The oligosaccharide fraction of samples of manuka (Leptospermum), heather (Calluna), clover (Trifolium) and beech honeydew (Nothofagus) honeys from New Zealand was separated from the monosaccharides and then analysed by high performance anion-exchange chromatography with pulsed amperometric detection (hpaec-pad). Significant oligosaccharide components of manuka honey were isomaltose (or maltulose), kojibiose, turanose (or gentiobiose), nigerose and maltose which was the major component. The composition of clover honey was identical to that of manuka, while heather honey differed from these two only because isomaltose was the major component. Beech honeydew honey was characterised by the complexity of the oligosaccharide composition. The trisaccharides melezitose and panose were the most abundant components. No differences were observed between the oligosaccharide compositions of manuka honeys which did or did not exhibit non-peroxide residual antibacterial activity. Manuka honey was shown to be derived from nectar and not honeydew as has been suggested.     

Simplex lattice mixture design approach on the rheological behavior of glucomannan based salep-honey drink mixtures: An optimization study based on the sensory properties

The rheological properties of salep drink sweetened with different honeys were measured using a controlled-stress rheometer. Mixture design experiments were used to study the effect of interactions among pine, flower and highland honeys on the rheological properties of salep-honey drink mixture (SHDM) samples. In addition, product optimization was carried out using the ridge analysis to determine the optimum mixture proportions based on sensory properties of SHDM samples. Flower honey was the component showing the highest effect on the consistency coefficient values of SHDM samples. The preference of panelists was more prominent for the SHDM samples including the higher concentrations of highland honey with respect to odour and overall preference parameters. Optimum values of pine, flower and highland honeys in the mixture were found to be 0–85%, 0–40% and 15–100%, respectively, with respect to sensory properties. In addition, ridge analysis results revealed that the SHDM should include 65% highland honey, 35% pine honey and no flower honey to obtain the maximum overall preference score (7.24). The consistency coefficient and flow behavior index values of the sample to get maximum overall preference score (7.24) were predicted to be 3.650 Pa sⁿ and 0.435, respectively.     

Evolution of fructose and glucose in honey over one year: influence of induced granulation

Evolution of fructose and glucose over 1 year has been evaluated in 30 honey samples from Burgos (N. Spain). The influence of the induced granulation process in this evolution was also determined. Each sample was divided into two aliquots of 500 g and aseptically bottled. One aliquot was directly stored and the second induced to crystallise by seeding with 10% of finely crystallised honey. Analyses of moisture content, pH, fructose and glucose were carried out over 1 year, once each 4 months. Both, fructose and glucose increased in most samples. Induced-crystallised samples did not show any significant differences in the evolution of the two sugars in comparsion with directly stored samples. Linear correlations were found, for both fructose and glucose, between samples directly stored and honeys in which granulation was induced. These results are clearly different from those reported in previous papers where decrease of monosaccharides below their original values was described. pH of honey might promote reversion of monosaccharides and the formation of disaccharides and trisaccharides. This investigation has demonstrated the possibility of formation of monosaccharides, by the hydrolysis of higher sugars, as a process predominant over the reversion. No statistical relationship was found between pH of honey samples and their fructose and glucose content evolution.     

Quantitative analysis of physical and chemical measurands in honey by mid-infrared spectrometry

Fourier transform infrared spectroscopy (FT-IR) was used to determine 20 different measurands in honey. The reference values for 144 honey samples of different botanical origin were determined by classical physical and chemical methods. Partial least squares regression was used to develop the calibration models for the measurands studied. They were validated using independent samples and proved satisfying accuracies for the determination of water (R ²=0.99), glucose (0.94), fructose (0.84), sucrose (0.91), melezitose (0.98) and monosaccharide content (0.82) as well as fructose/glucose ratio (0.98), glucose/water ratio (0.94), electrical conductivity (0.98), pH-value (0.87) and free acidity (0.96). The prediction accuracy for hydroxymethylfurfural, proline and the minor sugars maltose, turanose, erlose, trehalose, isomaltose and kojibiose was rather poor. The results demonstrate that mid-infrared spectrometry is a valuable, rapid and non-destructive tool for the quantitative analysis of the most important measurands in honey.     

The sugars of honey—A review

Surveys of floral honey composition have established that the three major components are fructose, glucose, and water, averaging 38.2, 31.3 and 17.2%, respectively. Glucose and fructose are the only monosaccharides in honey and it is these sugars, combined in various forms, that comprise the di- and trisaccharide fractions of floral honey. Several laboratories, utilising various chemical and physical methods, have been responsible for the isolation and characterisation of ten disaccharides, ten trisaccharides, and two higher sugars from floral honey. Several of these occur only rarely in nature, and the trisaccharide erlose, produced by the action of honeybee invertase on sucrose, was first discovered as a component of honey. Honeydew honey is produced by the honeybee from honeydew deposits left by various hemipterous insects on their host plant. Honeydew contains a more complex mixture of sugars than does nectar, and honeydew honey is appreciably higher in reducing disaccharides and higher sugars than is floral honey. The trisaccharide melizitose, not found in floral honey, is often present in levels exceeding 10% in honeydew honey. The precipitation of glucose from honey, termed granulation, is often technologically undesirable as it is sometimes followed by fermentation. Indices such as the glucose/water ratio have been used to predict granulation tendency. Small amounts of hydroxymethylfurfural (HMF) occur naturally in honey, resulting from the acid catalysed dehydration of the hexoses, particularly fructose. High levels of HMF suggest adulteration of honey with acid inverted invert syrup and several methods are available for its determination. The conversion of nectar and honeydew to the complex array of honey sugars by the honeybee involves a variety of chemical and biochemical processes, some of which are now understood, while others remain to be elucidated.     

Carbohydrate composition and electrical conductivity of different origin honeys from Lithuania

The main task of this study was to characterize Lithuanian honeys obtained from various sources by their carbohydrate composition and electrical conductivity and to determine if there is any dependence between these characteristics and pollen content. Twenty six samples of honey collected in Lithuania in 2006 during flowering season were analyzed by gas chromatography. Botanical source of honey samples was established by the melissopalynological method: 15 of analyzed samples were unifloral rape (winter and spring), 7 willow and 4 polyfloral honeys. Fructose, glucose, sucrose, maltose, isomaltose, turanose, trehalose, palatinose, cellobiose, raffinose and panose were identified and quantified in all samples. Glucose was predominant in 22 out of 26 samples. The mean values of fructose and glucose varied from 329.2 to 400.0 and from 346.0 to 426.3 mg/g honey, respectively. The amount of sucrose was 0.7-2.5 mg/g. Some correlations between sugar concentration and the content of pollen were established. The ratios of fructose/glucose, maltose/isomaltose, maltose/turanose, sucrose/turanose, which may be used as indicators for honey authenticity, were calculated. In addition, electrical conductivity was measured and it was found that it varied from 0.27 to 0.89 mS/cm. Unifloral rape honeys had the lowest electrical conductivity. Data obtained was thoroughly compared with previously published results and it was found that the characteristics of Lithuanian honeys in most cases meet international requirements for natural honey. However, the information on honey sugar composition and electrical conductivity was not sufficient for the reliable determination of the botanical origin of honey.     

Analysis of minority honey components: Possible use for the evaluation of honey quality

The minerals (Al, B, Ca, Cu, Mg, Mn, Ni, Zn) of 24 authentic Czech nectar and honeydew honey samples (2003 and 2004 harvests) were determined, to find the relationship between their content and the origin or type of honey. The concentrations of analytes in the digests, obtained via optimised dry decomposition of honey samples, were measured by flame atomic absorption spectrometry (F-AAS), as well as optical emission spectrometry with inductively coupled plasma (ICP-OES). With regard to its speed of analysis and cost, ICP-OES was the more favourable method. By combining the analytical data and electrolytic conductivities of samples, the honey samples could be divided into two groups – honeydew honeys and nectar honeys. Like Slovak and Polish honeys, samples of Czech honeys had higher nickel levels than honeys originating from other parts of the world.     

Palynological and physicochemical data characterisation of honeys produced in the Entre‐Douro e Minho region of Portugal

Honey legislation has been addressed to establish the minimum marketing level of the product and the need for consumer protection through correct denominations. Research oriented toward assessment of floral origin and physicochemical properties may increase the commercial value of these products. The characteristics of thirty‐one honeys produced in the Entre‐Douro e Minho region in Portugal were studied. Pollen features and some physicochemical parameters (moisture, ash, pH, free acidity, electrical conductivity, hydroxymethylfurfural contain, apparent sucrose, reducing sugars and diastase activity) were determined. The samples were found to meet international honey specifications. The present study found a linear regression between the ash content of honeys and their specific conductivity. Five samples are listed as Eucalyptus honey, one sample as Citrus honey, and twenty‐five samples as multifloral honeys. Of the total, 87.1% exceeded the quality parameters and should be labelled as ‘virgin’ honey.     

Raw Millefiori honey is packed full of antioxidants

Total polyphenols, flavonoids and antioxidant power of raw honey samples from two of the most common Italian varieties, i.e., Millefiori and Acacia, were evaluated. Phenolic content, expressed as caffeic acid equivalents, ranged from 12.5 to 17.5 mg/100 g and from 3 to 11 mg/100 g in Millefiori and Acacia honeys, respectively. All Millefiori samples exhibited the highest flavonoid concentration being between 1.23 and 2.93 mg catechin equivalents (CE)/100 g honey. Total flavonoids in 100 g Acacia honeys were in the range of 0.45–1.01 mg CE. Acacia honeys had lower total antioxidant power, as assessed by ferric reducing/antioxidant power assay, than Millefiori. The relationship between phenolic content and antioxidant power was discussed. Comparative experimental analysis was performed with an artificial honey and processed honeys. Raw Millefiori honey is rich in both amount and variety of antioxidant substances, and its inclusion in the diet may be recommended to complement other polyphenol sources.     

Pollen spectrum and physico‐chemical attributes of heather (Erica sp.) honeys of north Portugal

BACKGROUND: Honey legislation has been addressed to establish the minimum marketing level of the product and the need for consumer protection through correct denominations. Research oriented toward assessment of floral origin and physico‐chemical properties may increase the commercial value of these products. The characteristics of 23 unifloral honeys of Erica sp., from Portugal, were studied. Pollen features and some physicochemical parameters (moisture, ash, pH, free acidity, electrical conductivity, hydroxymethylfurfural content, apparent sucrose, reducing sugars and diastase activity) were determined. RESULTS: All honey samples can be classified as monofloral Erica sp., they gave a mean value of 56% of Erica pollen type. The families Fabaceae and Rosaceae provided the greatest number of pollen types with 8 and 4 pollen types each respectively. The second most important pollen type is Eucalyptus, present in 69.6% of the samples. All honey samples met the international physicochemical quality standards. The present study found a linear correlation (R = 0.996) between the ash content of honeys and their specific conductivity. CONCLUSION: All honey samples can be classified as monofloral Erica sp. Unifloral honeys are increasingly requested and appreciated, despite their higher prices. The samples were found to meet all major international honey specifications. Copyright © 2009 Society of Chemical Industry     

Gas chromatographic–mass spectrometric characterisation of tri- and tetrasaccharides in honey

A GC–MS method has been used to characterize tri- and tetrasaccharides in honey after their derivatization into trimethylsilyloxime derivatives. Based on retention data and mass spectra, a total of 25 trisaccharides were characterized; 12 being unequivocally identified using standards and two of them detected for the first time in honey. Erlose and panose were the major trisaccharides in the 12 honeys under analysis, their concentrations ranging 30–1214 mg 100 g⁻¹ of honey and 17–863 mg 100 g⁻¹ of honey, respectively. The GC–MS method also allowed the analysis of tetrasaccharides. Besides nystose, another nine tetrasaccharides were characterized; six of them were sucrose derivatives. Tetrasaccharides were present in concentrations lower than 230 mg 100 g⁻¹ of honey.     

Volatile and carbohydrate composition of rare unifloral honeys from Spain

Volatile composition and carbohydrate content of Spanish honey samples from uncommon botanical origins have been studied by gas chromatography coupled to mass spectrometry. About 100 volatile compounds were identified; some of them appeared to be characteristic of particular honey types, such as methyl salycilate in willow (Salix spp.), 2,6,6-trimethyl-2,4-cycloheptadien-1-one (eucarvone) in almond tree (Prunus dulcis) and isophorone in strawberry-tree (Arbutus unedo). Concentration ranges for major carbohydrates were similar to those previously reported in other honeys with different botanical origins, although concentrations of maltulose in avocado honeys (Persea americana) and of melezitose in Quercus ilex honeys were higher. Some carbohydrate alcohols could also be considered as markers of honey botanical origin, such as quercitol for Q. ilex and perseitol for avocado.     

Differentiation of blossom and honeydew honeys using multivariate analysis on the physicochemical parameters and sugar composition

Multivariate analysis was applied on physicochemical parameters (moisture, water activity, electric conductivity, colour, hydroxymethyl furfural, acidity, pH, proline, diastase and invertase), sugar composition (fructose, glucose, sucrose, maltose, isomaltose, trehalose, turanose and melezitose) and palinological parameters determined in blossom and suspected honeydew honeys in order to differentiate them. The majority of the physicochemical, sugar composition and palinological parameters evaluated presented significant differences in the mean values between the suspected honeydew and blossom honeys, with the exception of moisture, water activity, diastase, fructose and maltose. Blossom honey samples tend to differentiate from the suspected honeydew honeys after applying factor analysis on the physicochemical parameters and sugar composition. Stepwise linear discriminant analysis allows the correct classification of all blossom honeys, and only one honeydew honey was erroneously included as blossom honey. So, the use of multivariate analysis on physicochemical parameters and sugar composition can be a useful tool to differentiate these types of honeys.     

STUDIES ON LIBYAN HONEYS

Ten honey samples representing various floral types were obtained from different areas in Libya. Two other samples were obtained from hives, where bees were fed on sugar syrup and date syrup, respectively. The chemical composition and some characteristics of these samples were studied. The data obtained generally showed that the specifications of honeys produced in Libya conformed with those required for table honey. The application of thin-layer chromatography on cellulose-coated plates for the analysis of honey sugars yielded clear resolution and discrete spots. Some measures — such as high level of calcium, low level of potassium and UV-absorption spectra of honeys were suggested to be used for identifying the sugar-honeys and for ensuring the quality of blossom honeys. An attempt has been made to predict the granulation behavior of honeys and a derived regression formula was suggested.     

Evaluation of the phenolic content,antioxidant activity and colour of Slovenian honey

Honey samples from the seven most common honey types in Slovenia were screened for total phenolic content by the modified Folin–Ciocalteu method, for potential antioxidant activity using the ferric reducing antioxidant power (FRAP) assay and by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method for antiradical activity. In addition the colour characteristics of honey samples were analysed. The results of the study showed that total phenolic content, antioxidant activity and colour parameters differ widely among different honey types. Phenolic content expressed as gallic acid equivalent ranged from 44.8 mg/kg in acacia honey to 241.4 mg/kg in fir honey. Antioxidant activity was the lowest in the brightest acacia and lime honeys and the highest in darker honeys, namely fir, spruce and forest. The colour of the Slovenian honeys, analysed in this study was very variable and ranged from pale yellow to dark brown. Correlations between the parameters analysed were found to be statistically significant (p < 0.05).     

A comparative study on phenolic profile,vitamin C content and antioxidant activity of Italian honeys of different botanical origin

The aim of our study was to identify and quantify the phenolic acids, flavonoids and vitamin C and to evaluate the antioxidant activity in ninety Italian honeys of different botanical origins (chestnut, sulla, eucalyptus, citrus and multifloral). The results showed that total phenolic and flavonoid contents varied from 11.08 to 14.26 mg GAE per 100 g honey and from 5.82 to 12.52 mg QE per 100 g honey, respectively. HPLC–UV analysis showed a similar but quantitatively different phenolic profile of the studied honeys. Vitamin C is present in all samples. Multifloral honey showed the highest amount of the detected total phenolic compounds and the highest vitamin C content. The DPPH value varied from 55.06 to 75.37%. Among the unifloral honeys, chestnut honey presented the highest levels of phenolic acids, flavonoids and vitamin C, which are closely associated with its high antioxidant activity. The results show that honey contains high amount of biologically active compounds, which play an important role in defining the nutraceutical quality of the product, and that the distribution of these compounds is influenced by the botanical origin.     

Physicochemical characteristics of minor monofloral honeys from Tenerife,Spain

Physicochemical parameters (moisture, water activity, electrical conductivity, colour, hydroxymethyl furfural, acidity, pH, proline, diastase and invertase) and sugar composition (fructose, glucose, sucrose, maltose, isomaltose, trehalose, turanose and melezitose) were determined in 85 honeys belonging to nine minor monofloral honeys such as avocado (Persea americana), barrilla (Messembryanthemum crystallinum), heather (Erica arborea), agave o pitera (Agave americana), poleo (Bystropogon origanifolius), relinchón (Hirstfeldia incana), tedera (Aspalthium bituminosum), malpica (Carlina xeranthemoides) and oregano (Origanum virens) from Tenerife in order to typify them for the first time. Most of the studied honeys are characterized because their specific pollens are under-represented. All the honey samples showed values of all the parameters determined within the legally established intervals. All the physicochemical and sugar composition parameters, with the exception of diastase, presented significant differences in the mean values between the honeys analyzed. Applying univariate statistical analysis, the following parameters (moisture, acidity, electrical conductivity, fructose, sucrose and melezitose) allow to distinguish all the types of honeys studied without overlap. Heather and avocado honeys showed the most differential physicochemical characteristics with respect to the rest of monofloral honeys.